Stabilize default_alloc_error_handler

Closes #66741

Author: Amanieu

compiler/rustc_error_messages/locales/en-US/metadata.ftl

@@ -166,12 +166,6 @@ metadata_conflicting_alloc_error_handler =
 metadata_global_alloc_required =
     no global memory allocator found but one is required; link to std or add `#[global_allocator]` to a static item that implements the GlobalAlloc trait
 
-metadata_alloc_func_required =
-    `#[alloc_error_handler]` function required, but not found
-
-metadata_missing_alloc_error_handler =
-    use `#![feature(default_alloc_error_handler)]` for a default error handler
-
 metadata_no_transitive_needs_dep =
     the crate `{$crate_name}` cannot depend on a crate that needs {$needs_crate_name}, but it depends on `{$deps_crate_name}`
 

compiler/rustc_feature/src/accepted.rs

@@ -126,6 +126,8 @@ declare_features! (
     (accepted, copy_closures, "1.26.0", Some(44490), None),
     /// Allows `crate` in paths.
     (accepted, crate_in_paths, "1.30.0", Some(45477), None),
+    /// Allows rustc to inject a default alloc_error_handler
+    (accepted, default_alloc_error_handler, "CURRENT_RUSTC_VERSION", Some(66741), None),
     /// Allows using assigning a default type to type parameters in algebraic data type definitions.
     (accepted, default_type_params, "1.0.0", None, None),
     /// Allows `#[deprecated]` attribute.

compiler/rustc_feature/src/active.rs

@@ -366,8 +366,6 @@ declare_features! (
     (active, debugger_visualizer, "1.62.0", Some(95939), None),
     /// Allows declarative macros 2.0 (`macro`).
     (active, decl_macro, "1.17.0", Some(39412), None),
-    /// Allows rustc to inject a default alloc_error_handler
-    (active, default_alloc_error_handler, "1.48.0", Some(66741), None),
     /// Allows default type parameters to influence type inference.
     (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
     /// Allows using `#[deprecated_safe]` to deprecate the safeness of a function or trait

compiler/rustc_metadata/src/creader.rs

@@ -1,10 +1,9 @@
 //! Validates all used crates and extern libraries and loads their metadata
 
 use crate::errors::{
-    AllocFuncRequired, ConflictingAllocErrorHandler, ConflictingGlobalAlloc, CrateNotPanicRuntime,
-    GlobalAllocRequired, MissingAllocErrorHandler, NoMultipleAllocErrorHandler,
-    NoMultipleGlobalAlloc, NoPanicStrategy, NoTransitiveNeedsDep, NotProfilerRuntime,
-    ProfilerBuiltinsNeedsCore,
+    ConflictingAllocErrorHandler, ConflictingGlobalAlloc, CrateNotPanicRuntime,
+    GlobalAllocRequired, NoMultipleAllocErrorHandler, NoMultipleGlobalAlloc, NoPanicStrategy,
+    NoTransitiveNeedsDep, NotProfilerRuntime, ProfilerBuiltinsNeedsCore,
 };
 use crate::locator::{CrateError, CrateLocator, CratePaths};
 use crate::rmeta::{CrateDep, CrateMetadata, CrateNumMap, CrateRoot, MetadataBlob};
@@ -892,10 +891,6 @@ impl<'a> CrateLoader<'a> {
         } else {
             // The alloc crate provides a default allocation error handler if
             // one isn't specified.
-            if !self.sess.features_untracked().default_alloc_error_handler {
-                self.sess.emit_err(AllocFuncRequired);
-                self.sess.emit_note(MissingAllocErrorHandler);
-            }
             self.cstore.alloc_error_handler_kind = Some(AllocatorKind::Default);
         }
     }

compiler/rustc_metadata/src/errors.rs

@@ -371,14 +371,6 @@ pub struct ConflictingAllocErrorHandler {
 #[diag(metadata_global_alloc_required)]
 pub struct GlobalAllocRequired;
 
-#[derive(Diagnostic)]
-#[diag(metadata_alloc_func_required)]
-pub struct AllocFuncRequired;
-
-#[derive(Diagnostic)]
-#[diag(metadata_missing_alloc_error_handler)]
-pub struct MissingAllocErrorHandler;
-
 #[derive(Diagnostic)]
 #[diag(metadata_no_transitive_needs_dep)]
 pub struct NoTransitiveNeedsDep<'a> {

src/test/ui/allocator/no_std-alloc-error-handler-default.rs

@@ -6,10 +6,8 @@
 // only-linux
 // compile-flags:-C panic=abort
 // aux-build:helper.rs
-// gate-test-default_alloc_error_handler
 
 #![feature(start, rustc_private, new_uninit, panic_info_message, lang_items)]
-#![feature(default_alloc_error_handler)]
 #![no_std]
 
 extern crate alloc;