From 0f2dfc550807b9a98143c3cdfdeb90a65a5496bb Mon Sep 17 00:00:00 2001
From: therealyingtong <yingtong@z.cash>
Date: Tue, 8 Jun 2021 00:20:09 +0800
Subject: [PATCH] Use UtilitiesInstructions::Var instead of internal associated
 type.

Co-authored-by: Jack Grigg <jack@electriccoin.co>
---
 src/circuit/gadget/utilities/cond_swap.rs   | 31 +++------------------
 src/circuit/gadget/utilities/enable_flag.rs | 11 ++------
 src/circuit/gadget/utilities/plonk.rs       | 28 ++++++++-----------
 3 files changed, 19 insertions(+), 51 deletions(-)

diff --git a/src/circuit/gadget/utilities/cond_swap.rs b/src/circuit/gadget/utilities/cond_swap.rs
index f2d6ed89..8a805b7d 100644
--- a/src/circuit/gadget/utilities/cond_swap.rs
+++ b/src/circuit/gadget/utilities/cond_swap.rs
@@ -8,27 +8,15 @@ use pasta_curves::arithmetic::FieldExt;
 use std::marker::PhantomData;
 
 pub trait CondSwapInstructions<F: FieldExt>: UtilitiesInstructions<F> {
-    /// Variable representing cell with a certain value in the circuit.
-    type Var;
-
     #[allow(clippy::type_complexity)]
     /// Given an input pair (x,y) and a `swap` boolean flag, return
     /// (y,x) if `swap` is set, else (x,y) if `swap` is not set.
     fn swap(
         &self,
         layouter: impl Layouter<F>,
-        pair: (
-            <Self as CondSwapInstructions<F>>::Var,
-            <Self as CondSwapInstructions<F>>::Var,
-        ),
+        pair: (Self::Var, Self::Var),
         swap: Option<bool>,
-    ) -> Result<
-        (
-            <Self as CondSwapInstructions<F>>::Var,
-            <Self as CondSwapInstructions<F>>::Var,
-        ),
-        Error,
-    >;
+    ) -> Result<(Self::Var, Self::Var), Error>;
 }
 
 /// A chip implementing a conditional swap.
@@ -67,24 +55,13 @@ impl<F: FieldExt> UtilitiesInstructions<F> for CondSwapChip<F> {
 }
 
 impl<F: FieldExt> CondSwapInstructions<F> for CondSwapChip<F> {
-    type Var = CellValue<F>;
-
     #[allow(clippy::type_complexity)]
     fn swap(
         &self,
         mut layouter: impl Layouter<F>,
-        pair: (
-            <Self as CondSwapInstructions<F>>::Var,
-            <Self as CondSwapInstructions<F>>::Var,
-        ),
+        pair: (Self::Var, Self::Var),
         swap: Option<bool>,
-    ) -> Result<
-        (
-            <Self as CondSwapInstructions<F>>::Var,
-            <Self as CondSwapInstructions<F>>::Var,
-        ),
-        Error,
-    > {
+    ) -> Result<(Self::Var, Self::Var), Error> {
         let config = self.config();
 
         layouter.assign_region(
diff --git a/src/circuit/gadget/utilities/enable_flag.rs b/src/circuit/gadget/utilities/enable_flag.rs
index 2ccc4fda..2497f3a3 100644
--- a/src/circuit/gadget/utilities/enable_flag.rs
+++ b/src/circuit/gadget/utilities/enable_flag.rs
@@ -1,4 +1,4 @@
-use super::{copy, CellValue, UtilitiesInstructions, Var};
+use super::{copy, CellValue, UtilitiesInstructions};
 use halo2::{
     circuit::{Chip, Layouter},
     plonk::{Advice, Column, ConstraintSystem, Error, Expression, Permutation, Selector},
@@ -8,15 +8,12 @@ use pasta_curves::arithmetic::FieldExt;
 use std::marker::PhantomData;
 
 pub trait EnableFlagInstructions<F: FieldExt>: UtilitiesInstructions<F> {
-    /// Variable representing cell with a certain value in the circuit.
-    type Var: Var<F>;
-
     /// Given a `value` and an `enable_flag`, check that either `value = 0`
     /// or `enable_flag = 1`.
     fn enable_flag(
         &self,
         layouter: impl Layouter<F>,
-        value: <Self as EnableFlagInstructions<F>>::Var,
+        value: Self::Var,
         enable_flag: Option<bool>,
     ) -> Result<(), Error>;
 }
@@ -54,12 +51,10 @@ impl<F: FieldExt> UtilitiesInstructions<F> for EnableFlagChip<F> {
 }
 
 impl<F: FieldExt> EnableFlagInstructions<F> for EnableFlagChip<F> {
-    type Var = CellValue<F>;
-
     fn enable_flag(
         &self,
         mut layouter: impl Layouter<F>,
-        value: <Self as EnableFlagInstructions<F>>::Var,
+        value: Self::Var,
         enable_flag: Option<bool>,
     ) -> Result<(), Error> {
         let config = self.config().clone();
diff --git a/src/circuit/gadget/utilities/plonk.rs b/src/circuit/gadget/utilities/plonk.rs
index a6437723..29d7c889 100644
--- a/src/circuit/gadget/utilities/plonk.rs
+++ b/src/circuit/gadget/utilities/plonk.rs
@@ -10,15 +10,13 @@ use std::marker::PhantomData;
 #[allow(clippy::upper_case_acronyms)]
 #[allow(clippy::too_many_arguments)]
 pub trait PLONKInstructions<F: FieldExt>: UtilitiesInstructions<F> {
-    type Var;
-
     // Checks that a * sm * b = c * sc
     fn mul(
         &self,
         layouter: impl Layouter<F>,
-        a: <Self as PLONKInstructions<F>>::Var,
-        b: <Self as PLONKInstructions<F>>::Var,
-        c: <Self as PLONKInstructions<F>>::Var,
+        a: Self::Var,
+        b: Self::Var,
+        c: Self::Var,
         sc: Option<F>,
         sm: Option<F>,
     ) -> Result<(), Error>;
@@ -26,9 +24,9 @@ pub trait PLONKInstructions<F: FieldExt>: UtilitiesInstructions<F> {
     fn add(
         &self,
         layouter: impl Layouter<F>,
-        a: <Self as PLONKInstructions<F>>::Var,
-        b: <Self as PLONKInstructions<F>>::Var,
-        c: <Self as PLONKInstructions<F>>::Var,
+        a: Self::Var,
+        b: Self::Var,
+        c: Self::Var,
         sa: Option<F>,
         sb: Option<F>,
         sc: Option<F>,
@@ -77,14 +75,12 @@ impl<F: FieldExt> UtilitiesInstructions<F> for PLONKChip<F> {
 
 #[allow(clippy::upper_case_acronyms)]
 impl<F: FieldExt> PLONKInstructions<F> for PLONKChip<F> {
-    type Var = CellValue<F>;
-
     fn mul(
         &self,
         mut layouter: impl Layouter<F>,
-        a: <Self as PLONKInstructions<F>>::Var,
-        b: <Self as PLONKInstructions<F>>::Var,
-        c: <Self as PLONKInstructions<F>>::Var,
+        a: Self::Var,
+        b: Self::Var,
+        c: Self::Var,
         sc: Option<F>,
         sm: Option<F>,
     ) -> Result<(), Error> {
@@ -129,9 +125,9 @@ impl<F: FieldExt> PLONKInstructions<F> for PLONKChip<F> {
     fn add(
         &self,
         mut layouter: impl Layouter<F>,
-        a: <Self as PLONKInstructions<F>>::Var,
-        b: <Self as PLONKInstructions<F>>::Var,
-        c: <Self as PLONKInstructions<F>>::Var,
+        a: Self::Var,
+        b: Self::Var,
+        c: Self::Var,
         sa: Option<F>,
         sb: Option<F>,
         sc: Option<F>,