diff --git a/clang/lib/Parse/ParseExpr.cpp b/clang/lib/Parse/ParseExpr.cpp
index d65a3ec279deb7e3829b17978c9c0f8a6e79a58e..abd3ccd2bbf83bf334a653fe80efe429ec220e1d 100644
--- a/clang/lib/Parse/ParseExpr.cpp
+++ b/clang/lib/Parse/ParseExpr.cpp
@@ -1073,9 +1073,9 @@ ExprResult Parser::ParseCastExpression(
       return ParseOptionalBSCScopeSpecifier(
           ParseKind, isAddressOfOperand, NotCastExpr, isTypeCast,
           isVectorLiteral, NotPrimaryExpression, HasBSCScopeSpec);
+    } else {
+      return ExprError();
     }
-    // Fall through; this isn't a message send.
-    LLVM_FALLTHROUGH;
 #endif
 
   case tok::identifier: {      // primary-expression: identifier
diff --git a/clang/test/BSC/Negative/Generic/StructAndFunction/struct_parse_fuzz_fix/struct_parse_fuzz_fix.cbs b/clang/test/BSC/Negative/Generic/StructAndFunction/struct_parse_fuzz_fix/struct_parse_fuzz_fix.cbs
new file mode 100644
index 0000000000000000000000000000000000000000..b64942fce3518c458cf8c56a9b40d890add2f123
--- /dev/null
+++ b/clang/test/BSC/Negative/Generic/StructAndFunction/struct_parse_fuzz_fix/struct_parse_fuzz_fix.cbs
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void func1(){
+    +struct SomeStruct<void>; // expected-error{{explicit specialization of undeclared template struct 'SomeStruct'}}
+}
+
+void func2(){
+    -struct SomeStruct<void>; // expected-error{{explicit specialization of undeclared template struct 'SomeStruct'}}
+}
+
+void func3(){
+    *struct SomeStruct<void>; // expected-error{{explicit specialization of undeclared template struct 'SomeStruct'}}
+}
+
+void func4(){
+    \struct SomeStruct<void>; // expected-error{{expected expression}}
+}
+
+void func5(){
+    >struct SomeStruct<void>; // expected-error{{expected expression}} expected-error{{explicit specialization of undeclared template struct 'SomeStruct'}}
+}
+
+void func6(int n) { // expected-note{{to match this '{'}}
+    switch (n) { // expected-note{{to match this '{'}}
+        g_noise.getTaskCount+;+ // expected-error{{use of undeclared identifier 'g_noise'}} expected-error{{expected expression}}
+        struct PollResult<struct Void> s = task->future->poll(); // expected-error{{explicit specialization of undeclared template struct 'PollResult'}} expected-error{{expected '}'}} expected-error{{expected '}'}}