fixes #21207; reports redefinition error in the definition of enums (#21217)

* fixes #21207;  reports redefinition in the enums

* add a test

compiler/semtypes.nim

@@ -73,7 +73,7 @@ proc semEnum(c: PContext, n: PNode, prev: PType): PType =
   rawAddSon(result, base)
   let isPure = result.sym != nil and sfPure in result.sym.flags
   var symbols: TStrTable
-  if isPure: initStrTable(symbols)
+  initStrTable(symbols)
   var hasNull = false
   for i in 1..<n.len:
     if n[i].kind == nkEmpty: continue
@@ -145,7 +145,7 @@ proc semEnum(c: PContext, n: PNode, prev: PType): PType =
         addInterfaceOverloadableSymAt(c, c.currentScope, e)
       else:
         declarePureEnumField(c, e)
-    if isPure and (let conflict = strTableInclReportConflict(symbols, e); conflict != nil):
+    if (let conflict = strTableInclReportConflict(symbols, e); conflict != nil):
       wrongRedefinition(c, e.info, e.name.s, conflict.info)
     inc(counter)
   if isPure and sfExported in result.sym.flags:

tests/enum/tredefinition.nim

@@ -0,0 +1,9 @@
+discard """
+  cmd: '''nim check --hints:off $file'''
+  action: reject
+nimout: '''
+tredefinition.nim(9, 25) Error: redefinition of 'Key_a'; previous declaration here: tredefinition.nim(9, 18)
+'''
+"""
+
+type Key* = enum Key_A, Key_a