Add self-comparison warnings for fields.

This expands very slightly what -Wtautological-compare considers to be
tautological to include implicit accesses to C++ fields and ObjC ivars.
I don't want to turn this into a full expression-identity check, but
these additions seem pretty well-contained, and maintain the theme
of checking for "x == x".

<rdar://problem/14431127>

llvm-svn: 190118

1 files changed, 23 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/self-comparison.cpp b/clang/test/SemaCXX/self-comparison.cpp
new file mode 100644
index 00000000000..fb15ec84306
--- /dev/null
+++ b/clang/test/SemaCXX/self-comparison.cpp
@@ -0,0 +1,23 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+int foo(int x) {
+  return x == x; // expected-warning {{self-comparison always evaluates to true}}
+}
+
+struct X {
+  bool operator==(const X &x);
+};
+
+struct A {
+  int x;
+  X x2;
+  int a[3];
+  int b[3];
+  bool f() { return x == x; } // expected-warning {{self-comparison always evaluates to true}}
+  bool g() { return x2 == x2; } // no-warning
+  bool h() { return a == b; } // expected-warning {{array comparison always evaluates to false}}
+  bool i() {
+    int c[3];
+    return a == c; // expected-warning {{array comparison always evaluates to false}}
+  }
+};