This implements the wording changes of CWG2374, which clarifies the
wording of P0138 to forbid e.g. direct-list-initialization of a scoped
enumeration from a different scoped enumeration.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?
gcc/cp/ChangeLog:
DR 2374
* decl.c (is_direct_enum_init): Check the implicit
convertibility requirement added by CWG 2374.
gcc/testsuite/ChangeLog:
DR 2374
* g++.dg/cpp1z/direct-enum-init2.C: New test.
---
gcc/cp/decl.c | 8 +++++++-
gcc/testsuite/g++.dg/cpp1z/direct-enum-init2.C | 8 ++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/direct-enum-init2.C
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index b81de8ef934..60dc2bf182d 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -6191,7 +6191,13 @@ is_direct_enum_init (tree type, tree init)
&& ENUM_FIXED_UNDERLYING_TYPE_P (type)
&& TREE_CODE (init) == CONSTRUCTOR
&& CONSTRUCTOR_IS_DIRECT_INIT (init)
- && CONSTRUCTOR_NELTS (init) == 1)
+ && CONSTRUCTOR_NELTS (init) == 1
+ /* DR 2374: The single element needs to be implicitly
+ convertible to the underlying type of the enum. */
+ && can_convert_arg (ENUM_UNDERLYING_TYPE (type),
+ TREE_TYPE (CONSTRUCTOR_ELT (init, 0)->value),
+ CONSTRUCTOR_ELT (init, 0)->value,
+ LOOKUP_IMPLICIT, tf_none))
return true;
return false;
}
diff --git a/gcc/testsuite/g++.dg/cpp1z/direct-enum-init2.C
b/gcc/testsuite/g++.dg/cpp1z/direct-enum-init2.C
new file mode 100644
index 00000000000..5b94a8d00fe
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/direct-enum-init2.C
@@ -0,0 +1,8 @@
+// DR 2374
+// { dg-do compile { target c++17 } }
+
+enum class Orange;
+enum class Apple;
+
+extern Orange o;
+Apple a{o}; // { dg-error "cannot convert" }
--
2.31.1.362.g311531c9de
