PR c++/92032 - DR 1601: Promotion of enum with fixed underlying type.

I've been messing with compare_ics recently and noticed that we don't
implement CWG 1601, which should be fairly easy.  Thus this patch.

The motivating example is 
  enum E : char { e };
  void f(char);
  void f(int);
  void g() {
    f(e);
  }
where the call to f was ambiguous but we should choose f(char).

Currently we give f(int) cr_promotion in standard_conversion, while
f(char) remains cr_std, which is worse than cr_promotion.  So I thought
I'd give it cr_promotion also and then add a tiebreaker to compare_ics.

	* call.c (standard_conversion): When converting an enumeration with
	a fixed underlying type to the underlying type, give it the cr_promotion
	rank.
	(compare_ics): Implement a tiebreaker as per CWG 1601.

	* g++.dg/cpp0x/scoped_enum10.C: New test.
	* g++.dg/cpp0x/scoped_enum11.C: New test.

From-SVN: r276766

3 files changed, 78 insertions, 0 deletions

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9318655..f1e3a99 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2019-10-09  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/92032 - DR 1601: Promotion of enum with fixed underlying	type.
+	* g++.dg/cpp0x/scoped_enum10.C: New test.
+	* g++.dg/cpp0x/scoped_enum11.C: New test.
+
 2019-10-08  Andrew Sutton  <asutton@lock3software.com>
 
 	* lib/target-supports.exp (check_effective_target_concepts): Check
diff --git a/gcc/testsuite/g++.dg/cpp0x/scoped_enum10.C b/gcc/testsuite/g++.dg/cpp0x/scoped_enum10.C
new file mode 100644
index 0000000..054b908
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/scoped_enum10.C
@@ -0,0 +1,37 @@
+// PR c++/92032 - DR 1601: Promotion of enumeration with fixed underlying type.
+// { dg-do compile { target c++11 } }
+
+enum E : char { e };
+enum F : int { f };
+enum G : long { g };
+enum H : unsigned { h };
+
+int f1(char);
+void f1(int);
+
+void f2(int);
+int f2(char);
+
+int f3(int);
+void f3(short);
+
+int f4(long);
+void f4(int);
+
+void f5(unsigned);
+int f5(int);
+
+int f6(unsigned);
+void f6(int);
+
+void
+test ()
+{
+  int r = 0;
+  r += f1 (e);
+  r += f2 (e);
+  r += f3 (f);
+  r += f4 (g);
+  r += f5 (f);
+  r += f6 (h);
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/scoped_enum11.C b/gcc/testsuite/g++.dg/cpp0x/scoped_enum11.C
new file mode 100644
index 0000000..e6dcfba
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/scoped_enum11.C
@@ -0,0 +1,35 @@
+// PR c++/92032 - DR 1601: Promotion of enumeration with fixed underlying type.
+// { dg-do compile { target c++11 } }
+
+enum E1 : long { e1 };
+enum E2 : short { e2 };
+
+int f1(short);
+void f1(int);
+
+void f2(int);
+int f2(short);
+
+void f3(int);
+int f3(long);
+
+int f4(short);
+void f4(long);
+
+int f5(int);
+void f5(long);
+
+int f6(unsigned int); // { dg-message "candidate" }
+void f6(long); // { dg-message "candidate" }
+
+void
+fn ()
+{
+  int r = 0;
+  r += f1 (e2);
+  r += f2 (e2);
+  r += f3 (e1);
+  r += f4 (e2);
+  r += f5 (e2);
+  r += f6 (e2); // { dg-error "ambiguous" }
+}