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!

1 files changed, 36 insertions, 69 deletions

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index bff9de5c652..7c55ac9cce2 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -174,10 +174,8 @@ impl<'a> Parser<'a> {
                 self.parse_expr_prefix(attrs)?
             }
         };
-        let last_type_ascription_set = self.last_type_ascription.is_some();
 
         if !self.should_continue_as_assoc_expr(&lhs) {
-            self.last_type_ascription = None;
             return Ok(lhs);
         }
 
@@ -296,14 +294,22 @@ impl<'a> Parser<'a> {
                 continue;
             }
 
+            // Special cases:
+            if op.node == AssocOp::As {
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
+                continue;
+            } else if op.node == AssocOp::DotDot || op.node == AssocOp::DotDotEq {
+                // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
+                // generalise it to the Fixity::None code.
+                lhs = self.parse_expr_range(prec, lhs, op.node, cur_op_span)?;
+                break;
+            }
+
             let op = op.node;
             // Special cases:
             if op == AssocOp::As {
                 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
                 continue;
-            } else if op == AssocOp::Colon {
-                lhs = self.parse_assoc_op_ascribe(lhs, lhs_span)?;
-                continue;
             } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
                 // If we didn't have to handle `x..`/`x..=`, it would be pretty easy to
                 // generalise it to the Fixity::None code.
@@ -364,7 +370,7 @@ impl<'a> Parser<'a> {
                     let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
                     self.mk_expr(span, aopexpr)
                 }
-                AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
+                AssocOp::As | AssocOp::DotDot | AssocOp::DotDotEq => {
                     self.span_bug(span, "AssocOp should have been handled by special case")
                 }
             };
@@ -373,9 +379,7 @@ impl<'a> Parser<'a> {
                 break;
             }
         }
-        if last_type_ascription_set {
-            self.last_type_ascription = None;
-        }
+
         Ok(lhs)
     }
 
@@ -615,7 +619,9 @@ impl<'a> Parser<'a> {
             token::Ident(..) if this.may_recover() && this.is_mistaken_not_ident_negation() => {
                 make_it!(this, attrs, |this, _| this.recover_not_expr(lo))
             }
-            _ => return this.parse_expr_dot_or_call(Some(attrs)),
+            _ => {
+                return this.parse_expr_dot_or_call(Some(attrs));
+            }
         }
     }
 
@@ -743,7 +749,7 @@ impl<'a> Parser<'a> {
                     (
                         // `foo: `
                         ExprKind::Path(None, ast::Path { segments, .. }),
-                        TokenKind::Ident(kw::For | kw::Loop | kw::While, false),
+                        token::Ident(kw::For | kw::Loop | kw::While, false),
                     ) if segments.len() == 1 => {
                         let snapshot = self.create_snapshot_for_diagnostic();
                         let label = Label {
@@ -838,21 +844,19 @@ impl<'a> Parser<'a> {
         &mut self,
         cast_expr: P<Expr>,
     ) -> PResult<'a, P<Expr>> {
+        if let ExprKind::Type(_, _) = cast_expr.kind {
+            panic!("ExprKind::Type must not be parsed");
+        }
+
         let span = cast_expr.span;
-        let (cast_kind, maybe_ascription_span) =
-            if let ExprKind::Type(ascripted_expr, _) = &cast_expr.kind {
-                ("type ascription", Some(ascripted_expr.span.shrink_to_hi().with_hi(span.hi())))
-            } else {
-                ("cast", None)
-            };
 
         let with_postfix = self.parse_expr_dot_or_call_with_(cast_expr, span)?;
 
         // Check if an illegal postfix operator has been added after the cast.
         // If the resulting expression is not a cast, it is an illegal postfix operator.
-        if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
+        if !matches!(with_postfix.kind, ExprKind::Cast(_, _)) {
             let msg = format!(
-                "{cast_kind} cannot be followed by {}",
+                "cast cannot be followed by {}",
                 match with_postfix.kind {
                     ExprKind::Index(_, _) => "indexing",
                     ExprKind::Try(_) => "`?`",
@@ -878,44 +882,13 @@ impl<'a> Parser<'a> {
                 );
             };
 
-            // If type ascription is "likely an error", the user will already be getting a useful
-            // help message, and doesn't need a second.
-            if self.last_type_ascription.map_or(false, |last_ascription| last_ascription.1) {
-                self.maybe_annotate_with_ascription(&mut err, false);
-            } else if let Some(ascription_span) = maybe_ascription_span {
-                let is_nightly = self.sess.unstable_features.is_nightly_build();
-                if is_nightly {
-                    suggest_parens(&mut err);
-                }
-                err.span_suggestion(
-                    ascription_span,
-                    &format!(
-                        "{}remove the type ascription",
-                        if is_nightly { "alternatively, " } else { "" }
-                    ),
-                    "",
-                    if is_nightly {
-                        Applicability::MaybeIncorrect
-                    } else {
-                        Applicability::MachineApplicable
-                    },
-                );
-            } else {
-                suggest_parens(&mut err);
-            }
+            suggest_parens(&mut err);
+
             err.emit();
         };
         Ok(with_postfix)
     }
 
-    fn parse_assoc_op_ascribe(&mut self, lhs: P<Expr>, lhs_span: Span) -> PResult<'a, P<Expr>> {
-        let maybe_path = self.could_ascription_be_path(&lhs.kind);
-        self.last_type_ascription = Some((self.prev_token.span, maybe_path));
-        let lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
-        self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
-        Ok(lhs)
-    }
-
     /// Parse `& mut? <expr>` or `& raw [ const | mut ] <expr>`.
     fn parse_expr_borrow(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
         self.expect_and()?;
@@ -1010,7 +983,7 @@ impl<'a> Parser<'a> {
             };
             if has_dot {
                 // expr.f
-                e = self.parse_expr_dot_suffix(lo, e)?;
+                e = self.parse_dot_suffix_expr(lo, e)?;
                 continue;
             }
             if self.expr_is_complete(&e) {
@@ -1024,13 +997,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn look_ahead_type_ascription_as_field(&mut self) -> bool {
-        self.look_ahead(1, |t| t.is_ident())
-            && self.look_ahead(2, |t| t == &token::Colon)
-            && self.look_ahead(3, |t| t.can_begin_expr())
-    }
-
-    fn parse_expr_dot_suffix(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
+    fn parse_dot_suffix_expr(&mut self, lo: Span, base: P<Expr>) -> PResult<'a, P<Expr>> {
         match self.token.uninterpolate().kind {
             token::Ident(..) => self.parse_dot_suffix(base, lo),
             token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
@@ -1183,9 +1150,7 @@ impl<'a> Parser<'a> {
 
     /// Parse a function call expression, `expr(...)`.
     fn parse_expr_fn_call(&mut self, lo: Span, fun: P<Expr>) -> P<Expr> {
-        let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
-            && self.look_ahead_type_ascription_as_field()
-        {
+        let snapshot = if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
             Some((self.create_snapshot_for_diagnostic(), fun.kind.clone()))
         } else {
             None
@@ -1216,7 +1181,6 @@ impl<'a> Parser<'a> {
         if !self.may_recover() {
             return None;
         }
-
         match (seq.as_mut(), snapshot) {
             (Err(err), Some((mut snapshot, ExprKind::Path(None, path)))) => {
                 snapshot.bump(); // `(`
@@ -1260,9 +1224,7 @@ impl<'a> Parser<'a> {
                         return Some(self.mk_expr_err(span));
                     }
                     Ok(_) => {}
-                    Err(mut err) => {
-                        err.emit();
-                    }
+                    Err(err) => err.cancel(),
                 }
             }
             _ => {}
@@ -1516,7 +1478,6 @@ impl<'a> Parser<'a> {
             let mac = P(MacCall {
                 path,
                 args: self.parse_delim_args()?,
-                prior_type_ascription: self.last_type_ascription,
             });
             (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
         } else if self.check(&token::OpenDelim(Delimiter::Brace))
@@ -1535,7 +1496,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse `'label: $expr`. The label is already parsed.
-    fn parse_expr_labeled(
+    pub(super) fn parse_expr_labeled(
         &mut self,
         label_: Label,
         mut consume_colon: bool,
@@ -3013,6 +2974,11 @@ impl<'a> Parser<'a> {
                     } else {
                         e.span_label(pth.span, "while parsing this struct");
                     }
+
+                    if !recover {
+                        return Err(e);
+                    }
+
                     e.emit();
 
                     // If the next token is a comma, then try to parse
@@ -3024,6 +2990,7 @@ impl<'a> Parser<'a> {
                             break;
                         }
                     }
+
                     None
                 }
             };