[clang-tidy] Add a checker for code that looks like a delegate constructors but doesn't delegate.

Summary:
class Foo {
  Foo() {
    Foo(42); // oops
  }
  Foo(int);
};

This is valid code but it does nothing and we can't emit a warning in clang
because there might be side effects. The checker emits a warning for this
pattern and also for base class initializers written in this style.

There is some overlap with the unused-rtti checker but they follow different
goals and fire in different places most of the time.

Reviewers: alexfh, djasper

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4667

llvm-svn: 214397

1 files changed, 54 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/misc-undelegated-constructor.cpp b/clang-tools-extra/test/clang-tidy/misc-undelegated-constructor.cpp
new file mode 100644
index 00000000000..09d683b8e75
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/misc-undelegated-constructor.cpp
@@ -0,0 +1,54 @@
+// RUN: clang-tidy -checks='-*,misc-undelegated-constructor' %s -- -std=c++11 2>&1 | FileCheck %s -implicit-check-not='{{warning:|error:}}'
+
+struct Ctor;
+Ctor foo();
+
+struct Ctor {
+  Ctor();
+  Ctor(int);
+  Ctor(int, int);
+  Ctor(Ctor *i) {
+    Ctor();
+// CHECK: :[[@LINE-1]]:5: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+    Ctor(0);
+// CHECK: :[[@LINE-1]]:5: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+    Ctor(1, 2);
+// CHECK: :[[@LINE-1]]:5: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+    foo();
+  }
+};
+
+Ctor::Ctor() {
+  Ctor(1);
+// CHECK: :[[@LINE-1]]:3: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+}
+
+Ctor::Ctor(int i) : Ctor(i, 1) {} // properly delegated.
+
+struct Dtor {
+  Dtor();
+  Dtor(int);
+  Dtor(int, int);
+  Dtor(Ctor *i) {
+    Dtor();
+// CHECK: :[[@LINE-1]]:5: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+    Dtor(0);
+// CHECK: :[[@LINE-1]]:5: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+    Dtor(1, 2);
+// CHECK: :[[@LINE-1]]:5: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+  }
+  ~Dtor();
+};
+
+struct Base {};
+struct Derived : public Base {
+  Derived() { Base(); }
+// CHECK: :[[@LINE-1]]:15: warning: did you intend to call a delegated constructor? A temporary object is created here instead
+};
+
+template <typename T>
+struct TDerived : public Base {
+  TDerived() { Base(); }
+};
+
+TDerived<int> t;