[clang-tidy] Use cxxStdInitializerListExpr in modernize-use-emplace

[kuhar]

Summary

Use the cxxStdInitializerListExp matcher from ASTMatchers.h instead of a local one.

[aaron.ballman]

LGTM!

clang-tidy/modernize/UseEmplaceCheck.cpp

 namespace tidy {
 namespace modernize {
 
 namespace {
 AST_MATCHER(DeclRefExpr, hasExplicitTemplateArgs) {
   return Node.hasExplicitTemplateArgs();
 }
 
-namespace impl {
-// FIXME: This matcher should be replaced by a matcher from ASTMatcher.h
-const ast_matchers::internal::VariadicDynCastAllOfMatcher<Stmt,
-    CXXStdInitializerListExpr> cxxStdInitializerListExpr;
-} // namespace impl
-
 const auto DefaultContainersWithPushBack =
     "::std::vector; ::std::list; ::std::deque";
 const auto DefaultSmartPointers =
     "::std::shared_ptr; ::std::unique_ptr; ::std::auto_ptr; ::std::weak_ptr";
 } // namespace
 
 UseEmplaceCheck::UseEmplaceCheck(StringRef Name, ClangTidyContext *Context)
     : ClangTidyCheck(Name, Context),
void UseEmplaceCheck::registerMatchers(MatchFinder *Finder) {
   // We would call another constructor.
   auto ConstructingDerived =
       hasParent(implicitCastExpr(hasCastKind(CastKind::CK_DerivedToBase)));
 
   // emplace_back can't access private constructor.
   auto IsPrivateCtor = hasDeclaration(cxxConstructorDecl(isPrivate()));
 
   auto HasInitList = anyOf(has(ignoringImplicit(initListExpr())),
-                           has(impl::cxxStdInitializerListExpr()));
-  // FIXME: Replace internal C++ initializer list matcher with one from
-  // ASTMatchers.h
+                           has(cxxStdInitializerListExpr()));
 
   // FIXME: Discard 0/NULL (as nullptr), static inline const data members,
   // overloaded functions and template names.
   auto SoughtConstructExpr =
       cxxConstructExpr(
           unless(anyOf(IsCtorOfSmartPtr, HasInitList, BitFieldAsArgument,
                        InitializerListAsArgument, NewExprAsArgument,
                        ConstructingDerived, IsPrivateCtor)))