[gcc r11-8444] c++: _Complex template parameter [PR100634]

[gcc r11-8444] c++: _Complex template parameter [PR100634]

[Jason Merrill]

https://gcc.gnu.org/g:b54e50285c716fabc3980c5383c4898018a60b28

commit r11-8444-gb54e50285c716fabc3980c5383c4898018a60b28
Author: Jason Merrill <jason@redhat.com>
Date:   Wed May 19 17:33:21 2021 -0400

    c++: _Complex template parameter [PR100634]
    
    We were crashing because invalid_nontype_parm_type_p allowed _Complex
    template parms, but convert_nontype_argument didn't know what to do for
    them.  Let's just disallow it, people can and should use std::complex
    instead.
    
            PR c++/100634
    
    gcc/cp/ChangeLog:
    
            * pt.c (invalid_nontype_parm_type_p): Return true for COMPLEX_TYPE.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/cpp2a/nontype-complex1.C: New test.

Diff:
---
 gcc/cp/pt.c                                   | 2 ++
 gcc/testsuite/g++.dg/cpp2a/nontype-complex1.C | 8 ++++++++
 2 files changed, 10 insertions(+)

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d30876ced9c..1434beb80f4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -26620,6 +26620,8 @@ invalid_nontype_parm_type_p (tree type, tsubst_flags_t complain)
   else if (cxx_dialect >= cxx11
 	   && TREE_CODE (type) == BOUND_TEMPLATE_TEMPLATE_PARM)
     return false;
+  else if (TREE_CODE (type) == COMPLEX_TYPE)
+    /* Fall through.  */;
   else if (VOID_TYPE_P (type))
     /* Fall through.  */;
   else if (cxx_dialect >= cxx20)
diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-complex1.C b/gcc/testsuite/g++.dg/cpp2a/nontype-complex1.C
new file mode 100644
index 00000000000..4de2168ef60
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-complex1.C
@@ -0,0 +1,8 @@
+// PR c++/100634
+// { dg-do compile { target c++20 } }
+// { dg-options "" }
+
+// We could support _Complex template arguments, but better I think to make
+// people use a standard type instead.
+template<_Complex int> struct ComplexInt {}; // { dg-error "not a valid type" }
+using CI = ComplexInt<1 + 3i>;