Add modernize-use-default check to clang-tidy.

Summary:
Add a check that replaces empty bodies of special member functions with '= default;'.
For now, it is only implemented for the default constructor and the destructor, which are the easier cases.
The copy-constructor and the copy-assignment operator cases will be implemented later.

I applied this check to the llvm code base and found 627 warnings (385 in llvm, 9 in compiler-rt, 220 in clang and 13 in clang-tools-extra).
Applying the fixes didn't break any build or test, it only caused a -Wpedantic warning in lib/Target/Mips/MipsOptionRecord.h:33 becaused it replaced
virtual ~MipsOptionRecord(){}; to virtual ~MipsOptionRecord()= default;;

Reviewers: klimek

Subscribers: george.burgess.iv, Eugene.Zelenko, alexfh, cfe-commits

Differential Revision: http://reviews.llvm.org/D13871

llvm-svn: 250897

1 files changed, 137 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/modernize-use-default.cpp b/clang-tools-extra/test/clang-tidy/modernize-use-default.cpp
new file mode 100644
index 00000000000..9e4a5513336
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/modernize-use-default.cpp
@@ -0,0 +1,137 @@
+// RUN: %python %S/check_clang_tidy.py %s modernize-use-default %t
+
+class A {
+public:
+  A();
+  ~A();
+};
+
+A::A() {}
+// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: use '= default' to define a trivial default constructor [modernize-use-default]
+// CHECK-FIXES: A::A() = default;
+A::~A() {}
+// CHECK-MESSAGES: :[[@LINE-1]]:1: warning: use '= default' to define a trivial destructor [modernize-use-default]
+// CHECK-FIXES: A::~A() = default;
+
+// Inline definitions.
+class B {
+public:
+  B() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: B() = default;
+  ~B() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: ~B() = default;
+};
+
+void f();
+
+class C {
+public:
+  // Non-empty constructor body.
+  C() { f(); }
+  // Non-empty destructor body.
+  ~C() { f(); }
+};
+
+class D {
+public:
+  // Constructor with initializer.
+  D() : Field(5) {}
+  // Constructor with arguments.
+  D(int Arg1, int Arg2) {}
+  int Field;
+};
+
+// Private constructor/destructor.
+class E {
+  E() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: E() = default;
+  ~E() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: ~E() = default;
+};
+
+// struct.
+struct F {
+  F() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: F() = default;
+  ~F() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: F() = default;
+};
+
+// Deleted constructor/destructor.
+class G {
+public:
+  G() = delete;
+  ~G() = delete;
+};
+
+// Do not remove other keywords.
+class H {
+public:
+  explicit H() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: explicit H() = default;
+  virtual ~H() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: virtual ~H() = default;
+};
+
+// Nested class.
+struct I {
+  struct II {
+    II() {}
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: use '= default'
+    // CHECK-FIXES: II() = default;
+    ~II() {}
+    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: use '= default'
+    // CHECK-FIXES: ~II() = default;
+  };
+  int Int;
+};
+
+// Class template.
+template <class T>
+class J {
+public:
+  J() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: J() = default;
+  ~J() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: ~J() = default;
+};
+
+// Non user-provided constructor/destructor.
+struct K {
+  int Int;
+};
+void g() {
+  K *PtrK = new K();
+  PtrK->~K();
+  delete PtrK;
+}
+
+// Already using default.
+struct L {
+  L() = default;
+  ~L() = default;
+};
+struct M {
+  M();
+  ~M();
+};
+M::M() = default;
+M::~M() = default;
+
+// Delegating constructor and overriden destructor.
+struct N : H {
+  N() : H() {}
+  ~N() override {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: ~N() override = default;
+};