1 files changed, 129 insertions, 0 deletions
diff --git a/clang-tools-extra/test/clang-tidy/abseil-str-cat-append.cpp b/clang-tools-extra/test/clang-tidy/abseil-str-cat-append.cpp
new file mode 100644
index 00000000000..9a12733880a
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/abseil-str-cat-append.cpp
@@ -0,0 +1,129 @@
+// RUN: %check_clang_tidy %s abseil-str-cat-append %t -- -- -I%S -std=c++11
+
+typedef unsigned __INT16_TYPE__ char16;
+typedef unsigned __INT32_TYPE__ char32;
+typedef __SIZE_TYPE__ size;
+
+namespace std {
+template <typename T>
+class allocator {};
+template <typename T>
+class char_traits {};
+template <typename C, typename T, typename A>
+struct basic_string {
+  typedef basic_string<C, T, A> _Type;
+  basic_string();
+  basic_string(const C* p, const A& a = A());
+
+  const C* c_str() const;
+  const C* data() const;
+
+  _Type& append(const C* s);
+  _Type& append(const C* s, size n);
+  _Type& assign(const C* s);
+  _Type& assign(const C* s, size n);
+
+  int compare(const _Type&) const;
+  int compare(const C* s) const;
+  int compare(size pos, size len, const _Type&) const;
+  int compare(size pos, size len, const C* s) const;
+
+  size find(const _Type& str, size pos = 0) const;
+  size find(const C* s, size pos = 0) const;
+  size find(const C* s, size pos, size n) const;
+
+  _Type& insert(size pos, const _Type& str);
+  _Type& insert(size pos, const C* s);
+  _Type& insert(size pos, const C* s, size n);
+
+  _Type& operator+=(const _Type& str);
+  _Type& operator+=(const C* s);
+  _Type& operator=(const _Type& str);
+  _Type& operator=(const C* s);
+};
+
+typedef basic_string<char, std::char_traits<char>, std::allocator<char>> string;
+typedef basic_string<wchar_t, std::char_traits<wchar_t>,
+                     std::allocator<wchar_t>>
+    wstring;
+typedef basic_string<char16, std::char_traits<char16>, std::allocator<char16>>
+    u16string;
+typedef basic_string<char32, std::char_traits<char32>, std::allocator<char32>>
+    u32string;
+}  // namespace std
+
+std::string operator+(const std::string&, const std::string&);
+std::string operator+(const std::string&, const char*);
+std::string operator+(const char*, const std::string&);
+
+bool operator==(const std::string&, const std::string&);
+bool operator==(const std::string&, const char*);
+bool operator==(const char*, const std::string&);
+
+namespace llvm {
+struct StringRef {
+  StringRef(const char* p);
+  StringRef(const std::string&);
+};
+}  // namespace llvm
+
+namespace absl {
+
+struct AlphaNum {
+  AlphaNum(int i);
+  AlphaNum(double f);
+  AlphaNum(const char* c_str);
+  AlphaNum(const std::string& str);
+
+ private:
+  AlphaNum(const AlphaNum&);
+  AlphaNum& operator=(const AlphaNum&);
+};
+
+std::string StrCat(const AlphaNum& A);
+std::string StrCat(const AlphaNum& A, const AlphaNum& B);
+
+template <typename A>
+void Foo(A& a) {
+  a = StrCat(a);
+}
+
+void Bar() {
+  std::string A, B;
+  Foo<std::string>(A);
+
+  std::string C = StrCat(A);
+  A = StrCat(A);
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: call to 'absl::StrCat' has no effect
+  A = StrCat(A, B);
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: call 'absl::StrAppend' instead of 'absl::StrCat' when appending to a string to avoid a performance penalty
+// CHECK-FIXES: {{^}}  StrAppend(&A, B);
+  B = StrCat(A, B);
+
+#define M(X) X = StrCat(X, A)
+  M(B);
+// CHECK-MESSAGES: [[@LINE-1]]:5: warning: call 'absl::StrAppend' instead of 'absl::StrCat' when appending to a string to avoid a performance penalty
+// CHECK-FIXES: #define M(X) X = StrCat(X, A)
+}
+
+void Regression_SelfAppend() {
+  std::string A;
+  A = StrCat(A, A);
+}
+
+}  // namespace absl
+
+void OutsideAbsl() {
+  std::string A, B;
+  A = absl::StrCat(A, B);
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: call 'absl::StrAppend' instead of 'absl::StrCat' when appending to a string to avoid a performance penalty
+// CHECK-FIXES: {{^}}  StrAppend(&A, B);
+}
+
+void OutisdeUsingAbsl() {
+  std::string A, B;
+  using absl::StrCat;
+  A = StrCat(A, B);
+// CHECK-MESSAGES: [[@LINE-1]]:3: warning: call 'absl::StrAppend' instead of 'absl::StrCat' when appending to a string to avoid a performance penalty
+// CHECK-FIXES: {{^}}  StrAppend(&A, B);
+}