Add JSRESOLVE_DETECTING (246964, r=shaver).

js/src/js.c

@@ -1775,11 +1775,15 @@ its_enumerate(JSContext *cx, JSObject *obj)
 }
 
 static JSBool
-its_resolve(JSContext *cx, JSObject *obj, jsval id)
+its_resolve(JSContext *cx, JSObject *obj, jsval id, uintN flags,
+            JSObject **objp)
 {
     if (its_noisy) {
-        fprintf(gOutFile, "resolving its property %s\n",
-               JS_GetStringBytes(JS_ValueToString(cx, id)));
+        fprintf(gOutFile, "resolving its property %s, flags {%s,%s,%s}\n",
+               JS_GetStringBytes(JS_ValueToString(cx, id)),
+               (flags & JSRESOLVE_QUALIFIED) ? "qualified" : "",
+               (flags & JSRESOLVE_ASSIGNING) ? "assigning" : "",
+               (flags & JSRESOLVE_DETECTING) ? "detecting" : "");
     }
     return JS_TRUE;
 }
@@ -1800,9 +1804,10 @@ its_finalize(JSContext *cx, JSObject *obj)
 }
 
 static JSClass its_class = {
-    "It", 0,
+    "It", JSCLASS_NEW_RESOLVE,
     its_addProperty,  its_delProperty,  its_getProperty,  its_setProperty,
-    its_enumerate,    its_resolve,      its_convert,      its_finalize
+    its_enumerate,    (JSResolveOp)its_resolve,
+                                        its_convert,      its_finalize
 };
 
 JSErrorFormatString jsShell_ErrorFormatString[JSErr_Limit] = {

js/src/jsapi.h

@@ -826,6 +826,7 @@ JS_IdToValue(JSContext *cx, jsid id, jsval *vp);
 
 #define JSRESOLVE_QUALIFIED     0x01    /* resolve a qualified property id */
 #define JSRESOLVE_ASSIGNING     0x02    /* resolve on the left of assignment */
+#define JSRESOLVE_DETECTING     0x04    /* 'if (o.p)...' or '(o.p) ?...:...' */
 
 extern JS_PUBLIC_API(JSBool)
 JS_PropertyStub(JSContext *cx, JSObject *obj, jsval id, jsval *vp);

js/src/jsobj.c

@@ -2400,6 +2400,8 @@ js_LookupProperty(JSContext *cx, JSObject *obj, jsid id, JSObject **objp,
     uint32 generation;
     JSNewResolveOp newresolve;
     uintN flags;
+    jsbytecode *pc;
+    const JSCodeSpec *cs;
     uint32 format;
     JSBool ok;
 
@@ -2454,13 +2456,20 @@ js_LookupProperty(JSContext *cx, JSObject *obj, jsid id, JSObject **objp,
                 if (clasp->flags & JSCLASS_NEW_RESOLVE) {
                     newresolve = (JSNewResolveOp)resolve;
                     flags = 0;
-                    if (cx->fp && cx->fp->pc) {
-                        format = js_CodeSpec[*cx->fp->pc].format;
+                    if (cx->fp && (pc = cx->fp->pc)) {
+                        cs = &js_CodeSpec[*pc];
+                        format = cs->format;
                         if ((format & JOF_MODEMASK) != JOF_NAME)
                             flags |= JSRESOLVE_QUALIFIED;
                         if ((format & JOF_ASSIGNING) ||
                             (cx->fp->flags & JSFRAME_ASSIGNING)) {
                             flags |= JSRESOLVE_ASSIGNING;
+                        } else {
+                            pc += cs->length;
+                            while (*pc == JSOP_GROUP)
+                                pc++;
+                            if (*pc == JSOP_IFEQ)
+                                flags |= JSRESOLVE_DETECTING;
                         }
                     }
                     obj2 = (clasp->flags & JSCLASS_NEW_RESOLVE_GETS_START)