check double negation

1 files changed, 10 insertions, 3 deletions

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index a14f576eedc..d1dc4ce1e99 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -284,6 +284,7 @@ impl<'a> Parser<'a> {
             if self.prev_token == token::BinOp(token::Minus)
                 && self.token == token::BinOp(token::Minus)
                 && self.prev_token.span.between(self.token.span).is_empty()
+                && !self.look_ahead(1, |tok| tok.can_begin_expr())
             {
                 let op_span = self.prev_token.span.to(self.token.span);
                 // Eat the second `-`
@@ -560,7 +561,10 @@ impl<'a> Parser<'a> {
             token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)),
             // `~expr`
             token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)),
-
+            // // `-expr`
+            // token::BinOp(token::Minus) => {
+            //     make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
+            // }
             // `*expr`
             token::BinOp(token::Star) => {
                 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
@@ -604,17 +608,20 @@ impl<'a> Parser<'a> {
             }
             // Recover from `--x`:
             token::BinOp(token::Minus)
-                if this.look_ahead(1, |t| *t == token::BinOp(token::Minus)) =>
+                if this.look_ahead(1, |t| *t == token::BinOp(token::Minus))
+                    && !this.token.can_begin_expr() =>
             {
                 let starts_stmt = this.prev_token == token::Semi
                     || this.prev_token == token::CloseDelim(Delimiter::Brace);
                 let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
+                // if !this.token.can_begin_expr() {
                 // Eat both `-`s.
                 this.bump();
                 this.bump();
-
                 let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
                 this.recover_from_prefix_decrement(operand_expr, pre_span, starts_stmt)
+
+                // }
             }
             // `-expr`
             token::BinOp(token::Minus) => {