[clang-tidy] Fix a regression issue introduced by r285239.

Summary:
r285239 changes the behavior of AST CXXDefaultArgExpr node.

Update `modernize-use-nullptr` to handle CXXDefaultArgExpr correctly.

Reviewers: alexfh

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D26301

llvm-svn: 286156

1 files changed, 8 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
index 059c0c5073f..401b10b7f8c 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -190,13 +190,21 @@ public:
   // within a cast expression.
   bool VisitStmt(Stmt *S) {
     CastExpr *C = dyn_cast<CastExpr>(S);
+    // Catch the castExpr inside cxxDefaultArgExpr.
+    if (auto *E = dyn_cast<CXXDefaultArgExpr>(S))
+      C = dyn_cast<CastExpr>(E->getExpr());
     if (!C) {
       FirstSubExpr = nullptr;
       return true;
     }
+
     if (!FirstSubExpr)
       FirstSubExpr = C->getSubExpr()->IgnoreParens();
 
+    // Ignore the expr if it is already a nullptr literal expr.
+    if (isa<CXXNullPtrLiteralExpr>(FirstSubExpr))
+      return true;
+
     if (C->getCastKind() != CK_NullToPointer &&
         C->getCastKind() != CK_NullToMemberPointer) {
       return true;