On 5/5/23 13:36, Patrick Palka wrote:
This extends the PR93107 fix, which made us do resolve_nondeduced_context
on the elements of an initializer list during auto deduction, to happen
for CTAD as well.

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

        PR c++/106214
        PR c++/93107

gcc/cp/ChangeLog:

        * pt.cc (do_auto_deduction): Move up resolve_nondeduced_context
        calls to happen before do_class_deduction.  Add some error_mark_node
        tests.

Maybe move them even higher? I suppose it shouldn't actually make a difference, but this seems to make sense right after the early returns.

OK either way.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp1z/class-deduction114.C: New test.
---
  gcc/cp/pt.cc                                  | 27 +++++++++---------
  .../g++.dg/cpp1z/class-deduction114.C         | 28 +++++++++++++++++++
  2 files changed, 41 insertions(+), 14 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction114.C

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8d66fde9f11..94e1664d00c 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -30793,7 +30793,7 @@ do_auto_deduction (tree type, tree init, tree auto_node,
                   int flags /* = LOOKUP_NORMAL */,
                   tree tmpl /* = NULL_TREE */)
  {
-  if (init == error_mark_node)
+  if (type == error_mark_node || init == error_mark_node)
      return error_mark_node;
if (init && type_dependent_expression_p (init)
@@ -30827,6 +30827,17 @@ do_auto_deduction (tree type, tree init, tree 
auto_node,
                                        /*return*/true)))
      init = r;
+ if (init && BRACE_ENCLOSED_INITIALIZER_P (init))
+    {
+      /* We don't recurse here because we can't deduce from a nested
+        initializer_list.  */
+      if (CONSTRUCTOR_ELTS (init))
+       for (constructor_elt &elt : CONSTRUCTOR_ELTS (init))
+         elt.value = resolve_nondeduced_context (elt.value, complain);
+    }
+  else if (init)
+    init = resolve_nondeduced_context (init, complain);
+
    if (tree ctmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node))
      /* C++17 class template argument deduction.  */
      return do_class_deduction (type, ctmpl, init, flags, complain);
@@ -30861,24 +30872,12 @@ do_auto_deduction (tree type, tree init, tree 
auto_node,
        }
      }
- if (type == error_mark_node)
+  if (type == error_mark_node || init == error_mark_node)
      return error_mark_node;
- if (BRACE_ENCLOSED_INITIALIZER_P (init))
-    {
-      /* We don't recurse here because we can't deduce from a nested
-        initializer_list.  */
-      if (CONSTRUCTOR_ELTS (init))
-       for (constructor_elt &elt : CONSTRUCTOR_ELTS (init))
-         elt.value = resolve_nondeduced_context (elt.value, complain);
-    }
-  else
-    init = resolve_nondeduced_context (init, complain);
-
    tree targs;
    if (context == adc_decomp_type
        && auto_node == type
-      && init != error_mark_node
        && TREE_CODE (TREE_TYPE (init)) == ARRAY_TYPE)
      {
        /* [dcl.struct.bind]/1 - if decomposition declaration has no 
ref-qualifiers
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction114.C 
b/gcc/testsuite/g++.dg/cpp1z/class-deduction114.C
new file mode 100644
index 00000000000..ba6921d1b96
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction114.C
@@ -0,0 +1,28 @@
+// PR c++/106214
+// { dg-do compile { target c++17 } }
+// A version of cpp0x/initlist-deduce3.C using list CTAD instead
+// of ordinary auto deduction from std::initializer_list.
+
+using size_t = decltype(sizeof 0);
+
+namespace std {
+  template<typename T> struct initializer_list {
+    const T *ptr;
+    size_t n;
+    initializer_list(const T*, size_t);
+  };
+}
+
+template<typename T>
+void Task() {}
+
+template<class T>
+struct vector {
+  vector(std::initializer_list<T>);
+};
+
+vector a = &Task<int>; // { dg-error "deduction|no match" }
+vector b = { &Task<int> };
+vector e{ &Task<int> };
+vector f = { &Task<int>, &Task<int> };
+vector d = { static_cast<void(*)()>(&Task<int>) };

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