[C++ PATCH] PR c++/88419 - C++17 ICE with class template arg deduction.

[Jason Merrill]

Just like in make_constrained_auto, we need to defer setting TYPE_CANONICAL
until we've set fields that will affect structural_comptypes.

Tested x86_64-pc-linux-gnu, applying to trunk.

        * pt.c (make_template_placeholder): Set TYPE_CANONICAL after
        CLASS_PLACEHOLDER_TEMPLATE.
---
 gcc/cp/pt.c                                   |  4 +++-
 .../g++.dg/cpp1z/class-deduction62.C          | 22 +++++++++++++++++++
 gcc/cp/ChangeLog                              |  6 +++++
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/class-deduction62.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index a212be8c747..bd0a3d13bbe 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -26619,8 +26619,10 @@ make_auto (void)
 tree
 make_template_placeholder (tree tmpl)
 {
-  tree t = make_auto_1 (auto_identifier, true);
+  tree t = make_auto_1 (auto_identifier, false);
   CLASS_PLACEHOLDER_TEMPLATE (t) = tmpl;
+  /* Our canonical type depends on the placeholder.  */
+  TYPE_CANONICAL (t) = canonical_type_parameter (t);
   return t;
 }
 
diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction62.C 
b/gcc/testsuite/g++.dg/cpp1z/class-deduction62.C
new file mode 100644
index 00000000000..2baa3acb8c1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction62.C
@@ -0,0 +1,22 @@
+// PR c++/88419
+// { dg-do compile { target c++17 } }
+
+template<class> struct ref_view {
+  template<class T> ref_view(T&&);
+};
+
+template<class R> ref_view(R&) -> ref_view<R>;
+
+struct ref_fn {
+  template<class R> auto operator()(R r) const
+    noexcept(noexcept(ref_view{r}));
+};
+
+template<class R> struct indirect_view {
+  indirect_view(R);
+};
+
+struct indirect_fn {
+  template<class R> auto operator()(R r) const
+    noexcept(noexcept(indirect_view{r}));
+};
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 824d007d36c..228100ab21f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-02-21  Jason Merrill  <ja...@redhat.com>
+
+       PR c++/88419 - C++17 ICE with class template arg deduction.
+       * pt.c (make_template_placeholder): Set TYPE_CANONICAL after
+       CLASS_PLACEHOLDER_TEMPLATE.
+
 2019-02-21  Jakub Jelinek  <ja...@redhat.com>
 
        PR c++/89285

base-commit: 7f5c3ac2885e80c108b8f1e022b0eefa394fab82
-- 
2.20.1