c++-coroutines - merge trunk r278894.

2019-12-02  Iain Sandoe  <iain@sandoe.co.uk>

	Merge trunk r278894.



git-svn-id: https://gcc.gnu.org/svn/gcc/branches/c++-coroutines@278895 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 27 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias1.C b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias1.C
new file mode 100644
index 00000000000..ed47eb38f1b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/class-deduction-alias1.C
@@ -0,0 +1,27 @@
+// Testcase from P1814R0
+// { dg-do compile { target c++2a } }
+
+template <class T> struct identity { using type = T; };
+template <class T> using identity_t = typename identity<T>::type;
+template <class T> concept Int = __is_same_as (T, int);
+
+template <class T, class U> struct C {
+  C(T, U);			// #1 { dg-message "constraint" }
+};
+template<class T, class U>
+C(T, U) -> C<T, identity_t<U>>; // #2 { dg-message "constraint" }
+
+template<class V>
+using A = C<V *, V *>;
+
+template<Int W>
+using B = A<W>;
+    
+int i{};
+double d{};
+A a1(&i, &i); // { dg-bogus "" "Deduces A<int>" }
+A a2(i, i);   // { dg-error "" "cannot deduce V * from i" }
+A a3(&i, &d); // { dg-error "" } #1: Cannot deduce (V*, V*) from (int *, double *) 
+                              // #2: Cannot deduce A<V> from C<int *, double *>
+B b1(&i, &i); // { dg-bogus "" "Deduces B<int>" }
+B b2(&d, &d); // { dg-error "" "cannot deduce B<W> from C<double *, double *>" }