fixes #23952; Size/Signedness issues with unordered enums (#24356)

fixes #23952

It reorders `type Foo = enum A, B = -1` to `type Foo = enum B = -1, A`
so that `firstOrd` etc. continue to work.

(cherry picked from commit 294b1566e7)

compiler/semtypes.nim

@@ -84,6 +84,7 @@ proc semEnum(c: PContext, n: PNode, prev: PType): PType =
   let isPure = result.sym != nil and sfPure in result.sym.flags
   var symbols: TStrTable = initStrTable()
   var hasNull = false
+  var needsReorder = false
   for i in 1..<n.len:
     if n[i].kind == nkEmpty: continue
     var useAutoCounter = false
@@ -122,7 +123,9 @@ proc semEnum(c: PContext, n: PNode, prev: PType): PType =
         else:
           localError(c.config, v.info, errOrdinalTypeExpected % typeToString(v.typ, preferDesc))
       if i != 1:
-        if x != counter: incl(result.flags, tfEnumHasHoles)
+        if x != counter:
+          needsReorder = true
+          incl(result.flags, tfEnumHasHoles)
       e.ast = strVal # might be nil
       counter = x
     of nkSym:
@@ -173,6 +176,13 @@ proc semEnum(c: PContext, n: PNode, prev: PType): PType =
         localError(c.config, n[i].info, errOverflowInEnumX % [e.name.s, $high(typeof(counter))])
     else:
       inc(counter)
+
+  if needsReorder:
+    result.n.sons.sort(
+      proc (x, y: PNode): int =
+        result = cmp(x.sym.position, y.sym.position)
+    )
+
   if isPure and sfExported in result.sym.flags:
     addPureEnum(c, LazySym(sym: result.sym))
   if tfNotNil in e.typ.flags and not hasNull:

tests/enum/tenum.nim

@@ -197,7 +197,7 @@ block: # unordered enum
         b = 0
 
     doAssert (ord(a), ord(b)) == (1, 0)
-    doAssert unordered_enum.toSeq == @[a, b]
+    doAssert unordered_enum.toSeq == @[b, a]
 
   block:
     type
@@ -227,7 +227,7 @@ block: # unordered enum
         d
 
     doAssert (ord(a), ord(b), ord(c), ord(d)) == (7, 6, 5, 8)
-    doAssert unordered_enum.toSeq == @[a, b, c, d]
+    doAssert unordered_enum.toSeq == @[c, b, a, d]
 
   block:
     type
@@ -265,3 +265,21 @@ block: # unordered enum
         seC = "foo"
 
     doAssert (ord(seA), ord(seB), ord(seC)) == (3, 2, 4)
+
+block: # bug #23952
+  block:
+    proc foo =
+      type Foo = enum A B = -1
+      doAssert cast[Foo](-1) == B
+      doAssert ord(A) == 0
+    static: foo()
+    foo()
+
+  block:
+    proc foo =
+      type Foo = enum A B=8, C=1
+      let s1 = {A}
+      let s2 = {B}
+      doAssert s1 != s2
+    static: foo()
+    foo()