Lay the ground work for resoving PR7047. This doesn't actually fix it because

default arguments to template parameters don't have a DeclContext when
instantiated, and so we can't detect that we're in an instantiation context as
opposed to the definition context. However, it fixes the more commonly-occuring
cases in TMP code that use devolve to this type of tautology after
substitution.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108044 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 48 insertions, 0 deletions

diff --git a/test/SemaTemplate/self-comparison.cpp b/test/SemaTemplate/self-comparison.cpp
new file mode 100644
index 0000000000..50ab660e65
--- /dev/null
+++ b/test/SemaTemplate/self-comparison.cpp
@@ -0,0 +1,48 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+template <int A, int B> void foo() {
+  (void)(A == A); // expected-warning {{self-comparison always evaluates to true}}
+  (void)(A == B);
+}
+template <int A, int B> struct S1 {
+  void foo() {
+    (void)(A == A); // expected-warning {{self-comparison always evaluates to true}}
+    (void)(A == B);
+  }
+};
+
+template <int A, int B> struct S2 {
+  template <typename T> T foo() {
+    (void)(A == A); // expected-warning {{self-comparison always evaluates to true}}
+    (void)(A == B);
+  }
+};
+
+struct S3 {
+  template <int A, int B> void foo() {
+    (void)(A == A); // expected-warning {{self-comparison always evaluates to true}}
+    (void)(A == B);
+  }
+};
+
+template <int A> struct S4 {
+  template <int B> void foo() {
+    (void)(A == A); // expected-warning {{self-comparison always evaluates to true}}
+    (void)(A == B);
+  }
+};
+
+const int N = 42;
+template <int X> void foo2() {
+  (void)(X == N);
+  (void)(N == X);
+}
+
+void test() {
+  foo<1, 1>();
+  S1<1, 1> s1; s1.foo();
+  S2<1, 1> s2; s2.foo<void>();
+  S3 s3; s3.foo<1, 1>();
+  S4<1> s4; s4.foo<1>();
+  foo2<N>();
+}