Warn on explicit copy constructors.

Summary:
The Google C++ Style Guide doesn't require copy constructors to be
declared explicit, but some people do this by mistake. Make this check detect
and fix such cases.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D3541

llvm-svn: 207531

clang-tools-extra/unittests/clang-tidy/GoogleModuleTest.cpp

@@ -37,6 +37,16 @@ TEST(ExplicitConstructorCheckTest, OutOfLineDefinitions) {
                 "class C { C(int i); }; C::C(int i) {}"));
 }
 
+TEST(ExplicitConstructorCheckTest, RemoveExplicit) {
+  EXPECT_EQ("class A { A(const A&); };\n"
+            "class B { /*asdf*/  B(const B&); };\n"
+            "class C { /*asdf*/  C(const C&); };",
+            runCheckOnCode<ExplicitConstructorCheck>(
+                "class A { explicit    A(const A&); };\n"
+                "class B { explicit   /*asdf*/  B(const B&); };\n"
+                "class C { explicit/*asdf*/  C(const C&); };"));
+}
+
 } // namespace test
 } // namespace tidy
 } // namespace clang