C++ PATCH for c++/56039 (ICE with lambda in template argument)

[Jason Merrill]

A lambda in a template argument is ill-formed, but we shouldn't ICE.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit d31ae27e292c03ab16feb0ac714ec62b12165444
Author: Jason Merrill <ja...@redhat.com>
Date:   Mon Mar 11 16:35:02 2013 -0400

    	PR c++/56039
    	* tree.c (strip_typedefs_expr): Complain about lambda, don't abort.

diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 9707825..713ec86 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -1421,7 +1421,8 @@ strip_typedefs_expr (tree t)
       }
 
     case LAMBDA_EXPR:
-      gcc_unreachable ();
+      error ("lambda-expression in a constant expression");
+      return error_mark_node;
 
     default:
       break;
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-sfinae1.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-sfinae1.C
new file mode 100644
index 0000000..973f8a7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-sfinae1.C
@@ -0,0 +1,55 @@
+// PR c++/56039
+// { dg-do compile { target c++11 } }
+
+template <bool> struct BoolSink { typedef void type; };
+
+template <typename T, typename U>
+struct AddRvalueReferenceImpl { typedef T type; };
+
+template <typename T>
+struct AddRvalueReferenceImpl<T, typename BoolSink<false &&
+      [] {
+         extern T &&tref;
+      }>::type> {		// { dg-error "lambda" }
+   typedef T &&type;
+};
+
+template <typename T>
+struct AddRvalueReference : AddRvalueReferenceImpl<T, void> { };
+
+namespace ImplHelpers {
+   template <typename T>
+   typename AddRvalueReference<T>::type create(void) { }
+}
+
+template <typename T, typename U, typename ...Args>
+struct IsConstructibleImpl { enum { value = 0 }; };
+
+template <typename T, typename ...Args>
+struct IsConstructibleImpl<T, typename BoolSink<false &&
+      [] {
+         T t( ::ImplHelpers::create<Args>() ...);
+      }>::type, Args ...> {	// { dg-error "lambda" }
+   enum { value = 1 };
+};
+
+template <typename T, typename ...Args>
+struct IsConstructible : IsConstructibleImpl<T, void, Args ...> { };
+
+struct DestroyMe {
+   ~DestroyMe() = delete;
+};
+
+static_assert(+IsConstructible<int>::value, "error");
+static_assert(!IsConstructible<void>::value, "error");
+static_assert(+IsConstructible<int [1]>::value, "error");
+static_assert(!IsConstructible<DestroyMe>::value, "error");
+static_assert(!IsConstructible<int *, char *>::value, "error");
+
+static_assert(+IsConstructible<int &&, int>::value, "error");
+static_assert(!IsConstructible<int &&, int &>::value, "error");
+static_assert(+IsConstructible<int &&, int &&>::value, "error");
+
+// { dg-prune-output "expected" }
+// { dg-prune-output "does not name a class" }
+// { dg-prune-output "static assertion" }