[PATCH] c++: CONSTRUCTORs are non-deduced contexts [PR104291]

[Patrick Palka via Gcc-patches]

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

        PR c++/104291

gcc/cp/ChangeLog:

        * pt.cc (for_each_template_parm_r) <case CONSTRUCTOR>: Don't
        walk subtrees if !include_nondeduced_p.  Simplify given that
        cp_walk_subtrees already walks TYPE_PTRMEMFUNC_FN_TYPE_RAW.

gcc/testsuite/ChangeLog:

        * g++.dg/template/partial20.C: New test.
---
 gcc/cp/pt.cc                              | 7 +------
 gcc/testsuite/g++.dg/template/partial20.C | 7 +++++++
 2 files changed, 8 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/partial20.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 2f82b167853..feee629f1dd 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -10525,12 +10525,6 @@ for_each_template_parm_r (tree *tp, int 
*walk_subtrees, void *d)
       *walk_subtrees = 0;
       break;
 
-    case CONSTRUCTOR:
-      if (TREE_TYPE (t) && TYPE_PTRMEMFUNC_P (TREE_TYPE (t))
-         && pfd->include_nondeduced_p)
-       WALK_SUBTREE (TYPE_PTRMEMFUNC_FN_TYPE (TREE_TYPE (t)));
-      break;
-
     case INDIRECT_REF:
     case COMPONENT_REF:
       /* If there's no type, then this thing must be some expression
@@ -10539,6 +10533,7 @@ for_each_template_parm_r (tree *tp, int *walk_subtrees, 
void *d)
        return error_mark_node;
       break;
 
+    case CONSTRUCTOR:
     case TRAIT_EXPR:
     case PLUS_EXPR:
     case MULT_EXPR:
diff --git a/gcc/testsuite/g++.dg/template/partial20.C 
b/gcc/testsuite/g++.dg/template/partial20.C
new file mode 100644
index 00000000000..161d796b1c2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/partial20.C
@@ -0,0 +1,7 @@
+// PR c++/104291
+// { dg-do compile { target c++20 } }
+
+struct A { int x; };
+
+template<auto> struct B;
+template<int x> struct B<A{x}> { }; // { dg-error "not deducible" }
-- 
2.35.0