From 36381fabaf18a6dfa0e9ee27b5045c2e8cf1c8ed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 10:02:09 -0700
Subject: [PATCH 1/9] Warn on `repr` without hints

---
 src/librustc/diagnostics.rs    |  1 +
 src/librustc/hir/check_attr.rs | 17 ++++++++++++++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/librustc/diagnostics.rs b/src/librustc/diagnostics.rs
index 61f05ca347358..a526967aff0aa 100644
--- a/src/librustc/diagnostics.rs
+++ b/src/librustc/diagnostics.rs
@@ -2139,6 +2139,7 @@ register_diagnostics! {
     E0657, // `impl Trait` can only capture lifetimes bound at the fn level
     E0687, // in-band lifetimes cannot be used in `fn`/`Fn` syntax
     E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
+    E0689, // `#[repr]` must have a hint
 
     E0906, // closures cannot be static
 }
diff --git a/src/librustc/hir/check_attr.rs b/src/librustc/hir/check_attr.rs
index 591cb9d5ad6c2..1e642b98e18ce 100644
--- a/src/librustc/hir/check_attr.rs
+++ b/src/librustc/hir/check_attr.rs
@@ -154,7 +154,22 @@ impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
         let hints: Vec<_> = item.attrs
             .iter()
             .filter(|attr| attr.name() == "repr")
-            .filter_map(|attr| attr.meta_item_list())
+            .filter_map(|attr| {
+                let list = attr.meta_item_list();
+                let mut has_hints = false;
+                if let Some(ref list) = list {
+                    has_hints = !list.is_empty();
+                }
+                if !has_hints {
+                    span_warn!(
+                        self.tcx.sess,
+                        item.span,
+                        E0689,
+                        "`repr` attribute cannot be empty",
+                    );
+                }
+                list
+            })
             .flat_map(|hints| hints)
             .collect();
 

From 2c7099baeb6be82fcfec630b00d8a8175f5329f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 12:31:43 -0700
Subject: [PATCH 2/9] Expand output and suggestions, fix tests

---
 src/librustc/diagnostics.rs                   |   1 -
 src/librustc/hir/check_attr.rs                |  59 +++-
 .../issue-43106-gating-of-builtin-attrs.rs    |   5 +
 ...issue-43106-gating-of-builtin-attrs.stderr | 329 ++++++++++--------
 src/test/ui/suggestions/repr.rs               |  28 ++
 src/test/ui/suggestions/repr.stderr           |  24 ++
 6 files changed, 292 insertions(+), 154 deletions(-)
 create mode 100644 src/test/ui/suggestions/repr.rs
 create mode 100644 src/test/ui/suggestions/repr.stderr

diff --git a/src/librustc/diagnostics.rs b/src/librustc/diagnostics.rs
index a526967aff0aa..61f05ca347358 100644
--- a/src/librustc/diagnostics.rs
+++ b/src/librustc/diagnostics.rs
@@ -2139,7 +2139,6 @@ register_diagnostics! {
     E0657, // `impl Trait` can only capture lifetimes bound at the fn level
     E0687, // in-band lifetimes cannot be used in `fn`/`Fn` syntax
     E0688, // in-band lifetimes cannot be mixed with explicit lifetime binders
-    E0689, // `#[repr]` must have a hint
 
     E0906, // closures cannot be static
 }
diff --git a/src/librustc/hir/check_attr.rs b/src/librustc/hir/check_attr.rs
index 1e642b98e18ce..5c7c9a05964e0 100644
--- a/src/librustc/hir/check_attr.rs
+++ b/src/librustc/hir/check_attr.rs
@@ -14,7 +14,7 @@
 //! conflicts between multiple such attributes attached to the same
 //! item.
 
-use syntax_pos::Span;
+use syntax_pos::{BytePos, Span};
 use ty::TyCtxt;
 
 use hir;
@@ -156,17 +156,54 @@ impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
             .filter(|attr| attr.name() == "repr")
             .filter_map(|attr| {
                 let list = attr.meta_item_list();
-                let mut has_hints = false;
-                if let Some(ref list) = list {
-                    has_hints = !list.is_empty();
-                }
+
+                // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
+                // no hints (``#[repr]`)
+                let has_hints = list.as_ref().map(|ref list| !list.is_empty()).unwrap_or(false);
                 if !has_hints {
-                    span_warn!(
-                        self.tcx.sess,
-                        item.span,
-                        E0689,
-                        "`repr` attribute cannot be empty",
-                    );
+                    let mut suggested = false;
+                    let mut warn = if let Some(ref lit) = attr.value_str() {
+                        // avoid warning about empty `repr` on `#[repr = "foo"]`
+                        let sp = match format!("{}", lit).as_ref() {
+                            "C" | "packed" | "rust" | "u*" | "i*" => {
+                                let lo = attr.span.lo() + BytePos(2);
+                                let hi = attr.span.hi() - BytePos(1);
+                                suggested = true;
+                                attr.span.with_lo(lo).with_hi(hi)
+                            }
+                            _ => attr.span,  // the literal wasn't a valid `repr` arg
+                        };
+                        let mut warn = self.tcx.sess.struct_span_warn(
+                            sp,
+                            "`repr` attribute isn't configurable with a literal",
+                        );
+                        if suggested {
+                            // if the literal could have been a valid `repr` arg,
+                            // suggest the correct syntax
+                            warn.span_suggestion(
+                                sp,
+                                "give `repr` a hint",
+                                format!("repr({})", lit),
+                            );
+                        } else {
+                            warn.span_label(attr.span, "needs a hint");
+                        }
+                        warn
+                    } else {
+                        let mut warn = self.tcx.sess.struct_span_warn(
+                            attr.span,
+                            "`repr` attribute must have a hint",
+                        );
+                        warn.span_label(attr.span, "needs a hint");
+                        warn
+                    };
+                    if !suggested {
+                        warn.help("valid hints include `#[repr(C)]`, `#[repr(packed)]` and \
+                                   `#[repr(rust)]`");
+                        warn.note("for more information, visit \
+                                   <https://doc.rust-lang.org/nomicon/other-reprs.html>");
+                    }
+                    warn.emit();
                 }
                 list
             })
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
index 76fb09f27bedf..4ba4464e87fa5 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
@@ -309,20 +309,25 @@ mod bench {
 
 #[repr = "3900"]
 //~^ WARN unused attribute
+//~| WARN `repr` attribute isn't configurable with a literal
 mod repr {
     mod inner { #![repr="3900"] }
     //~^ WARN unused attribute
+    //~| WARN `repr` attribute isn't configurable with a literal
 
     #[repr = "3900"] fn f() { }
     //~^ WARN unused attribute
+    //~| WARN `repr` attribute isn't configurable with a literal
 
     struct S;
 
     #[repr = "3900"] type T = S;
     //~^ WARN unused attribute
+    //~| WARN `repr` attribute isn't configurable with a literal
 
     #[repr = "3900"] impl S { }
     //~^ WARN unused attribute
+    //~| WARN `repr` attribute isn't configurable with a literal
 }
 
 #[path = "3800"]
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
index f8e5f58ca0e89..6754e51707318 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
@@ -1,11 +1,11 @@
 warning: macro_escape is a deprecated synonym for macro_use
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:493:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:498:1
    |
 LL | #[macro_escape]
    | ^^^^^^^^^^^^^^^
 
 warning: macro_escape is a deprecated synonym for macro_use
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:496:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:501:17
    |
 LL |     mod inner { #![macro_escape] }
    |                 ^^^^^^^^^^^^^^^^
@@ -186,6 +186,51 @@ warning: unknown lint: `x5100`
 LL |     #[deny(x5100)] impl S { }
    |            ^^^^^
 
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:310:1
+   |
+LL | #[repr = "3900"]
+   | ^^^^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:314:17
+   |
+LL |     mod inner { #![repr="3900"] }
+   |                 ^^^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:318:5
+   |
+LL |     #[repr = "3900"] fn f() { }
+   |     ^^^^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:324:5
+   |
+LL |     #[repr = "3900"] type T = S;
+   |     ^^^^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:328:5
+   |
+LL |     #[repr = "3900"] impl S { }
+   |     ^^^^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
 warning: unused attribute
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:192:5
    |
@@ -343,25 +388,25 @@ LL | #[start = "4300"]
    | ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:313:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:314:17
    |
 LL |     mod inner { #![repr="3900"] }
    |                 ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:316:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:318:5
    |
 LL |     #[repr = "3900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:321:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:324:5
    |
 LL |     #[repr = "3900"] type T = S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:324:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:328:5
    |
 LL |     #[repr = "3900"] impl S { }
    |     ^^^^^^^^^^^^^^^^
@@ -373,103 +418,103 @@ LL | #[repr = "3900"]
    | ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:332:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:337:5
    |
 LL |     #[path = "3800"] fn f() { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:335:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:340:5
    |
 LL |     #[path = "3800"]  struct S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:338:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:343:5
    |
 LL |     #[path = "3800"] type T = S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:341:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:346:5
    |
 LL |     #[path = "3800"] impl S { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:348:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:353:17
    |
 LL |     mod inner { #![abi="3700"] }
    |                 ^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:351:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:356:5
    |
 LL |     #[abi = "3700"] fn f() { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:354:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:359:5
    |
 LL |     #[abi = "3700"] struct S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:357:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:362:5
    |
 LL |     #[abi = "3700"] type T = S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:360:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:365:5
    |
 LL |     #[abi = "3700"] impl S { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:345:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:350:1
    |
 LL | #[abi = "3700"]
    | ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:367:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:372:17
    |
 LL |     mod inner { #![automatically_derived="3600"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:370:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:375:5
    |
 LL |     #[automatically_derived = "3600"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:373:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:378:5
    |
 LL |     #[automatically_derived = "3600"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:376:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:381:5
    |
 LL |     #[automatically_derived = "3600"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:379:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:384:5
    |
 LL |     #[automatically_derived = "3600"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:364:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:369:1
    |
 LL | #[automatically_derived = "3600"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: function is marked #[no_mangle], but not exported
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:387:27
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:392:27
    |
 LL |     #[no_mangle = "3500"] fn f() { }
    |                           -^^^^^^^^^
@@ -479,709 +524,709 @@ LL |     #[no_mangle = "3500"] fn f() { }
    = note: #[warn(private_no_mangle_fns)] on by default
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:400:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:405:17
    |
 LL |     mod inner { #![no_link="3400"] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:403:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:408:5
    |
 LL |     #[no_link = "3400"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:406:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:411:5
    |
 LL |     #[no_link = "3400"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:409:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:414:5
    |
 LL |     #[no_link = "3400"]type T = S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:412:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:417:5
    |
 LL |     #[no_link = "3400"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:397:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:402:1
    |
 LL | #[no_link = "3400"]
    | ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:419:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:424:17
    |
 LL |     mod inner { #![should_panic="3200"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:422:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:427:5
    |
 LL |     #[should_panic = "3200"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:425:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:430:5
    |
 LL |     #[should_panic = "3200"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:428:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:433:5
    |
 LL |     #[should_panic = "3200"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:431:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:436:5
    |
 LL |     #[should_panic = "3200"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:416:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:421:1
    |
 LL | #[should_panic = "3200"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:438:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:443:17
    |
 LL |     mod inner { #![ignore="3100"] }
    |                 ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:441:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:446:5
    |
 LL |     #[ignore = "3100"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:444:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:449:5
    |
 LL |     #[ignore = "3100"] struct S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:447:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:452:5
    |
 LL |     #[ignore = "3100"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:450:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:455:5
    |
 LL |     #[ignore = "3100"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:435:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:440:1
    |
 LL | #[ignore = "3100"]
    | ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:457:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:462:17
    |
 LL |     mod inner { #![no_implicit_prelude="3000"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:460:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:465:5
    |
 LL |     #[no_implicit_prelude = "3000"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:463:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:468:5
    |
 LL |     #[no_implicit_prelude = "3000"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:466:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:471:5
    |
 LL |     #[no_implicit_prelude = "3000"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:469:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:474:5
    |
 LL |     #[no_implicit_prelude = "3000"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:454:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:459:1
    |
 LL | #[no_implicit_prelude = "3000"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:476:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:481:17
    |
 LL |     mod inner { #![reexport_test_harness_main="2900"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:479:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:484:5
    |
 LL |     #[reexport_test_harness_main = "2900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:482:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:487:5
    |
 LL |     #[reexport_test_harness_main = "2900"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:485:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:490:5
    |
 LL |     #[reexport_test_harness_main = "2900"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:488:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:493:5
    |
 LL |     #[reexport_test_harness_main = "2900"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:473:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:478:1
    |
 LL | #[reexport_test_harness_main = "2900"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:499:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:504:5
    |
 LL |     #[macro_escape] fn f() { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:502:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:507:5
    |
 LL |     #[macro_escape] struct S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:505:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:510:5
    |
 LL |     #[macro_escape] type T = S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:508:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:513:5
    |
 LL |     #[macro_escape] impl S { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:516:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:521:17
    |
 LL |     mod inner { #![no_std="2600"] }
    |                 ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:516:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:521:17
    |
 LL |     mod inner { #![no_std="2600"] }
    |                 ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:520:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:525:5
    |
 LL |     #[no_std = "2600"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:520:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:525:5
    |
 LL |     #[no_std = "2600"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:524:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:529:5
    |
 LL |     #[no_std = "2600"] struct S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:524:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:529:5
    |
 LL |     #[no_std = "2600"] struct S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:528:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:533:5
    |
 LL |     #[no_std = "2600"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:528:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:533:5
    |
 LL |     #[no_std = "2600"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:532:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:537:5
    |
 LL |     #[no_std = "2600"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:532:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:537:5
    |
 LL |     #[no_std = "2600"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:512:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:517:1
    |
 LL | #[no_std = "2600"]
    | ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:512:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:517:1
    |
 LL | #[no_std = "2600"]
    | ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:671:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:676:17
    |
 LL |     mod inner { #![crate_name="0900"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:671:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:676:17
    |
 LL |     mod inner { #![crate_name="0900"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:675:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:680:5
    |
 LL |     #[crate_name = "0900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:675:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:680:5
    |
 LL |     #[crate_name = "0900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:679:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:684:5
    |
 LL |     #[crate_name = "0900"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:679:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:684:5
    |
 LL |     #[crate_name = "0900"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:683:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:688:5
    |
 LL |     #[crate_name = "0900"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:683:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:688:5
    |
 LL |     #[crate_name = "0900"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:687:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:692:5
    |
 LL |     #[crate_name = "0900"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:687:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:692:5
    |
 LL |     #[crate_name = "0900"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:667:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:672:1
    |
 LL | #[crate_name = "0900"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:667:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:672:1
    |
 LL | #[crate_name = "0900"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:696:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:701:17
    |
 LL |     mod inner { #![crate_type="0800"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:696:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:701:17
    |
 LL |     mod inner { #![crate_type="0800"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:700:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:705:5
    |
 LL |     #[crate_type = "0800"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:700:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:705:5
    |
 LL |     #[crate_type = "0800"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:704:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:709:5
    |
 LL |     #[crate_type = "0800"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:704:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:709:5
    |
 LL |     #[crate_type = "0800"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:708:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:713:5
    |
 LL |     #[crate_type = "0800"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:708:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:713:5
    |
 LL |     #[crate_type = "0800"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:712:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:717:5
    |
 LL |     #[crate_type = "0800"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:712:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:717:5
    |
 LL |     #[crate_type = "0800"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:692:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:697:1
    |
 LL | #[crate_type = "0800"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:692:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:697:1
    |
 LL | #[crate_type = "0800"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:721:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:726:17
    |
 LL |     mod inner { #![feature(x0600)] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:721:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:726:17
    |
 LL |     mod inner { #![feature(x0600)] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:725:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:730:5
    |
 LL |     #[feature(x0600)] fn f() { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:725:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:730:5
    |
 LL |     #[feature(x0600)] fn f() { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:729:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:734:5
    |
 LL |     #[feature(x0600)] struct S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:729:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:734:5
    |
 LL |     #[feature(x0600)] struct S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:733:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:738:5
    |
 LL |     #[feature(x0600)] type T = S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:733:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:738:5
    |
 LL |     #[feature(x0600)] type T = S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:737:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:742:5
    |
 LL |     #[feature(x0600)] impl S { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:737:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:742:5
    |
 LL |     #[feature(x0600)] impl S { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:717:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:722:1
    |
 LL | #[feature(x0600)]
    | ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:717:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:722:1
    |
 LL | #[feature(x0600)]
    | ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:747:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:752:17
    |
 LL |     mod inner { #![no_main="0400"] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:747:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:752:17
    |
 LL |     mod inner { #![no_main="0400"] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:751:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:756:5
    |
 LL |     #[no_main = "0400"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:751:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:756:5
    |
 LL |     #[no_main = "0400"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:755:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:760:5
    |
 LL |     #[no_main = "0400"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:755:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:760:5
    |
 LL |     #[no_main = "0400"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:759:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:764:5
    |
 LL |     #[no_main = "0400"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:759:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:764:5
    |
 LL |     #[no_main = "0400"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:763:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:768:5
    |
 LL |     #[no_main = "0400"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:763:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:768:5
    |
 LL |     #[no_main = "0400"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:743:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:748:1
    |
 LL | #[no_main = "0400"]
    | ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:743:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:748:1
    |
 LL | #[no_main = "0400"]
    | ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:785:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:790:17
    |
 LL |     mod inner { #![recursion_limit="0200"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:785:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:790:17
    |
 LL |     mod inner { #![recursion_limit="0200"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:789:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:794:5
    |
 LL |     #[recursion_limit="0200"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:789:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:794:5
    |
 LL |     #[recursion_limit="0200"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:793:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:798:5
    |
 LL |     #[recursion_limit="0200"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:793:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:798:5
    |
 LL |     #[recursion_limit="0200"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:797:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:802:5
    |
 LL |     #[recursion_limit="0200"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:797:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:802:5
    |
 LL |     #[recursion_limit="0200"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:801:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:806:5
    |
 LL |     #[recursion_limit="0200"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:801:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:806:5
    |
 LL |     #[recursion_limit="0200"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:781:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:786:1
    |
 LL | #[recursion_limit="0200"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:781:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:786:1
    |
 LL | #[recursion_limit="0200"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:810:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:815:17
    |
 LL |     mod inner { #![type_length_limit="0100"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:810:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:815:17
    |
 LL |     mod inner { #![type_length_limit="0100"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:814:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:819:5
    |
 LL |     #[type_length_limit="0100"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:814:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:819:5
    |
 LL |     #[type_length_limit="0100"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:818:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:823:5
    |
 LL |     #[type_length_limit="0100"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:818:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:823:5
    |
 LL |     #[type_length_limit="0100"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:822:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:827:5
    |
 LL |     #[type_length_limit="0100"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:822:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:827:5
    |
 LL |     #[type_length_limit="0100"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:826:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:831:5
    |
 LL |     #[type_length_limit="0100"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:826:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:831:5
    |
 LL |     #[type_length_limit="0100"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:806:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:811:1
    |
 LL | #[type_length_limit="0100"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:806:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:811:1
    |
 LL | #[type_length_limit="0100"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1259,7 +1304,7 @@ LL | #![proc_macro_derive          = "2500"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: compilation successful
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:837:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:842:1
    |
 LL | / fn main() { //~ ERROR compilation successful
 LL | |     println!("Hello World");
diff --git a/src/test/ui/suggestions/repr.rs b/src/test/ui/suggestions/repr.rs
new file mode 100644
index 0000000000000..312f60202c6c2
--- /dev/null
+++ b/src/test/ui/suggestions/repr.rs
@@ -0,0 +1,28 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-pass
+
+#[repr]
+//^ WARN `repr` attribute must have a hint
+struct _A {}
+
+#[repr = "B"]
+//^ WARN `repr` attribute isn't configurable with a literal
+struct _B {}
+
+#[repr = "C"]
+//^ WARN `repr` attribute isn't configurable with a literal
+struct _C {}
+
+#[repr(C)]
+struct _D {}
+
+fn main() {}
diff --git a/src/test/ui/suggestions/repr.stderr b/src/test/ui/suggestions/repr.stderr
new file mode 100644
index 0000000000000..6ed246d0d2c29
--- /dev/null
+++ b/src/test/ui/suggestions/repr.stderr
@@ -0,0 +1,24 @@
+warning: `repr` attribute must have a hint
+  --> $DIR/repr.rs:13:1
+   |
+LL | #[repr]
+   | ^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/repr.rs:17:1
+   |
+LL | #[repr = "B"]
+   | ^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/repr.rs:21:3
+   |
+LL | #[repr = "C"]
+   |   ^^^^^^^^^^ help: give `repr` a hint: `repr(C)`
+

From 3580de8c6d6aa39a4b81a851deaf8bb9b6baf66d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 14:11:48 -0700
Subject: [PATCH 3/9] Turn warning into lint

---
 src/librustc/hir/check_attr.rs                |  56 +--
 src/librustc/lint/builtin.rs                  |   6 +
 src/librustc_lint/builtin.rs                  |  69 +++
 src/librustc_lint/lib.rs                      |   1 +
 .../issue-43106-gating-of-builtin-attrs.rs    |   4 +-
 ...issue-43106-gating-of-builtin-attrs.stderr | 436 +++++++++---------
 src/test/ui/suggestions/repr.stderr           |   1 +
 7 files changed, 305 insertions(+), 268 deletions(-)

diff --git a/src/librustc/hir/check_attr.rs b/src/librustc/hir/check_attr.rs
index 5c7c9a05964e0..591cb9d5ad6c2 100644
--- a/src/librustc/hir/check_attr.rs
+++ b/src/librustc/hir/check_attr.rs
@@ -14,7 +14,7 @@
 //! conflicts between multiple such attributes attached to the same
 //! item.
 
-use syntax_pos::{BytePos, Span};
+use syntax_pos::Span;
 use ty::TyCtxt;
 
 use hir;
@@ -154,59 +154,7 @@ impl<'a, 'tcx> CheckAttrVisitor<'a, 'tcx> {
         let hints: Vec<_> = item.attrs
             .iter()
             .filter(|attr| attr.name() == "repr")
-            .filter_map(|attr| {
-                let list = attr.meta_item_list();
-
-                // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
-                // no hints (``#[repr]`)
-                let has_hints = list.as_ref().map(|ref list| !list.is_empty()).unwrap_or(false);
-                if !has_hints {
-                    let mut suggested = false;
-                    let mut warn = if let Some(ref lit) = attr.value_str() {
-                        // avoid warning about empty `repr` on `#[repr = "foo"]`
-                        let sp = match format!("{}", lit).as_ref() {
-                            "C" | "packed" | "rust" | "u*" | "i*" => {
-                                let lo = attr.span.lo() + BytePos(2);
-                                let hi = attr.span.hi() - BytePos(1);
-                                suggested = true;
-                                attr.span.with_lo(lo).with_hi(hi)
-                            }
-                            _ => attr.span,  // the literal wasn't a valid `repr` arg
-                        };
-                        let mut warn = self.tcx.sess.struct_span_warn(
-                            sp,
-                            "`repr` attribute isn't configurable with a literal",
-                        );
-                        if suggested {
-                            // if the literal could have been a valid `repr` arg,
-                            // suggest the correct syntax
-                            warn.span_suggestion(
-                                sp,
-                                "give `repr` a hint",
-                                format!("repr({})", lit),
-                            );
-                        } else {
-                            warn.span_label(attr.span, "needs a hint");
-                        }
-                        warn
-                    } else {
-                        let mut warn = self.tcx.sess.struct_span_warn(
-                            attr.span,
-                            "`repr` attribute must have a hint",
-                        );
-                        warn.span_label(attr.span, "needs a hint");
-                        warn
-                    };
-                    if !suggested {
-                        warn.help("valid hints include `#[repr(C)]`, `#[repr(packed)]` and \
-                                   `#[repr(rust)]`");
-                        warn.note("for more information, visit \
-                                   <https://doc.rust-lang.org/nomicon/other-reprs.html>");
-                    }
-                    warn.emit();
-                }
-                list
-            })
+            .filter_map(|attr| attr.meta_item_list())
             .flat_map(|hints| hints)
             .collect();
 
diff --git a/src/librustc/lint/builtin.rs b/src/librustc/lint/builtin.rs
index de583e81ca831..9fa6230670b67 100644
--- a/src/librustc/lint/builtin.rs
+++ b/src/librustc/lint/builtin.rs
@@ -206,6 +206,12 @@ declare_lint! {
     "potentially-conflicting impls were erroneously allowed"
 }
 
+declare_lint! {
+    pub BAD_REPR,
+    Warn,
+    "detects incorrect use of `repr` attribute"
+}
+
 declare_lint! {
     pub DEPRECATED,
     Warn,
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 79c7a79114761..fbd153982b7c4 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -673,6 +673,75 @@ impl EarlyLintPass for AnonymousParameters {
     }
 }
 
+/// Checks for incorrect use use of `repr` attributes.
+#[derive(Clone)]
+pub struct BadRepr;
+
+impl LintPass for BadRepr {
+    fn get_lints(&self) -> LintArray {
+        lint_array!()
+    }
+}
+
+impl EarlyLintPass for BadRepr {
+    fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
+        if attr.name() == "repr" {
+            let list = attr.meta_item_list();
+
+            // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
+            // no hints (``#[repr]`)
+            let has_hints = list.as_ref().map(|ref list| !list.is_empty()).unwrap_or(false);
+            if !has_hints {
+                let mut suggested = false;
+                let mut warn = if let Some(ref lit) = attr.value_str() {
+                    // avoid warning about empty `repr` on `#[repr = "foo"]`
+                    let sp = match format!("{}", lit).as_ref() {
+                        "C" | "packed" | "rust" | "u*" | "i*" => {
+                            let lo = attr.span.lo() + BytePos(2);
+                            let hi = attr.span.hi() - BytePos(1);
+                            suggested = true;
+                            attr.span.with_lo(lo).with_hi(hi)
+                        }
+                        _ => attr.span,  // the literal wasn't a valid `repr` arg
+                    };
+                    let mut warn = cx.struct_span_lint(
+                        BAD_REPR,
+                        sp,
+                        "`repr` attribute isn't configurable with a literal",
+                    );
+                    if suggested {
+                        // if the literal could have been a valid `repr` arg,
+                        // suggest the correct syntax
+                        warn.span_suggestion(
+                            sp,
+                            "give `repr` a hint",
+                            format!("repr({})", lit),
+                        );
+                    } else {
+                        warn.span_label(attr.span, "needs a hint");
+                    }
+                    warn
+                } else {
+                    let mut warn = cx.struct_span_lint(
+                        BAD_REPR,
+                        attr.span,
+                        "`repr` attribute must have a hint",
+                    );
+                    warn.span_label(attr.span, "needs a hint");
+                    warn
+                };
+                if !suggested {
+                    warn.help("valid hints include `#[repr(C)]`, `#[repr(packed)]` and \
+                               `#[repr(rust)]`");
+                    warn.note("for more information, visit \
+                               <https://doc.rust-lang.org/nomicon/other-reprs.html>");
+                }
+                warn.emit();
+            }
+        }
+    }
+}
+
 /// Checks for use of attributes which have been deprecated.
 #[derive(Clone)]
 pub struct DeprecatedAttr {
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index d6ce5b2ea57fe..e1106281f4523 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -107,6 +107,7 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                        UnusedImportBraces,
                        AnonymousParameters,
                        UnusedDocComment,
+                       BadRepr,
                        );
 
     add_early_builtin_with_new!(sess,
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
index 4ba4464e87fa5..db50b9514430c 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.rs
@@ -59,7 +59,9 @@
 #![start                     = "x4300"] //~ WARN unused attribute
 // see issue-43106-gating-of-test.rs for crate-level; but non crate-level is below at "4200"
 // see issue-43106-gating-of-bench.rs for crate-level; but non crate-level is below at "4100"
-#![repr                       = "3900"] //~ WARN unused attribute
+#![repr                       = "3900"]
+//~^ WARN unused attribute
+//~| WARN `repr` attribute isn't configurable with a literal
 #![path                       = "3800"] //~ WARN unused attribute
 #![abi                        = "3700"] //~ WARN unused attribute
 #![automatically_derived      = "3600"] //~ WARN unused attribute
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
index 6754e51707318..013504c554def 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
@@ -1,11 +1,11 @@
 warning: macro_escape is a deprecated synonym for macro_use
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:498:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:500:1
    |
 LL | #[macro_escape]
    | ^^^^^^^^^^^^^^^
 
 warning: macro_escape is a deprecated synonym for macro_use
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:501:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:503:17
    |
 LL |     mod inner { #![macro_escape] }
    |                 ^^^^^^^^^^^^^^^^
@@ -43,169 +43,161 @@ LL | #![deny                        (x5100)] //~ WARN unknown lint: `x5100`
    |                                 ^^^^^
 
 warning: unknown lint: `x5400`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:112:8
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:114:8
    |
 LL | #[warn(x5400)]
    |        ^^^^^
 
 warning: unknown lint: `x5400`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:115:25
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:117:25
    |
 LL |     mod inner { #![warn(x5400)] }
    |                         ^^^^^
 
 warning: unknown lint: `x5400`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:118:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:120:12
    |
 LL |     #[warn(x5400)] fn f() { }
    |            ^^^^^
 
 warning: unknown lint: `x5400`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:121:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:123:12
    |
 LL |     #[warn(x5400)] struct S;
    |            ^^^^^
 
 warning: unknown lint: `x5400`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:124:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:126:12
    |
 LL |     #[warn(x5400)] type T = S;
    |            ^^^^^
 
 warning: unknown lint: `x5400`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:127:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:129:12
    |
 LL |     #[warn(x5400)] impl S { }
    |            ^^^^^
 
 warning: unknown lint: `x5300`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:131:9
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:133:9
    |
 LL | #[allow(x5300)]
    |         ^^^^^
 
 warning: unknown lint: `x5300`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:134:26
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:136:26
    |
 LL |     mod inner { #![allow(x5300)] }
    |                          ^^^^^
 
 warning: unknown lint: `x5300`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:137:13
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:139:13
    |
 LL |     #[allow(x5300)] fn f() { }
    |             ^^^^^
 
 warning: unknown lint: `x5300`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:140:13
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:142:13
    |
 LL |     #[allow(x5300)] struct S;
    |             ^^^^^
 
 warning: unknown lint: `x5300`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:143:13
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:145:13
    |
 LL |     #[allow(x5300)] type T = S;
    |             ^^^^^
 
 warning: unknown lint: `x5300`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:146:13
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:148:13
    |
 LL |     #[allow(x5300)] impl S { }
    |             ^^^^^
 
 warning: unknown lint: `x5200`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:150:10
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:152:10
    |
 LL | #[forbid(x5200)]
    |          ^^^^^
 
 warning: unknown lint: `x5200`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:153:27
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:155:27
    |
 LL |     mod inner { #![forbid(x5200)] }
    |                           ^^^^^
 
 warning: unknown lint: `x5200`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:156:14
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:158:14
    |
 LL |     #[forbid(x5200)] fn f() { }
    |              ^^^^^
 
 warning: unknown lint: `x5200`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:159:14
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:161:14
    |
 LL |     #[forbid(x5200)] struct S;
    |              ^^^^^
 
 warning: unknown lint: `x5200`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:162:14
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:164:14
    |
 LL |     #[forbid(x5200)] type T = S;
    |              ^^^^^
 
 warning: unknown lint: `x5200`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:165:14
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:167:14
    |
 LL |     #[forbid(x5200)] impl S { }
    |              ^^^^^
 
 warning: unknown lint: `x5100`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:169:8
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:171:8
    |
 LL | #[deny(x5100)]
    |        ^^^^^
 
 warning: unknown lint: `x5100`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:172:25
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:174:25
    |
 LL |     mod inner { #![deny(x5100)] }
    |                         ^^^^^
 
 warning: unknown lint: `x5100`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:175:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:177:12
    |
 LL |     #[deny(x5100)] fn f() { }
    |            ^^^^^
 
 warning: unknown lint: `x5100`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:178:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:180:12
    |
 LL |     #[deny(x5100)] struct S;
    |            ^^^^^
 
 warning: unknown lint: `x5100`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:181:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:183:12
    |
 LL |     #[deny(x5100)] type T = S;
    |            ^^^^^
 
 warning: unknown lint: `x5100`
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:184:12
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:186:12
    |
 LL |     #[deny(x5100)] impl S { }
    |            ^^^^^
 
 warning: `repr` attribute isn't configurable with a literal
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:310:1
-   |
-LL | #[repr = "3900"]
-   | ^^^^^^^^^^^^^^^^ needs a hint
-   |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
-
-warning: `repr` attribute isn't configurable with a literal
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:314:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:316:17
    |
 LL |     mod inner { #![repr="3900"] }
    |                 ^^^^^^^^^^^^^^^ needs a hint
    |
+   = note: #[warn(bad_repr)] on by default
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:318:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:320:5
    |
 LL |     #[repr = "3900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^ needs a hint
@@ -214,7 +206,7 @@ LL |     #[repr = "3900"] fn f() { }
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:324:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:326:5
    |
 LL |     #[repr = "3900"] type T = S;
    |     ^^^^^^^^^^^^^^^^ needs a hint
@@ -223,7 +215,7 @@ LL |     #[repr = "3900"] type T = S;
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:328:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:330:5
    |
 LL |     #[repr = "3900"] impl S { }
    |     ^^^^^^^^^^^^^^^^ needs a hint
@@ -231,8 +223,26 @@ LL |     #[repr = "3900"] impl S { }
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:312:1
+   |
+LL | #[repr = "3900"]
+   | ^^^^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
+warning: `repr` attribute isn't configurable with a literal
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:62:1
+   |
+LL | #![repr                       = "3900"]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ needs a hint
+   |
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:192:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:194:5
    |
 LL |     #[macro_use] fn f() { }
    |     ^^^^^^^^^^^^
@@ -244,277 +254,277 @@ LL | #![warn(unused_attributes, unknown_lints)]
    |         ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:195:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:197:5
    |
 LL |     #[macro_use] struct S;
    |     ^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:198:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:200:5
    |
 LL |     #[macro_use] type T = S;
    |     ^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:201:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:203:5
    |
 LL |     #[macro_use] impl S { }
    |     ^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:208:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:210:17
    |
 LL |     mod inner { #![macro_export="4800"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:211:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:213:5
    |
 LL |     #[macro_export = "4800"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:214:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:216:5
    |
 LL |     #[macro_export = "4800"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:217:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:219:5
    |
 LL |     #[macro_export = "4800"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:220:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:222:5
    |
 LL |     #[macro_export = "4800"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:205:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:207:1
    |
 LL | #[macro_export = "4800"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:227:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:229:17
    |
 LL |     mod inner { #![plugin_registrar="4700"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:232:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:234:5
    |
 LL |     #[plugin_registrar = "4700"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:235:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:237:5
    |
 LL |     #[plugin_registrar = "4700"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:238:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:240:5
    |
 LL |     #[plugin_registrar = "4700"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:224:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:226:1
    |
 LL | #[plugin_registrar = "4700"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:245:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:247:17
    |
 LL |     mod inner { #![main="4300"] }
    |                 ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:250:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:252:5
    |
 LL |     #[main = "4400"] struct S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:253:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:255:5
    |
 LL |     #[main = "4400"] type T = S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:256:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:258:5
    |
 LL |     #[main = "4400"] impl S { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:242:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:244:1
    |
 LL | #[main = "4400"]
    | ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:263:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:265:17
    |
 LL |     mod inner { #![start="4300"] }
    |                 ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:268:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:270:5
    |
 LL |     #[start = "4300"] struct S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:271:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:273:5
    |
 LL |     #[start = "4300"] type T = S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:274:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:276:5
    |
 LL |     #[start = "4300"] impl S { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:260:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:262:1
    |
 LL | #[start = "4300"]
    | ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:314:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:316:17
    |
 LL |     mod inner { #![repr="3900"] }
    |                 ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:318:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:320:5
    |
 LL |     #[repr = "3900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:324:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:326:5
    |
 LL |     #[repr = "3900"] type T = S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:328:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:330:5
    |
 LL |     #[repr = "3900"] impl S { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:310:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:312:1
    |
 LL | #[repr = "3900"]
    | ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:337:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:339:5
    |
 LL |     #[path = "3800"] fn f() { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:340:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:342:5
    |
 LL |     #[path = "3800"]  struct S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:343:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:345:5
    |
 LL |     #[path = "3800"] type T = S;
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:346:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:348:5
    |
 LL |     #[path = "3800"] impl S { }
    |     ^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:353:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:355:17
    |
 LL |     mod inner { #![abi="3700"] }
    |                 ^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:356:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:358:5
    |
 LL |     #[abi = "3700"] fn f() { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:359:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:361:5
    |
 LL |     #[abi = "3700"] struct S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:362:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:364:5
    |
 LL |     #[abi = "3700"] type T = S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:365:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:367:5
    |
 LL |     #[abi = "3700"] impl S { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:350:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:352:1
    |
 LL | #[abi = "3700"]
    | ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:372:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:374:17
    |
 LL |     mod inner { #![automatically_derived="3600"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:375:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:377:5
    |
 LL |     #[automatically_derived = "3600"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:378:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:380:5
    |
 LL |     #[automatically_derived = "3600"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:381:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:383:5
    |
 LL |     #[automatically_derived = "3600"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:384:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:386:5
    |
 LL |     #[automatically_derived = "3600"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:369:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:371:1
    |
 LL | #[automatically_derived = "3600"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: function is marked #[no_mangle], but not exported
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:392:27
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:394:27
    |
 LL |     #[no_mangle = "3500"] fn f() { }
    |                           -^^^^^^^^^
@@ -524,709 +534,709 @@ LL |     #[no_mangle = "3500"] fn f() { }
    = note: #[warn(private_no_mangle_fns)] on by default
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:405:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:407:17
    |
 LL |     mod inner { #![no_link="3400"] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:408:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:410:5
    |
 LL |     #[no_link = "3400"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:411:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:413:5
    |
 LL |     #[no_link = "3400"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:414:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:416:5
    |
 LL |     #[no_link = "3400"]type T = S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:417:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:419:5
    |
 LL |     #[no_link = "3400"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:402:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:404:1
    |
 LL | #[no_link = "3400"]
    | ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:424:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:426:17
    |
 LL |     mod inner { #![should_panic="3200"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:427:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:429:5
    |
 LL |     #[should_panic = "3200"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:430:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:432:5
    |
 LL |     #[should_panic = "3200"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:433:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:435:5
    |
 LL |     #[should_panic = "3200"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:436:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:438:5
    |
 LL |     #[should_panic = "3200"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:421:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:423:1
    |
 LL | #[should_panic = "3200"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:443:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:445:17
    |
 LL |     mod inner { #![ignore="3100"] }
    |                 ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:446:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:448:5
    |
 LL |     #[ignore = "3100"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:449:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:451:5
    |
 LL |     #[ignore = "3100"] struct S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:452:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:454:5
    |
 LL |     #[ignore = "3100"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:455:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:457:5
    |
 LL |     #[ignore = "3100"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:440:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:442:1
    |
 LL | #[ignore = "3100"]
    | ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:462:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:464:17
    |
 LL |     mod inner { #![no_implicit_prelude="3000"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:465:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:467:5
    |
 LL |     #[no_implicit_prelude = "3000"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:468:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:470:5
    |
 LL |     #[no_implicit_prelude = "3000"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:471:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:473:5
    |
 LL |     #[no_implicit_prelude = "3000"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:474:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:476:5
    |
 LL |     #[no_implicit_prelude = "3000"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:459:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:461:1
    |
 LL | #[no_implicit_prelude = "3000"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:481:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:483:17
    |
 LL |     mod inner { #![reexport_test_harness_main="2900"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:484:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:486:5
    |
 LL |     #[reexport_test_harness_main = "2900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:487:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:489:5
    |
 LL |     #[reexport_test_harness_main = "2900"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:490:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:492:5
    |
 LL |     #[reexport_test_harness_main = "2900"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:493:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:495:5
    |
 LL |     #[reexport_test_harness_main = "2900"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:478:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:480:1
    |
 LL | #[reexport_test_harness_main = "2900"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:504:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:506:5
    |
 LL |     #[macro_escape] fn f() { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:507:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:509:5
    |
 LL |     #[macro_escape] struct S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:510:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:512:5
    |
 LL |     #[macro_escape] type T = S;
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:513:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:515:5
    |
 LL |     #[macro_escape] impl S { }
    |     ^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:521:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:523:17
    |
 LL |     mod inner { #![no_std="2600"] }
    |                 ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:521:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:523:17
    |
 LL |     mod inner { #![no_std="2600"] }
    |                 ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:525:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:527:5
    |
 LL |     #[no_std = "2600"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:525:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:527:5
    |
 LL |     #[no_std = "2600"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:529:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:531:5
    |
 LL |     #[no_std = "2600"] struct S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:529:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:531:5
    |
 LL |     #[no_std = "2600"] struct S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:533:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:535:5
    |
 LL |     #[no_std = "2600"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:533:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:535:5
    |
 LL |     #[no_std = "2600"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:537:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:539:5
    |
 LL |     #[no_std = "2600"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:537:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:539:5
    |
 LL |     #[no_std = "2600"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:517:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:519:1
    |
 LL | #[no_std = "2600"]
    | ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:517:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:519:1
    |
 LL | #[no_std = "2600"]
    | ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:676:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:678:17
    |
 LL |     mod inner { #![crate_name="0900"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:676:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:678:17
    |
 LL |     mod inner { #![crate_name="0900"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:680:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:682:5
    |
 LL |     #[crate_name = "0900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:680:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:682:5
    |
 LL |     #[crate_name = "0900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:684:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:686:5
    |
 LL |     #[crate_name = "0900"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:684:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:686:5
    |
 LL |     #[crate_name = "0900"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:688:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:690:5
    |
 LL |     #[crate_name = "0900"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:688:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:690:5
    |
 LL |     #[crate_name = "0900"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:692:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:694:5
    |
 LL |     #[crate_name = "0900"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:692:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:694:5
    |
 LL |     #[crate_name = "0900"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:672:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:674:1
    |
 LL | #[crate_name = "0900"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:672:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:674:1
    |
 LL | #[crate_name = "0900"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:701:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:703:17
    |
 LL |     mod inner { #![crate_type="0800"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:701:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:703:17
    |
 LL |     mod inner { #![crate_type="0800"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:705:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:707:5
    |
 LL |     #[crate_type = "0800"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:705:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:707:5
    |
 LL |     #[crate_type = "0800"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:709:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:711:5
    |
 LL |     #[crate_type = "0800"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:709:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:711:5
    |
 LL |     #[crate_type = "0800"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:713:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:715:5
    |
 LL |     #[crate_type = "0800"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:713:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:715:5
    |
 LL |     #[crate_type = "0800"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:717:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:719:5
    |
 LL |     #[crate_type = "0800"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:717:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:719:5
    |
 LL |     #[crate_type = "0800"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:697:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:699:1
    |
 LL | #[crate_type = "0800"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:697:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:699:1
    |
 LL | #[crate_type = "0800"]
    | ^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:726:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:728:17
    |
 LL |     mod inner { #![feature(x0600)] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:726:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:728:17
    |
 LL |     mod inner { #![feature(x0600)] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:730:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:732:5
    |
 LL |     #[feature(x0600)] fn f() { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:730:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:732:5
    |
 LL |     #[feature(x0600)] fn f() { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:734:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:736:5
    |
 LL |     #[feature(x0600)] struct S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:734:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:736:5
    |
 LL |     #[feature(x0600)] struct S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:738:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:740:5
    |
 LL |     #[feature(x0600)] type T = S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:738:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:740:5
    |
 LL |     #[feature(x0600)] type T = S;
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:742:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:744:5
    |
 LL |     #[feature(x0600)] impl S { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:742:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:744:5
    |
 LL |     #[feature(x0600)] impl S { }
    |     ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:722:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:724:1
    |
 LL | #[feature(x0600)]
    | ^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:722:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:724:1
    |
 LL | #[feature(x0600)]
    | ^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:752:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:754:17
    |
 LL |     mod inner { #![no_main="0400"] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:752:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:754:17
    |
 LL |     mod inner { #![no_main="0400"] }
    |                 ^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:756:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:758:5
    |
 LL |     #[no_main = "0400"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:756:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:758:5
    |
 LL |     #[no_main = "0400"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:760:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:762:5
    |
 LL |     #[no_main = "0400"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:760:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:762:5
    |
 LL |     #[no_main = "0400"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:764:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:766:5
    |
 LL |     #[no_main = "0400"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:764:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:766:5
    |
 LL |     #[no_main = "0400"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:768:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:770:5
    |
 LL |     #[no_main = "0400"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:768:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:770:5
    |
 LL |     #[no_main = "0400"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:748:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:750:1
    |
 LL | #[no_main = "0400"]
    | ^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:748:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:750:1
    |
 LL | #[no_main = "0400"]
    | ^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:790:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:792:17
    |
 LL |     mod inner { #![recursion_limit="0200"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:790:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:792:17
    |
 LL |     mod inner { #![recursion_limit="0200"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:794:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:796:5
    |
 LL |     #[recursion_limit="0200"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:794:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:796:5
    |
 LL |     #[recursion_limit="0200"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:798:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:800:5
    |
 LL |     #[recursion_limit="0200"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:798:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:800:5
    |
 LL |     #[recursion_limit="0200"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:802:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:804:5
    |
 LL |     #[recursion_limit="0200"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:802:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:804:5
    |
 LL |     #[recursion_limit="0200"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:806:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:808:5
    |
 LL |     #[recursion_limit="0200"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:806:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:808:5
    |
 LL |     #[recursion_limit="0200"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:786:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:788:1
    |
 LL | #[recursion_limit="0200"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:786:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:788:1
    |
 LL | #[recursion_limit="0200"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:815:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:817:17
    |
 LL |     mod inner { #![type_length_limit="0100"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be in the root module
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:815:17
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:817:17
    |
 LL |     mod inner { #![type_length_limit="0100"] }
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:819:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:821:5
    |
 LL |     #[type_length_limit="0100"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:819:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:821:5
    |
 LL |     #[type_length_limit="0100"] fn f() { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:823:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:825:5
    |
 LL |     #[type_length_limit="0100"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:823:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:825:5
    |
 LL |     #[type_length_limit="0100"] struct S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:827:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:829:5
    |
 LL |     #[type_length_limit="0100"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:827:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:829:5
    |
 LL |     #[type_length_limit="0100"] type T = S;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:831:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:833:5
    |
 LL |     #[type_length_limit="0100"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:831:5
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:833:5
    |
 LL |     #[type_length_limit="0100"] impl S { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:811:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:813:1
    |
 LL | #[type_length_limit="0100"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: crate-level attribute should be an inner attribute: add an exclamation mark: #![foo]
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:811:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:813:1
    |
 LL | #[type_length_limit="0100"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1258,53 +1268,53 @@ LL | #![start                     = "x4300"] //~ WARN unused attribute
 warning: unused attribute
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:62:1
    |
-LL | #![repr                       = "3900"] //~ WARN unused attribute
+LL | #![repr                       = "3900"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:63:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:65:1
    |
 LL | #![path                       = "3800"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:64:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:66:1
    |
 LL | #![abi                        = "3700"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:65:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:67:1
    |
 LL | #![automatically_derived      = "3600"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:67:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:69:1
    |
 LL | #![no_link                    = "3400"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:69:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:71:1
    |
 LL | #![should_panic               = "3200"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:70:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:72:1
    |
 LL | #![ignore                     = "3100"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused attribute
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:76:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:78:1
    |
 LL | #![proc_macro_derive          = "2500"] //~ WARN unused attribute
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: compilation successful
-  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:842:1
+  --> $DIR/issue-43106-gating-of-builtin-attrs.rs:844:1
    |
 LL | / fn main() { //~ ERROR compilation successful
 LL | |     println!("Hello World");
diff --git a/src/test/ui/suggestions/repr.stderr b/src/test/ui/suggestions/repr.stderr
index 6ed246d0d2c29..24a22a81c4aa0 100644
--- a/src/test/ui/suggestions/repr.stderr
+++ b/src/test/ui/suggestions/repr.stderr
@@ -4,6 +4,7 @@ warning: `repr` attribute must have a hint
 LL | #[repr]
    | ^^^^^^^ needs a hint
    |
+   = note: #[warn(bad_repr)] on by default
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 

From 48e45eec30312e7490f3b24c7692d06f83d47d38 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 14:18:13 -0700
Subject: [PATCH 4/9] Add `transparent` as valid `repr` hint

---
 src/librustc_lint/builtin.rs                         |  6 +++---
 .../issue-43106-gating-of-builtin-attrs.stderr       | 12 ++++++------
 src/test/ui/suggestions/repr.stderr                  |  4 ++--
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index fbd153982b7c4..b1b1440fbd282 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -696,7 +696,7 @@ impl EarlyLintPass for BadRepr {
                 let mut warn = if let Some(ref lit) = attr.value_str() {
                     // avoid warning about empty `repr` on `#[repr = "foo"]`
                     let sp = match format!("{}", lit).as_ref() {
-                        "C" | "packed" | "rust" | "u*" | "i*" => {
+                        "C" | "packed" | "rust" | "u*" | "i*" | "transparent" => {
                             let lo = attr.span.lo() + BytePos(2);
                             let hi = attr.span.hi() - BytePos(1);
                             suggested = true;
@@ -731,8 +731,8 @@ impl EarlyLintPass for BadRepr {
                     warn
                 };
                 if !suggested {
-                    warn.help("valid hints include `#[repr(C)]`, `#[repr(packed)]` and \
-                               `#[repr(rust)]`");
+                    warn.help("valid hints include `#[repr(C)]`, `#[repr(packed)]`, \
+                               `#[repr(rust)]` and `#[repr(transparent)]`");
                     warn.note("for more information, visit \
                                <https://doc.rust-lang.org/nomicon/other-reprs.html>");
                 }
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
index 013504c554def..2b6396249bb82 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
@@ -193,7 +193,7 @@ LL |     mod inner { #![repr="3900"] }
    |                 ^^^^^^^^^^^^^^^ needs a hint
    |
    = note: #[warn(bad_repr)] on by default
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -202,7 +202,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL |     #[repr = "3900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -211,7 +211,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL |     #[repr = "3900"] type T = S;
    |     ^^^^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -220,7 +220,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL |     #[repr = "3900"] impl S { }
    |     ^^^^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -229,7 +229,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL | #[repr = "3900"]
    | ^^^^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -238,7 +238,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL | #![repr                       = "3900"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: unused attribute
diff --git a/src/test/ui/suggestions/repr.stderr b/src/test/ui/suggestions/repr.stderr
index 24a22a81c4aa0..efc7e0fd2bed5 100644
--- a/src/test/ui/suggestions/repr.stderr
+++ b/src/test/ui/suggestions/repr.stderr
@@ -5,7 +5,7 @@ LL | #[repr]
    | ^^^^^^^ needs a hint
    |
    = note: #[warn(bad_repr)] on by default
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -14,7 +14,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL | #[repr = "B"]
    | ^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]` and `#[repr(rust)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
 
 warning: `repr` attribute isn't configurable with a literal

From 451eb66a53efdad9886bfb1525a217a3ca5beb1f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 14:25:57 -0700
Subject: [PATCH 5/9] Expand (fix) u* and i* `repr` hints

---
 src/librustc_lint/builtin.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index b1b1440fbd282..0987197db26c2 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -696,7 +696,9 @@ impl EarlyLintPass for BadRepr {
                 let mut warn = if let Some(ref lit) = attr.value_str() {
                     // avoid warning about empty `repr` on `#[repr = "foo"]`
                     let sp = match format!("{}", lit).as_ref() {
-                        "C" | "packed" | "rust" | "u*" | "i*" | "transparent" => {
+                        | "C" | "packed" | "rust" | "transparent"
+                        | "u8" | "u16" | "u32" | "u64" | "u128"
+                        | "i8" | "i16" | "i32" | "i64" | "i128" => {
                             let lo = attr.span.lo() + BytePos(2);
                             let hi = attr.span.hi() - BytePos(1);
                             suggested = true;

From 9a80c2b99473d504c6e16d8fe55d3344d770320c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 14:33:07 -0700
Subject: [PATCH 6/9] Change repr documentation link

---
 src/librustc_lint/builtin.rs                         |  2 +-
 .../issue-43106-gating-of-builtin-attrs.stderr       | 12 ++++++------
 src/test/ui/suggestions/repr.stderr                  |  4 ++--
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 0987197db26c2..0688e47606f72 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -736,7 +736,7 @@ impl EarlyLintPass for BadRepr {
                     warn.help("valid hints include `#[repr(C)]`, `#[repr(packed)]`, \
                                `#[repr(rust)]` and `#[repr(transparent)]`");
                     warn.note("for more information, visit \
-                               <https://doc.rust-lang.org/nomicon/other-reprs.html>");
+                               <https://doc.rust-lang.org/reference/type-layout.html>");
                 }
                 warn.emit();
             }
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
index 2b6396249bb82..f351a9e69d011 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
@@ -194,7 +194,7 @@ LL |     mod inner { #![repr="3900"] }
    |
    = note: #[warn(bad_repr)] on by default
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:320:5
@@ -203,7 +203,7 @@ LL |     #[repr = "3900"] fn f() { }
    |     ^^^^^^^^^^^^^^^^ needs a hint
    |
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:326:5
@@ -212,7 +212,7 @@ LL |     #[repr = "3900"] type T = S;
    |     ^^^^^^^^^^^^^^^^ needs a hint
    |
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:330:5
@@ -221,7 +221,7 @@ LL |     #[repr = "3900"] impl S { }
    |     ^^^^^^^^^^^^^^^^ needs a hint
    |
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:312:1
@@ -230,7 +230,7 @@ LL | #[repr = "3900"]
    | ^^^^^^^^^^^^^^^^ needs a hint
    |
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:62:1
@@ -239,7 +239,7 @@ LL | #![repr                       = "3900"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ needs a hint
    |
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: unused attribute
   --> $DIR/issue-43106-gating-of-builtin-attrs.rs:194:5
diff --git a/src/test/ui/suggestions/repr.stderr b/src/test/ui/suggestions/repr.stderr
index efc7e0fd2bed5..83f5bb48f7a08 100644
--- a/src/test/ui/suggestions/repr.stderr
+++ b/src/test/ui/suggestions/repr.stderr
@@ -6,7 +6,7 @@ LL | #[repr]
    |
    = note: #[warn(bad_repr)] on by default
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
   --> $DIR/repr.rs:17:1
@@ -15,7 +15,7 @@ LL | #[repr = "B"]
    | ^^^^^^^^^^^^^ needs a hint
    |
    = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
-   = note: for more information, visit <https://doc.rust-lang.org/nomicon/other-reprs.html>
+   = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
   --> $DIR/repr.rs:21:3

From b3810f61da08bc986ffd854361e957e4b8d42560 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 14:34:07 -0700
Subject: [PATCH 7/9] Add i/u size

---
 src/librustc_lint/builtin.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 0688e47606f72..5c05fdb5621a7 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -697,8 +697,8 @@ impl EarlyLintPass for BadRepr {
                     // avoid warning about empty `repr` on `#[repr = "foo"]`
                     let sp = match format!("{}", lit).as_ref() {
                         | "C" | "packed" | "rust" | "transparent"
-                        | "u8" | "u16" | "u32" | "u64" | "u128"
-                        | "i8" | "i16" | "i32" | "i64" | "i128" => {
+                        | "u8" | "u16" | "u32" | "u64" | "u128" | "usize"
+                        | "i8" | "i16" | "i32" | "i64" | "i128" | "isize" => {
                             let lo = attr.span.lo() + BytePos(2);
                             let hi = attr.span.hi() - BytePos(1);
                             suggested = true;

From 3cc09c8380ed22d4aa9b3b0896b88707b4034b3b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 15:48:08 -0700
Subject: [PATCH 8/9] Use consistent span for repr attr suggestion

---
 src/librustc_lint/builtin.rs                  | 58 +++++++++++--------
 src/test/compile-fail/issue-43988.rs          |  3 +-
 ...issue-43106-gating-of-builtin-attrs.stderr |  4 +-
 src/test/ui/suggestions/repr.stderr           |  4 +-
 4 files changed, 41 insertions(+), 28 deletions(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index 5c05fdb5621a7..d95e0d77d86d3 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -687,6 +687,18 @@ impl EarlyLintPass for BadRepr {
     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
         if attr.name() == "repr" {
             let list = attr.meta_item_list();
+            let outer = match attr.style {
+                ast::AttrStyle::Outer => true,
+                ast::AttrStyle::Inner => false,
+            };
+
+            let repr_str = move |lit: &str| {
+                if outer {
+                    format!("#[repr({})]", lit)
+                } else {
+                    format!("#![repr({})]", lit)
+                }
+            };
 
             // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
             // no hints (``#[repr]`)
@@ -695,33 +707,28 @@ impl EarlyLintPass for BadRepr {
                 let mut suggested = false;
                 let mut warn = if let Some(ref lit) = attr.value_str() {
                     // avoid warning about empty `repr` on `#[repr = "foo"]`
-                    let sp = match format!("{}", lit).as_ref() {
+                    let mut warn = cx.struct_span_lint(
+                        BAD_REPR,
+                        attr.span,
+                        "`repr` attribute isn't configurable with a literal",
+                    );
+                    match format!("{}", lit).as_ref() {
                         | "C" | "packed" | "rust" | "transparent"
                         | "u8" | "u16" | "u32" | "u64" | "u128" | "usize"
                         | "i8" | "i16" | "i32" | "i64" | "i128" | "isize" => {
-                            let lo = attr.span.lo() + BytePos(2);
-                            let hi = attr.span.hi() - BytePos(1);
+                            // if the literal could have been a valid `repr` arg,
+                            // suggest the correct syntax
+                            warn.span_suggestion(
+                                attr.span,
+                                "give `repr` a hint",
+                                repr_str(&lit.as_str()),
+                            );
                             suggested = true;
-                            attr.span.with_lo(lo).with_hi(hi)
                         }
-                        _ => attr.span,  // the literal wasn't a valid `repr` arg
+                        _ => {  // the literal wasn't a valid `repr` arg
+                            warn.span_label(attr.span, "needs a hint");
+                        }
                     };
-                    let mut warn = cx.struct_span_lint(
-                        BAD_REPR,
-                        sp,
-                        "`repr` attribute isn't configurable with a literal",
-                    );
-                    if suggested {
-                        // if the literal could have been a valid `repr` arg,
-                        // suggest the correct syntax
-                        warn.span_suggestion(
-                            sp,
-                            "give `repr` a hint",
-                            format!("repr({})", lit),
-                        );
-                    } else {
-                        warn.span_label(attr.span, "needs a hint");
-                    }
                     warn
                 } else {
                     let mut warn = cx.struct_span_lint(
@@ -733,8 +740,13 @@ impl EarlyLintPass for BadRepr {
                     warn
                 };
                 if !suggested {
-                    warn.help("valid hints include `#[repr(C)]`, `#[repr(packed)]`, \
-                               `#[repr(rust)]` and `#[repr(transparent)]`");
+                    warn.help(&format!(
+                        "valid hints include `{}`, `{}`, `{}` and `{}`",
+                        repr_str("C"),
+                        repr_str("packed"),
+                        repr_str("rust"),
+                        repr_str("transparent"),
+                    ));
                     warn.note("for more information, visit \
                                <https://doc.rust-lang.org/reference/type-layout.html>");
                 }
diff --git a/src/test/compile-fail/issue-43988.rs b/src/test/compile-fail/issue-43988.rs
index 0dfa9f6f0d341..6361af7648258 100644
--- a/src/test/compile-fail/issue-43988.rs
+++ b/src/test/compile-fail/issue-43988.rs
@@ -34,6 +34,7 @@ fn main() {
     #[repr]
     let _y = "123";
     //~^^ ERROR attribute should not be applied to a statement
+    //~| WARN `repr` attribute must have a hint
 
 
     fn foo() {}
@@ -44,5 +45,5 @@ fn main() {
 
     let _z = #[repr] 1;
     //~^ ERROR attribute should not be applied to an expression
-
+    //~| WARN `repr` attribute must have a hint
 }
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
index f351a9e69d011..3569eecd883f6 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
@@ -193,7 +193,7 @@ LL |     mod inner { #![repr="3900"] }
    |                 ^^^^^^^^^^^^^^^ needs a hint
    |
    = note: #[warn(bad_repr)] on by default
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
+   = help: valid hints include `#![repr(C)]`, `#![repr(packed)]`, `#![repr(rust)]` and `#![repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -238,7 +238,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL | #![repr                       = "3900"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
+   = help: valid hints include `#![repr(C)]`, `#![repr(packed)]`, `#![repr(rust)]` and `#![repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: unused attribute
diff --git a/src/test/ui/suggestions/repr.stderr b/src/test/ui/suggestions/repr.stderr
index 83f5bb48f7a08..7a99d8c04488f 100644
--- a/src/test/ui/suggestions/repr.stderr
+++ b/src/test/ui/suggestions/repr.stderr
@@ -18,8 +18,8 @@ LL | #[repr = "B"]
    = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
-  --> $DIR/repr.rs:21:3
+  --> $DIR/repr.rs:21:1
    |
 LL | #[repr = "C"]
-   |   ^^^^^^^^^^ help: give `repr` a hint: `repr(C)`
+   | ^^^^^^^^^^^^^ help: give `repr` a hint: `#[repr(C)]`
 

From 0e3f19d3f179c179ccde3a2f15e9e429483f6903 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Wed, 6 Jun 2018 17:39:58 -0700
Subject: [PATCH 9/9] Do not account for inner/outer attr

---
 src/librustc_lint/builtin.rs                         | 12 +-----------
 .../issue-43106-gating-of-builtin-attrs.stderr       |  4 ++--
 2 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index d95e0d77d86d3..b3b737ab28329 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -687,18 +687,8 @@ impl EarlyLintPass for BadRepr {
     fn check_attribute(&mut self, cx: &EarlyContext, attr: &ast::Attribute) {
         if attr.name() == "repr" {
             let list = attr.meta_item_list();
-            let outer = match attr.style {
-                ast::AttrStyle::Outer => true,
-                ast::AttrStyle::Inner => false,
-            };
 
-            let repr_str = move |lit: &str| {
-                if outer {
-                    format!("#[repr({})]", lit)
-                } else {
-                    format!("#![repr({})]", lit)
-                }
-            };
+            let repr_str = |lit: &str| { format!("#[repr({})]", lit) };
 
             // Emit warnings with `repr` either has a literal assignment (`#[repr = "C"]`) or
             // no hints (``#[repr]`)
diff --git a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
index 3569eecd883f6..f351a9e69d011 100644
--- a/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
+++ b/src/test/ui/feature-gate/issue-43106-gating-of-builtin-attrs.stderr
@@ -193,7 +193,7 @@ LL |     mod inner { #![repr="3900"] }
    |                 ^^^^^^^^^^^^^^^ needs a hint
    |
    = note: #[warn(bad_repr)] on by default
-   = help: valid hints include `#![repr(C)]`, `#![repr(packed)]`, `#![repr(rust)]` and `#![repr(transparent)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: `repr` attribute isn't configurable with a literal
@@ -238,7 +238,7 @@ warning: `repr` attribute isn't configurable with a literal
 LL | #![repr                       = "3900"]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ needs a hint
    |
-   = help: valid hints include `#![repr(C)]`, `#![repr(packed)]`, `#![repr(rust)]` and `#![repr(transparent)]`
+   = help: valid hints include `#[repr(C)]`, `#[repr(packed)]`, `#[repr(rust)]` and `#[repr(transparent)]`
    = note: for more information, visit <https://doc.rust-lang.org/reference/type-layout.html>
 
 warning: unused attribute