clang-tidy: Count template constructors in modernize-use-default-member-init

[MarcoFalke]

Summary

The check should bomb out when there are multiple constructors. However, it didn't count template constructors.

Add a negative test case TwoConstructorsTpl and make it pass.

[MarcoFalke]

Simplify patch and remove test case failing on Windows, but passing on Linux

[MarcoFalke]

Remove both test cases that pass on current main on Linux, but fail on Windows. Seems unrelated to add/fix them here.

[oleg.smolsky]

Nice!

[carlosgalvezp]

Looks good, thanks! Please document change in the Release Notes.

[MarcoFalke]

Thanks. Added release note. Lmk if I should go ahead and merge this.

[MarcoFalke]

mv release note, rebase

[carlosgalvezp]

Thanks for the fix!

clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp

 
 void UseDefaultMemberInitCheck::checkDefaultInit(
     const MatchFinder::MatchResult &Result, const CXXCtorInitializer *Init) {
   const FieldDecl *Field = Init->getAnyMember();
 
   // Check whether we have multiple hand-written constructors and bomb out, as
   // it is hard to reconcile their sets of member initializers.
   const auto *ClassDecl = cast<CXXRecordDecl>(Field->getParent());
-  if (llvm::count_if(ClassDecl->ctors(), [](const CXXConstructorDecl *Ctor) {
+  if (llvm::count_if(ClassDecl->decls(), [](const Decl *D) {
+        if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(D))
           return !Ctor->isCopyOrMoveConstructor();
+        if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(D))
+          return isa<CXXConstructorDecl>(FTD->getTemplatedDecl());
+        return false;
       }) > 1)
     return;
 
   SourceLocation StartLoc = Field->getBeginLoc();
   if (StartLoc.isMacroID() && IgnoreMacros)
     return;
 
   SourceLocation FieldEnd =

clang-tools-extra/test/clang-tidy/checkers/modernize/use-default-member-init.cpp

 
 // We cannot reconcile these initializers.
 struct TwoConstructors {
     TwoConstructors(int) : i(7) {}
     TwoConstructors(int, int) : i(8) {}
     int i;
 };
 
+struct TwoConstructorsTpl {
+  TwoConstructorsTpl() : i{7} {}
+  template <typename T> TwoConstructorsTpl(T, int) : i(8) {}
+  int i;
+};
+
+struct PositiveConstructorTpl {
+  template <typename T> PositiveConstructorTpl(T, int) : i(8) {}
+  // CHECK-FIXES: PositiveConstructorTpl(T, int)  {}
+  int i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'i'
+  // CHECK-FIXES: int i{8};
+};
+
 struct PositiveNotDefaultOOLInt {
   PositiveNotDefaultOOLInt(int);
   int i;
   // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'i'
   // CHECK-FIXES: int i{7};
 };
 
 PositiveNotDefaultOOLInt::PositiveNotDefaultOOLInt(int) : i(7) {}

 struct NegativeTemplate {
     NegativeTemplate() : t() {}
     T t;
 };
 
 NegativeTemplate<int> nti;
 NegativeTemplate<double> ntd;
 
+template <typename T> struct PositiveTemplate {
+  PositiveTemplate() : i(9) {}
+  // CHECK-FIXES: PositiveTemplate()  {}
+  int i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'i'
+  // CHECK-FIXES: int i{9};
+};
+
 struct NegativeDefaultMember {
   NegativeDefaultMember() {}
   int i = 2;
 };
 
 struct NegativeClass : S {
   NegativeClass() : s() {}
   S s;