Fix a crash in cppcoreguidelines-pro-type-member-init when checking a type with a template parameter as a base class.

[michael_miller]

Summary

Fixed a crash in cppcoreguidelines-pro-type-member-init when encountering a type that uses one of its template parameters as a base when compiling for C++98.

[hokein]

LGTM. Thanks for the quick fix!

clang-tidy/cppcoreguidelines/ProTypeMemberInitCheck.cpp

computeInsertions(const CXXConstructorDecl::init_const_range &Inits,
   return Insertions;
 }
 
 // Gets the list of bases and members that could possibly be initialized, in
 // order as they appear in the class declaration.
 void getInitializationsInOrder(const CXXRecordDecl *ClassDecl,
                                SmallVectorImpl<const NamedDecl *> &Decls) {
   Decls.clear();
-  for (const auto &Base : ClassDecl->bases())
-    Decls.emplace_back(getCanonicalRecordDecl(Base.getType()));
+  for (const auto &Base : ClassDecl->bases()) {
+    // Decl may be null if the base class is a template parameter.
+    if (const NamedDecl *Decl = getCanonicalRecordDecl(Base.getType())) {
+      Decls.emplace_back(Decl);
+    }
+  }
   Decls.append(ClassDecl->fields().begin(), ClassDecl->fields().end());
 }
 
 template <typename T>
 void fixInitializerList(const ASTContext &Context, DiagnosticBuilder &Diag,
                         const CXXConstructorDecl *Ctor,
                         const SmallPtrSetImpl<const T *> &DeclsToInit) {
   // Do not propose fixes in macros since we cannot place them correctly.

test/clang-tidy/cppcoreguidelines-pro-type-member-init-cxx98.cpp

 };
 
 struct NegativeAggregateType {
   int X;
   int Y;
   int Z;
 };
 
-struct NonTrivialType {
+struct TrivialType {
   int X;
   int Y;
 };
 
 struct PositiveUninitializedBaseOrdering : public NegativeAggregateType,
-                                           public NonTrivialType {
-  PositiveUninitializedBaseOrdering() : NegativeAggregateType(), NonTrivialType(), B() {}
+                                           public TrivialType {
+  PositiveUninitializedBaseOrdering() : NegativeAggregateType(), TrivialType(), B() {}
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: constructor does not initialize these fields: A
-  // CHECK-FIXES: PositiveUninitializedBaseOrdering() : NegativeAggregateType(), NonTrivialType(), A(), B() {}
+  // CHECK-FIXES: PositiveUninitializedBaseOrdering() : NegativeAggregateType(), TrivialType(), A(), B() {}
 
   // This is somewhat pathological with the base class initializer at the end...
-  PositiveUninitializedBaseOrdering(int) : B(), NonTrivialType(), A() {}
+  PositiveUninitializedBaseOrdering(int) : B(), TrivialType(), A() {}
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: constructor does not initialize these bases: NegativeAggregateType
-  // CHECK-FIXES: PositiveUninitializedBaseOrdering(int) : B(), NegativeAggregateType(), NonTrivialType(), A() {}
+  // CHECK-FIXES: PositiveUninitializedBaseOrdering(int) : B(), NegativeAggregateType(), TrivialType(), A() {}
 
   PositiveUninitializedBaseOrdering(float) : NegativeAggregateType(), A() {}
-  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: constructor does not initialize these bases: NonTrivialType
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: constructor does not initialize these bases: TrivialType
   // CHECK-MESSAGES: :[[@LINE-2]]:3: warning: constructor does not initialize these fields: B
-  // CHECK-FIXES: PositiveUninitializedBaseOrdering(float) : NegativeAggregateType(), NonTrivialType(), A(), B() {}
+  // CHECK-FIXES: PositiveUninitializedBaseOrdering(float) : NegativeAggregateType(), TrivialType(), A(), B() {}
 
   int A, B;
 };
+
+template <class T>
+class PositiveTemplateBase : T {
+public:
+  PositiveTemplateBase() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: constructor does not initialize these fields: X
+  // CHECK-FIXES: PositiveTemplateBase() : X() {}
+
+  int X;
+};