Rollup merge of rust-lang#122806 - compiler-errors:type-ascribe, r=fmease

Make `type_ascribe!` not a built-in

The only weird thing is the macro expansion note. I wonder if we should suppress these 🤔

r? ```@fmease``` since you told me about builtin# lol

Author: matthiaskrgr

compiler/rustc_builtin_macros/src/lib.rs

@@ -49,7 +49,6 @@ mod log_syntax;
 mod source_util;
 mod test;
 mod trace_macros;
-mod type_ascribe;
 mod util;
 
 pub mod asm;
@@ -99,7 +98,6 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         std_panic: edition_panic::expand_panic,
         stringify: source_util::expand_stringify,
         trace_macros: trace_macros::expand_trace_macros,
-        type_ascribe: type_ascribe::expand_type_ascribe,
         unreachable: edition_panic::expand_unreachable,
         // tidy-alphabetical-end
     }

compiler/rustc_builtin_macros/src/type_ascribe.rs

@@ -1939,11 +1939,11 @@ impl<'a> Parser<'a> {
     /// Parse `builtin # ident(args,*)`.
     fn parse_expr_builtin(&mut self) -> PResult<'a, P<Expr>> {
         self.parse_builtin(|this, lo, ident| {
-            if ident.name == sym::offset_of {
-                return Ok(Some(this.parse_expr_offset_of(lo)?));
-            }
-
-            Ok(None)
+            Ok(match ident.name {
+                sym::offset_of => Some(this.parse_expr_offset_of(lo)?),
+                sym::type_ascribe => Some(this.parse_expr_type_ascribe(lo)?),
+                _ => None,
+            })
         })
     }
 
@@ -1978,6 +1978,7 @@ impl<'a> Parser<'a> {
         ret
     }
 
+    /// Built-in macro for `offset_of!` expressions.
     pub(crate) fn parse_expr_offset_of(&mut self, lo: Span) -> PResult<'a, P<Expr>> {
         let container = self.parse_ty()?;
         self.expect(&TokenKind::Comma)?;
@@ -2007,6 +2008,15 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr(span, ExprKind::OffsetOf(container, fields)))
     }
 
+    /// Built-in macro for type ascription expressions.
+    pub(crate) fn parse_expr_type_ascribe(&mut self, lo: Span) -> PResult<'a, P<Expr>> {
+        let expr = self.parse_expr()?;
+        self.expect(&token::Comma)?;
+        let ty = self.parse_ty()?;
+        let span = lo.to(self.token.span);
+        Ok(self.mk_expr(span, ExprKind::Type(expr, ty)))
+    }
+
     /// Returns a string literal if the next token is a string literal.
     /// In case of error returns `Some(lit)` if the next token is a literal with a wrong kind,
     /// and returns `None` if the next token is not literal at all.

compiler/rustc_parse/src/parser/expr.rs

@@ -1704,14 +1704,14 @@ pub(crate) mod builtin {
     }
 
     /// Unstable placeholder for type ascription.
-    #[rustc_builtin_macro]
+    #[allow_internal_unstable(builtin_syntax)]
     #[unstable(
         feature = "type_ascription",
         issue = "23416",
         reason = "placeholder syntax for type ascription"
     )]
     pub macro type_ascribe($expr:expr, $ty:ty) {
-        /* compiler built-in */
+        builtin # type_ascribe($expr, $ty)
     }
 
     /// Unstable implementation detail of the `rustc` compiler, do not use.

library/core/src/macros/mod.rs

@@ -75,24 +75,32 @@ error[E0745]: cannot take address of a temporary
    |
 LL |     let ref_ascribe = &raw const type_ascribe!(2, i32);
    |                                  ^^^^^^^^^^^^^^^^^^^^^ temporary value
+   |
+   = note: this error originates in the macro `type_ascribe` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0745]: cannot take address of a temporary
   --> $DIR/raw-ref-temp.rs:27:36
    |
 LL |     let mut_ref_ascribe = &raw mut type_ascribe!(3, i32);
    |                                    ^^^^^^^^^^^^^^^^^^^^^ temporary value
+   |
+   = note: this error originates in the macro `type_ascribe` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0745]: cannot take address of a temporary
   --> $DIR/raw-ref-temp.rs:29:40
    |
 LL |     let ascribe_field_ref = &raw const type_ascribe!(PAIR.0, i32);
    |                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^ temporary value
+   |
+   = note: this error originates in the macro `type_ascribe` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0745]: cannot take address of a temporary
   --> $DIR/raw-ref-temp.rs:30:38
    |
 LL |     let ascribe_index_ref = &raw mut type_ascribe!(ARRAY[0], i32);
    |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ temporary value
+   |
+   = note: this error originates in the macro `type_ascribe` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 16 previous errors
 

tests/ui/raw-ref-op/raw-ref-temp.stderr

@@ -12,6 +12,7 @@ note: the lint level is defined here
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
+   = note: this error originates in the macro `type_ascribe` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error
 

tests/ui/reachable/expr_type.stderr

@@ -17,6 +17,8 @@ LL | fn main() {
    |          - expected `()` because of default return type
 LL |     type_ascribe!(0, u8<e<5>=e>)
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `u8`
+   |
+   = note: this error originates in the macro `type_ascribe` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 3 previous errors