Update code comments after review

Co-authored-by: Daira Hopwood <daira@jacaranda.org>
Co-authored-by: ying tong <yingtong@z.cash>

src/circuit/gadget/ecc/chip.rs

@@ -183,8 +183,8 @@ impl EccChip {
         // mul::complete::Config:
         // - advices[9]: z_complete
         //
-        // I have not yet figured out where constants[1] is used in an equality constraint
-        // but we get synthesis errors without it.
+        // mul::Config:
+        // - constants[1]: Setting `z_init` to zero.
         //
         // TODO: Refactor away from `impl From<EccConfig> for _` so that sub-configs can
         // equality-enable the columns they need to.

src/circuit/gadget/sinsemilla/chip.rs

@@ -116,9 +116,9 @@ impl SinsemillaChip {
         lookup: (Column<Fixed>, Column<Fixed>, Column<Fixed>),
         constants: [Column<Fixed>; 6], // TODO: replace with public inputs API
     ) -> <Self as Chip<pallas::Base>>::Config {
-        // This chip requires all advice columns and the `constants` fixed column to be
-        // equality-enabled. The advice columns are equality-enabled by the calls to
-        // LookupRangeCheckConfig::configure.
+        // This chip requires all advice columns and the `constants` fixed columns to be
+        // equality-enabled. The advice columns and the first five `constants` columns
+        // are equality-enabled by the calls to LookupRangeCheckConfig::configure.
         let lookup_config_0 =
             LookupRangeCheckConfig::configure(meta, advices[0], constants[0], lookup.0);
         let lookup_config_1 =

src/circuit/gadget/sinsemilla/merkle/chip.rs

@@ -53,8 +53,7 @@ impl MerkleChip {
         meta: &mut ConstraintSystem<pallas::Base>,
         sinsemilla_config: SinsemillaConfig,
     ) -> MerkleConfig {
-        // TODO: Check whether these advice columns were equality-enabled by
-        // SinsemillaConfig. We require all five columns to be equality-enabled.
+        // All five advice columns are equality-enabled by SinsemillaConfig.
         let advices = sinsemilla_config.advices();
         let cond_swap_config = CondSwapChip::configure(meta, advices);