Auto merge of #80851 - m-ou-se:panic-2021, r=petrochenkov

Implement Rust 2021 panic

This implements the Rust 2021 versions of `panic!()`. See #80162 and rust-lang/rfcs#3007.

It does so by replacing `{std, core}::panic!()` by a bulitin macro that expands to either `$crate::panic::panic_2015!(..)` or `$crate::panic::panic_2021!(..)` depending on the edition of the caller.

This does not yet make std's panic an alias for core's panic on Rust 2021 as the RFC proposes. That will be a separate change: c5273bd That change is blocked on figuring out what to do with #80846 first.

Author: bors

compiler/rustc_builtin_macros/src/lib.rs

@@ -33,6 +33,7 @@ mod global_allocator;
 mod global_asm;
 mod llvm_asm;
 mod log_syntax;
+mod panic;
 mod source_util;
 mod test;
 mod trace_macros;
@@ -76,6 +77,8 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         log_syntax: log_syntax::expand_log_syntax,
         module_path: source_util::expand_mod,
         option_env: env::expand_option_env,
+        core_panic: panic::expand_panic,
+        std_panic: panic::expand_panic,
         stringify: source_util::expand_stringify,
         trace_macros: trace_macros::expand_trace_macros,
     }

compiler/rustc_builtin_macros/src/panic.rs

@@ -0,0 +1,48 @@
+use rustc_ast::ptr::P;
+use rustc_ast::tokenstream::{DelimSpan, TokenStream};
+use rustc_ast::*;
+use rustc_expand::base::*;
+use rustc_span::symbol::sym;
+use rustc_span::Span;
+
+// This expands to either
+// - `$crate::panic::panic_2015!(...)` or
+// - `$crate::panic::panic_2021!(...)`
+// depending on the edition.
+//
+// This is used for both std::panic!() and core::panic!().
+//
+// `$crate` will refer to either the `std` or `core` crate depending on which
+// one we're expanding from.
+pub fn expand_panic<'cx>(
+    cx: &'cx mut ExtCtxt<'_>,
+    sp: Span,
+    tts: TokenStream,
+) -> Box<dyn MacResult + 'cx> {
+    let panic = if sp.rust_2021() { sym::panic_2021 } else { sym::panic_2015 };
+
+    let sp = cx.with_call_site_ctxt(sp);
+
+    MacEager::expr(
+        cx.expr(
+            sp,
+            ExprKind::MacCall(MacCall {
+                path: Path {
+                    span: sp,
+                    segments: cx
+                        .std_path(&[sym::panic, panic])
+                        .into_iter()
+                        .map(|ident| PathSegment::from_ident(ident))
+                        .collect(),
+                    tokens: None,
+                },
+                args: P(MacArgs::Delimited(
+                    DelimSpan::from_single(sp),
+                    MacDelimiter::Parenthesis,
+                    tts,
+                )),
+                prior_type_ascription: None,
+            }),
+        ),
+    )
+}

compiler/rustc_lint/src/panic_fmt.rs

@@ -19,10 +19,9 @@ declare_lint! {
     ///
     /// ### Explanation
     ///
-    /// `panic!("{}")` panics with the message `"{}"`, as a `panic!()` invocation
-    /// with a single argument does not use `format_args!()`.
-    /// A future edition of Rust will interpret this string as format string,
-    /// which would break this.
+    /// In Rust 2018 and earlier, `panic!("{}")` panics with the message `"{}"`,
+    /// as a `panic!()` invocation with a single argument does not use `format_args!()`.
+    /// Rust 2021 interprets this string as format string, which breaks this.
     PANIC_FMT,
     Warn,
     "detect braces in single-argument panic!() invocations",
@@ -50,8 +49,8 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
         if let ast::LitKind::Str(sym, _) = lit.node {
             let mut expn = f.span.ctxt().outer_expn_data();
             if let Some(id) = expn.macro_def_id {
-                if cx.tcx.is_diagnostic_item(sym::std_panic_macro, id)
-                    || cx.tcx.is_diagnostic_item(sym::core_panic_macro, id)
+                if cx.tcx.is_diagnostic_item(sym::std_panic_2015_macro, id)
+                    || cx.tcx.is_diagnostic_item(sym::core_panic_2015_macro, id)
                 {
                     let fmt = sym.as_str();
                     if !fmt.contains(&['{', '}'][..]) {
@@ -75,9 +74,15 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
                     let n_arguments =
                         (&mut fmt_parser).filter(|a| matches!(a, Piece::NextArgument(_))).count();
 
-                    // Unwrap another level of macro expansion if this panic!()
-                    // was expanded from assert!() or debug_assert!().
-                    for &assert in &[sym::assert_macro, sym::debug_assert_macro] {
+                    // Unwrap more levels of macro expansion, as panic_2015!()
+                    // was likely expanded from panic!() and possibly from
+                    // [debug_]assert!().
+                    for &assert in &[
+                        sym::std_panic_macro,
+                        sym::core_panic_macro,
+                        sym::assert_macro,
+                        sym::debug_assert_macro,
+                    ] {
                         let parent = expn.call_site.ctxt().outer_expn_data();
                         if parent
                             .macro_def_id

compiler/rustc_span/src/symbol.rs

@@ -398,6 +398,8 @@ symbols! {
         copysignf64,
         core,
         core_intrinsics,
+        core_panic,
+        core_panic_2015_macro,
         core_panic_macro,
         cosf32,
         cosf64,
@@ -795,6 +797,8 @@ symbols! {
         owned_box,
         packed,
         panic,
+        panic_2015,
+        panic_2021,
         panic_abort,
         panic_bounds_check,
         panic_handler,
@@ -1096,6 +1100,8 @@ symbols! {
         staticlib,
         std,
         std_inject,
+        std_panic,
+        std_panic_2015_macro,
         std_panic_macro,
         stmt,
         stmt_expr_attributes,

library/core/src/macros/mod.rs

@@ -1,6 +1,7 @@
+#[cfg(bootstrap)]
 #[doc(include = "panic.md")]
 #[macro_export]
-#[allow_internal_unstable(core_panic, const_caller_location)]
+#[allow_internal_unstable(core_panic)]
 #[stable(feature = "core", since = "1.6.0")]
 #[rustc_diagnostic_item = "core_panic_macro"]
 macro_rules! panic {
@@ -18,6 +19,21 @@ macro_rules! panic {
     );
 }
 
+#[cfg(not(bootstrap))]
+#[doc(include = "panic.md")]
+#[macro_export]
+#[rustc_builtin_macro = "core_panic"]
+#[allow_internal_unstable(edition_panic)]
+#[stable(feature = "core", since = "1.6.0")]
+#[rustc_diagnostic_item = "core_panic_macro"]
+macro_rules! panic {
+    // Expands to either `$crate::panic::panic_2015` or `$crate::panic::panic_2021`
+    // depending on the edition of the caller.
+    ($($arg:tt)*) => {
+        /* compiler built-in */
+    };
+}
+
 /// Asserts that two expressions are equal to each other (using [`PartialEq`]).
 ///
 /// On panic, this macro will print the values of the expressions with their

library/core/src/panic.rs

@@ -5,6 +5,40 @@
 use crate::any::Any;
 use crate::fmt;
 
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+#[allow_internal_unstable(core_panic)]
+#[rustc_diagnostic_item = "core_panic_2015_macro"]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro panic_2015 {
+    () => (
+        $crate::panicking::panic("explicit panic")
+    ),
+    ($msg:literal $(,)?) => (
+        $crate::panicking::panic($msg)
+    ),
+    ($msg:expr $(,)?) => (
+        $crate::panicking::panic_str($msg)
+    ),
+    ($fmt:expr, $($arg:tt)+) => (
+        $crate::panicking::panic_fmt($crate::format_args!($fmt, $($arg)+))
+    ),
+}
+
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+#[allow_internal_unstable(core_panic)]
+#[rustc_diagnostic_item = "core_panic_2021_macro"]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro panic_2021 {
+    () => (
+        $crate::panicking::panic("explicit panic")
+    ),
+    ($($t:tt)+) => (
+        $crate::panicking::panic_fmt($crate::format_args!($($t)+))
+    ),
+}
+
 /// A struct providing information about a panic.
 ///
 /// `PanicInfo` structure is passed to a panic hook set by the [`set_hook`]

library/std/src/lib.rs

@@ -259,6 +259,7 @@
 #![feature(dropck_eyepatch)]
 #![feature(duration_constants)]
 #![feature(duration_zero)]
+#![feature(edition_panic)]
 #![feature(exact_size_is_empty)]
 #![feature(exhaustive_patterns)]
 #![feature(extend_one)]

library/std/src/macros.rs

@@ -4,6 +4,7 @@
 //! library. Each macro is available for use when linking against the standard
 //! library.
 
+#[cfg(bootstrap)]
 #[doc(include = "../../core/src/macros/panic.md")]
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -17,6 +18,21 @@ macro_rules! panic {
     });
 }
 
+#[cfg(not(bootstrap))]
+#[doc(include = "../../core/src/macros/panic.md")]
+#[macro_export]
+#[rustc_builtin_macro = "std_panic"]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[allow_internal_unstable(edition_panic)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_macro")]
+macro_rules! panic {
+    // Expands to either `$crate::panic::panic_2015` or `$crate::panic::panic_2021`
+    // depending on the edition of the caller.
+    ($($arg:tt)*) => {
+        /* compiler built-in */
+    };
+}
+
 /// Prints to the standard output.
 ///
 /// Equivalent to the [`println!`] macro except that a newline is not printed at

library/std/src/panic.rs

@@ -18,6 +18,27 @@ use crate::sync::{Arc, Mutex, RwLock};
 use crate::task::{Context, Poll};
 use crate::thread::Result;
 
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+#[allow_internal_unstable(libstd_sys_internals)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_2015_macro")]
+#[rustc_macro_transparency = "semitransparent"]
+pub macro panic_2015 {
+    () => ({
+        $crate::rt::begin_panic("explicit panic")
+    }),
+    ($msg:expr $(,)?) => ({
+        $crate::rt::begin_panic($msg)
+    }),
+    ($fmt:expr, $($arg:tt)+) => ({
+        $crate::rt::begin_panic_fmt(&$crate::format_args!($fmt, $($arg)+))
+    }),
+}
+
+#[doc(hidden)]
+#[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
+pub use core::panic::panic_2021;
+
 #[stable(feature = "panic_hooks", since = "1.10.0")]
 pub use crate::panicking::{set_hook, take_hook};
 

src/test/mir-opt/const_prop/control_flow_simplification.hello.ConstProp.diff

@@ -4,7 +4,7 @@
   fn hello() -> () {
       let mut _0: ();                      // return place in scope 0 at $DIR/control-flow-simplification.rs:11:14: 11:14
       let mut _1: bool;                    // in scope 0 at $DIR/control-flow-simplification.rs:12:8: 12:21
-      let mut _2: !;                       // in scope 0 at $SRC_DIR/std/src/macros.rs:LL:COL
+      let mut _2: !;                       // in scope 0 at $SRC_DIR/std/src/panic.rs:LL:COL
 
       bb0: {
           StorageLive(_1);                 // scope 0 at $DIR/control-flow-simplification.rs:12:8: 12:21
@@ -15,16 +15,16 @@
       }
 
       bb1: {
-          StorageLive(_2);                 // scope 0 at $SRC_DIR/std/src/macros.rs:LL:COL
-          begin_panic::<&str>(const "explicit panic"); // scope 0 at $SRC_DIR/std/src/macros.rs:LL:COL
+          StorageLive(_2);                 // scope 0 at $SRC_DIR/std/src/panic.rs:LL:COL
+          begin_panic::<&str>(const "explicit panic"); // scope 0 at $SRC_DIR/std/src/panic.rs:LL:COL
                                            // mir::Constant
-                                           // + span: $SRC_DIR/std/src/macros.rs:LL:COL
+                                           // + span: $SRC_DIR/std/src/panic.rs:LL:COL
                                            // + literal: Const { ty: fn(&str) -> ! {std::rt::begin_panic::<&str>}, val: Value(Scalar(<ZST>)) }
                                            // ty::Const
                                            // + ty: &str
                                            // + val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 })
                                            // mir::Constant
-                                           // + span: $SRC_DIR/std/src/macros.rs:LL:COL
+                                           // + span: $SRC_DIR/std/src/panic.rs:LL:COL
                                            // + literal: Const { ty: &str, val: Value(Slice { data: Allocation { bytes: [101, 120, 112, 108, 105, 99, 105, 116, 32, 112, 97, 110, 105, 99], relocations: Relocations(SortedMap { data: [] }), init_mask: InitMask { blocks: [16383], len: Size { raw: 14 } }, size: Size { raw: 14 }, align: Align { pow2: 0 }, mutability: Not, extra: () }, start: 0, end: 14 }) }
       }