Auto merge of #3801 - RalfJung:rustup, r=RalfJung

Rustup

4 files changed, 16 insertions, 12 deletions

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index ccf8dcdf0b6..cf5d65708ab 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -694,12 +694,12 @@ impl<'a> Parser<'a> {
                         // `foo: `
                         ExprKind::Path(None, ast::Path { segments, .. }),
                         token::Ident(kw::For | kw::Loop | kw::While, IdentIsRaw::No),
-                    ) if segments.len() == 1 => {
+                    ) if let [segment] = segments.as_slice() => {
                         let snapshot = self.create_snapshot_for_diagnostic();
                         let label = Label {
                             ident: Ident::from_str_and_span(
-                                &format!("'{}", segments[0].ident),
-                                segments[0].ident.span,
+                                &format!("'{}", segment.ident),
+                                segment.ident.span,
                             ),
                         };
                         match self.parse_expr_labeled(label, false) {
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index baa5eb2df63..8775d792c3d 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -471,9 +471,8 @@ impl<'a> Parser<'a> {
             Err(mut err) => {
                 // Maybe the user misspelled `macro_rules` (issue #91227)
                 if self.token.is_ident()
-                    && path.segments.len() == 1
-                    && edit_distance("macro_rules", &path.segments[0].ident.to_string(), 2)
-                        .is_some()
+                    && let [segment] = path.segments.as_slice()
+                    && edit_distance("macro_rules", &segment.ident.to_string(), 2).is_some()
                 {
                     err.span_suggestion(
                         path.span,
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 70d2c98d4f1..6f82d6b9826 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -826,7 +826,8 @@ impl<'a> Parser<'a> {
             // We can only resolve single-segment paths at the moment, because multi-segment paths
             // require type-checking: see `visit_generic_arg` in `src/librustc_resolve/late.rs`.
             ast::ExprKind::Path(None, path)
-                if path.segments.len() == 1 && path.segments[0].args.is_none() =>
+                if let [segment] = path.segments.as_slice()
+                    && segment.args.is_none() =>
             {
                 true
             }
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index b3efb87a4a2..b206f134f0e 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -408,10 +408,14 @@ impl<'a> Parser<'a> {
     fn parse_initializer(&mut self, eq_optional: bool) -> PResult<'a, Option<P<Expr>>> {
         let eq_consumed = match self.token.kind {
             token::BinOpEq(..) => {
-                // Recover `let x <op>= 1` as `let x = 1`
+                // Recover `let x <op>= 1` as `let x = 1` We must not use `+ BytePos(1)` here
+                // because `<op>` can be a multi-byte lookalike that was recovered, e.g. `➖=` (the
+                // `➖` is a U+2796 Heavy Minus Sign Unicode Character) that was recovered as a
+                // `-=`.
+                let extra_op_span = self.psess.source_map().start_point(self.token.span);
                 self.dcx().emit_err(errors::CompoundAssignmentExpressionInLet {
                     span: self.token.span,
-                    suggestion: self.token.span.with_hi(self.token.span.lo() + BytePos(1)),
+                    suggestion: extra_op_span,
                 });
                 self.bump();
                 true
@@ -672,7 +676,7 @@ impl<'a> Parser<'a> {
 
                             match &expr.kind {
                                 ExprKind::Path(None, ast::Path { segments, .. })
-                                    if segments.len() == 1 =>
+                                    if let [segment] = segments.as_slice() =>
                                 {
                                     if self.token == token::Colon
                                         && self.look_ahead(1, |token| {
@@ -689,8 +693,8 @@ impl<'a> Parser<'a> {
                                         let snapshot = self.create_snapshot_for_diagnostic();
                                         let label = Label {
                                             ident: Ident::from_str_and_span(
-                                                &format!("'{}", segments[0].ident),
-                                                segments[0].ident.span,
+                                                &format!("'{}", segment.ident),
+                                                segment.ident.span,
                                             ),
                                         };
                                         match self.parse_expr_labeled(label, false) {