Suggest swapping the order of `ref` and `box`

1 files changed, 8 insertions, 2 deletions

diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 15491cac56a..8f5f4459d64 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -5,8 +5,8 @@ use crate::errors::{
     ExpectedCommaAfterPatternField, GenericArgsInPatRequireTurbofishSyntax,
     InclusiveRangeExtraEquals, InclusiveRangeMatchArrow, InclusiveRangeNoEnd, InvalidMutInPattern,
     PatternOnWrongSideOfAt, RefMutOrderIncorrect, RemoveLet, RepeatedMutInPattern,
-    TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg, TrailingVertNotAllowed,
-    UnexpectedLifetimeInPattern, UnexpectedVertVertBeforeFunctionParam,
+    SwitchRefBoxOrder, TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg,
+    TrailingVertNotAllowed, UnexpectedLifetimeInPattern, UnexpectedVertVertBeforeFunctionParam,
     UnexpectedVertVertInPattern,
 };
 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
@@ -374,6 +374,12 @@ impl<'a> Parser<'a> {
         } else if self.eat_keyword(kw::Mut) {
             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.
+                let span = self.prev_token.span.to(self.token.span);
+                return Err(self.sess.create_err(SwitchRefBoxOrder { span }));
+            }
             // Parse ref ident @ pat / ref mut ident @ pat
             let mutbl = self.parse_mutability();
             self.parse_pat_ident(BindingAnnotation(ByRef::Yes, mutbl), syntax_loc)?