From 2c7ea1c4c5f7dde562bac684a59ad67f1f062726 Mon Sep 17 00:00:00 2001
From: Nathan James <n.james93@hotmail.co.uk>
Date: Fri, 3 Apr 2020 19:40:59 +0100
Subject: [PATCH] [clang-tidy] Address false positive in
 modernize-use-default-member-init

Summary: Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=45363 | incorrect warning emitted by "modernize-use-default-member-init" (new to 10.0.0) ]].

Reviewers: aaron.ballman, alexfh, gribozavr2

Reviewed By: aaron.ballman

Subscribers: xazax.hun, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77199
---
 .../clang-tidy/modernize/UseDefaultMemberInitCheck.cpp   | 16 ++++++++++++++--
 .../checkers/modernize-use-default-member-init.cpp       | 14 ++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
index cb275ab..04cc7aa 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp
@@ -17,6 +17,12 @@ namespace clang {
 namespace tidy {
 namespace modernize {
 
+namespace {
+AST_MATCHER_P(InitListExpr, initCountIs, unsigned, N) {
+  return Node.getNumInits() == N;
+}
+} // namespace
+
 static StringRef getValueOfValueInit(const QualType InitType) {
   switch (InitType->getScalarTypeKind()) {
   case Type::STK_CPointer:
@@ -190,7 +196,7 @@ void UseDefaultMemberInitCheck::storeOptions(
 }
 
 void UseDefaultMemberInitCheck::registerMatchers(MatchFinder *Finder) {
-  auto Init =
+  auto InitBase =
       anyOf(stringLiteral(), characterLiteral(), integerLiteral(),
             unaryOperator(hasAnyOperatorName("+", "-"),
                           hasUnaryOperand(integerLiteral())),
@@ -198,7 +204,13 @@ void UseDefaultMemberInitCheck::registerMatchers(MatchFinder *Finder) {
             unaryOperator(hasAnyOperatorName("+", "-"),
                           hasUnaryOperand(floatLiteral())),
             cxxBoolLiteral(), cxxNullPtrLiteralExpr(), implicitValueInitExpr(),
-            initListExpr(), declRefExpr(to(enumConstantDecl())));
+            declRefExpr(to(enumConstantDecl())));
+
+  auto Init =
+      anyOf(initListExpr(anyOf(
+                allOf(initCountIs(1), hasInit(0, ignoringImplicit(InitBase))),
+                initCountIs(0))),
+            InitBase);
 
   Finder->addMatcher(
       cxxConstructorDecl(
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 3570fcf..60344e0 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
@@ -432,3 +432,17 @@ private:
   // CHECK-MESSAGES: :[[@LINE-2]]:10: warning: use default member initializer for 'k' [modernize-use-default-member-init]
   // CHECK-FIXES: int i{5}, k{8};
 };
+
+struct PR45363 {
+  // Ensure no warning is emitted here
+  PR45363(int i = 0) : m_i{i} {}
+  int m_i;
+};
+
+struct EmptyBracedIntDefault {
+  EmptyBracedIntDefault() : m_i{} {}
+  int m_i;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: use default member initializer for 'm_i' [modernize-use-default-member-init]
+  // CHECK-FIXES:      {{^  }}EmptyBracedIntDefault()  {}
+  // CHECK-FIXES-NEXT: {{^  }}int m_i{};
+};
-- 
2.7.4