[clang-tidy] Const std::move() argument ClangTidy check

ClangTidy check for finding cases when std::move() is called with const or
trivially copyable arguments, that doesn't lead to any move or argument but it
makes copy. FixIt generates patch for removing call of std::move().

Patch by Vadym Doroshenko! (+ a couple of minor fixes)

Differential Revision: http://reviews.llvm.org/D12031

llvm-svn: 254070

1 files changed, 73 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/move-const-arg.cpp b/clang-tools-extra/test/clang-tidy/move-const-arg.cpp
new file mode 100644
index 00000000000..015c1a39049
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/move-const-arg.cpp
@@ -0,0 +1,73 @@
+// RUN: %check_clang_tidy %s misc-move-const-arg %t -- -- -std=c++11
+
+namespace std {
+template <typename> struct remove_reference;
+
+template <typename _Tp> struct remove_reference { typedef _Tp type; };
+
+template <typename _Tp> struct remove_reference<_Tp &> { typedef _Tp type; };
+
+template <typename _Tp> struct remove_reference<_Tp &&> { typedef _Tp type; };
+
+template <typename _Tp>
+constexpr typename std::remove_reference<_Tp>::type &&move(_Tp &&__t);
+
+} // namespace std
+
+class A {
+public:
+  A() {}
+  A(const A &rhs) {}
+  A(A &&rhs) {}
+};
+
+int f1() {
+  return std::move(42);
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: std::move of the expression of trivially-copyable type has no effect; remove std::move() [misc-move-const-arg]
+  // CHECK-FIXES: return 42;
+}
+
+int f2(int x2) {
+  return std::move(x2);
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: std::move of the variable of trivially-copyable type
+  // CHECK-FIXES: return x2;
+}
+
+int *f3(int *x3) {
+  return std::move(x3);
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: std::move of the variable of trivially-copyable type
+  // CHECK-FIXES: return x3;
+}
+
+A f4(A x4) { return std::move(x4); }
+
+A f5(const A x5) {
+  return std::move(x5);
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: std::move of the const variable
+  // CHECK-FIXES: return x5;
+}
+
+template <typename T> T f6(const T x6) { return std::move(x6); }
+
+void f7() { int a = f6(10); }
+
+#define M1(x) x
+void f8() {
+  const A a;
+  M1(A b = std::move(a);)
+  // CHECK-MESSAGES: :[[@LINE-1]]:12: warning: std::move of the const variable
+  // CHECK-FIXES: M1(A b = a;)
+}
+
+#define M2(x) std::move(x)
+int f9() { return M2(1); }
+
+template <typename T> T f10(const int x10) {
+  return std::move(x10);
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: std::move of the const variable
+  // CHECK-FIXES: return x10;
+}
+void f11() {
+  f10<int>(1);
+  f10<double>(1);
+}