[WIP] Remove type ascription syntax

compiler/rustc_ast/src/ast.rs

@@ -1579,7 +1579,6 @@ pub enum ClosureBinder {
 pub struct MacCall {
     pub path: Path,
     pub args: P<DelimArgs>,
-    pub prior_type_ascription: Option<(Span, bool)>,
 }
 
 impl MacCall {

compiler/rustc_ast/src/mut_visit.rs

@@ -611,7 +611,7 @@ pub fn noop_visit_attribute<T: MutVisitor>(attr: &mut Attribute, vis: &mut T) {
 }
 
 pub fn noop_visit_mac<T: MutVisitor>(mac: &mut MacCall, vis: &mut T) {
-    let MacCall { path, args, prior_type_ascription: _ } = mac;
+    let MacCall { path, args } = mac;
     vis.visit_path(path);
     visit_delim_args(args, vis);
 }

compiler/rustc_ast/src/util/parser.rs

@@ -53,8 +53,6 @@ pub enum AssocOp {
     DotDot,
     /// `..=` range
     DotDotEq,
-    /// `:`
-    Colon,
 }
 
 #[derive(PartialEq, Debug)]
@@ -96,7 +94,6 @@ impl AssocOp {
             token::DotDotEq => Some(DotDotEq),
             // DotDotDot is no longer supported, but we need some way to display the error
             token::DotDotDot => Some(DotDotEq),
-            token::Colon => Some(Colon),
             // `<-` should probably be `< -`
             token::LArrow => Some(Less),
             _ if t.is_keyword(kw::As) => Some(As),
@@ -133,7 +130,7 @@ impl AssocOp {
     pub fn precedence(&self) -> usize {
         use AssocOp::*;
         match *self {
-            As | Colon => 14,
+            As => 14,
             Multiply | Divide | Modulus => 13,
             Add | Subtract => 12,
             ShiftLeft | ShiftRight => 11,
@@ -156,7 +153,7 @@ impl AssocOp {
             Assign | AssignOp(_) => Fixity::Right,
             As | Multiply | Divide | Modulus | Add | Subtract | ShiftLeft | ShiftRight | BitAnd
             | BitXor | BitOr | Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual
-            | LAnd | LOr | Colon => Fixity::Left,
+            | LAnd | LOr => Fixity::Left,
             DotDot | DotDotEq => Fixity::None,
         }
     }
@@ -166,8 +163,9 @@ impl AssocOp {
         match *self {
             Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual => true,
             Assign | AssignOp(_) | As | Multiply | Divide | Modulus | Add | Subtract
-            | ShiftLeft | ShiftRight | BitAnd | BitXor | BitOr | LAnd | LOr | DotDot | DotDotEq
-            | Colon => false,
+            | ShiftLeft | ShiftRight | BitAnd | BitXor | BitOr | LAnd | LOr | DotDot | DotDotEq => {
+                false
+            }
         }
     }
 
@@ -177,7 +175,7 @@ impl AssocOp {
             Assign | AssignOp(_) => true,
             Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual | As | Multiply
             | Divide | Modulus | Add | Subtract | ShiftLeft | ShiftRight | BitAnd | BitXor
-            | BitOr | LAnd | LOr | DotDot | DotDotEq | Colon => false,
+            | BitOr | LAnd | LOr | DotDot | DotDotEq => false,
         }
     }
 
@@ -202,7 +200,7 @@ impl AssocOp {
             BitOr => Some(BinOpKind::BitOr),
             LAnd => Some(BinOpKind::And),
             LOr => Some(BinOpKind::Or),
-            Assign | AssignOp(_) | As | DotDot | DotDotEq | Colon => None,
+            Assign | AssignOp(_) | As | DotDot | DotDotEq => None,
         }
     }
 
@@ -223,10 +221,9 @@ impl AssocOp {
             Greater | // `{ 42 } > 3`
             GreaterEqual | // `{ 42 } >= 3`
             AssignOp(_) | // `{ 42 } +=`
-            As | // `{ 42 } as usize`
             // Equal | // `{ 42 } == { 42 }`    Accepting these here would regress incorrect
             // NotEqual | // `{ 42 } != { 42 }  struct literals parser recovery.
-            Colon, // `{ 42 }: usize`
+            As // `{ 42 } as usize`
         )
     }
 }
@@ -254,7 +251,6 @@ pub enum ExprPrecedence {
     Binary(BinOpKind),
 
     Cast,
-    Type,
 
     Assign,
     AssignOp,
@@ -312,7 +308,6 @@ impl ExprPrecedence {
             // Binop-like expr kinds, handled by `AssocOp`.
             ExprPrecedence::Binary(op) => AssocOp::from_ast_binop(op).precedence() as i8,
             ExprPrecedence::Cast => AssocOp::As.precedence() as i8,
-            ExprPrecedence::Type => AssocOp::Colon.precedence() as i8,
 
             ExprPrecedence::Assign |
             ExprPrecedence::AssignOp => AssocOp::Assign.precedence() as i8,

compiler/rustc_ast_pretty/src/pprust/state/expr.rs

@@ -336,10 +336,16 @@ impl<'a> State<'a> {
                 self.print_type(ty);
             }
             ast::ExprKind::Type(expr, ty) => {
-                let prec = AssocOp::Colon.precedence() as i8;
-                self.print_expr_maybe_paren(expr, prec);
-                self.word_space(":");
+                self.word("type_ascribe!(");
+                self.ibox(0);
+                self.print_expr(expr);
+
+                self.word(",");
+                self.space_if_not_bol();
                 self.print_type(ty);
+
+                self.end();
+                self.word(")");
             }
             ast::ExprKind::Let(pat, scrutinee, _) => {
                 self.print_let(pat, scrutinee);

compiler/rustc_builtin_macros/src/asm.rs

@@ -68,7 +68,6 @@ pub fn parse_asm_args<'a>(
                 // After a template string, we always expect *only* a comma...
                 let mut err = diag.struct_span_err(p.token.span, "expected token: `,`");
                 err.span_label(p.token.span, "expected `,`");
-                p.maybe_annotate_with_ascription(&mut err, false);
                 return Err(err);
             } else {
                 // ...after that delegate to `expect` to also include the other expected tokens.

compiler/rustc_builtin_macros/src/assert.rs

@@ -59,7 +59,6 @@ pub fn expand_assert<'cx>(
                     delim: MacDelimiter::Parenthesis,
                     tokens,
                 }),
-                prior_type_ascription: None,
             })),
         );
         expr_if_not(cx, call_site_span, cond_expr, then, None)

compiler/rustc_builtin_macros/src/assert/context.rs

@@ -182,7 +182,6 @@ impl<'cx, 'a> Context<'cx, 'a> {
                     delim: MacDelimiter::Parenthesis,
                     tokens: initial.into_iter().chain(captures).collect::<TokenStream>(),
                 }),
-                prior_type_ascription: None,
             })),
         )
     }

compiler/rustc_builtin_macros/src/edition_panic.rs

@@ -63,7 +63,6 @@ fn expand<'cx>(
                     delim: MacDelimiter::Parenthesis,
                     tokens: tts,
                 }),
-                prior_type_ascription: None,
             })),
         ),
     )

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

@@ -373,6 +373,14 @@ parse_maybe_fn_typo_with_impl = you might have meant to write `impl` instead of
 parse_expected_fn_path_found_fn_keyword = expected identifier, found keyword `fn`
     .suggestion = use `Fn` to refer to the trait
 
+parse_path_single_colon = path separator must be a double colon
+    .suggestion = use a double colon instead
+
+parse_colon_as_semi = statements are terminated with a semicolon
+    .suggestion = use a semicolon instead
+
+parse_type_ascription_removed = type ascription syntax has been removed, see issue #101728 <https://github.com/rust-lang/rust/issues/101728>
+
 parse_where_clause_before_tuple_struct_body = where clauses are not allowed before tuple struct bodies
     .label = unexpected where clause
     .name_label = while parsing this tuple struct

compiler/rustc_expand/src/base.rs

@@ -991,7 +991,6 @@ pub struct ExpansionData {
     pub depth: usize,
     pub module: Rc<ModuleData>,
     pub dir_ownership: DirOwnership,
-    pub prior_type_ascription: Option<(Span, bool)>,
     /// Some parent node that is close to this macro call
     pub lint_node_id: NodeId,
     pub is_trailing_mac: bool,
@@ -1040,7 +1039,6 @@ impl<'a> ExtCtxt<'a> {
                 depth: 0,
                 module: Default::default(),
                 dir_ownership: DirOwnership::Owned { relative: None },
-                prior_type_ascription: None,
                 lint_node_id: ast::CRATE_NODE_ID,
                 is_trailing_mac: false,
             },

compiler/rustc_expand/src/expand.rs

@@ -657,16 +657,13 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     self.parse_ast_fragment(tok_result, fragment_kind, &mac.path, span)
                 }
                 SyntaxExtensionKind::LegacyBang(expander) => {
-                    let prev = self.cx.current_expansion.prior_type_ascription;
-                    self.cx.current_expansion.prior_type_ascription = mac.prior_type_ascription;
                     let tok_result = expander.expand(self.cx, span, mac.args.tokens.clone());
                     let result = if let Some(result) = fragment_kind.make_from(tok_result) {
                         result
                     } else {
                         self.error_wrong_fragment_kind(fragment_kind, &mac, span);
                         fragment_kind.dummy(span)
                     };
-                    self.cx.current_expansion.prior_type_ascription = prev;
                     result
                 }
                 _ => unreachable!(),

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -239,8 +239,7 @@ fn expand_macro<'cx>(
                 trace_macros_note(&mut cx.expansions, sp, msg);
             }
 
-            let mut p = Parser::new(sess, tts, false, None);
-            p.last_type_ascription = cx.current_expansion.prior_type_ascription;
+            let p = Parser::new(sess, tts, false, None);
 
             if is_local {
                 cx.resolver.record_macro_rule_usage(node_id, i);

compiler/rustc_expand/src/placeholders.rs

@@ -21,7 +21,6 @@ pub fn placeholder(
                 delim: ast::MacDelimiter::Parenthesis,
                 tokens: ast::tokenstream::TokenStream::new(Vec::new()),
             }),
-            prior_type_ascription: None,
         })
     }
 

compiler/rustc_hir_pretty/src/lib.rs

@@ -1413,10 +1413,16 @@ impl<'a> State<'a> {
                 self.print_type(ty);
             }
             hir::ExprKind::Type(expr, ty) => {
-                let prec = AssocOp::Colon.precedence() as i8;
-                self.print_expr_maybe_paren(expr, prec);
-                self.word_space(":");
+                self.word("type_ascribe!(");
+                self.ibox(0);
+                self.print_expr(expr);
+
+                self.word(",");
+                self.space_if_not_bol();
                 self.print_type(ty);
+
+                self.end();
+                self.word(")");
             }
             hir::ExprKind::DropTemps(init) => {
                 // Print `{`:

compiler/rustc_parse/src/errors.rs

@@ -1256,6 +1256,28 @@ pub(crate) struct ExpectedFnPathFoundFnKeyword {
     pub fn_token_span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_path_single_colon)]
+pub(crate) struct PathSingleColon {
+    #[primary_span]
+    #[suggestion(applicability = "machine-applicable", code = "::")]
+    pub span: Span,
+
+    #[note(parse_type_ascription_removed)]
+    pub type_ascription: Option<()>,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_colon_as_semi)]
+pub(crate) struct ColonAsSemi {
+    #[primary_span]
+    #[suggestion(applicability = "machine-applicable", code = ";")]
+    pub span: Span,
+
+    #[note(parse_type_ascription_removed)]
+    pub type_ascription: Option<()>,
+}
+
 #[derive(Diagnostic)]
 #[diag(parse_where_clause_before_tuple_struct_body)]
 pub(crate) struct WhereClauseBeforeTupleStructBody {