fixes #23419; internal error with void in generic array instantiation (#23550)

fixes #23419

`void` is only supported as fields of objects/tuples. It shouldn't allow
void in the array.

I didn't merge it with taField because that flag is also used for
tyLent, which is allowed in the fields of other types.

(cherry picked from commit 185e06c923)

compiler/typeallowed.nim

@@ -27,6 +27,7 @@ type
     taProcContextIsNotMacro
     taIsCastable
     taIsDefaultField
+    taVoid # only allow direct void fields of objects/tuples
 
   TTypeAllowedFlags* = set[TTypeAllowedFlag]
 
@@ -58,6 +59,8 @@ proc typeAllowedAux(marker: var IntSet, typ: PType, kind: TSymKind,
   if typ == nil: return nil
   if containsOrIncl(marker, typ.id): return nil
   var t = skipTypes(typ, abstractInst-{tyTypeDesc, tySink})
+
+  let flags = if t.kind == tyVoid: flags else: flags-{taVoid}
   case t.kind
   of tyVar, tyLent:
     if kind in {skProc, skFunc, skConst} and (views notin c.features):
@@ -113,7 +116,7 @@ proc typeAllowedAux(marker: var IntSet, typ: PType, kind: TSymKind,
   of tyStatic:
     if kind notin {skParam}: result = t
   of tyVoid:
-    if taField notin flags: result = t
+    if taVoid notin flags: result = t
   of tyTypeClasses:
     if tfGenericTypeParam in t.flags or taConcept in flags: #or taField notin flags:
       discard
@@ -184,7 +187,7 @@ proc typeAllowedAux(marker: var IntSet, typ: PType, kind: TSymKind,
         t.kind == tyObject and t[0] != nil and taIsDefaultField notin flags:
       result = t
     else:
-      let flags = flags+{taField}
+      let flags = flags+{taField, taVoid}
       for i in 0..<t.len:
         result = typeAllowedAux(marker, t[i], kind, c, flags)
         if result != nil: break

tests/errmsgs/t23419.nim

@@ -0,0 +1,5 @@
+discard """
+  errormsg: "invalid type: 'void' in this context: '(array[0..-1, void],)' for var"
+"""
+
+var a: (array[0, void], )