Improve the 'modernize-use-default-member-init'

We want to deal with non-default constructors that just happen to
contain constant initializers. There was already a negative test case,
it is now a positive one. We find and refactor this case:

struct PositiveNotDefaultInt {
  PositiveNotDefaultInt(int) : i(7) {}
  int i;
};

4 files changed, 56 insertions, 18 deletions

diff --git a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
index 6e7e37236b19..d57a88d66883 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
@@ -212,17 +212,14 @@ void UseDefaultMemberInitCheck::registerMatchers(MatchFinder *Finder) {
             InitBase);
 
   Finder->addMatcher(
-      cxxConstructorDecl(
-          isDefaultConstructor(),
-          forEachConstructorInitializer(
-              cxxCtorInitializer(
-                  forField(unless(anyOf(getLangOpts().CPlusPlus20
-                                            ? unless(anything())
-                                            : isBitField(),
-                                        hasInClassInitializer(anything()),
-                                        hasParent(recordDecl(isUnion()))))),
-                  withInitializer(Init))
-                  .bind("default"))),
+      cxxConstructorDecl(forEachConstructorInitializer(
+          cxxCtorInitializer(
+              forField(unless(anyOf(
+                  getLangOpts().CPlusPlus20 ? unless(anything()) : isBitField(),
+                  hasInClassInitializer(anything()),
+                  hasParent(recordDecl(isUnion()))))),
+              withInitializer(Init))
+              .bind("default"))),
       this);
 
   Finder->addMatcher(
@@ -248,6 +245,14 @@ 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 = dyn_cast<CXXRecordDecl>(Field->getParent());
+  if (llvm::count_if(ClassDecl->ctors(), [](const CXXConstructorDecl *Ctor) {
+        return !Ctor->isCopyOrMoveConstructor();
+      }) > 1)
+    return;
+
   SourceLocation StartLoc = Field->getBeginLoc();
   if (StartLoc.isMacroID() && IgnoreMacros)
     return;
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 6f8a25e0d04f..5d330d1d2e3c 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -73,6 +73,9 @@ Improvements to clang-tidy
 - Added support for `NOLINTBEGIN` ... `NOLINTEND` comments to suppress
   Clang-Tidy warnings over multiple lines.
 
+- Generalized the `modernize-use-default-member-init` check to handle non-default
+  constructors.
+
 New checks
 ^^^^^^^^^^
 
diff --git a/clang-tools-extra/docs/clang-tidy/checks/modernize-use-default-member-init.rst b/clang-tools-extra/docs/clang-tidy/checks/modernize-use-default-member-init.rst
index a77415301ef6..2d3ed3801493 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/modernize-use-default-member-init.rst
+++ b/clang-tools-extra/docs/clang-tidy/checks/modernize-use-default-member-init.rst
@@ -3,7 +3,7 @@
 modernize-use-default-member-init
 =================================
 
-This check converts a default constructor's member initializers into the new
+This check converts constructors' member initializers into the new
 default member initializers in C++11. Other member initializers that match the
 default member initializer are removed. This can reduce repeated code or allow
 use of '= default'.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize-use-default-member-init.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize-use-default-member-init.cpp
index 27c947820d9c..464cfbdeacb8 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize-use-default-member-init.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize-use-default-member-init.cpp
@@ -45,6 +45,42 @@ struct PositiveInt {
   // CHECK-FIXES: int j{1};
 };
 
+struct PositiveNotDefaultInt {
+  PositiveNotDefaultInt(int) : i(7) {}
+  // CHECK-FIXES: PositiveNotDefaultInt(int)  {}
+  int i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'i'
+  // CHECK-FIXES: int i{7};
+};
+
+// We cannot reconcile these initializers.
+struct TwoConstructors {
+    TwoConstructors(int) : i(7) {}
+    TwoConstructors(int, int) : i(8) {}
+    int i;
+};
+
+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) {}
+// CHECK-FIXES: PositiveNotDefaultOOLInt::PositiveNotDefaultOOLInt(int)  {}
+
+struct PositiveNotDefaultOOLInt2 {
+  PositiveNotDefaultOOLInt2(int, int);
+  int i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'i'
+  // CHECK-FIXES: int i{7};
+  int j;
+};
+
+PositiveNotDefaultOOLInt2::PositiveNotDefaultOOLInt2(int, int arg) : i(7), j(arg) {}
+// CHECK-FIXES: PositiveNotDefaultOOLInt2::PositiveNotDefaultOOLInt2(int, int arg) :  j(arg) {}
+
 struct PositiveUnaryMinusInt {
   PositiveUnaryMinusInt() : j(-1) {}
   // CHECK-FIXES: PositiveUnaryMinusInt()  {}
@@ -234,12 +270,6 @@ struct NegativeBitField
   int i : 5;
 };
 
-struct NegativeNotDefaultInt
-{
-  NegativeNotDefaultInt(int) : i(7) {}
-  int i;
-};
-
 struct NegativeDefaultArg
 {
   NegativeDefaultArg(int i = 4) : i(i) {}