[PATCH 1/2] c++ modules: streaming enum with no enumerators [PR102600]

[Patrick Palka via Gcc-patches]

For an enum declaration, has_definition returns true iff its TYPE_VALUES
field is non-empty.  But this will wrongly return false for an enum that's
defined to have no enumerators as in the below testcase.

This patch fixes has_definition for such enums by checking OPAQUE_ENUM_P
instead, which should always give us the right answer here.

Tested on x86_64-pc-linux-gnu, does this look OK for trunk?

        PR c++/102600

gcc/cp/ChangeLog:

        * module.cc (has_definition): For an enum declaration, check
        OPAQUE_ENUM_P instead of TYPE_VALUES.

gcc/testsuite/ChangeLog:

        * g++.dg/modules/enum-9_a.H: New test.
        * g++.dg/modules/enum-9_b.C: New test.
---
 gcc/cp/module.cc                        | 3 ++-
 gcc/testsuite/g++.dg/modules/enum-9_a.H | 5 +++++
 gcc/testsuite/g++.dg/modules/enum-9_b.C | 8 ++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/enum-9_a.H
 create mode 100644 gcc/testsuite/g++.dg/modules/enum-9_b.C

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 2c2f9a9a8cb..cc704817718 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -11443,7 +11443,8 @@ has_definition (tree decl)
        if (type == TYPE_MAIN_VARIANT (type)
            && decl == TYPE_NAME (type)
            && (TREE_CODE (type) == ENUMERAL_TYPE
-               ? TYPE_VALUES (type) : TYPE_FIELDS (type)))
+               ? !OPAQUE_ENUM_P (type)
+               : TYPE_FIELDS (type) != NULL_TREE))
          return true;
       }
       break;
diff --git a/gcc/testsuite/g++.dg/modules/enum-9_a.H 
b/gcc/testsuite/g++.dg/modules/enum-9_a.H
new file mode 100644
index 00000000000..1aecabfd0bd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/enum-9_a.H
@@ -0,0 +1,5 @@
+// PR c++/102600
+// { dg-additional-options -fmodule-header }
+// { dg-module-cmi {} }
+
+enum class byte : unsigned char { };
diff --git a/gcc/testsuite/g++.dg/modules/enum-9_b.C 
b/gcc/testsuite/g++.dg/modules/enum-9_b.C
new file mode 100644
index 00000000000..aa1fdf21444
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/enum-9_b.C
@@ -0,0 +1,8 @@
+// PR c++/102600
+// { dg-additional-options -fmodules-ts }
+
+import "enum-9_a.H";
+
+void push(byte) {}
+void write(char v) { push(static_cast<byte>(v)); }
+int main() { write(char{}); }
-- 
2.38.0.118.g4732897cf0