fixes #12015 by also checking kind of typeNode (#12016)

* fixes #12015 by also checking kind of `typeNode`

If a tuple field is aliased it'll appear the same as a ref type in a
call to `getType` if only for the kind of the resulting `NimNode` is
checked (that is a `nnkBracketExpr`)

* fix test case due to #12017 and add more realistic test case

Adds an additional test case, which includes generics and is closer to
the real failure I encountered

* remove previous fix and fix differently after all

The previous fix was incomplete, because it failed for generics.

Note that the `of "tuple"` is not actually needed, the
`nnkBracketExpr` branch in the `else` branch would catch it too, but I
decided to introduce it for clarity. However, the latter is actually
needed, because it seems for aliases of `seq` we end up in it.

* update comment about global `%` proc in json test

lib/pure/json.nim

@@ -1369,11 +1369,20 @@ proc createConstructor(typeSym, jsonNode: NimNode): NimNode =
           for `forLoopI` in 0 ..< `jsonNode`.len: list[`forLoopI`] =`constructorNode`;
           list
         )
-
+    of "tuple":
+      let typeNode = getTypeImpl(typeSym)
+      result = createConstructor(typeNode, jsonNode)
     else:
-      # Generic type.
+      # Generic type or some `seq[T]` alias
       let obj = getType(typeSym)
-      result = processType(typeSym, obj, jsonNode, false)
+      case obj.kind
+      of nnkBracketExpr:
+        # probably a `seq[T]` alias
+        let typeNode = getTypeImpl(typeSym)
+        result = createConstructor(typeNode, jsonNode)
+      else:
+        # generic type
+        result = processType(typeSym, obj, jsonNode, false)
   of nnkSym:
     # Handle JsonNode.
     if ($typeSym).cmpIgnoreStyle("jsonnode") == 0:
@@ -1385,7 +1394,7 @@ proc createConstructor(typeSym, jsonNode: NimNode): NimNode =
     if typeNode.typeKind == ntyDistinct:
       result = createConstructor(typeNode, jsonNode)
     elif obj.kind == nnkBracketExpr:
-      # When `Sym "Foo"` turns out to be a `ref object`.
+      # When `Sym "Foo"` turns out to be a `ref object` or `tuple`
       result = createConstructor(obj, jsonNode)
     else:
       result = processType(typeSym, obj, jsonNode, false)