make jsffi properly gensym (#22539)

fixes #21208

lib/js/jsffi.nim

@@ -227,36 +227,40 @@ macro `.`*(obj: JsObject, field: untyped): JsObject =
     assert obj.a.to(int) == 20
   if validJsName($field):
     let importString = "#." & $field
+    let helperName = genSym(nskProc, "helper")
     result = quote do:
-      proc helper(o: JsObject): JsObject
-        {.importjs: `importString`, gensym.}
-      helper(`obj`)
+      proc `helperName`(o: JsObject): JsObject
+        {.importjs: `importString`.}
+      `helperName`(`obj`)
   else:
     if not mangledNames.hasKey($field):
       mangledNames[$field] = mangleJsName($field)
     let importString = "#." & mangledNames[$field]
+    let helperName = genSym(nskProc, "helper")
     result = quote do:
-      proc helper(o: JsObject): JsObject
-        {.importjs: `importString`, gensym.}
-      helper(`obj`)
+      proc `helperName`(o: JsObject): JsObject
+        {.importjs: `importString`.}
+      `helperName`(`obj`)
 
 macro `.=`*(obj: JsObject, field, value: untyped): untyped =
   ## Experimental dot accessor (set) for type JsObject.
   ## Sets the value of a property of name `field` in a JsObject `x` to `value`.
   if validJsName($field):
     let importString = "#." & $field & " = #"
+    let helperName = genSym(nskProc, "helper")
     result = quote do:
-      proc helper(o: JsObject, v: auto)
-        {.importjs: `importString`, gensym.}
-      helper(`obj`, `value`)
+      proc `helperName`(o: JsObject, v: auto)
+        {.importjs: `importString`.}
+      `helperName`(`obj`, `value`)
   else:
     if not mangledNames.hasKey($field):
       mangledNames[$field] = mangleJsName($field)
     let importString = "#." & mangledNames[$field] & " = #"
+    let helperName = genSym(nskProc, "helper")
     result = quote do:
-      proc helper(o: JsObject, v: auto)
-        {.importjs: `importString`, gensym.}
-      helper(`obj`, `value`)
+      proc `helperName`(o: JsObject, v: auto)
+        {.importjs: `importString`.}
+      `helperName`(`obj`, `value`)
 
 macro `.()`*(obj: JsObject,
              field: untyped,
@@ -283,10 +287,11 @@ macro `.()`*(obj: JsObject,
     if not mangledNames.hasKey($field):
       mangledNames[$field] = mangleJsName($field)
     importString = "#." & mangledNames[$field] & "(@)"
-  result = quote:
-    proc helper(o: JsObject): JsObject
-      {.importjs: `importString`, gensym, discardable.}
-    helper(`obj`)
+  let helperName = genSym(nskProc, "helper")
+  result = quote do:
+    proc `helperName`(o: JsObject): JsObject
+      {.importjs: `importString`, discardable.}
+    `helperName`(`obj`)
   for idx in 0 ..< args.len:
     let paramName = newIdentNode("param" & $idx)
     result[0][3].add newIdentDefs(paramName, newIdentNode("JsObject"))
@@ -303,10 +308,11 @@ macro `.`*[K: cstring, V](obj: JsAssoc[K, V],
     if not mangledNames.hasKey($field):
       mangledNames[$field] = mangleJsName($field)
     importString = "#." & mangledNames[$field]
+  let helperName = genSym(nskProc, "helper")
   result = quote do:
-    proc helper(o: type(`obj`)): `obj`.V
-      {.importjs: `importString`, gensym.}
-    helper(`obj`)
+    proc `helperName`(o: type(`obj`)): `obj`.V
+      {.importjs: `importString`.}
+    `helperName`(`obj`)
 
 macro `.=`*[K: cstring, V](obj: JsAssoc[K, V],
                                     field: untyped,
@@ -320,10 +326,11 @@ macro `.=`*[K: cstring, V](obj: JsAssoc[K, V],
     if not mangledNames.hasKey($field):
       mangledNames[$field] = mangleJsName($field)
     importString = "#." & mangledNames[$field] & " = #"
+  let helperName = genSym(nskProc, "helper")
   result = quote do:
-    proc helper(o: type(`obj`), v: `obj`.V)
-      {.importjs: `importString`, gensym.}
-    helper(`obj`, `value`)
+    proc `helperName`(o: type(`obj`), v: `obj`.V)
+      {.importjs: `importString`.}
+    `helperName`(`obj`, `value`)
 
 macro `.()`*[K: cstring, V: proc](obj: JsAssoc[K, V],
                                            field: untyped,

tests/js/tjsffi.nim

@@ -265,3 +265,9 @@ block: # test **
   doAssert to(`**`(a + a, b), int) == 2
 
   doAssert to(`**`(toJs(1) + toJs(1), toJs(2)), int) == 4
+
+block: # issue #21208
+  type MyEnum = enum baz
+  var obj: JsObject
+  {.emit: "`obj` = {bar: {baz: 123}}".}
+  discard obj.bar.baz