Rollup merge of rust-lang#63095 - Centril:incomplete-features-lint, r=varkor

Turn `INCOMPLETE_FEATURES` into lint

We do this because it is annoying to see the warning when building rustc and because this is better from a "separation of concerns" POV.

The drawback to this change is that this will respect `--cap-lints`.
Also note that this is not a buffered lint so if there are fatal parser errors then the lint will not trigger.

r? @varkor

Author: Centril

src/liballoc/lib.rs

@@ -63,6 +63,7 @@
 #![warn(missing_debug_implementations)]
 #![deny(intra_doc_link_resolution_failure)] // rustdoc is run without -D warnings
 #![allow(explicit_outlives_requirements)]
+#![cfg_attr(not(bootstrap), allow(incomplete_features))]
 
 #![cfg_attr(not(test), feature(generator_trait))]
 #![cfg_attr(test, feature(test))]

src/libcore/lib.rs

@@ -63,6 +63,7 @@
 #![warn(missing_debug_implementations)]
 #![deny(intra_doc_link_resolution_failure)] // rustdoc is run without -D warnings
 #![allow(explicit_outlives_requirements)]
+#![cfg_attr(not(bootstrap), allow(incomplete_features))]
 
 #![feature(allow_internal_unstable)]
 #![feature(arbitrary_self_types)]

src/librustc_lint/builtin.rs

@@ -33,13 +33,12 @@ use lint::{LintPass, LateLintPass, EarlyLintPass, EarlyContext};
 use rustc::util::nodemap::FxHashSet;
 
 use syntax::tokenstream::{TokenTree, TokenStream};
-use syntax::ast;
+use syntax::ast::{self, Expr};
 use syntax::ptr::P;
-use syntax::ast::Expr;
 use syntax::attr::{self, HasAttrs, AttributeTemplate};
 use syntax::source_map::Spanned;
 use syntax::edition::Edition;
-use syntax::feature_gate::{AttributeGate, AttributeType};
+use syntax::feature_gate::{self, AttributeGate, AttributeType};
 use syntax::feature_gate::{Stability, deprecated_attributes};
 use syntax_pos::{BytePos, Span, SyntaxContext};
 use syntax::symbol::{Symbol, kw, sym};
@@ -1831,3 +1830,35 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ExplicitOutlivesRequirements {
         }
     }
 }
+
+declare_lint! {
+    pub INCOMPLETE_FEATURES,
+    Warn,
+    "incomplete features that may function improperly in some or all cases"
+}
+
+declare_lint_pass!(
+    /// Check for used feature gates in `INCOMPLETE_FEATURES` in `feature_gate.rs`.
+    IncompleteFeatures => [INCOMPLETE_FEATURES]
+);
+
+impl EarlyLintPass for IncompleteFeatures {
+    fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
+        let features = cx.sess.features_untracked();
+        features.declared_lang_features
+            .iter().map(|(name, span, _)| (name, span))
+            .chain(features.declared_lib_features.iter().map(|(name, span)| (name, span)))
+            .filter(|(name, _)| feature_gate::INCOMPLETE_FEATURES.iter().any(|f| name == &f))
+            .for_each(|(name, &span)| {
+                cx.struct_span_lint(
+                    INCOMPLETE_FEATURES,
+                    span,
+                    &format!(
+                        "the feature `{}` is incomplete and may cause the compiler to crash",
+                        name,
+                    )
+                )
+                .emit();
+            });
+    }
+}

src/librustc_lint/lib.rs

@@ -97,6 +97,7 @@ macro_rules! early_lint_passes {
             DeprecatedAttr: DeprecatedAttr::new(),
             WhileTrue: WhileTrue,
             NonAsciiIdents: NonAsciiIdents,
+            IncompleteFeatures: IncompleteFeatures,
         ]);
     )
 }

src/libsyntax/feature_gate.rs

@@ -569,10 +569,10 @@ declare_features! (
     // -------------------------------------------------------------------------
 );
 
-// Some features are known to be incomplete and using them is likely to have
-// unanticipated results, such as compiler crashes. We warn the user about these
-// to alert them.
-const INCOMPLETE_FEATURES: &[Symbol] = &[
+/// Some features are known to be incomplete and using them is likely to have
+/// unanticipated results, such as compiler crashes. We warn the user about these
+/// to alert them.
+pub const INCOMPLETE_FEATURES: &[Symbol] = &[
     sym::impl_trait_in_bindings,
     sym::generic_associated_types,
     sym::const_generics,
@@ -2338,15 +2338,6 @@ pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
             }
 
             let name = mi.name_or_empty();
-            if INCOMPLETE_FEATURES.iter().any(|f| name == *f) {
-                span_handler.struct_span_warn(
-                    mi.span(),
-                    &format!(
-                        "the feature `{}` is incomplete and may cause the compiler to crash",
-                        name
-                    )
-                ).emit();
-            }
 
             if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
                 if *edition <= crate_edition {

src/test/ui/associated-type-bounds/duplicate.stderr

@@ -3,6 +3,8 @@ warning: the feature `impl_trait_in_bindings` is incomplete and may cause the co
    |
 LL | #![feature(impl_trait_in_bindings)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0719]: the value of the associated type `Item` (from the trait `std::iter::Iterator`) is already specified
   --> $DIR/duplicate.rs:12:36

src/test/ui/associated-type-bounds/dyn-lcsit.stderr

@@ -3,4 +3,6 @@ warning: the feature `impl_trait_in_bindings` is incomplete and may cause the co
    |
 LL | #![feature(impl_trait_in_bindings)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/associated-type-bounds/lcsit.stderr

@@ -3,4 +3,6 @@ warning: the feature `impl_trait_in_bindings` is incomplete and may cause the co
    |
 LL | #![feature(impl_trait_in_bindings)]
    |            ^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/apit-with-const-param.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/array-wrapper-struct-ctor.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/broken-mir-1.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/broken-mir-2.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0277]: arrays only have std trait implementations for lengths 0..=32
   --> $DIR/broken-mir-2.rs:7:36

src/test/ui/const-generics/cannot-infer-const-args.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0282]: type annotations needed
   --> $DIR/cannot-infer-const-args.rs:9:5

src/test/ui/const-generics/cannot-infer-type-for-const-param.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/concrete-const-as-fn-arg.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/concrete-const-impl-method.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/condition-in-trait-const-arg.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/const-arg-in-fn.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/const-expression-parameter.stderr

@@ -9,6 +9,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error: aborting due to previous error
 

src/test/ui/const-generics/const-fn-with-const-param.stderr

@@ -1,9 +1,3 @@
-warning: the feature `const_generics` is incomplete and may cause the compiler to crash
-  --> $DIR/const-fn-with-const-param.rs:1:12
-   |
-LL | #![feature(const_generics)]
-   |            ^^^^^^^^^^^^^^
-
 error: const parameters are not permitted in `const fn`
   --> $DIR/const-fn-with-const-param.rs:4:1
    |
@@ -13,5 +7,13 @@ LL | |     X
 LL | | }
    | |_^
 
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/const-fn-with-const-param.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error: aborting due to previous error
 

src/test/ui/const-generics/const-generic-array-wrapper.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/const-param-before-other-params.rs

@@ -1,5 +1,4 @@
 #![feature(const_generics)]
-//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
 
 fn bar<const X: (), 'a>(_: &'a ()) {
     //~^ ERROR lifetime parameters must be declared prior to const parameters

src/test/ui/const-generics/const-param-before-other-params.stderr

@@ -1,17 +1,11 @@
-warning: the feature `const_generics` is incomplete and may cause the compiler to crash
-  --> $DIR/const-param-before-other-params.rs:1:12
-   |
-LL | #![feature(const_generics)]
-   |            ^^^^^^^^^^^^^^
-
 error: lifetime parameters must be declared prior to const parameters
-  --> $DIR/const-param-before-other-params.rs:4:21
+  --> $DIR/const-param-before-other-params.rs:3:21
    |
 LL | fn bar<const X: (), 'a>(_: &'a ()) {
    |       --------------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, const X: ()>`
 
 error: type parameters must be declared prior to const parameters
-  --> $DIR/const-param-before-other-params.rs:8:21
+  --> $DIR/const-param-before-other-params.rs:7:21
    |
 LL | fn foo<const X: (), T>(_: &T) {
    |       --------------^- help: reorder the parameters: lifetimes, then types, then consts: `<T, const X: ()>`

src/test/ui/const-generics/const-param-from-outer-fn.stderr

@@ -1,9 +1,3 @@
-warning: the feature `const_generics` is incomplete and may cause the compiler to crash
-  --> $DIR/const-param-from-outer-fn.rs:1:12
-   |
-LL | #![feature(const_generics)]
-   |            ^^^^^^^^^^^^^^
-
 error[E0401]: can't use generic parameters from outer function
   --> $DIR/const-param-from-outer-fn.rs:6:9
    |
@@ -14,6 +8,14 @@ LL |     fn bar() -> u32 {
 LL |         X
    |         ^ use of generic parameter from outer function
 
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/const-param-from-outer-fn.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
 error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0401`.

src/test/ui/const-generics/const-param-in-trait.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/const-param-type-depends-on-type-param.stderr

@@ -1,14 +1,16 @@
+error[E0671]: const parameters cannot depend on type parameters
+  --> $DIR/const-param-type-depends-on-type-param.rs:9:34
+   |
+LL | pub struct Dependent<T, const X: T>([(); X]);
+   |                                  ^ const parameter depends on type parameter
+
 warning: the feature `const_generics` is incomplete and may cause the compiler to crash
   --> $DIR/const-param-type-depends-on-type-param.rs:1:12
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
-
-error[E0671]: const parameters cannot depend on type parameters
-  --> $DIR/const-param-type-depends-on-type-param.rs:9:34
    |
-LL | pub struct Dependent<T, const X: T>([(); X]);
-   |                                  ^ const parameter depends on type parameter
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0392]: parameter `T` is never used
   --> $DIR/const-param-type-depends-on-type-param.rs:9:22

src/test/ui/const-generics/const-parameter-uppercase-lint.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error: const parameter `x` should have an upper case name
   --> $DIR/const-parameter-uppercase-lint.rs:6:15

src/test/ui/const-generics/const-types.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/derive-debug-array-wrapper.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0277]: arrays only have std trait implementations for lengths 0..=32
   --> $DIR/derive-debug-array-wrapper.rs:6:5

src/test/ui/const-generics/fn-taking-const-generic-array.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/impl-const-generic-struct.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/incorrect-number-of-const-args.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error[E0107]: wrong number of const arguments: expected 2, found 1
   --> $DIR/incorrect-number-of-const-args.rs:9:5

src/test/ui/const-generics/issue-60818-struct-constructors.stderr

@@ -3,4 +3,6 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 

src/test/ui/const-generics/issue-61336-1.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error: array lengths can't depend on generic parameters
   --> $DIR/issue-61336-1.rs:5:9

src/test/ui/const-generics/issue-61336-2.stderr

@@ -3,6 +3,8 @@ warning: the feature `const_generics` is incomplete and may cause the compiler t
    |
 LL | #![feature(const_generics)]
    |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
 
 error: array lengths can't depend on generic parameters
   --> $DIR/issue-61336-2.rs:5:9