fix #16822 (#16884)

* see whether it breaks

* fix #16884

* correct

* fix #14574

compiler/jsgen.nim

@@ -1077,10 +1077,10 @@ proc genAsgnAux(p: PProc, x, y: PNode, noCopyNeeded: bool) =
       # supports proc getF(): var T
       if x.kind in {nkHiddenDeref, nkDerefExpr} and x[0].kind in nkCallKinds:
           lineF(p, "nimCopy($1, $2, $3);$n",
-                [a.res, b.res, genTypeInfo(p, y.typ)])
+                [a.res, b.res, genTypeInfo(p, x.typ)])
       else:
         lineF(p, "$1 = nimCopy($1, $2, $3);$n",
-              [a.res, b.res, genTypeInfo(p, y.typ)])
+              [a.res, b.res, genTypeInfo(p, x.typ)])
   of etyBaseIndex:
     if a.typ != etyBaseIndex or b.typ != etyBaseIndex:
       if y.kind == nkCall:

tests/js/t16822.nim

@@ -0,0 +1,29 @@
+block: # bug #16822
+  var scores: seq[(set[char], int)] = @{{'/'} : 10}
+
+  var x1: set[char]
+  for item in items(scores):
+    x1 = item[0]
+
+  doAssert x1 == {'/'}
+
+  var x2: set[char]
+  for (chars, value) in items(scores):
+    x2 = chars
+
+  doAssert x2 == {'/'}
+
+block: # bug #14574
+  proc fn(): auto =
+    let a = @[("foo", (12, 13))]
+    for (k,v) in a:
+      return (k,v)
+  doAssert fn() == ("foo", (12, 13))
+
+block: # bug #14574
+  iterator fn[T](a:T): lent T = yield a
+  let a = (10, (11,))
+  proc bar(): auto =
+    for (x,y) in fn(a):
+      return (x,y)
+  doAssert bar() == (10, (11,))

tests/stdlib/tjsonutils.nim

@@ -42,7 +42,6 @@ template fn() =
 
   block:
     testRoundtrip({"z": "Z", "y": "Y"}.toOrderedTable): """{"z":"Z","y":"Y"}"""
-    when not defined(js): # pending https://github.com/nim-lang/Nim/issues/14574
     testRoundtrip({"z": (f1: 'f'), }.toTable): """{"z":{"f1":102}}"""
 
   block: