[clang-tidy] new check 'readability-isolate-declaration'

Summary:
This patch introduces a new clang-tidy check that matches on all `declStmt` that declare more then one variable
and transform them into one statement per declaration if possible.

It currently only focusses on variable declarations but should be extended to cover more kinds of declarations in the future.
It is related to https://reviews.llvm.org/D27621 and does use it's extensive test-suite. Thank you to firolino for his work!

Reviewers: rsmith, aaron.ballman, alexfh, hokein, kbobyrev

Reviewed By: aaron.ballman

Subscribers: ZaMaZaN4iK, mgehre, nemanjai, kbarton, lebedev.ri, Eugene.Zelenko, mgorny, xazax.hun, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D51949

llvm-svn: 345735

4 files changed, 592 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/readability-isolate-declaration-cxx17.cpp b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration-cxx17.cpp
new file mode 100644
index 00000000000..623eafeee5f
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration-cxx17.cpp
@@ -0,0 +1,103 @@
+// RUN: %check_clang_tidy %s readability-isolate-declaration %t -- -- -std=c++17
+
+template <typename T1, typename T2>
+struct pair {
+  T1 first;
+  T2 second;
+  pair(T1 v1, T2 v2) : first(v1), second(v2) {}
+
+  template <int N>
+  decltype(auto) get() const {
+    if constexpr (N == 0)
+      return first;
+    else if constexpr (N == 1)
+      return second;
+  }
+};
+
+void forbidden_transformations() {
+  if (int i = 42, j = i; i == j)
+    ;
+  switch (int i = 12, j = 14; i)
+    ;
+
+  auto [i, j] = pair<int, int>(42, 42);
+}
+
+struct SomeClass {
+  SomeClass() = default;
+  SomeClass(int value);
+};
+
+namespace std {
+template <typename T>
+class initializer_list {};
+
+template <typename T>
+class vector {
+public:
+  vector() = default;
+  vector(initializer_list<T> init) {}
+};
+
+class string {
+public:
+  string() = default;
+  string(const char *) {}
+};
+
+namespace string_literals {
+string operator""s(const char *, decltype(sizeof(int))) {
+  return string();
+}
+} // namespace string_literals
+} // namespace std
+
+namespace Types {
+typedef int MyType;
+} // namespace Types
+
+int touch1, touch2;
+
+void modern() {
+  auto autoInt1 = 3, autoInt2 = 4;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: auto autoInt1 = 3;
+  // CHECK-FIXES: {{^  }}auto autoInt2 = 4;
+
+  decltype(int()) declnottouch = 4;
+  decltype(int()) declint1 = 5, declint2 = 3;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: decltype(int()) declint1 = 5;
+  // CHECK-FIXES: {{^  }}decltype(int()) declint2 = 3;
+
+  std::vector<int> vectorA = {1, 2}, vectorB = {1, 2, 3}, vectorC({1, 1, 1});
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: std::vector<int> vectorA = {1, 2};
+  // CHECK-FIXES: {{^  }}std::vector<int> vectorB = {1, 2, 3};
+  // CHECK-FIXES: {{^  }}std::vector<int> vectorC({1, 1, 1});
+
+  using uType = int;
+  uType utype1, utype2;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: uType utype1;
+  // CHECK-FIXES: {{^  }}uType utype2;
+
+  Types::MyType mytype1, mytype2, mytype3 = 3;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: Types::MyType mytype1;
+  // CHECK-FIXES: {{^  }}Types::MyType mytype2;
+  // CHECK-FIXES: {{^  }}Types::MyType mytype3 = 3;
+
+  {
+    using namespace std::string_literals;
+
+    std::vector<std::string> s{"foo"s, "bar"s}, t{"foo"s}, u, a({"hey", "you"}), bb = {"h", "a"};
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: std::vector<std::string> s{"foo"s, "bar"s};
+    // CHECK-FIXES: {{^    }}std::vector<std::string> t{"foo"s};
+    // CHECK-FIXES: {{^    }}std::vector<std::string> u;
+    // CHECK-FIXES: {{^    }}std::vector<std::string> a({"hey", "you"});
+    // CHECK-FIXES: {{^    }}std::vector<std::string> bb = {"h", "a"};
+  }
+}
diff --git a/clang-tools-extra/test/clang-tidy/readability-isolate-declaration-fixing.cpp b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration-fixing.cpp
new file mode 100644
index 00000000000..3bd1982b34f
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration-fixing.cpp
@@ -0,0 +1,64 @@
+// RUN: %check_clang_tidy %s readability-isolate-declaration %t
+// XFAIL: *
+
+struct S {
+  int a;
+  const int b;
+  void f() {}
+};
+
+void member_pointers() {
+  // FIXME: Memberpointers are transformed incorrect. Emit only a warning
+  // for now.
+  int S::*p = &S::a, S::*const q = &S::a;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int S::*p = &S::a;
+  // CHECK-FIXES: {{^  }}int S::*const q = &S::a;
+
+  int /* :: */ S::*pp2 = &S::a, var1 = 0;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int /* :: */ S::*pp2 = &S::a;
+  // CHECK-FIXES: {{^  }}int var1 = 0;
+
+  const int S::*r = &S::b, S::*t;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: const int S::*r = &S::b;
+  // CHECK-FIXES: {{^  }}const int S::*t;
+
+  {
+    int S::*mdpa1[2] = {&S::a, &S::a}, var1 = 0;
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: int S::*mdpa1[2] = {&S::a, &S::a};
+    // CHECK-FIXES: {{^    }}int var1 = 0;
+
+    int S ::**mdpa2[2] = {&p, &pp2}, var2 = 0;
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: int S ::**mdpa2[2] = {&p, &pp2};
+    // CHECK-FIXES: {{^    }}int var2 = 0;
+
+    void (S::*mdfp1)() = &S::f, (S::*mdfp2)() = &S::f;
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: void (S::*mdfp1)() = &S::f;
+    // CHECK-FIXES: {{^    }}void (S::*mdfp2)() = &S::f;
+
+    void (S::*mdfpa1[2])() = {&S::f, &S::f}, (S::*mdfpa2)() = &S::f;
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: void (S::*mdfpa1[2])() = {&S::f, &S::f};
+    // CHECK-FIXES: {{^    }}void (S::*mdfpa2)() = &S::f;
+
+    void (S::* * mdfpa3[2])() = {&mdfpa1[0], &mdfpa1[1]}, (S::*mdfpa4)() = &S::f;
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: void (S::* * mdfpa3[2])() = {&mdfpa1[0], &mdfpa1[1]};
+    // CHECK-FIXES: {{^    }}void (S::*mdfpa4)() = &S::f;
+  }
+
+  class CS {
+  public:
+    int a;
+    const int b;
+  };
+  int const CS ::*pp = &CS::a, CS::*const qq = &CS::a;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int const CS ::*pp = &CS::a;
+  // CHECK-FIXES: {{^  }}int const CS::*const qq = &CS::a;
+}
diff --git a/clang-tools-extra/test/clang-tidy/readability-isolate-declaration.c b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration.c
new file mode 100644
index 00000000000..e09a581fa9f
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration.c
@@ -0,0 +1,13 @@
+// RUN: %check_clang_tidy %s readability-isolate-declaration %t
+
+void c_specific() {
+  void (*signal(int sig, void (*func)(int)))(int);
+  int i = sizeof(struct S { int i; });
+  int j = sizeof(struct T { int i; }), k;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int j = sizeof(struct T { int i; });
+  // CHECK-FIXES: {{^  }}int k;
+
+  void g(struct U { int i; } s);                // One decl
+  void h(struct V { int i; } s), m(int i, ...); // Two decls
+}
diff --git a/clang-tools-extra/test/clang-tidy/readability-isolate-declaration.cpp b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration.cpp
new file mode 100644
index 00000000000..65d1d32014e
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/readability-isolate-declaration.cpp
@@ -0,0 +1,412 @@
+// RUN: %check_clang_tidy %s readability-isolate-declaration %t
+
+void f() {
+  int i;
+}
+
+void f2() {
+  int i, j, *k, lala = 42;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int i;
+  // CHECK-FIXES: {{^  }}int j;
+  // CHECK-FIXES: {{^  }}int *k;
+  // CHECK-FIXES: {{^  }}int lala = 42;
+
+  int normal, weird = /* comment */ 42;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int normal;
+  // CHECK-FIXES: {{^  }}int weird = /* comment */ 42;
+
+  int /* here is a comment */ v1,
+      // another comment
+      v2 = 42 // Ok, more comments
+      ;
+  // CHECK-MESSAGES: [[@LINE-4]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int /* here is a comment */ v1;
+  // CHECK-FIXES: {{^  }}int /* here is a comment */ // another comment
+  // CHECK-FIXES: {{^      }}v2 = 42 // Ok, more comments
+  // CHECK-FIXES: {{^      }};
+
+  auto int1 = 42, int2 = 0, int3 = 43;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: auto int1 = 42;
+  // CHECK-FIXES: {{^  }}auto int2 = 0;
+  // CHECK-FIXES: {{^  }}auto int3 = 43;
+
+  decltype(auto) ptr1 = &int1, ptr2 = &int1;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: decltype(auto) ptr1 = &int1;
+  // CHECK-FIXES: {{^  }}decltype(auto) ptr2 = &int1;
+
+  decltype(k) ptr3 = &int1, ptr4 = &int1;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: decltype(k) ptr3 = &int1;
+  // CHECK-FIXES: {{^  }}decltype(k) ptr4 = &int1;
+}
+
+void f3() {
+  int i, *pointer1;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int i;
+  // CHECK-FIXES: {{^  }}int *pointer1;
+  //
+  int *pointer2 = nullptr, *pointer3 = &i;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int *pointer2 = nullptr;
+  // CHECK-FIXES: {{^  }}int *pointer3 = &i;
+
+  int *(i_ptr) = nullptr, *((i_ptr2));
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int *(i_ptr) = nullptr;
+  // CHECK-FIXES: {{^  }}int *((i_ptr2));
+
+  float(*f_ptr)[42], (((f_value))) = 42;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: float (*f_ptr)[42];
+  // CHECK-FIXES: {{^  }}float (((f_value))) = 42;
+
+  float(((*f_ptr2)))[42], ((*f_ptr3)), f_value2 = 42.f;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: float (((*f_ptr2)))[42];
+  // CHECK-FIXES: {{^  }}float ((*f_ptr3));
+  // CHECK-FIXES: {{^  }}float f_value2 = 42.f;
+
+  float(((*f_ptr4)))[42], *f_ptr5, ((f_value3));
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: float (((*f_ptr4)))[42];
+  // CHECK-FIXES: {{^  }}float *f_ptr5;
+  // CHECK-FIXES: {{^  }}float ((f_value3));
+
+  void(((*f2))(int)), (*g2)(int, float);
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: void (((*f2))(int));
+  // CHECK-FIXES: {{^  }}void (*g2)(int, float);
+
+  float(*(*(*f_ptr6)))[42], (*f_ptr7);
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: float (*(*(*f_ptr6)))[42];
+  // CHECK-FIXES: {{^  }}float (*f_ptr7);
+}
+
+void f4() {
+  double d = 42. /* foo */, z = 43., /* hi */ y, c /* */ /*  */, l = 2.;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: double d = 42. /* foo */;
+  // CHECK-FIXES: {{^  }}double z = 43.;
+  // CHECK-FIXES: {{^  }}double /* hi */ y;
+  // CHECK-FIXES: {{^  }}double c /* */ /*  */;
+  // CHECK-FIXES: {{^  }}double l = 2.;
+}
+
+struct SomeClass {
+  SomeClass() = default;
+  SomeClass(int value);
+};
+
+class Point {
+  double x;
+  double y;
+
+public:
+  Point(double x, double y) : x(x), y(y) {}
+};
+
+class Rectangle {
+  Point TopLeft;
+  Point BottomRight;
+
+public:
+  Rectangle(Point TopLeft, Point BottomRight) : TopLeft(TopLeft), BottomRight(BottomRight) {}
+};
+
+void f5() {
+  SomeClass v1, v2(42), v3{42}, v4(42.5);
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: SomeClass v1;
+  // CHECK-FIXES: {{^  }}SomeClass v2(42);
+  // CHECK-FIXES: {{^  }}SomeClass v3{42};
+  // CHECK-FIXES: {{^  }}SomeClass v4(42.5);
+
+  SomeClass v5 = 42, *p1 = nullptr;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: SomeClass v5 = 42;
+  // CHECK-FIXES: {{^  }}SomeClass *p1 = nullptr;
+
+  Point P1(0., 2.), P2{2., 0.};
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: Point P1(0., 2.);
+  // CHECK-FIXES: {{^  }}Point P2{2., 0.};
+
+  Rectangle R1({0., 0.}, {1., -2.}), R2{{0., 1.}, {1., 0.}}, R3(P1, P2), R4{P1, P2};
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: Rectangle R1({0., 0.}, {1., -2.});
+  // CHECK-FIXES: {{^  }}Rectangle R2{{[{][{]}}0., 1.}, {1., 0.{{[}][}]}};
+  // CHECK-FIXES: {{^  }}Rectangle R3(P1, P2);
+  // CHECK-FIXES: {{^  }}Rectangle R4{P1, P2};
+}
+
+void f6() {
+  int array1[] = {1, 2, 3, 4}, array2[] = {1, 2, 3}, value1, value2 = 42;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int array1[] = {1, 2, 3, 4};
+  // CHECK-FIXES: {{^  }}int array2[] = {1, 2, 3};
+  // CHECK-FIXES: {{^  }}int value1;
+  // CHECK-FIXES: {{^  }}int value2 = 42;
+}
+
+template <typename T>
+struct TemplatedType {
+  TemplatedType() = default;
+  TemplatedType(T value);
+};
+
+void f7() {
+  TemplatedType<int> TT1(42), TT2{42}, TT3;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: TemplatedType<int> TT1(42);
+  // CHECK-FIXES: {{^  }}TemplatedType<int> TT2{42};
+  // CHECK-FIXES: {{^  }}TemplatedType<int> TT3;
+  //
+  TemplatedType<int *> *TT4(nullptr), TT5, **TT6 = nullptr, *const *const TT7{nullptr};
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: TemplatedType<int *> *TT4(nullptr);
+  // CHECK-FIXES: {{^  }}TemplatedType<int *> TT5;
+  // CHECK-FIXES: {{^  }}TemplatedType<int *> **TT6 = nullptr;
+  // CHECK-FIXES: {{^  }}TemplatedType<int *> *const *const TT7{nullptr};
+
+  TemplatedType<int &> **TT8(nullptr), *TT9;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: TemplatedType<int &> **TT8(nullptr);
+  // CHECK-FIXES: {{^  }}TemplatedType<int &> *TT9;
+
+  TemplatedType<int *> TT10{nullptr}, *TT11(nullptr);
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: TemplatedType<int *> TT10{nullptr};
+  // CHECK-FIXES: {{^  }}TemplatedType<int *> *TT11(nullptr);
+}
+
+void forbidden_transformations() {
+  for (int i = 0, j = 42; i < j; ++i)
+    ;
+}
+
+#define NULL 0
+#define MY_NICE_TYPE int **
+#define VAR_NAME(name) name##__LINE__
+#define A_BUNCH_OF_VARIABLES int m1 = 42, m2 = 43, m3 = 44;
+
+void macros() {
+  int *p1 = NULL, *p2 = NULL;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int *p1 = NULL;
+  // CHECK-FIXES: {{^  }}int *p2 = NULL;
+
+  // Macros are involved, so there will be no transformation
+  MY_NICE_TYPE p3, v1, v2;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+
+  int VAR_NAME(v3),
+      VAR_NAME(v4),
+      VAR_NAME(v5);
+  // CHECK-MESSAGES: [[@LINE-3]]:3: warning: multiple declarations in a single statement reduces readability
+
+  A_BUNCH_OF_VARIABLES
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+
+  int Unconditional,
+  // Explanatory comment.
+#if CONFIGURATION
+      IfConfigured = 42,
+#else
+      IfConfigured = 0;
+#endif
+  // CHECK-MESSAGES: [[@LINE-7]]:3: warning: multiple declarations in a single statement reduces readability
+}
+
+void dontTouchParameter(int param1, int param2) {}
+
+struct StructOne {
+  StructOne() {}
+  StructOne(int b) {}
+
+  int member1, member2;
+  // TODO: Handle FieldDecl's as well
+};
+
+using PointerType = int;
+
+struct {
+  int i;
+} AS1, AS2;
+struct TemT {
+  template <typename T>
+  T *getAs() {
+    return nullptr;
+  }
+} TT1, TT2;
+
+void complex_typedefs() {
+  typedef int *IntPtr;
+  typedef int ArrayType[2];
+  typedef int FunType(void);
+
+  IntPtr intptr1, intptr2 = nullptr, intptr3;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: IntPtr intptr1;
+  // CHECK-FIXES: {{^  }}IntPtr intptr2 = nullptr;
+  // CHECK-FIXES: {{^  }}IntPtr intptr3;
+
+  IntPtr *DoublePtr1 = nullptr, **TriplePtr, SinglePtr = nullptr;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: IntPtr *DoublePtr1 = nullptr;
+  // CHECK-FIXES: {{^  }}IntPtr **TriplePtr;
+  // CHECK-FIXES: {{^  }}IntPtr SinglePtr = nullptr;
+
+  IntPtr intptr_array1[2], intptr_array2[4] = {nullptr, nullptr, nullptr, nullptr};
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: IntPtr intptr_array1[2];
+  // CHECK-FIXES: {{^  }}IntPtr intptr_array2[4] = {nullptr, nullptr, nullptr, nullptr};
+
+  ArrayType arraytype1, arraytype2 = {1}, arraytype3;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: ArrayType arraytype1;
+  // CHECK-FIXES: {{^  }}ArrayType arraytype2 = {1};
+  // CHECK-FIXES: {{^  }}ArrayType arraytype3;
+
+  // Don't touch function declarations.
+  FunType funtype1, funtype2, functype3;
+
+  for (int index1 = 0, index2 = 0;;) {
+    int localFor1 = 1, localFor2 = 2;
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: int localFor1 = 1;
+    // CHECK-FIXES: {{^    }}int localFor2 = 2;
+  }
+
+  StructOne s1, s2(23), s3, s4(3), *sptr = new StructOne(2);
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: StructOne s1;
+  // CHECK-FIXES: {{^  }}StructOne s2(23);
+  // CHECK-FIXES: {{^  }}StructOne s3;
+  // CHECK-FIXES: {{^  }}StructOne s4(3);
+  // CHECK-FIXES: {{^  }}StructOne *sptr = new StructOne(2);
+
+  struct StructOne cs1, cs2(42);
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: struct StructOne cs1;
+  // CHECK-FIXES: {{^  }}struct StructOne cs2(42);
+
+  int *ptrArray[3], dummy, **ptrArray2[5], twoDim[2][3], *twoDimPtr[2][3];
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int *ptrArray[3];
+  // CHECK-FIXES: {{^  }}int dummy;
+  // CHECK-FIXES: {{^  }}int **ptrArray2[5];
+  // CHECK-FIXES: {{^  }}int twoDim[2][3];
+  // CHECK-FIXES: {{^  }}int *twoDimPtr[2][3];
+
+  {
+    void f1(int), g1(int, float);
+  }
+
+  {
+    void gg(int, float);
+
+    void (*f2)(int), (*g2)(int, float) = gg;
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: void (*f2)(int);
+    // CHECK-FIXES: {{^    }}void (*g2)(int, float) = gg;
+
+    void /*(*/ (/*(*/ *f3)(int), (*g3)(int, float);
+    // CHECK-MESSAGES: [[@LINE-1]]:5: warning: multiple declarations in a single statement reduces readability
+    // CHECK-FIXES: void /*(*/ (/*(*/ *f3)(int);
+    // CHECK-FIXES: {{^    }}void /*(*/ (*g3)(int, float);
+  }
+
+  // clang-format off
+  auto returner = []() { return int(32); };
+  int intfunction = returner(), intarray[] =
+          {
+                  1,
+                  2,
+                  3,
+                  4
+          }, bb = 4;
+  // CHECK-MESSAGES: [[@LINE-7]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int intfunction = returner();
+  // CHECK-FIXES: {{^  }}int intarray[] =
+  // CHECK-FIXES: {{^          }}{
+  // CHECK-FIXES: {{^                  }}1,
+  // CHECK-FIXES: {{^                  }}2,
+  // CHECK-FIXES: {{^                  }}3,
+  // CHECK-FIXES: {{^                  }}4
+  // CHECK-FIXES: {{^          }}};
+  // CHECK-FIXES: {{^  }}int bb = 4;
+  // clang-format on
+
+  TemT *T1 = &TT1, *T2 = &TT2;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: TemT *T1 = &TT1;
+  // CHECK-FIXES: {{^  }}TemT *T2 = &TT2;
+
+  const PointerType *PT1 = T1->getAs<PointerType>(),
+                    *PT2 = T2->getAs<PointerType>();
+  // CHECK-MESSAGES: [[@LINE-2]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: const PointerType *PT1 = T1->getAs<PointerType>();
+  // CHECK-FIXES: {{^  }}const PointerType *PT2 = T2->getAs<PointerType>();
+
+  const int *p1 = nullptr;
+  const int *p2 = nullptr;
+
+  const int *&pref1 = p1, *&pref2 = p2;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: const int *&pref1 = p1;
+  // CHECK-FIXES: {{^  }}const int *&pref2 = p2;
+
+  // clang-format off
+  const char *literal1 = "clang"   "test"\
+                         "one",
+             *literal2 = "empty", literal3[] = "three";
+  // CHECK-MESSAGES: [[@LINE-3]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: const char *literal1 = "clang"   "test"\
+  // CHECK-FIXES: {{^                         }}"one";
+  // CHECK-FIXES: {{^  }}const char *literal2 = "empty";
+  // CHECK-FIXES: {{^  }}const char literal3[] = "three";
+  // clang-format on
+}
+
+void g() try {
+  int i, j;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: int i;
+  // CHECK-FIXES: {{^  }}int j;
+} catch (...) {
+}
+
+struct S {
+  int a;
+  const int b;
+  void f() {}
+};
+
+void memberPointers() {
+  typedef const int S::*MemPtr;
+  MemPtr aaa = &S::a, bbb = &S::b;
+  // CHECK-MESSAGES: [[@LINE-1]]:3: warning: multiple declarations in a single statement reduces readability
+  // CHECK-FIXES: MemPtr aaa = &S::a;
+  // CHECK-FIXES: {{^  }}MemPtr bbb = &S::b;
+}
+
+typedef int *tptr, tbt;
+typedef int (&tfp)(int, long), tarr[10];
+typedef int tarr2[10], tct;
+
+template <typename A, typename B>
+void should_not_be_touched(A, B);
+
+int variable, function(void);
+
+int call_func_with_sideeffect();
+void bad_if_decl() {
+  if (true)
+    int i, j, k = call_func_with_sideeffect();
+}