PR c++/85706 - class deduction under decltype

	* pt.c (for_each_template_parm_r): Handle DECLTYPE_TYPE.  Clear
	*walk_subtrees whether or not we walked into the operand.
	(type_uses_auto): Only look at deduced contexts.

From-SVN: r260066

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index aa42de2c05f2f21a9de241b5c3f59f3e29fc4b84..bf56581327ca91760ca2f62222ac0634777435c1 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2018-05-08  Jason Merrill  <jason@redhat.com>
+
+       PR c++/85706 - class deduction under decltype
+       * pt.c (for_each_template_parm_r): Handle DECLTYPE_TYPE.  Clear
+       *walk_subtrees whether or not we walked into the operand.
+       (type_uses_auto): Only look at deduced contexts.
+
 2018-05-08  Paolo Carlini  <paolo.carlini@oracle.com>
 
        PR c++/84588

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index c604f46f7425fc385b5873552b53a3317d489f03..180dfd6861c1c910e01cb12b2291d3be880da056 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -9829,6 +9829,7 @@ for_each_template_parm_r (tree *tp, int *walk_subtrees, void *d)
       break;
 
     case TYPEOF_TYPE:
+    case DECLTYPE_TYPE:
     case UNDERLYING_TYPE:
       if (pfd->include_nondeduced_p
          && for_each_template_parm (TYPE_VALUES_RAW (t), fn, data,
@@ -9836,6 +9837,7 @@ for_each_template_parm_r (tree *tp, int *walk_subtrees, void *d)
                                     pfd->include_nondeduced_p,
                                     pfd->any_fn))
        return error_mark_node;
+      *walk_subtrees = false;
       break;
 
     case FUNCTION_DECL:
@@ -26862,7 +26864,7 @@ type_uses_auto (tree type)
         them.  */
       if (uses_template_parms (type))
        return for_each_template_parm (type, is_auto_r, /*data*/NULL,
-                                      /*visited*/NULL, /*nondeduced*/true);
+                                      /*visited*/NULL, /*nondeduced*/false);
       else
        return NULL_TREE;
     }

diff --git a/gcc/testsuite/g++.dg/concepts/class-deduction2.C b/gcc/testsuite/g++.dg/concepts/class-deduction2.C
new file mode 100644 (file)
index 0000000..286e59a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/class-deduction2.C
@@ -0,0 +1,9 @@
+// PR c++/85706
+// { dg-additional-options "-std=c++17 -fconcepts" }
+
+template<class T> struct S {
+  S(T);
+};
+
+template<class = void>
+auto f() -> decltype(S(42)); // error