Don't try to validate invalid decls (#5086)

We should not try to validate template arguments for invalid decls.
Doing so seems to result in infinte recursion that eventually kills the
compiler... so let's not do that.

Fixes #3455

tools/clang/lib/Sema/SemaHLSL.cpp

@@ -4944,6 +4944,8 @@ public:
         case AR_TOBJ_COMPOUND:
           {
             const RecordDecl* recordDecl = recordType->getDecl();
+            if (recordDecl->isInvalidDecl())
+              return false;
             RecordDecl::field_iterator begin = recordDecl->field_begin();
             RecordDecl::field_iterator end = recordDecl->field_end();
             bool result = true;

tools/clang/test/HLSL/invalid-decl-template-arg.hlsl

@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct FOOO_A_B { // expected-note{{'FOOO_A_B' declared here}} expected-note{{definition of 'FOOO_A_B' is not complete until the closing '}'}}
+  FOOO_A v0; // expected-error{{unknown type name 'FOOO_A'; did you mean 'FOOO_A_B'}} expected-error{{field has incomplete type 'FOOO_A_B}}
+};
+
+RWStructuredBuffer<FOOO_A_B> Input;
+
+void main() {}

tools/clang/unittests/HLSL/VerifierTest.cpp

@@ -54,6 +54,7 @@ public:
   TEST_METHOD(RunIncompleteType)
   TEST_METHOD(RunIndexingOperator)
   TEST_METHOD(RunIntrinsicExamples)
+  TEST_METHOD(RunInvalidDeclTemplateArg)
   TEST_METHOD(RunMatrixAssignments)
   TEST_METHOD(RunMatrixSyntax)
   TEST_METHOD(RunMatrixSyntaxExactPrecision)
@@ -256,6 +257,10 @@ TEST_F(VerifierTest, RunIntrinsicExamples) {
   CheckVerifiesHLSL(L"intrinsic-examples.hlsl");
 }
 
+TEST_F(VerifierTest, RunInvalidDeclTemplateArg) {
+  CheckVerifiesHLSL(L"invalid-decl-template-arg.hlsl");
+}
+
 TEST_F(VerifierTest, RunMatrixAssignments) {
   CheckVerifiesHLSL(L"matrix-assignments.hlsl");
 }