Improve error message

2 files changed, 17 insertions, 0 deletions

diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 3ae9b6dad99..6738cc4a120 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -3041,3 +3041,12 @@ pub struct UnsafeAttrOutsideUnsafeSuggestion {
     #[suggestion_part(code = ")")]
     pub right: Span,
 }
+
+#[derive(Diagnostic)]
+#[diag(parse_binder_before_modifiers)]
+pub struct BinderBeforeModifiers {
+    #[primary_span]
+    pub binder_span: Span,
+    #[label]
+    pub modifiers_span: Span,
+}
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 24183ac1218..306029ca94c 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -989,7 +989,10 @@ impl<'a> Parser<'a> {
         leading_token: &Token,
     ) -> PResult<'a, GenericBound> {
         let (mut lifetime_defs, binder_span) = self.parse_late_bound_lifetime_defs()?;
+
+        let modifiers_lo = self.token.span;
         let modifiers = self.parse_trait_bound_modifiers()?;
+        let modifiers_span = modifiers_lo.to(self.prev_token.span);
 
         // Recover erroneous lifetime bound with modifiers or binder.
         // e.g. `T: for<'a> 'a` or `T: ~const 'a`.
@@ -998,6 +1001,11 @@ impl<'a> Parser<'a> {
             return self.parse_generic_lt_bound(lo, has_parens);
         }
 
+        if let (more_lifetime_defs, Some(binder_span)) = self.parse_late_bound_lifetime_defs()? {
+            lifetime_defs.extend(more_lifetime_defs);
+            self.dcx().emit_err(errors::BinderBeforeModifiers { binder_span, modifiers_span });
+        }
+
         let mut path = if self.token.is_keyword(kw::Fn)
             && self.look_ahead(1, |tok| tok.kind == TokenKind::OpenDelim(Delimiter::Parenthesis))
             && let Some(path) = self.recover_path_from_fn()