The issue here is that declval<T>().d is considered instantiation-dependent
within a template, as the access to 'd' might depend on the particular
specialization. But when we're deducing template arguments for a call, we
know that the call and the arguments are non-dependent, so we can do the
substitution as though we aren't in a template. Which strictly speaking we
aren't, since the default argument is considered a separate definition.
Tested x86_64-pc-linux-gnu, applying to trunk.
* pt.c (type_unification_real): Accept a dependent result in
template context.
---
gcc/cp/pt.c | 9 ++++++++-
gcc/testsuite/g++.dg/cpp0x/fntmpdefarg11.C | 15 +++++++++++++++
gcc/cp/ChangeLog | 6 ++++++
3 files changed, 29 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/fntmpdefarg11.C
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0acc16d1b92..6c15419e9cc 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -21005,8 +21005,15 @@ type_unification_real (tree tparms,
}
else
{
+ /* Even if the call is happening in template context, getting
+ here means it's non-dependent, and a default argument is
+ considered a separate definition under [temp.decls], so we can
+ do this substitution without processing_template_decl. This
+ is important if the default argument contains something that
+ might be instantiation-dependent like access (87480). */
+ processing_template_decl_sentinel s;
tree substed = NULL_TREE;
- if (saw_undeduced == 1 && processing_template_decl == 0)
+ if (saw_undeduced == 1)
{
/* First instatiate in template context, in case we still
depend on undeduced template parameters. */
diff --git a/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg11.C
b/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg11.C
new file mode 100644
index 00000000000..86c8ea93f4d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/fntmpdefarg11.C
@@ -0,0 +1,15 @@
+// PR c++/87480
+// { dg-do compile { target c++11 } }
+
+template<typename T> T&& declval();
+
+template <typename T, typename = decltype(declval<T>().d)> void f(T) { }
+
+struct A {
+ double d;
+};
+
+template <typename>
+void j(A& a) {
+ f(a);
+}
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 2157496745e..09fb3f2935c 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-03-20 Jason Merrill <ja...@redhat.com>
+
+ PR c++/87480 - decltype of member access in default template arg
+ * pt.c (type_unification_real): Accept a dependent result in
+ template context.
+
2019-03-19 Martin Sebor <mse...@redhat.com>
PR tree-optimization/89688
base-commit: fcf9e045198f89f01e8a2e57724a8e6cc4d04cda
--
2.20.1
