re PR c++/82307 (unscoped enum-base incorrect cast)

/cp
2017-10-24  Mukesh Kapoor  <mukesh.kapoor@oracle.com>
	    Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/82307
	* cvt.c (type_promotes_to): Implement C++17, 7.6/4, about unscoped
	enumeration type whose underlying type is fixed.

/testsuite
2017-10-24  Mukesh Kapoor  <mukesh.kapoor@oracle.com>
	    Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/82307
	* g++.dg/cpp0x/enum35.C: New.
	* g++.dg/cpp0x/enum36.C: Likewise.

Co-Authored-By: Paolo Carlini <paolo.carlini@oracle.com>

From-SVN: r254046

gcc/cp/ChangeLog

+2017-10-24  Mukesh Kapoor  <mukesh.kapoor@oracle.com>
+	    Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/82307
+	* cvt.c (type_promotes_to): Implement C++17, 7.6/4, about unscoped
+	enumeration type whose underlying type is fixed.
+
 2017-10-23  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	PR c++/80449

gcc/cp/cvt.c

@@ -1834,12 +1834,27 @@ type_promotes_to (tree type)
 	   || type == char32_type_node
 	   || type == wchar_type_node)
     {
+      tree prom = type;
+
+      if (TREE_CODE (type) == ENUMERAL_TYPE)
+	{
+	  prom = ENUM_UNDERLYING_TYPE (prom);
+	  if (!ENUM_IS_SCOPED (type)
+	      && ENUM_FIXED_UNDERLYING_TYPE_P (type))
+	    {
+	      /* ISO C++17, 7.6/4.  A prvalue of an unscoped enumeration type
+		 whose underlying type is fixed (10.2) can be converted to a
+		 prvalue of its underlying type. Moreover, if integral promotion
+		 can be applied to its underlying type, a prvalue of an unscoped
+		 enumeration type whose underlying type is fixed can also be 
+		 converted to a prvalue of the promoted underlying type.  */
+	      return type_promotes_to (prom);
+	    }
+	}
+
       int precision = MAX (TYPE_PRECISION (type),
 			   TYPE_PRECISION (integer_type_node));
       tree totype = c_common_type_for_size (precision, 0);
-      tree prom = type;
-      if (TREE_CODE (prom) == ENUMERAL_TYPE)
-	prom = ENUM_UNDERLYING_TYPE (prom);
       if (TYPE_UNSIGNED (prom)
 	  && ! int_fits_type_p (TYPE_MAX_VALUE (prom), totype))
 	prom = c_common_type_for_size (precision, 1);

gcc/testsuite/ChangeLog

+2017-10-24  Mukesh Kapoor  <mukesh.kapoor@oracle.com>
+	    Paolo Carlini  <paolo.carlini@oracle.com>
+
+	PR c++/82307
+	* g++.dg/cpp0x/enum35.C: New.
+	* g++.dg/cpp0x/enum36.C: Likewise.
+
 2017-10-24  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR target/82659

gcc/testsuite/g++.dg/cpp0x/enum35.C

+// PR c++/82307
+// { dg-do run { target c++11 } }
+
+#include <cassert>
+
+enum : unsigned long long { VAL };
+
+bool foo (unsigned long long) { return true; }
+bool foo (int) { return false; }
+
+int main()
+{
+  assert (foo(VAL));
+}

gcc/testsuite/g++.dg/cpp0x/enum36.C

+// PR c++/82307
+// { dg-do run { target c++11 } }
+
+#include <cassert>
+
+enum : short { VAL };
+
+bool foo (int) { return true; }
+bool foo (unsigned long long) { return false; }
+
+int main()
+{
+  assert (foo (VAL));
+}