[clang-tidy] Fix an assertion failure in cppcoreguidelines-pro-type-member-init.

[hokein]

Summary

The matcher for matching "class with default constructor" still match
some classes without default constructor, which trigger an assert at
Line 307. This patch makes the matcher more strict.

[aaron.ballman]

LGTM

clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp

30

I think this should be a public AST matcher rather than a private one; it seems like it would be generally useful (along with some of the other similar has* functions). However, I think it's fine for this patch.

[hokein]

clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp

30

+1, will do it in a follow-up.

clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp

 using llvm::SmallPtrSetImpl;
 
 namespace clang {
 namespace tidy {
 namespace cppcoreguidelines {
 
 namespace {
 
+AST_MATCHER(CXXRecordDecl, hasDefaultConstructor) {
+  return Node.hasDefaultConstructor();
+}
+
 // Iterate over all the fields in a record type, both direct and indirect (e.g.
 // if the record contains an anonmyous struct). If OneFieldPerUnion is true and
 // the record type (or indirect field) is a union, forEachField will stop after
 // the first field.
 template <typename T, typename Func>
 void forEachField(const RecordDecl &Record, const T &Fields,
                   bool OneFieldPerUnion, Func &&Fn) {
   for (const FieldDecl *F : Fields) {
Finder->addMatcher(
           .bind("ctor"),
       this);
 
   // Match classes with a default constructor that is defaulted or is not in the
   // AST.
   Finder->addMatcher(
       cxxRecordDecl(
           isDefinition(), unless(isInstantiated()),
+          hasDefaultConstructor(),
           anyOf(has(cxxConstructorDecl(isDefaultConstructor(), isDefaulted(),
                                        unless(isImplicit()))),
                 unless(has(cxxConstructorDecl()))),
           unless(isTriviallyDefaultConstructible()))
           .bind("record"),
       this);
 
   auto HasDefaultConstructor = hasInitializer(

test/clang-tidy/cppcoreguidelines-pro-type-member-init.cpp

struct NegativeEmptyArrayMember {
   NegativeEmptyArrayMember() {}
   char e[0];
 };
 
 struct NegativeIncompleteArrayMember {
   NegativeIncompleteArrayMember() {}
   char e[];
 };
+
+template <typename T> class NoCrash {
+  class B : public NoCrash {
+    template <typename U> B(U u) {}
+  };
+};