Allow rustc_const_stable and rustc_const_unstable

gcc/rust/ChangeLog:

	* expand/rust-macro-builtins.cc
	(MacroBuiltin::builtin_transcribers):
	Add entries for "rustc_const_stable" and "rustc_const_unstable".
	* util/rust-attributes.cc
	(__definitions): Add entries for RUSTC_CONST_STABLE and
	RUSTC_CONST_UNSTABLE.
	* util/rust-attribute-values.h
	(Attributes::RUSTC_CONST_STABLE): New.
	(Attributes::RUSTC_CONST_UNSTABLE): New.

gcc/testsuite/ChangeLog:

	* rust/compile/rustc_const_stable.rs:
	Enable feature rustc_attrs, expect no errors.
	* rust/compile/rustc_const_unstable.rs: New test.

Signed-off-by: Owen Avery <[email protected]>

gcc/rust/expand/rust-macro-builtins.cc

@@ -123,6 +123,8 @@ std::unordered_map<std::string, AST::MacroTranscriberFunc>
     {"test_case", MacroBuiltin::sorry},
     {"global_allocator", MacroBuiltin::sorry},
     {"cfg_accessible", MacroBuiltin::sorry},
+    {"rustc_const_stable", MacroBuiltin::sorry},
+    {"rustc_const_unstable", MacroBuiltin::sorry},
     /* Derive builtins do not need a real transcriber, but still need one. It
        should however never be called since builtin derive macros get expanded
        differently, and benefit from knowing on what kind of items they are

gcc/rust/util/rust-attribute-values.h

@@ -53,6 +53,8 @@ class Attributes
     = "rustc_inherit_overflow_checks";
   static constexpr auto &STABLE = "stable";
   static constexpr auto &UNSTABLE = "unstable";
+  static constexpr auto &RUSTC_CONST_STABLE = "rustc_const_stable";
+  static constexpr auto &RUSTC_CONST_UNSTABLE = "rustc_const_unstable";
 };
 } // namespace Values
 } // namespace Rust

gcc/rust/util/rust-attributes.cc

@@ -61,7 +61,10 @@ static const BuiltinAttrDefinition __definitions[]
      {Attrs::RUSTC_DEPRECATED, STATIC_ANALYSIS},
      {Attrs::RUSTC_INHERIT_OVERFLOW_CHECKS, CODE_GENERATION},
      {Attrs::STABLE, STATIC_ANALYSIS},
-     {Attrs::UNSTABLE, STATIC_ANALYSIS}};
+     {Attrs::UNSTABLE, STATIC_ANALYSIS},
+     // assuming we keep these for static analysis
+     {Attrs::RUSTC_CONST_STABLE, STATIC_ANALYSIS},
+     {Attrs::RUSTC_CONST_UNSTABLE, STATIC_ANALYSIS}};
 
 BuiltinAttributeMappings *
 BuiltinAttributeMappings::get ()

gcc/testsuite/rust/compile/rustc_const_stable.rs

@@ -1,2 +1,4 @@
+#![feature(rustc_attrs)]
+
 #[rustc_const_stable(feature = "const_ascii_ctype_on_intrinsics", since = "1.47.0")]
-pub fn foo() {} // { dg-error "macro not found" "" { target *-*-* } .-1 }
+pub fn foo() {}

gcc/testsuite/rust/compile/rustc_const_unstable.rs

@@ -0,0 +1,4 @@
+#![feature(rustc_attrs)]
+
+#[rustc_const_unstable(feature = "const_ascii_ctype_on_intrinsics", issue = "1234")]
+pub fn foo() {}