Re: [PATCH] c++: double non-dep folding from finish_compound_literal [PR104565]

[Jason Merrill via Gcc-patches]

On 2/16/22 15:26, Patrick Palka wrote:

In finish_compound_literal, we perform non-dependent expr folding before
calling check_narrowing (ever since r9-5973).  But ever since r10-7096,
check_narrowing also performs non-dependent expr folding of its own.
This double folding cause tsubst to see non-templated trees during the
second folding, which causes a spurious error in the below testcase.

This patch removes this first folding operation; it now seems obviated
by the second one.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk/10/11?

OK for trunk now, release branches in about a month.

        PR c++/104565

gcc/cp/ChangeLog:

        * semantics.cc (finish_compound_literal): Don't perform
        non-dependent expr folding before calling check_narrowing.

gcc/testsuite/ChangeLog:

        * g++.dg/template/non-dependent22.C: New test.
---
  gcc/cp/semantics.cc                             | 10 +++-------
  gcc/testsuite/g++.dg/template/non-dependent22.C | 12 ++++++++++++
  2 files changed, 15 insertions(+), 7 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/template/non-dependent22.C

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 0cb17a6a8ab..114baa48710 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -3203,13 +3203,9 @@ finish_compound_literal (tree type, tree 
compound_literal,
      return error_mark_node;
    compound_literal = reshape_init (type, compound_literal, complain);
    if (SCALAR_TYPE_P (type)
-      && !BRACE_ENCLOSED_INITIALIZER_P (compound_literal))
-    {
-      tree t = instantiate_non_dependent_expr_sfinae (compound_literal,
-                                                     complain);
-      if (!check_narrowing (type, t, complain))
-       return error_mark_node;
-    }
+      && !BRACE_ENCLOSED_INITIALIZER_P (compound_literal)
+      && !check_narrowing (type, compound_literal, complain))
+    return error_mark_node;
    if (TREE_CODE (type) == ARRAY_TYPE
        && TYPE_DOMAIN (type) == NULL_TREE)
      {
diff --git a/gcc/testsuite/g++.dg/template/non-dependent22.C 
b/gcc/testsuite/g++.dg/template/non-dependent22.C
new file mode 100644
index 00000000000..83a6a13f15b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent22.C
@@ -0,0 +1,12 @@
+// PR c++/104565
+// { dg-do compile { target c++11 } }
+
+struct apa {
+  constexpr int n() const { return 3; }
+};
+
+template<class>
+int f() {
+  apa foo;
+  return int{foo.n()};  // no matching function for call to 'apa::n(apa*)'
+}