Issue with bounds

[gui1117]

compiling polkadot-sdk with the latest version fails with:

error[E0277]: the trait bound `parity_scale_codec::Compact<Balance>: MaxEncodedLen` is not satisfied
   --> substrate/primitives/staking/src/lib.rs:451:2
    |
451 |     MaxEncodedLen,
    |     ^^^^^^^^^^^^^ the trait `MaxEncodedLen` is not implemented for `parity_scale_codec::Compact<Balance>`

[gui1117]

So the PR 508 make use of compact type for max encoded len,
Then PR 512 also improve on the code.
Then PR 616 adds some bound for compact type.
Then the revert of 508 and 512 doesn't actually completely revert, and still make use of the compact type for max encoded len.

So now staking doesn't compile because Compact<Balance>: MaxEncodedLen is not bound.

solution:

• revert 508 completly (my preference)

diff --git a/derive/src/max_encoded_len.rs b/derive/src/max_encoded_len.rs
index 8a592e1..d773096 100644
--- a/derive/src/max_encoded_len.rs
+++ b/derive/src/max_encoded_len.rs
@@ -85,14 +85,8 @@ fn fields_length_expr(fields: &Fields, crate_path: &syn::Path) -> proc_macro2::T
        // caused the issue.
        let expansion = fields_iter.map(|field| {
                let ty = &field.ty;
-               if utils::is_compact(field) {
-                       quote_spanned! {
-                               ty.span() => .saturating_add(<#crate_path::Compact::<#ty> as #crate_path::MaxEncodedLen>::max_encoded_len())
-                       }
-               } else {
-                       quote_spanned! {
-                               ty.span() => .saturating_add(<#ty as #crate_path::MaxEncodedLen>::max_encoded_len())
-                       }
+               quote_spanned! {
+                       ty.span() => .saturating_add(<#ty as #crate_path::MaxEncodedLen>::max_encoded_len())
                }
        });
        quote! {

• try to do some fix, but they might introduce some breaking change:

diff --git a/derive/src/max_encoded_len.rs b/derive/src/max_encoded_len.rs
index 8a592e1..f09f6c8 100644
--- a/derive/src/max_encoded_len.rs
+++ b/derive/src/max_encoded_len.rs
@@ -44,7 +44,7 @@ pub fn derive_max_encoded_len(input: proc_macro::TokenStream) -> proc_macro::Tok
                None,
                has_dumb_trait_bound(&input.attrs),
                &crate_path,
-               false,
+               true,
        ) {
                return e.to_compile_error().into();
        }
@@ -87,7 +87,9 @@ fn fields_length_expr(fields: &Fields, crate_path: &syn::Path) -> proc_macro2::T
                let ty = &field.ty;
                if utils::is_compact(field) {
                        quote_spanned! {
-                               ty.span() => .saturating_add(<#crate_path::Compact::<#ty> as #crate_path::MaxEncodedLen>::max_encoded_len())
+                               ty.span() => .saturating_add(
+                                       <<#ty as #crate_path::HasCompact>::Type as #crate_path::MaxEncodedLen>::max_encoded_len()
+                               )
                        }
                } else {
                        quote_spanned! {

[gui1117]

I don't have much time to work on it for now, I can start again tomorrow.

[serban300]

@gui1117 I can take it

[serban300]

Now I see that there are multiple issues left even after fixing this one:

error[E0080]: evaluation of constant value failed
  --> substrate/client/network/src/protocol/message.rs:79:40
   |
79 |     #[derive(Debug, PartialEq, Eq, Clone, Encode, Decode)]
   |                                           ^^^^^^ the evaluated program panicked at 'Found variants that have duplicate indexes. Both `Consensus` and `RemoteCallResponse` have the index `6`. Use different indexes for each variant.', substrate/client/network/src/protocol/message.rs:79:43
   |
   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `::core::panic` (in Nightly builds, run with -Z macro-backtrace for more info)

Seems related to #653

error[E0277]: the trait bound `types::CollectionSetting: parity_scale_codec::Encode` is not satisfied
   --> substrate/frame/nfts/src/types.rs:259:10
    |
259 | pub enum CollectionSetting {
    |          ^^^^^^^^^^^^^^^^^ the trait `WrapperTypeEncode` is not implemented for `types::CollectionSetting`, which is required by `types::CollectionSetting: parity_scale_codec::Encode`
    |
    = help: the following other types implement trait `WrapperTypeEncode`:
              &T
              &mut T
              Arc<T>
              Cow<'_, T>
              Rc<T>
              bytes::bytes::Bytes
              parity_scale_codec::Ref<'_, T, U>
              sp_core::Bytes
            and 3 others
    = note: required for `types::CollectionSetting` to implement `parity_scale_codec::Encode`
note: required by a bound in `parity_scale_codec::MaxEncodedLen`
   --> /media/serban/data/workplace/sources/parity-scale-codec/src/max_encoded_len.rs:37:26
    |
37  | pub trait MaxEncodedLen: Encode {
    |                          ^^^^^^ required by this bound in `MaxEncodedLen`

error[E0277]: the trait bound `types::ItemSetting: parity_scale_codec::Encode` is not satisfied
   --> substrate/frame/nfts/src/types.rs:396:10
    |
396 | pub enum ItemSetting {
    |          ^^^^^^^^^^^ the trait `WrapperTypeEncode` is not implemented for `types::ItemSetting`, which is required by `types::ItemSetting: parity_scale_codec::Encode`
    |
    = help: the following other types implement trait `WrapperTypeEncode`:
              &T
              &mut T
              Arc<T>
              Cow<'_, T>
              Rc<T>
              bytes::bytes::Bytes
              parity_scale_codec::Ref<'_, T, U>
              sp_core::Bytes
            and 3 others
    = note: required for `types::ItemSetting` to implement `parity_scale_codec::Encode`
note: required by a bound in `parity_scale_codec::MaxEncodedLen`

Maybe there are others as well

Will tackle them one by one

[serban300]

Opened #693 for fixing this specific issue

Also opened a separate issues for the things mentiond above:

paritytech/polkadot-sdk#7400
#692