the trait Decode is not implemented for BoundedBTreeMap<ElectionScore, u32>

[jsdw]

This error crops up when attempting to build subxt against the latest substrate master.

It occurs because BoundedBTreeMap<K,V> is a generated struct that contains a BTreeMap<K,V>, and Decode is only implemented on BTreeMap<K,V> if K: Ord.

In the erroneous case, we generate a BoundedBTreeMap<ElectionScore, u32>, and ElectionScore is another generated type which gets the default derives that we apply to all generated types (which doesn't include Ord).

Adding Ord (and thus also adding PartialOrd, Eq, PartialEq) to all types doesn't work out (loads of things can't impl this).

The best idea I have offhand is to iterate through the type registry looking for anything called "BTreeMap", and then adding the type ID of the first parameter it takes to some list. Later, when we generate all of our types, make sure that those IDs get the extra traits that they need to allow Decoding when they are keys in a BTreeMap.