Auto merge of #53619 - japaric:panic-handler, r=SimonSapin

add #[panic_handler]; deprecate #[panic_implementation]

r? @SimonSapin
cc #44489

Author: bors

src/doc/unstable-book/src/language-features/used.md

@@ -87,7 +87,7 @@ This condition can be met using `#[used]` and `#[link_section]` plus a linker
 script.
 
 ``` rust,ignore
-#![feature(panic_implementation)]
+#![feature(panic_handler)]
 #![feature(used)]
 #![no_main]
 #![no_std]
@@ -102,8 +102,8 @@ extern "C" fn reset_handler() -> ! {
 #[used]
 static RESET_HANDLER: extern "C" fn() -> ! = reset_handler;
 
-#[panic_implementation]
-fn panic_impl(info: &PanicInfo) -> ! {
+#[panic_handler]
+fn panic(info: &PanicInfo) -> ! {
     loop {}
 }
 ```

src/librustc/middle/dead.rs

@@ -293,7 +293,9 @@ fn has_allow_dead_code_or_lang_attr(tcx: TyCtxt,
     }
 
     // (To be) stable attribute for #[lang = "panic_impl"]
-    if attr::contains_name(attrs, "panic_implementation") {
+    if attr::contains_name(attrs, "panic_implementation") ||
+        attr::contains_name(attrs, "panic_handler")
+    {
         return true;
     }
 

src/librustc/middle/lang_items.rs

@@ -185,7 +185,9 @@ pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
             if let Some(value) = attribute.value_str() {
                 return Some((value, attribute.span));
             }
-        } else if attribute.check_name("panic_implementation") {
+        } else if attribute.check_name("panic_implementation") ||
+            attribute.check_name("panic_handler")
+        {
             return Some((Symbol::intern("panic_impl"), attribute.span))
         } else if attribute.check_name("alloc_error_handler") {
             return Some((Symbol::intern("oom"), attribute.span))

src/librustc/middle/weak_lang_items.rs

@@ -113,7 +113,7 @@ fn verify<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
            !whitelisted(tcx, lang_items::$item) &&
            items.$name().is_none() {
             if lang_items::$item == lang_items::PanicImplLangItem {
-                tcx.sess.err(&format!("`#[panic_implementation]` function required, \
+                tcx.sess.err(&format!("`#[panic_handler]` function required, \
                                         but not found"));
             } else if lang_items::$item == lang_items::OomLangItem {
                 tcx.sess.err(&format!("`#[alloc_error_handler]` function required, \

src/librustc_typeck/check/mod.rs

@@ -1172,8 +1172,7 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
                             if !generics.params.is_empty() {
                                 fcx.tcx.sess.span_err(
                                     span,
-                                    "`#[panic_implementation]` function should have no type \
-                                     parameters",
+                                    "should have no type parameters",
                                 );
                             }
                         }

src/libstd/lib.rs

@@ -309,7 +309,8 @@
 #![feature(doc_alias)]
 #![feature(doc_keyword)]
 #![feature(panic_info_message)]
-#![feature(panic_implementation)]
+#![cfg_attr(stage0, feature(panic_implementation))]
+#![cfg_attr(not(stage0), feature(panic_handler))]
 #![feature(non_exhaustive)]
 
 #![default_lib_allocator]

src/libstd/panicking.rs

@@ -319,7 +319,8 @@ pub fn panicking() -> bool {
 
 /// Entry point of panic from the libcore crate.
 #[cfg(not(test))]
-#[panic_implementation]
+#[cfg_attr(stage0, panic_implementation)]
+#[cfg_attr(not(stage0), panic_handler)]
 #[unwind(allowed)]
 pub fn rust_begin_panic(info: &PanicInfo) -> ! {
     continue_panic_fmt(&info)

src/libsyntax/feature_gate.rs

@@ -469,8 +469,9 @@ declare_features! (
     // Integer match exhaustiveness checking
     (active, exhaustive_integer_patterns, "1.30.0", Some(50907), None),
 
-    // #[panic_implementation]
+    // RFC 2070: #[panic_implementation] / #[panic_handler]
     (active, panic_implementation, "1.28.0", Some(44489), None),
+    (active, panic_handler, "1.30.0", Some(44489), None),
 
     // #[doc(keyword = "...")]
     (active, doc_keyword, "1.28.0", Some(51315), None),
@@ -1109,11 +1110,20 @@ pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeG
                                    "infer 'static lifetime requirements",
                                    cfg_fn!(infer_static_outlives_requirements))),
 
+    // RFC 2070 (deprecated attribute name)
+    ("panic_implementation",
+     Normal,
+     Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/44489\
+                                  #issuecomment-415140224"),
+           "panic_implementation",
+           "This attribute was renamed to `panic_handler`",
+           cfg_fn!(panic_implementation))),
+
     // RFC 2070
-    ("panic_implementation", Normal, Gated(Stability::Unstable,
-                           "panic_implementation",
-                           "#[panic_implementation] is an unstable feature",
-                           cfg_fn!(panic_implementation))),
+    ("panic_handler", Normal, Gated(Stability::Unstable,
+                                    "panic_handler",
+                                    "#[panic_handler] is an unstable feature",
+                                    cfg_fn!(panic_handler))),
 
     ("alloc_error_handler", Normal, Gated(Stability::Unstable,
                            "alloc_error_handler",

src/test/compile-fail/auxiliary/some-panic-impl.rs

@@ -11,12 +11,12 @@
 // no-prefer-dynamic
 
 #![crate_type = "rlib"]
-#![feature(panic_implementation)]
+#![feature(panic_handler)]
 #![no_std]
 
 use core::panic::PanicInfo;
 
-#[panic_implementation]
+#[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     loop {}
 }

src/test/compile-fail/panic-implementation-missing.rs renamed to src/test/compile-fail/panic-handler-missing.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: `#[panic_implementation]` function required, but not found
+// error-pattern: `#[panic_handler]` function required, but not found
 
 #![feature(lang_items)]
 #![no_main]