Move "frontend" column types from middleware to the frontend (privacy…

…-scaling-explorations#300)

Summary:
- move `Fixed`, `Advice`, `Instance`, `ColumnType`, `Column`, `sealed` from
  middleware to frontend
  - These types are only used in the frontend.  In particular, the `Fixed, Advice, Instance` types are used in the generic `Column<C>` type which is useful for the fronted because it brings type safety for column types; but in the backend it's unneeded because we use the simplified type `ColumnMid`.
- remove metadata::Column in favor of ColumnMid
- remove phase from `Advice`
  - I noticed that the phase in the `Advice` was redundant because a column always exists in the context of a `ConstraintSystem` which has the `advice_column_phase` with that same information.  This removal simplifies the code.
- Remove `From<(Any, usize)> for Column` in favor of using constructors in order to improve code clarity.  

* chore: simplify Column types

- remove phase from Advice
- remove metadata::Column in favour of ColumnMid
- move Fixed, Advice, Instance, ColumnType, Column, sealed from
  middleware to frontend

* chore: remove unneeded pubs

* chore: make Display for ColumnMid succint

* fix: set correct ColumnMid field order for sorting

* fix: update plonk_api test hardcoded vk

* fix: doc tests imports

* fix: address comments from @duguorong009 and @CPerezz

halo2_backend/src/plonk/circuit.rs

@@ -181,7 +181,7 @@ impl<F: Field> ConstraintSystemBack<F> {
 
     pub fn get_any_query_index(&self, column: ColumnMid, at: Rotation) -> usize {
         let queries = match column.column_type {
-            Any::Advice(_) => &self.advice_queries,
+            Any::Advice => &self.advice_queries,
             Any::Fixed => &self.fixed_queries,
             Any::Instance => &self.instance_queries,
         };

halo2_backend/src/plonk/evaluation.rs

@@ -456,7 +456,7 @@ impl<C: CurveAffine> Evaluator<C> {
                             for (values, permutation) in columns
                                 .iter()
                                 .map(|&column| match column.column_type {
-                                    Any::Advice(_) => &advice[column.index],
+                                    Any::Advice => &advice[column.index],
                                     Any::Fixed => &fixed[column.index],
                                     Any::Instance => &instance[column.index],
                                 })
@@ -467,7 +467,7 @@ impl<C: CurveAffine> Evaluator<C> {
 
                             let mut right = set.permutation_product_coset[idx];
                             for values in columns.iter().map(|&column| match column.column_type {
-                                Any::Advice(_) => &advice[column.index],
+                                Any::Advice => &advice[column.index],
                                 Any::Fixed => &fixed[column.index],
                                 Any::Instance => &instance[column.index],
                             }) {
@@ -698,9 +698,10 @@ impl<C: CurveAffine> GraphEvaluator<C> {
                         query.column_index,
                         rot_idx,
                     ))),
-                    Any::Advice(_) => self.add_calculation(Calculation::Store(
-                        ValueSource::Advice(query.column_index, rot_idx),
-                    )),
+                    Any::Advice => self.add_calculation(Calculation::Store(ValueSource::Advice(
+                        query.column_index,
+                        rot_idx,
+                    ))),
                     Any::Instance => self.add_calculation(Calculation::Store(
                         ValueSource::Instance(query.column_index, rot_idx),
                     )),
@@ -867,7 +868,7 @@ pub fn evaluate<F: Field, B: LagrangeBasis>(
                         let rot_idx = get_rotation_idx(idx, query.rotation.0, rot_scale, isize);
                         match query.column_type {
                             Any::Fixed => fixed[query.column_index][rot_idx],
-                            Any::Advice(_) => advice[query.column_index][rot_idx],
+                            Any::Advice => advice[query.column_index][rot_idx],
                             Any::Instance => instance[query.column_index][rot_idx],
                         }
                     }
@@ -886,7 +887,7 @@ pub fn evaluate<F: Field, B: LagrangeBasis>(
 mod test {
     use crate::plonk::circuit::{ExpressionBack, QueryBack, VarBack};
     use crate::poly::LagrangeCoeff;
-    use halo2_middleware::circuit::{Advice, Any, ChallengeMid};
+    use halo2_middleware::circuit::{Any, ChallengeMid};
     use halo2_middleware::poly::Rotation;
     use halo2curves::pasta::pallas::{Affine, Scalar};
 
@@ -969,7 +970,7 @@ mod test {
                 ExpressionBack::Var(Query(QueryBack {
                     index: 0,
                     column_index: col,
-                    column_type: Any::Advice(Advice { phase: 0 }),
+                    column_type: Any::Advice,
                     rotation: Rotation(rot),
                 })),
                 expected,

halo2_backend/src/plonk/keygen.rs

@@ -198,7 +198,7 @@ impl QueriesMap {
             .map
             .entry((col, rot))
             .or_insert_with(|| match col.column_type {
-                Any::Advice(_) => {
+                Any::Advice => {
                     self.advice.push((col, rot));
                     self.advice.len() - 1
                 }
@@ -219,7 +219,7 @@ impl QueriesMap {
         match expr {
             ExpressionMid::Constant(c) => ExpressionBack::Constant(*c),
             ExpressionMid::Var(VarMid::Query(query)) => {
-                let column = ColumnMid::new(query.column_index, query.column_type);
+                let column = ColumnMid::new(query.column_type, query.column_index);
                 let index = self.add(column, query.rotation);
                 ExpressionBack::Var(VarBack::Query(QueryBack {
                     index,
@@ -336,16 +336,7 @@ fn collect_queries<F: Field>(
 
     // Each column used in a copy constraint involves a query at rotation current.
     for column in &cs_mid.permutation.columns {
-        match column.column_type {
-            Any::Instance => {
-                queries.add(ColumnMid::new(column.index, Any::Instance), Rotation::cur())
-            }
-            Any::Fixed => queries.add(ColumnMid::new(column.index, Any::Fixed), Rotation::cur()),
-            Any::Advice(advice) => queries.add(
-                ColumnMid::new(column.index, Any::Advice(advice)),
-                Rotation::cur(),
-            ),
-        };
+        queries.add(*column, Rotation::cur());
     }
 
     let mut num_advice_queries = vec![0; cs_mid.num_advice_columns];

halo2_backend/src/plonk/lookup/verifier.rs

@@ -123,7 +123,7 @@ impl<C: CurveAffine> Evaluated<C> {
                                     index, column_type, ..
                                 }) => match column_type {
                                     Any::Fixed => fixed_evals[index],
-                                    Any::Advice(_) => advice_evals[index],
+                                    Any::Advice => advice_evals[index],
                                     Any::Instance => instance_evals[index],
                                 },
                             },

halo2_backend/src/plonk/permutation/prover.rs

@@ -102,7 +102,7 @@ pub(in crate::plonk) fn permutation_commit<
         // Iterate over each column of the permutation
         for (&column, permuted_column_values) in columns.iter().zip(permutations.iter()) {
             let values = match column.column_type {
-                Any::Advice(_) => advice,
+                Any::Advice => advice,
                 Any::Fixed => fixed,
                 Any::Instance => instance,
             };
@@ -125,7 +125,7 @@ pub(in crate::plonk) fn permutation_commit<
         for &column in columns.iter() {
             let omega = domain.get_omega();
             let values = match column.column_type {
-                Any::Advice(_) => advice,
+                Any::Advice => advice,
                 Any::Fixed => fixed,
                 Any::Instance => instance,
             };

halo2_backend/src/plonk/permutation/verifier.rs

@@ -160,7 +160,7 @@ impl<C: CurveAffine> Evaluated<C> {
                         for (eval, permutation_eval) in columns
                             .iter()
                             .map(|&column| match column.column_type {
-                                Any::Advice(_) => {
+                                Any::Advice => {
                                     advice_evals[vk.cs.get_any_query_index(column, Rotation::cur())]
                                 }
                                 Any::Fixed => {
@@ -181,7 +181,7 @@ impl<C: CurveAffine> Evaluated<C> {
                             * (<C::Scalar as PrimeField>::DELTA
                                 .pow_vartime([(chunk_index * chunk_len) as u64]));
                         for eval in columns.iter().map(|&column| match column.column_type {
-                            Any::Advice(_) => {
+                            Any::Advice => {
                                 advice_evals[vk.cs.get_any_query_index(column, Rotation::cur())]
                             }
                             Any::Fixed => {

halo2_backend/src/plonk/shuffle/verifier.rs

@@ -82,7 +82,7 @@ impl<C: CurveAffine> Evaluated<C> {
                                     index, column_type, ..
                                 }) => match column_type {
                                     Any::Fixed => fixed_evals[index],
-                                    Any::Advice(_) => advice_evals[index],
+                                    Any::Advice => advice_evals[index],
                                     Any::Instance => instance_evals[index],
                                 },
                             },

halo2_backend/src/plonk/verifier.rs

@@ -363,7 +363,7 @@ where
                                 &|var| match var {
                                     VarBack::Query(query) => match query.column_type {
                                         Any::Fixed => fixed_evals[query.index],
-                                        Any::Advice(_) => advice_evals[query.index],
+                                        Any::Advice => advice_evals[query.index],
                                         Any::Instance => instance_evals[query.index],
                                     },
                                     VarBack::Challenge(challenge) => challenges[challenge.index],

halo2_frontend/src/circuit.rs

@@ -4,10 +4,10 @@ use crate::plonk;
 use crate::plonk::{
     permutation,
     sealed::{self, SealedPhase},
-    Assignment, Circuit, ConstraintSystem, FirstPhase, FloorPlanner, SecondPhase, SelectorsToFixed,
-    ThirdPhase,
+    Advice, Assignment, Circuit, ConstraintSystem, FirstPhase, Fixed, FloorPlanner, Instance,
+    SecondPhase, SelectorsToFixed, ThirdPhase,
 };
-use halo2_middleware::circuit::{Advice, Any, CompiledCircuitV2, Fixed, Instance, PreprocessingV2};
+use halo2_middleware::circuit::{Any, CompiledCircuitV2, PreprocessingV2};
 use halo2_middleware::ff::{BatchInvert, Field};
 use std::collections::BTreeSet;
 use std::collections::HashMap;
@@ -130,14 +130,13 @@ pub fn compile_circuit<F: Field, ConcreteCircuit: Circuit<F>>(
 }
 
 pub struct WitnessCollection<'a, F: Field> {
-    pub k: u32,
-    pub current_phase: sealed::Phase,
-    pub advice: Vec<Vec<Assigned<F>>>,
-    // pub unblinded_advice: HashSet<usize>,
-    pub challenges: &'a HashMap<usize, F>,
-    pub instances: &'a [&'a [F]],
-    pub usable_rows: RangeTo<usize>,
-    pub _marker: std::marker::PhantomData<F>,
+    k: u32,
+    current_phase: sealed::Phase,
+    advice_column_phase: &'a Vec<sealed::Phase>,
+    advice: Vec<Vec<Assigned<F>>>,
+    challenges: &'a HashMap<usize, F>,
+    instances: &'a [&'a [F]],
+    usable_rows: RangeTo<usize>,
 }
 
 impl<'a, F: Field> Assignment<F> for WitnessCollection<'a, F> {
@@ -197,7 +196,8 @@ impl<'a, F: Field> Assignment<F> for WitnessCollection<'a, F> {
         AR: Into<String>,
     {
         // Ignore assignment of advice column in different phase than current one.
-        if self.current_phase.0 != column.column_type().phase {
+        let phase = self.advice_column_phase[column.index];
+        if self.current_phase != phase {
             return Ok(());
         }
 
@@ -326,6 +326,7 @@ impl<'a, F: Field, ConcreteCircuit: Circuit<F>> WitnessCalculator<'a, F, Concret
         let mut witness = WitnessCollection {
             k: self.k,
             current_phase,
+            advice_column_phase: &self.cs.advice_column_phase,
             advice: vec![vec![Assigned::Zero; self.n]; self.cs.num_advice_columns],
             instances: self.instances,
             challenges,
@@ -334,7 +335,6 @@ impl<'a, F: Field, ConcreteCircuit: Circuit<F>> WitnessCalculator<'a, F, Concret
             // number of blinding factors and an extra row for use in the
             // permutation argument.
             usable_rows: ..self.unusable_rows_start,
-            _marker: std::marker::PhantomData,
         };
 
         // Synthesize the circuit to obtain the witness and other information.

halo2_frontend/src/circuit/floor_planner/single_pass.rs

@@ -3,6 +3,7 @@ use std::collections::HashMap;
 use std::fmt;
 use std::marker::PhantomData;
 
+use halo2_middleware::circuit::Any;
 use halo2_middleware::ff::Field;
 
 use crate::plonk::Assigned;
@@ -12,9 +13,11 @@ use crate::{
         table_layouter::{compute_table_lengths, SimpleTableLayouter},
         Cell, Column, Layouter, Region, RegionIndex, RegionStart, Table, Value,
     },
-    plonk::{Assignment, Challenge, Circuit, Error, FloorPlanner, Selector, TableColumn},
+    plonk::{
+        Advice, Assignment, Challenge, Circuit, Error, Fixed, FloorPlanner, Instance, Selector,
+        TableColumn,
+    },
 };
-use halo2_middleware::circuit::{Advice, Any, Fixed, Instance};
 
 /// A simple [`FloorPlanner`] that performs minimal optimizations.
 ///
@@ -381,8 +384,7 @@ mod tests {
 
     use super::SimpleFloorPlanner;
     use crate::dev::MockProver;
-    use crate::plonk::{Circuit, Column, ConstraintSystem, Error};
-    use halo2_middleware::circuit::Advice;
+    use crate::plonk::{Advice, Circuit, Column, ConstraintSystem, Error};
 
     #[test]
     fn not_enough_columns_for_constants() {

halo2_frontend/src/circuit/floor_planner/v1.rs

@@ -1,5 +1,6 @@
 use std::fmt;
 
+use halo2_middleware::circuit::Any;
 use halo2_middleware::ff::Field;
 
 use crate::plonk::Assigned;
@@ -9,9 +10,11 @@ use crate::{
         table_layouter::{compute_table_lengths, SimpleTableLayouter},
         Cell, Column, Layouter, Region, RegionIndex, RegionStart, Table, Value,
     },
-    plonk::{Assignment, Challenge, Circuit, Error, FloorPlanner, Selector, TableColumn},
+    plonk::{
+        Advice, Assignment, Challenge, Circuit, Error, Fixed, FloorPlanner, Instance, Selector,
+        TableColumn,
+    },
 };
-use halo2_middleware::circuit::{Advice, Any, Fixed, Instance};
 
 pub mod strategy;
 
@@ -496,8 +499,7 @@ mod tests {
     use halo2curves::pasta::vesta;
 
     use crate::dev::MockProver;
-    use crate::plonk::{Circuit, Column, ConstraintSystem, Error};
-    use halo2_middleware::circuit::Advice;
+    use crate::plonk::{Advice, Circuit, Column, ConstraintSystem, Error};
 
     #[test]
     fn not_enough_columns_for_constants() {

halo2_frontend/src/circuit/floor_planner/v1/strategy.rs

@@ -206,7 +206,7 @@ pub fn slot_in_biggest_advice_first(
             .columns()
             .iter()
             .filter(|c| match c {
-                RegionColumn::Column(c) => matches!(c.column_type(), Any::Advice(_)),
+                RegionColumn::Column(c) => matches!(c.column_type(), Any::Advice),
                 _ => false,
             })
             .count();
@@ -252,23 +252,23 @@ fn test_slot_in() {
     let regions = vec![
         RegionShape {
             region_index: 0.into(),
-            columns: vec![Column::new(0, Any::advice()), Column::new(1, Any::advice())]
+            columns: vec![Column::new(0, Any::Advice), Column::new(1, Any::Advice)]
                 .into_iter()
                 .map(|a| a.into())
                 .collect(),
             row_count: 15,
         },
         RegionShape {
             region_index: 1.into(),
-            columns: vec![Column::new(2, Any::advice())]
+            columns: vec![Column::new(2, Any::Advice)]
                 .into_iter()
                 .map(|a| a.into())
                 .collect(),
             row_count: 10,
         },
         RegionShape {
             region_index: 2.into(),
-            columns: vec![Column::new(2, Any::advice()), Column::new(0, Any::advice())]
+            columns: vec![Column::new(2, Any::Advice), Column::new(0, Any::Advice)]
                 .into_iter()
                 .map(|a| a.into())
                 .collect(),

halo2_frontend/src/circuit/layouter.rs

@@ -4,13 +4,13 @@ use std::cmp;
 use std::collections::HashSet;
 use std::fmt;
 
+use halo2_middleware::circuit::Any;
 use halo2_middleware::ff::Field;
 
 pub use super::table_layouter::TableLayouter;
 use super::{Cell, RegionIndex, Value};
 use crate::plonk::Assigned;
-use crate::plonk::{Column, Error, Selector};
-use halo2_middleware::circuit::{Advice, Any, Fixed, Instance};
+use crate::plonk::{Advice, Column, Error, Fixed, Instance, Selector};
 
 /// Intermediate trait requirements for [`RegionLayouter`] when thread-safe regions are enabled.
 #[cfg(feature = "thread-safe-region")]