[clang-tidy] Make 'modernize-use-nullptr' check work on multiple nested implicit cast expressions.

Summary:
For some test cases like:

```
 int func(int, void*, void*);
(double)func(0, 0, 0);
```

The AST contains several `ImplicitCastExpr`s, so we should not only check on the first sub expression.

```
 `-CStyleCastExpr 0x7fe43a088938 <line:6:3, col:24> 'double' <NoOp>
      `-ImplicitCastExpr 0x7fe43a088920 <col:11, col:24> 'double' <IntegralToFloating>
        `-CallExpr 0x7fe43a0888a0 <col:11, col:24> 'int'
          |-ImplicitCastExpr 0x7fe43a088888 <col:11> 'int (*)(int, void *, void *)' <FunctionToPointerDecay>
          | `-DeclRefExpr 0x7fe43a0887d8 <col:11> 'int (int, void *, void *)' lvalue Function 0x7fe43a0886f0 'func1' 'int (int, void *, void *)'
          |-IntegerLiteral 0x7fe43a088800 <col:17> 'int' 0
          |-ImplicitCastExpr 0x7fe43a0888e0 <col:20> 'void *' <NullToPointer>
          | `-IntegerLiteral 0x7fe43a088820 <col:20> 'int' 0
          `-ImplicitCastExpr 0x7fe43a0888f8 <col:23> 'void *' <NullToPointer>
            `-IntegerLiteral 0x7fe43a088840 <col:23> 'int' 0
```

Reviewers: alexfh

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D17849

llvm-svn: 262698

1 files changed, 15 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/modernize-use-nullptr-basic.cpp b/clang-tools-extra/test/clang-tidy/modernize-use-nullptr-basic.cpp
index 6c317d761ac..7a953a70c77 100644
--- a/clang-tools-extra/test/clang-tidy/modernize-use-nullptr-basic.cpp
+++ b/clang-tools-extra/test/clang-tidy/modernize-use-nullptr-basic.cpp
@@ -327,6 +327,21 @@ void test_const_pointers() {
   // CHECK-FIXES: const int *const_p6 = static_cast<int*>(t ? t : static_cast<int*>(nullptr));
 }
 
+void test_nested_implicit_cast_expr() {
+  int func0(void*, void*);
+  int func1(int, void*, void*);
+
+  (double)func1(0, 0, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:20: warning: use nullptr
+  // CHECK-MESSAGES: :[[@LINE-2]]:23: warning: use nullptr
+  // CHECK-FIXES: (double)func1(0, nullptr, nullptr);
+  (double)func1(func0(0, 0), 0, 0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:23: warning: use nullptr
+  // CHECK-MESSAGES: :[[@LINE-2]]:26: warning: use nullptr
+  // CHECK-MESSAGES: :[[@LINE-3]]:30: warning: use nullptr
+  // CHECK-MESSAGES: :[[@LINE-4]]:33: warning: use nullptr
+  // CHECK-FIXES: (double)func1(func0(nullptr, nullptr), nullptr, nullptr);
+}
 
 // FIXME: currently, the check doesn't work as it should with templates.
 template<typename T>