fix #8821 (#15809)

(cherry picked from commit 544cb107c7)

tests/js/t8821.nim

@@ -0,0 +1,12 @@
+discard """
+  errormsg: "Your case statement contains too many branches, consider using if/else instead!"
+"""
+
+proc isInt32(i: int): bool =
+  case i 
+  of 1 .. 70000:
+    return true
+  else:
+    return false
+
+discard isInt32(1)