Re: [PATCH] c++: decltype of non-dependent call of class type [PR105386]

[Jason Merrill via Gcc-patches]

On 4/26/22 09:45, Patrick Palka wrote:

We need to pass tf_decltype when instantiating a non-dependent decltype
operand, like tsubst does in the dependent case, so that we avoid
materializing a temporary for a prvalue operand.

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

OK.

        PR c++/105386

gcc/cp/ChangeLog:

        * semantics.cc (finish_decltype_type): Pass tf_decltype to
        instantiate_non_dependent_expr_sfinae.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp0x/decltype81.C: New test.
---
  gcc/cp/semantics.cc                     |  2 +-
  gcc/testsuite/g++.dg/cpp0x/decltype81.C | 15 +++++++++++++++
  2 files changed, 16 insertions(+), 1 deletion(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp0x/decltype81.C

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index f08c0b6281f..ab48f11c9be 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -11252,7 +11252,7 @@ finish_decltype_type (tree expr, bool 
id_expression_or_member_access_p,
      }
    else if (processing_template_decl)
      {
-      expr = instantiate_non_dependent_expr_sfinae (expr, complain);
+      expr = instantiate_non_dependent_expr_sfinae (expr, 
complain|tf_decltype);
        if (expr == error_mark_node)
        return error_mark_node;
        /* Keep processing_template_decl cleared for the rest of the function
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype81.C 
b/gcc/testsuite/g++.dg/cpp0x/decltype81.C
new file mode 100644
index 00000000000..7d25db39d9c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype81.C
@@ -0,0 +1,15 @@
+// PR c++/105386
+// { dg-do compile { target c++11 } }
+
+template<class T> struct NoInst {
+  static_assert(sizeof(T) == 9999, "NoInst instantiated");
+};
+
+template<class T> NoInst<T> f(T);
+
+template<class>
+struct A {
+  using type = decltype(f(0));
+};
+
+A<int> a;