[PATCH] c++: Fix ICE with template codes in check_narrowing [PR91465]

[Marek Polacek]

In ed4f2c001a883b2456fc607a33f1c59f9c4ee65d I changed the call to
fold_non_dependent_expr in check_narrowing to maybe_constant_value.
That was the wrong thing to do as these tests show: check_narrowing
bails out for dependent expressions but we can still have template
codes like CAST_EXPR that don't have anything dependent in it so are
considered non-dependent.  But cxx_eval_* don't grok template codes,
so we need to call fold_non_dependent_expr instead which knows what
to do with template codes.  (I fully accept a "told you so".)

I'm passing tf_none to it, otherwise we'd emit a bogus error for
constexpr-ex4.C: there INIT is "A::operator int(&a)" and while
instantiating this CALL_EXPR (in a template) we call finish_call_expr
and that sees a BASELINK and so emits a new dummy object for 'this',
and then we complain about the wrong number of arguments, because now
we basically have two 'this's.  Which is exactly the problem I saw
recently in c++/92948.

Bootstrapped/regtested on x86_64-linux, ok for trunk and 9?

        PR c++/91465 - ICE with template codes in check_narrowing.
        * typeck2.c (check_narrowing): Call fold_non_dependent_expr
        instead of maybe_constant_value.

        * g++.dg/cpp0x/pr91465.C: New test.
        * g++.dg/cpp1z/pr91465.C: New test.
---
 gcc/cp/typeck2.c                     |  4 +++-
 gcc/testsuite/g++.dg/cpp0x/pr91465.C | 16 ++++++++++++++++
 gcc/testsuite/g++.dg/cpp1z/pr91465.C | 10 ++++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/pr91465.C
 create mode 100644 gcc/testsuite/g++.dg/cpp1z/pr91465.C

diff --git a/gcc/cp/typeck2.c b/gcc/cp/typeck2.c
index 371b203c29b..8f8e9703ac8 100644
--- a/gcc/cp/typeck2.c
+++ b/gcc/cp/typeck2.c
@@ -981,7 +981,9 @@ check_narrowing (tree type, tree init, tsubst_flags_t 
complain,
       return ok;
     }
 
-  init = maybe_constant_value (init);
+  init = fold_non_dependent_expr (init, tf_none);
+  if (init == error_mark_node)
+    return ok;
 
   /* If we were asked to only check constants, return early.  */
   if (const_only && !TREE_CONSTANT (init))
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr91465.C 
b/gcc/testsuite/g++.dg/cpp0x/pr91465.C
new file mode 100644
index 00000000000..e2021aa13e1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr91465.C
@@ -0,0 +1,16 @@
+// PR c++/91465 - ICE with template codes in check_narrowing.
+// { dg-do compile { target c++11 } }
+
+enum class D { X };
+enum class S { Z };
+
+D foo(S) { return D{}; }
+D foo(double) { return D{}; }
+
+template <typename>
+struct Bar {
+  D baz(S s)
+  {
+    return D{foo(s)};
+  }
+};
diff --git a/gcc/testsuite/g++.dg/cpp1z/pr91465.C 
b/gcc/testsuite/g++.dg/cpp1z/pr91465.C
new file mode 100644
index 00000000000..5b1205349d0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/pr91465.C
@@ -0,0 +1,10 @@
+// PR c++/91465 - ICE with template codes in check_narrowing.
+// { dg-do compile { target c++17 } }
+
+enum class E { Z };
+
+template <typename F>
+void foo(F)
+{
+  E{char(0)};
+}

base-commit: cb273d81a45092ceee793f0357526e291f03c7b7
-- 
Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA