fixes #20244; fixes castSizes warnings (#21102)

* fixes #20244; fixes castSizes warnings

* fixes js

* fixes js

* fixes js

* fixes

* typo

* extend using uint64

* Update lib/std/syncio.nim

compiler/ccgutils.nim

@@ -53,7 +53,7 @@ proc hashString*(conf: ConfigRef; s: string): BiggestInt =
     a = a + (a shl 3)
     a = a xor (a shr 11)
     a = a + (a shl 15)
-    result = cast[Hash](a)
+    result = cast[Hash](uint(a))
 
 template getUniqueType*(key: PType): PType = key
 

compiler/condsyms.nim

@@ -146,6 +146,7 @@ proc initDefines*(symbols: StringTableRef) =
   defineSymbol("nimHasCallsitePragma")
   defineSymbol("nimHasAmbiguousEnumHint")
 
+  defineSymbol("nimHasWarnCastSizes")
   defineSymbol("nimHasOutParams")
   defineSymbol("nimHasSystemRaisesDefect")
   defineSymbol("nimHasWarnUnnamedBreak")

compiler/nim.cfg

@@ -31,6 +31,10 @@ define:useStdoutAsStdmsg
   warning[ObservableStores]:off
 @end
 
+@if nimHasWarnCastSizes:
+  warning[CastSizes]:on
+@end
+
 @if nimHasWarningAsError:
   warningAsError[GcUnsafe2]:on
 @end