Re: [PATCH] c++: DEPENDENT_OPERATOR_TYPE as type of NTTP [PR104074]

[Jason Merrill via Gcc-patches]

On 1/18/22 11:08, Patrick Palka wrote:

We're incorrectly rejecting the below testcase during template argument
coercion because invalid_nontype_parm_type_p returns true for
DEPENDENT_OPERATOR_TYPE.

This patch fixes this by partially rewriting invalid_nontype_parm_type_p
in terms of WILDCARD_TYPE_P, of which DEPENDENT_OPERATOR_TYPE is one.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

OK

        PR c++/104074

gcc/cp/ChangeLog:

        * pt.c (invalid_nontype_parm_type_p): Use WILDCARD_TYPE_P so
        that we return false for DEPENDENT_OPERATOR_TYPE too.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp1z/nontype-auto20.C: New test.
---
  gcc/cp/pt.c                                 | 14 ++++++--------
  gcc/testsuite/g++.dg/cpp1z/nontype-auto20.C |  5 +++++
  2 files changed, 11 insertions(+), 8 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp1z/nontype-auto20.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0fa4a162354..e57613488d4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -26931,16 +26931,14 @@ invalid_nontype_parm_type_p (tree type, 
tsubst_flags_t complain)
        }
        return false;
      }
-  else if (TREE_CODE (type) == TYPENAME_TYPE)
-    return false;
-  else if (TREE_CODE (type) == DECLTYPE_TYPE)
-    return false;
    else if (TREE_CODE (type) == NULLPTR_TYPE)
      return false;
-  /* A bound template template parm could later be instantiated to have a valid
-     nontype parm type via an alias template.  */
-  else if (cxx_dialect >= cxx11
-          && TREE_CODE (type) == BOUND_TEMPLATE_TEMPLATE_PARM)
+  else if (TREE_CODE (type) == BOUND_TEMPLATE_TEMPLATE_PARM
+          && cxx_dialect < cxx11)
+    /* Fall through; before C++11 alias templates, a bound ttp
+       always instantiates to a class type.  */;
+  else if (WILDCARD_TYPE_P (type))
+    /* Any other wildcard type not already handled above is allowed.  */
      return false;
    else if (TREE_CODE (type) == COMPLEX_TYPE)
      /* Fall through.  */;
diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto20.C 
b/gcc/testsuite/g++.dg/cpp1z/nontype-auto20.C
new file mode 100644
index 00000000000..03eea91ce09
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto20.C
@@ -0,0 +1,5 @@
+// PR c++/104074
+// { dg-do compile { target c++17 } }
+
+template<auto> class gr_sp;
+template<class T> using gr_rp = gr_sp<+T::recycle>;