3 files changed, 27 insertions, 3 deletions
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 81a727182cd..63bf864f2a8 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -1610,6 +1610,14 @@ pub(crate) struct UnexpectedSelfInGenericParameters {
 }
 
 #[derive(Diagnostic)]
+#[diag(parse_unexpected_default_value_for_lifetime_in_generic_parameters)]
+pub(crate) struct UnexpectedDefaultValueForLifetimeInGenericParameters {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(parse_multiple_where_clauses)]
 pub(crate) struct MultipleWhereClauses {
     #[primary_span]
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index 585dfc518b3..23f49ec55a1 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -1,5 +1,6 @@
 use crate::errors::{
-    MultipleWhereClauses, UnexpectedSelfInGenericParameters, WhereClauseBeforeTupleStructBody,
+    MultipleWhereClauses, UnexpectedDefaultValueForLifetimeInGenericParameters,
+    UnexpectedSelfInGenericParameters, WhereClauseBeforeTupleStructBody,
     WhereClauseBeforeTupleStructBodySugg,
 };
 
@@ -145,6 +146,20 @@ impl<'a> Parser<'a> {
                         } else {
                             (None, Vec::new())
                         };
+
+                        if this.check_noexpect(&token::Eq)
+                            && this.look_ahead(1, |t| t.is_lifetime())
+                        {
+                            let lo = this.token.span;
+                            // Parse `= 'lifetime`.
+                            this.bump(); // `=`
+                            this.bump(); // `'lifetime`
+                            let span = lo.to(this.prev_token.span);
+                            this.sess.emit_err(
+                                UnexpectedDefaultValueForLifetimeInGenericParameters { span },
+                            );
+                        }
+
                         Some(ast::GenericParam {
                             ident: lifetime.ident,
                             id: lifetime.id,
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index a19ea04fa5e..5b92563fc35 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -694,8 +694,9 @@ impl<'a> Parser<'a> {
         // `where`, so stop if it's it.
         // We also continue if we find types (not traits), again for error recovery.
         while self.can_begin_bound()
-            || self.token.can_begin_type()
-            || (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))
+            || (self.may_recover()
+                && (self.token.can_begin_type()
+                    || (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))))
         {
             if self.token.is_keyword(kw::Dyn) {
                 // Account for `&dyn Trait + dyn Other`.