Bug 1383157 - change pn_type to a ParseNodeKind; r=jimb

MozReview-Commit-ID: 3woMGwYs3wY

--HG--
extra : rebase_source : 5bd7fc25a4cbfbc288ce19650831b484757689ed

js/src/frontend/ParseNode.h

@@ -179,7 +179,7 @@ class ObjectBox;
  *
  * The long comment after this enum block describes the kinds in detail.
  */
-enum ParseNodeKind
+enum ParseNodeKind : uint16_t
 {
 #define EMIT_ENUM(name) PNK_##name,
     FOR_EACH_PARSE_NODE_KIND(EMIT_ENUM)
@@ -450,7 +450,11 @@ class PropertyAccess;
 
 class ParseNode
 {
-    uint16_t pn_type;   /* PNK_* type */
+    ParseNodeKind pn_type;   /* PNK_* type */
+    // pn_op and pn_arity are not declared as the correct enum types
+    // due to difficulties with MS bitfield layout rules and a GCC
+    // bug.  See https://bugzilla.mozilla.org/show_bug.cgi?id=1383157#c4 for
+    // details.
     uint8_t pn_op;      /* see JSOp enum and jsopcode.tbl */
     uint8_t pn_arity:4; /* see ParseNodeArity enum */
     bool pn_parens:1;   /* this expr was enclosed in parens */
@@ -494,7 +498,7 @@ class ParseNode
 
     ParseNodeKind getKind() const {
         MOZ_ASSERT(pn_type < PNK_LIMIT);
-        return ParseNodeKind(pn_type);
+        return pn_type;
     }
     void setKind(ParseNodeKind kind) {
         MOZ_ASSERT(kind < PNK_LIMIT);