[clang] Invalidate a non-dependent-type RecordDecl when it has any dependent-type base class specifier.

This happens during the error-recovery, and it would esacpe all
dependent-type check guards in getTypeInfo/constexpr-evaluator code
paths, which lead to crashes.

Differential Revision: https://reviews.llvm.org/D102773

clang/lib/Sema/SemaDeclCXX.cpp

@@ -2508,6 +2508,14 @@ Sema::CheckBaseSpecifier(CXXRecordDecl *Class,
       }
     }
 
+    // Make sure that we don't make an ill-formed AST where the type of the
+    // Class is non-dependent and its attached base class specifier is an
+    // dependent type, which violates invariants in many clang code paths (e.g.
+    // constexpr evaluator). If this case happens (in errory-recovery mode), we
+    // explicitly mark the Class decl invalid. The diagnostic was already
+    // emitted.
+    if (!Class->getTypeForDecl()->isDependentType())
+      Class->setInvalidDecl();
     return new (Context) CXXBaseSpecifier(SpecifierRange, Virtual,
                                           Class->getTagKind() == TTK_Class,
                                           Access, TInfo, EllipsisLoc);

clang/test/SemaTemplate/temp_class_spec.cpp

@@ -375,3 +375,16 @@ class Bar<0> : public Foo<Z> { // expected-error{{partial specialization of 'Bar
   Bar() : Foo<Z>() {}
 };
 } // namespace
+
+namespace Crash {
+template<typename T>
+class Base {};
+
+template<typename T> class Foo;
+
+template <typename T>
+class Foo<int> : public Base<T> {}; // expected-error{{partial specialization of 'Foo' does not use any of its template parameters}}
+
+// verify that getASTRecordLayout doesn't crash on the ClassTemplateSpecializationDecl.
+constexpr int s = sizeof(Foo<int>);
+}