[clang-tidy] modernize-use-default default constructor bugfix

[malcolm.parsons]

Summary

Only member initializers that are written should prevent
using '= default' on a default constructor.

[malcolm.parsons]

ping

[alexfh]

LG. Thank you!

[malcolm.parsons]

I don't have commit access, so please commit this and D24652 for me.
Thanks.

clang-tidy/modernize/UseDefaultCheck.cpp

if (getLangOpts().CPlusPlus) {
     // Destructor.
     Finder->addMatcher(cxxDestructorDecl(isDefinition()).bind(SpecialFunction),
                        this);
     Finder->addMatcher(
         cxxConstructorDecl(
             isDefinition(),
             anyOf(
                 // Default constructor.
-                allOf(unless(hasAnyConstructorInitializer(anything())),
+                allOf(unless(hasAnyConstructorInitializer(isWritten())),
                       parameterCountIs(0)),
                 // Copy constructor.
                 allOf(isCopyConstructor(),
                       // Discard constructors that can be used as a copy
                       // constructor because all the other arguments have
                       // default values.
                       parameterCountIs(1))))
             .bind(SpecialFunction),
void UseDefaultCheck::check(const MatchFinder::MatchResult &Result) {
 
   if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(SpecialFunctionDecl)) {
     if (Ctor->getNumParams() == 0) {
       SpecialFunctionName = "default constructor";
     } else {
       if (!isCopyConstructorAndCanBeDefaulted(Result.Context, Ctor))
         return;
       SpecialFunctionName = "copy constructor";
-    }
       // If there are constructor initializers, they must be removed.
       if (Ctor->getNumCtorInitializers() != 0) {
         StartLoc = getColonLoc(Result.Context, Ctor);
         if (!StartLoc.isValid())
           return;
       }
+    }
   } else if (isa<CXXDestructorDecl>(SpecialFunctionDecl)) {
     SpecialFunctionName = "destructor";
   } else {
     if (!isCopyAssignmentAndCanBeDefaulted(Result.Context, SpecialFunctionDecl))
       return;
     SpecialFunctionName = "copy-assignment operator";
   }
 

test/clang-tidy/modernize-use-default.cpp

 public:
   // Constructor with initializer.
   IA() : Field(5) {}
   // Constructor with arguments.
   IA(int Arg1, int Arg2) {}
   int Field;
 };
 
+// Default member initializer
+class DMI {
+public:
+  DMI() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: DMI() = default;
+  int Field = 5;
+};
+
+// Class member
+class CM {
+public:
+  CM() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: CM() = default;
+  OL o;
+};
+
 // Private constructor/destructor.
 class Priv {
   Priv() {}
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
   // CHECK-FIXES: Priv() = default;
   ~Priv() {}
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
   // CHECK-FIXES: ~Priv() = default;