Scan destructors of aliased type class members

TypeToDeclAsWritten returns TypedefNameDecl in that case instead of
the original CXXRecordDecl. But Type::getAsCXXRecordDecl does the right
thing.

Found while investigating include-what-you-use#1499. The type of the _Hashtable member
of std::unordered_map is a typedef at least in the libstdc++
implementation.

iwyu.cc

@@ -609,9 +609,8 @@ class BaseAstVisitor : public RecursiveASTVisitor<Derived> {
       member_types.insert(it->getType().getTypePtr());
     }
     for (const Type* type : member_types) {
-      const NamedDecl* member_decl = TypeToDeclAsWritten(type);
       // We only want those fields that are c++ classes.
-      if (const CXXRecordDecl* cxx_field_decl = DynCastFrom(member_decl)) {
+      if (const CXXRecordDecl* cxx_field_decl = type->getAsCXXRecordDecl()) {
         if (const CXXDestructorDecl* field_dtor =
                 cxx_field_decl->getDestructor()) {
           if (!this->getDerived().TraverseImplicitDestructorCall(

tests/cxx/template_member_functions.cc

@@ -18,11 +18,22 @@ struct Tpl {
   static void StaticFn() {
     T t;
   }
+
+  ~Tpl() {
+    T t;
+  }
 };
 
 class IndirectClass;
 using NonProviding = Tpl<IndirectClass>;
 
+struct Struct {
+  // IWYU: IndirectClass is...*indirect.h
+  ~Struct() = default;
+
+  NonProviding member;
+};
+
 void Fn() {
   // IWYU: IndirectClass is...*indirect.h
   NonProviding::StaticFn();