Avoid unnecessary pattern parse errors on ref box

Author: estebank

compiler/rustc_parse/src/parser/pat.rs

@@ -391,10 +391,10 @@ impl<'a> Parser<'a> {
             self.parse_pat_ident_mut(syntax_loc)?
         } else if self.eat_keyword(kw::Ref) {
             if self.check_keyword(kw::Box) {
-                // Suggest `box ref` and quit parsing pattern to prevent series of
-                // misguided diagnostics from later stages of the compiler.
+                // Suggest `box ref`.
                 let span = self.prev_token.span.to(self.token.span);
-                return Err(self.sess.create_err(SwitchRefBoxOrder { span }));
+                self.bump();
+                self.sess.emit_err(SwitchRefBoxOrder { span });
             }
             // Parse ref ident @ pat / ref mut ident @ pat
             let mutbl = self.parse_mutability();

tests/ui/pattern/pattern-bad-ref-box-order.fixed

@@ -5,10 +5,8 @@
 
 fn foo(f: Option<Box<i32>>) {
     match f {
-        Some(box ref, _i) => {},
+        Some(box ref _i) => {},
         //~^ ERROR switch the order of `ref` and `box`
-        //~| ERROR expected one of `)`, `,`, or `|`, found `_i`
-        //~| ERROR this pattern has 2 fields, but the corresponding tuple variant has 1 field
         None => {}
     }
 }

tests/ui/pattern/pattern-bad-ref-box-order.rs

@@ -7,8 +7,6 @@ fn foo(f: Option<Box<i32>>) {
     match f {
         Some(ref box _i) => {},
         //~^ ERROR switch the order of `ref` and `box`
-        //~| ERROR expected one of `)`, `,`, or `|`, found `_i`
-        //~| ERROR this pattern has 2 fields, but the corresponding tuple variant has 1 field
         None => {}
     }
 }

tests/ui/pattern/pattern-bad-ref-box-order.stderr

@@ -4,23 +4,5 @@ error: switch the order of `ref` and `box`
 LL |         Some(ref box _i) => {},
    |              ^^^^^^^ help: swap them: `box ref`
 
-error: expected one of `)`, `,`, or `|`, found `_i`
-  --> $DIR/pattern-bad-ref-box-order.rs:8:22
-   |
-LL |         Some(ref box _i) => {},
-   |                     -^^ expected one of `)`, `,`, or `|`
-   |                     |
-   |                     help: missing `,`
-
-error[E0023]: this pattern has 2 fields, but the corresponding tuple variant has 1 field
-  --> $DIR/pattern-bad-ref-box-order.rs:8:22
-   |
-LL |         Some(ref box _i) => {},
-   |                      ^^ expected 1 field, found 2
-  --> $SRC_DIR/core/src/option.rs:LL:COL
-   |
-   = note: tuple variant has 1 field
-
-error: aborting due to 3 previous errors
+error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0023`.