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, 107 insertions, 20 deletions

diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index fbe5b88c49e..8e8788beeba 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -10,6 +10,8 @@ use super::{
 use crate::errors;
 use crate::maybe_whole;
 
+use crate::errors::MalformedLoopLabel;
+use ast::Label;
 use rustc_ast as ast;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, TokenKind};
@@ -19,7 +21,8 @@ use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, HasAttrs, Local, Stmt};
 use rustc_ast::{StmtKind, DUMMY_NODE_ID};
 use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
 use rustc_span::source_map::{BytePos, Span};
-use rustc_span::symbol::{kw, sym};
+use rustc_span::symbol::{kw, sym, Ident};
+
 use std::mem;
 use thin_vec::{thin_vec, ThinVec};
 
@@ -186,7 +189,7 @@ impl<'a> Parser<'a> {
             _ => MacStmtStyle::NoBraces,
         };
 
-        let mac = P(MacCall { path, args, prior_type_ascription: self.last_type_ascription });
+        let mac = P(MacCall { path, args });
 
         let kind = if (style == MacStmtStyle::Braces
             && self.token != token::Dot
@@ -546,10 +549,36 @@ impl<'a> Parser<'a> {
             }
             let stmt = match self.parse_full_stmt(recover) {
                 Err(mut err) if recover.yes() => {
-                    self.maybe_annotate_with_ascription(&mut err, false);
                     if let Some(ref mut snapshot) = snapshot {
                         snapshot.recover_diff_marker();
                     }
+                    if self.token == token::Colon {
+                        // if next token is following a colon, it's likely a path
+                        // and we can suggest a path separator
+                        let ident_span = self.prev_token.span;
+                        self.bump();
+                        if self.token.span.lo() == self.prev_token.span.hi() {
+                            err.span_suggestion_verbose(
+                                self.prev_token.span,
+                                "maybe write a path separator here",
+                                "::",
+                                Applicability::MaybeIncorrect,
+                            );
+                        }
+                        if self.look_ahead(1, |token| token == &token::Eq) {
+                            err.span_suggestion_verbose(
+                                ident_span.shrink_to_lo(),
+                                "you might have meant to introduce a new binding",
+                                "let ",
+                                Applicability::MaybeIncorrect,
+                            );
+                        }
+                        if self.sess.unstable_features.is_nightly_build() {
+                            // FIXME(Nilstrieb): Remove this again after a few months.
+                            err.note("type ascription syntax has been removed, see issue #101728 <https://github.com/rust-lang/rust/issues/101728>");
+                        }
+                    }
+
                     err.emit();
                     self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
                     Some(self.mk_stmt_err(self.token.span))
@@ -580,19 +609,25 @@ impl<'a> Parser<'a> {
         };
 
         let mut eat_semi = true;
+        let mut add_semi_to_stmt = false;
+
         match &mut stmt.kind {
             // Expression without semicolon.
             StmtKind::Expr(expr)
                 if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) => {
                 // Just check for errors and recover; do not eat semicolon yet.
                 // `expect_one_of` returns PResult<'a, bool /* recovered */>
-                let replace_with_err =
-                    match self.expect_one_of(&[], &[token::Semi, token::CloseDelim(Delimiter::Brace)]) {
+
+                let expect_result = self.expect_one_of(&[], &[token::Semi, token::CloseDelim(Delimiter::Brace)]);
+
+                let replace_with_err = 'break_recover: {
+                    match expect_result {
                     // Recover from parser, skip type error to avoid extra errors.
-                    Ok(true) => true,
-                    Err(mut e) => {
-                        if let TokenKind::DocComment(..) = self.token.kind &&
-                            let Ok(snippet) = self.span_to_snippet(self.token.span) {
+                        Ok(true) => true,
+                        Err(mut e) => {
+                            if let TokenKind::DocComment(..) = self.token.kind
+                                && let Ok(snippet) = self.span_to_snippet(self.token.span)
+                            {
                                 let sp = self.token.span;
                                 let marker = &snippet[..3];
                                 let (comment_marker, doc_comment_marker) = marker.split_at(2);
@@ -606,21 +641,72 @@ impl<'a> Parser<'a> {
                                     format!("{} {}", comment_marker, doc_comment_marker),
                                     Applicability::MaybeIncorrect,
                                 );
-                        }
+                            }
+
+                            if self.recover_colon_as_semi() {
+                                // recover_colon_as_semi has already emitted a nicer error.
+                                e.cancel();
+                                add_semi_to_stmt = true;
+                                eat_semi = false;
+
+                                break 'break_recover false;
+                            }
+
+                            match &expr.kind {
+                                ExprKind::Path(None, ast::Path { segments, .. }) if segments.len() == 1 => {
+                                    if self.token == token::Colon
+                                        && self.look_ahead(1, |token| {
+                                            token.is_whole_block() || matches!(
+                                                token.kind,
+                                                token::Ident(kw::For | kw::Loop | kw::While, false)
+                                                    | token::OpenDelim(Delimiter::Brace)
+                                            )
+                                        })
+                                    {
+                                        let snapshot = self.create_snapshot_for_diagnostic();
+                                        let label = Label {
+                                            ident: Ident::from_str_and_span(
+                                                &format!("'{}", segments[0].ident),
+                                                segments[0].ident.span,
+                                            ),
+                                        };
+                                        match self.parse_expr_labeled(label, false) {
+                                            Ok(labeled_expr) => {
+                                                e.cancel();
+                                                self.sess.emit_err(MalformedLoopLabel {
+                                                    span: label.ident.span,
+                                                    correct_label: label.ident,
+                                                });
+                                                *expr = labeled_expr;
+                                                break 'break_recover false;
+                                            }
+                                            Err(err) => {
+                                                err.cancel();
+                                                self.restore_snapshot(snapshot);
+                                            }
+                                        }
+                                    }
+                                }
+                                _ => {}
+                            }
 
-                        if let Err(mut e) =
-                            self.check_mistyped_turbofish_with_multiple_type_params(e, expr)
-                        {
-                            if recover.no() {
-                                return Err(e);
+                            if let Err(mut e) =
+                                self.check_mistyped_turbofish_with_multiple_type_params(e, expr)
+                            {
+                                if recover.no() {
+                                    return Err(e);
+                                }
+                                e.emit();
+                                self.recover_stmt();
                             }
-                            e.emit();
-                            self.recover_stmt();
+
+                            true
+
                         }
-                        true
+                        Ok(false) => false
                     }
-                    _ => false
                 };
+
                 if replace_with_err {
                     // We already emitted an error, so don't emit another type error
                     let sp = expr.span.to(self.prev_token.span);
@@ -643,9 +729,10 @@ impl<'a> Parser<'a> {
             StmtKind::Empty | StmtKind::Item(_) | StmtKind::Local(_) | StmtKind::Semi(_) => eat_semi = false,
         }
 
-        if eat_semi && self.eat(&token::Semi) {
+        if add_semi_to_stmt || (eat_semi && self.eat(&token::Semi)) {
             stmt = stmt.add_trailing_semicolon();
         }
+
         stmt.span = stmt.span.to(self.prev_token.span);
         Ok(Some(stmt))
     }