Add event support via #[event] and #[indexed] attributes

[tritao]

This PR adds two new attributes: #[event] and #[indexed].

The #[event] attribute marks a struct or enum as an event that can be emitted by a contract.

The #[indexed] attribute can be applied to fields within structs that are attributed with #[event]. This is particularly useful for event structs, allowing for efficient filtering and searching of emitted events based on the values of these fields.

When using this attribute, the indexed fields must be applied sequentially to the initial set of fields in a struct.

This attribute can only be applied to fields whose type is an exact size ABI type. The exact size ABI types include:

• bool
• u8, u16, u32, u64, u256
• numeric
• b256
• str[N]
• Tuples containing only exact size types
• Structs containing only exact size types
• Arrays of exact size types with a literal length
• Type aliases to exact size types

Additionally it causes the event types to be included in the JSON ABI representation for the contract and emits an offset for indexed fields.

#[event]
struct MyEventStruct {
    #[indexed]
    id: u64,
    sender: Identity,
}

#[event]
enum MyEventEnum {
    A: (),
    B: (),
}

[codspeed-hq]

CodSpeed Performance Report

Merging #7158 will not alter performance

_{Comparing tritao:indexed-events (f3875f2) with master (6553dce)}

Summary

✅ 25 untouched