Add JS_PROMISE_NOT_A_PROMISE to JSPromiseStateEnum (#1269)

Fixes: #1268

Author: bnoordhuis

quickjs.c

@@ -50558,7 +50558,7 @@ JSPromiseStateEnum JS_PromiseState(JSContext *ctx, JSValueConst promise)
 {
     JSPromiseData *s = JS_GetOpaque(promise, JS_CLASS_PROMISE);
     if (!s)
-        return -1;
+        return JS_PROMISE_NOT_A_PROMISE;
     return s->promise_state;
 }
 

quickjs.h

@@ -1013,7 +1013,9 @@ typedef struct {
 JS_EXTERN void JS_SetSharedArrayBufferFunctions(JSRuntime *rt, const JSSharedArrayBufferFunctions *sf);
 
 typedef enum JSPromiseStateEnum {
-    JS_PROMISE_PENDING,
+    // argument to JS_PromiseState() was not in fact a promise
+    JS_PROMISE_NOT_A_PROMISE = -1,
+    JS_PROMISE_PENDING       =  0,
     JS_PROMISE_FULFILLED,
     JS_PROMISE_REJECTED,
 } JSPromiseStateEnum;