Rip it out

My type ascription
Oh rip it out
Ah
If you think we live too much then
You can sacrifice diagnostics
Don't mix your garbage
Into my syntax
So many weird hacks keep diagnostics alive
Yet I don't even step outside
So many bad diagnostics keep tyasc alive
Yet tyasc doesn't even bother to survive!

Author: Noratrieb

compiler/rustc_ast/src/ast.rs

@@ -1580,7 +1580,6 @@ 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

@@ -631,7 +631,7 @@ 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`
+            // NotEqual | // `{ 42 } != { 42 }  struct literals parser recovery.
+            As // `{ 42 } as usize`
         )
     }
 }
@@ -254,7 +251,6 @@ pub enum ExprPrecedence {
     Binary(BinOpKind),
 
     Cast,
-    Type,
 
     Assign,
     AssignOp,
@@ -313,7 +309,6 @@ 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

@@ -341,10 +341,16 @@ 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

@@ -60,7 +60,6 @@ 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_expand/src/base.rs

@@ -992,7 +992,6 @@ 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,
@@ -1041,7 +1040,6 @@ 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

@@ -250,8 +250,7 @@ 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

@@ -1411,10 +1411,16 @@ 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/messages.ftl

@@ -420,6 +420,14 @@ 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_parse/src/errors.rs

@@ -1337,6 +1337,28 @@ 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 {