fixes #13671 [backport] (#13678)

(cherry picked from commit 5f6997794e)

compiler/semexprs.nim

@@ -508,7 +508,7 @@ proc changeType(c: PContext; n: PNode, newType: PType, check: bool) =
           addSon(a, m)
           changeType(m, tup.sons[i], check)
   of nkCharLit..nkUInt64Lit:
-    if check and n.kind != nkUInt64Lit:
+    if check and n.kind != nkUInt64Lit and not sameType(n.typ, newType):
       let value = n.intVal
       if value < firstOrd(c.config, newType) or value > lastOrd(c.config, newType):
         localError(c.config, n.info, "cannot convert " & $value &

tests/misc/tunsignedconv.nim

@@ -55,3 +55,8 @@ const x0 = fun()
 echo typeof(x0)
 
 discard $x0
+
+# bug #13671
+
+const x1 = cast[uint](-1)
+discard $(x1,)