Rework Microsoft __if_exists/__if_not_exists parsing and semantic

analysis to separate dependent names from non-dependent names. For
dependent names, we'll behave differently from Visual C++:

  - For __if_exists/__if_not_exists at class scope, we'll just warn
    and then ignore them.
  - For __if_exists/__if_not_exists in statements, we'll treat the
    inner statement as a compound statement, which we only instantiate
    in templates where the dependent name (after instantiation)
    exists. This behavior is different from VC++, but it's as close as
    we can get without encroaching ridiculousness.

The latter part (dependent statements) is not yet implemented.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@142864 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 53 insertions, 0 deletions

diff --git a/test/SemaTemplate/ms-if-exists.cpp b/test/SemaTemplate/ms-if-exists.cpp
new file mode 100644
index 0000000000..f22a8997b1
--- /dev/null
+++ b/test/SemaTemplate/ms-if-exists.cpp
@@ -0,0 +1,53 @@
+// RUN: %clang_cc1 -fms-extensions %s -verify
+
+struct Nontemplate {
+  typedef int type;
+};
+
+template<typename T>
+struct X {
+  __if_exists(Nontemplate::type) {
+    typedef Nontemplate::type type;
+  }
+
+  __if_exists(Nontemplate::value) {
+    typedef Nontemplate::value type2;
+  }
+
+  __if_not_exists(Nontemplate::value) {
+    typedef int type3;
+  }
+
+  __if_exists(T::X) { // expected-warning{{dependent __if_exists declarations are ignored}}
+    typedef T::X type4;
+  }
+};
+
+X<int>::type i1;
+X<int>::type2 i2; // expected-error{{no type named 'type2' in 'X<int>'}}
+X<int>::type3 i3;
+X<int>::type4 i4; // expected-error{{no type named 'type4' in 'X<int>'}}
+
+struct HasFoo { 
+  void foo();
+};
+struct HasBar { 
+  void bar(int);
+  void bar(float);
+};
+
+template<typename T>
+void f(T t) {
+  __if_exists(T::foo) {
+    { }
+    t.foo();
+  }
+
+  __if_not_exists(T::bar) {
+    int *i = t;
+    { }
+  }
+}
+
+template void f(HasFoo);
+template void f(HasBar);