Simplify encoding/decoding of signed integers

Fixes error in Nim 1.4.8

contractabi/decoding.nim

@@ -4,6 +4,7 @@ import pkg/stew/byteutils
 import pkg/questionable/results
 import pkg/upraises
 import ./encoding
+import ./integers
 
 push: {.upraises:[].}
 
@@ -19,6 +20,7 @@ type
     padLeft,
     padRight
   UInt = SomeUnsignedInt | StUint
+  Int = SomeSignedInt | StInt
 
 func read*(decoder: var AbiDecoder, T: type): ?!T
 
@@ -79,21 +81,8 @@ func read(decoder: var AbiDecoder, amount: int, padding=padLeft): ?!seq[byte] =
 func decode(decoder: var AbiDecoder, T: type UInt): ?!T =
   success T.fromBytesBE(?decoder.read(sizeof(T)))
 
-template unsigned(T: type SomeSignedInt): type SomeUnsignedInt =
-  when T is int8: uint8
-  elif T is int16: uint16
-  elif T is int32: uint32
-  elif T is int64: uint64
-  else: {.error "unsupported signed integer type".}
-
-func decode(decoder: var AbiDecoder, T: type SomeSignedInt): ?!T =
-  let bytes = ?decoder.read(sizeof(T))
-  let unsigned = T.unsigned.fromBytesBE(bytes)
-  let signed = cast[T](unsigned)
-  success signed
-
-func decode[bits](decoder: var AbiDecoder, T: type StInt[bits]): ?!T =
-  let unsigned = ?decoder.read(StUint[bits])
+func decode(decoder: var AbiDecoder, T: type Int): ?!T =
+  let unsigned = ?decoder.read(T.unsigned)
   success cast[T](unsigned)
 
 template basetype(Range: type range): untyped =

contractabi/encoding.nim

@@ -1,6 +1,7 @@
 import pkg/stint
 import pkg/upraises
 import pkg/stew/byteutils
+import ./integers
 
 export stint
 
@@ -83,14 +84,11 @@ func padright(encoder: var AbiEncoder, bytes: openArray[byte], padding=0'u8) =
 func encode(encoder: var AbiEncoder, value: SomeUnsignedInt | StUint) =
   encoder.padleft(value.toBytesBE)
 
-func encode[bits](encoder: var AbiEncoder, value: StInt[bits]) =
-  let bytes = value.stuint(bits).toBytesBE
+func encode(encoder: var AbiEncoder, value: SomeSignedInt | StInt) =
+  let bytes = value.unsigned.toBytesBE
   let padding = if value.isNegative: 0xFF'u8 else: 0x00'u8
   encoder.padleft(bytes, padding)
 
-func encode(encoder: var AbiEncoder, value: SomeSignedInt) =
-  encoder.write(value.to(StInt[64]))
-
 func encode(encoder: var AbiEncoder, value: bool) =
   encoder.encode(if value: 1'u8 else: 0'u8)
 

contractabi/integers.nim

@@ -0,0 +1,17 @@
+import pkg/stint
+
+template unsigned*(T: type SomeSignedInt): type SomeUnsignedInt =
+  when T is int8: uint8
+  elif T is int16: uint16
+  elif T is int32: uint32
+  elif T is int64: uint64
+  else: {.error "unsupported signed integer type".}
+
+template unsigned*(T: type StInt): type StUint =
+  StUint[T.bits]
+
+func unsigned*(value: SomeSignedInt): SomeUnsignedInt =
+  cast[typeof(value).unsigned](value)
+
+func unsigned*[bits](value: StInt[bits]): StUint[bits] =
+  value.stuint(bits)