remove ArrayDummySize with unchecked arrays (#5818)

lib/system/cellsets.nim

@@ -30,13 +30,12 @@ type
     key: ByteAddress   # start address at bit 0
     bits: array[BitIndex, int] # a bit vector
 
-  PPageDescArray = ptr array[ArrayDummySize, PPageDesc]
+  PPageDescArray = ptr UncheckedArray[PPageDesc]
   CellSet {.final, pure.} = object
     counter, max: int
     head: PPageDesc
     data: PPageDescArray
-
-  PCellArray = ptr array[ArrayDummySize, PCell]
+  PCellArray = ptr UncheckedArray[PCell]
   CellSeq {.final, pure.} = object
     len, cap: int
     d: PCellArray

lib/system/mmdisp.nim

@@ -34,7 +34,7 @@ const
 
 type
   PPointer = ptr pointer
-  ByteArray = array[0..ArrayDummySize, byte]
+  ByteArray = UncheckedArray[byte]
   PByte = ptr ByteArray
   PString = ptr string
 {.deprecated: [TByteArray: ByteArray].}

lib/system/sysio.nim

@@ -86,11 +86,11 @@ proc writeBuffer(f: File, buffer: pointer, len: Natural): int =
   checkErr(f)
 
 proc writeBytes(f: File, a: openArray[int8|uint8], start, len: Natural): int =
-  var x = cast[ptr array[ArrayDummySize, int8]](a)
-  result = writeBuffer(f, addr(x[start]), len)
+  var x = cast[ptr UncheckedArray[int8]](a)
+  result = writeBuffer(f, addr(x[int(start)]), len)
 proc writeChars(f: File, a: openArray[char], start, len: Natural): int =
-  var x = cast[ptr array[ArrayDummySize, int8]](a)
-  result = writeBuffer(f, addr(x[start]), len)
+  var x = cast[ptr UncheckedArray[int8]](a)
+  result = writeBuffer(f, addr(x[int(start)]), len)
 
 proc write(f: File, s: string) =
   if writeBuffer(f, cstring(s), s.len) != s.len:

lib/system/widestrs.nim

@@ -15,7 +15,7 @@ when not declared(NimString):
 
 type
   Utf16Char* = distinct int16
-  WideCString* = ref array[ArrayDummySize, Utf16Char]
+  WideCString* = ref UncheckedArray[Utf16Char]
 {.deprecated: [TUtf16Char: Utf16Char].}
 
 proc len*(w: WideCString): int =