contracts: update G2Point definition

codex/contracts/proofs.nim

@@ -10,13 +10,20 @@ type
   G1Point* = object
     x*: UInt256
     y*: UInt256
+  # A field element F_{p^2} encoded as `real + i * imag`
+  Fp2Element* = object
+    real*: UInt256
+    imag*: UInt256
   G2Point* = object
-    x*: array[2, UInt256]
+    x*: Fp2Element
-    y*: array[2, UInt256]
+    y*: Fp2Element
 
 func solidityType*(_: type G1Point): string =
   solidityType(G1Point.fieldTypes)
 
+func solidityType*(_: type Fp2Element): string =
+  solidityType(Fp2Element.fieldTypes)
+
 func solidityType*(_: type G2Point): string =
   solidityType(G2Point.fieldTypes)
 
@@ -26,6 +33,9 @@ func solidityType*(_: type Groth16Proof): string =
 func encode*(encoder: var AbiEncoder, point: G1Point) =
   encoder.write(point.fieldValues)
 
+func encode*(encoder: var AbiEncoder, element: Fp2Element) =
+  encoder.write(element.fieldValues)
+
 func encode*(encoder: var AbiEncoder, point: G2Point) =
   encoder.write(point.fieldValues)
 

codex/slots/proofs/backends/converters.nim

@@ -54,14 +54,14 @@ func toG1*(g: CircomG1): G1Point =
 
 func toG2*(g: CircomG2): G2Point =
   G2Point(
-    x: [
+    x: Fp2Element(
-      UInt256.fromBytesLE(g.x[0]),
+      real: UInt256.fromBytesLE(g.x[0]),
-      UInt256.fromBytesLE(g.x[1])
+      imag: UInt256.fromBytesLE(g.x[1])
-    ],
+    ),
-    y: [
+    y: Fp2Element(
-      UInt256.fromBytesLE(g.y[0]),
+      real: UInt256.fromBytesLE(g.y[0]),
-      UInt256.fromBytesLE(g.y[1])
+      imag: UInt256.fromBytesLE(g.y[1])
-    ])
+    ))
 
 func toGroth16Proof*(proof: CircomProof): Groth16Proof =
   Groth16Proof(

tests/examples.nim

@@ -78,8 +78,8 @@ proc example(_: type G1Point): G1Point =
 
 proc example(_: type G2Point): G2Point =
   G2Point(
-    x: [UInt256.example, UInt256.example],
+    x: Fp2Element(real: UInt256.example, imag: UInt256.example),
-    y: [UInt256.example, UInt256.example]
+    y: Fp2Element(real: UInt256.example, imag: UInt256.example)
   )
 
 proc example*(_: type Groth16Proof): Groth16Proof =