Fix encoding and decoding of embedded values

preserves.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version = "20221013"
+version = "20221016"
 author        = "Emery Hemingway"
 description   = "data model and serialization format"
 license       = "Unlicense"

src/preserves.nim

@@ -528,16 +528,14 @@ proc write*[E](str: Stream; pr: Preserve[E]) =
       str.write(value)
     str.write(0x84'u8)
   of pkEmbedded:
-    when not E is void:
-      str.write(0x86'u8)
-      str.write(pr.embed.toPreserve)
+    str.write(0x86'u8)
+    str.write(pr.embed.toPreserve)
 
 proc encode*[E](pr: Preserve[E]): seq[byte] =
   ## Return the binary-encoding of a Preserves value.
   let s = newStringStream()
   s.write pr
-  s.setPosition 0
-  result = cast[seq[byte]](s.readAll)
+  result = cast[seq[byte]](move s.data)
 
 proc decodePreserves*(s: Stream; E = void): Preserve[E] =
   ## Decode a Preserves value from a binary-encoded stream.
@@ -735,7 +733,7 @@ proc toPreserve*[T](x: T; E = void): Preserve[E] =
       else:
         toPreserve(val, E)
     when T.hasCustomPragma(unpreservable):
-      {.error: $T & " is unpreservable".}
+      raiseAssert($T & " is unpreservable")
     elif T.hasCustomPragma(preservesOr):
       var hasKind, hasVariant: bool
       for k, v in x.fieldPairs: