make parseEnum skip type aliases for enum type sym (#22727)

fixes #22726

(cherry picked from commit 51cb493b22)

lib/std/enumutils.nim

@@ -22,7 +22,8 @@ macro genEnumCaseStmt*(typ: typedesc, argSym: typed, default: typed,
   # a normalized string comparison to the `argSym` input.
   # string normalization is done using passed normalizer.
   let typ = typ.getTypeInst[1]
-  let impl = typ.getImpl[2]
+  let typSym = typ.getTypeImpl.getTypeInst # skip aliases etc to get type sym
+  let impl = typSym.getImpl[2]
   expectKind impl, nnkEnumTy
   let normalizerNode = quote: `normalizer`
   expectKind normalizerNode, nnkSym

tests/stdlib/tstrutils.nim

@@ -679,11 +679,22 @@ template main() =
       doAssert b == f2
       doAssert c == f3
 
-  block: # parseEnum TODO: merge above
-    type MyEnum = enum enA, enB, enC, enuD, enE
-    doAssert parseEnum[MyEnum]("enu_D") == enuD
+    block:
+      type MyEnum = enum enA, enB, enC, enuD, enE
+      doAssert parseEnum[MyEnum]("enu_D") == enuD
 
-    doAssert parseEnum("invalid enum value", enC) == enC
+      doAssert parseEnum("invalid enum value", enC) == enC
+    
+    block: # issue #22726
+      type SomeEnum = enum A, B, C
+
+      proc assignEnum(dest: var enum, s: string) =
+        type ty = typeof(dest)
+        dest = parseEnum[ty](s)
+      
+      var v: SomeEnum
+      v.assignEnum("A")
+      doAssert v == A
 
   block: # indentation
     doAssert 0 == indentation """