Support distinct types

contractabi/decoding.nim

@@ -1,3 +1,4 @@
+import std/typetraits
 import pkg/stint
 import pkg/stew/endians2
 import pkg/stew/byteutils
@@ -159,6 +160,9 @@ func decode[I,T](decoder: var AbiDecoder, _: type array[I,T]): ?!array[I,T] =
 func decode(decoder: var AbiDecoder, T: type string): ?!T =
   success string.fromBytes(?decoder.read(seq[byte]))
 
+func decode[T: distinct](decoder: var AbiDecoder, _: type T): ?!T =
+  success T(?decoder.read(distinctBase T))
+
 func readOffset(decoder: var AbiDecoder): ?!int =
   let offset = ?decoder.read(uint64)
   success decoder.currentTuple.start + offset.int

contractabi/encoding.nim

@@ -1,3 +1,4 @@
+import std/typetraits
 import pkg/stint
 import pkg/upraises
 import pkg/stew/byteutils
@@ -131,6 +132,10 @@ func encode(encoder: var AbiEncoder, tupl: tuple) =
     encoder.write(element)
   encoder.finishTuple()
 
+func encode(encoder: var AbiEncoder, value: distinct) =
+  type Base = distinctBase(typeof(value))
+  encoder.write(Base(value))
+
 func finish(encoder: var AbiEncoder): Tuple =
   doAssert encoder.stack.len == 1, "not all tuples were finished"
   doAssert encoder.stack[0].bytes.len mod 32 == 0, "encoding invariant broken"

contractabi/selector.nim

@@ -1,4 +1,5 @@
 import std/strutils
+import std/typetraits
 import pkg/nimcrypto
 import pkg/stint
 import pkg/stew/byteutils
@@ -60,6 +61,9 @@ func solidityType*(Tuple: type tuple): string =
     names.add(solidityType(typeof parameter))
   "(" & names.join(",") & ")"
 
+func solidityType*(T: distinct type): string =
+  solidityType(distinctBase T)
+
 func signature*(function: string, Parameters: type tuple = ()): string =
   function & solidityType(Parameters)
 

tests/contractabi/testDecoding.nim

@@ -3,6 +3,9 @@ import pkg/questionable/results
 import contractabi
 import ./examples
 
+type SomeDistinctType = distinct uint16
+func `==`*(a, b: SomeDistinctType): bool {.borrow.}
+
 suite "ABI decoding":
 
   proc checkDecode[T](value: T) =
@@ -140,3 +143,6 @@ suite "ABI decoding":
 
   test "decodes strings":
     checkDecode("hello!☺")
+
+  test "decodes distinct types as their base type":
+    checkDecode(SomeDistinctType(0xAABB'u16))

tests/contractabi/testEncoding.nim

@@ -138,6 +138,11 @@ suite "ABI encoding":
   test "encodes strings as UTF-8 byte sequence":
     check AbiEncoder.encode("hello!☺") == AbiEncoder.encode("hello!☺".toBytes)
 
+  test "encodes distinct types as their base type":
+    type SomeDistinctType = distinct uint16
+    let value = 0xAABB'u16
+    check AbiEncoder.encode(SomeDistinctType(value)) == AbiEncoder.encode(value)
+
   test "can determine whether types are dynamic or static":
     check static AbiEncoder.isStatic(uint8)
     check static AbiEncoder.isDynamic(seq[byte])

tests/contractabi/testSelector.nim

@@ -35,6 +35,10 @@ suite "function selector":
     check solidityType((Address, string, bool)) == "(address,string,bool)"
     check solidityType(SomeEnum) == "uint8"
 
+  test "translates distinct type into base type":
+    type SomeDistinctType = distinct uint16
+    check solidityType(SomeDistinctType) == solidityType(uint16)
+
   test "calculates solidity function selector":
     check $selector("transfer", (Address, UInt256)) == "0xa9059cbb"
     check $selector("transferFrom", (Address, Address, UInt256)) == "0x23b872dd"