Trait aliases

[michaeljklein]

Problem

Trait inheritance allows traits to require other traits, but explicitly including all required traits in functions or impl's can become repetitive.

Happy Case

Once #6314 is fixed, support some version of trait aliases, e.g., by desugaring a trait alias declaration:

trait Baz = Foo + Bar;

into (approximately):

trait Baz: Foo + Bar {}

impl<T> Baz for T where T: Foo + Bar {}

Either support something similar to this experimental Rust feature or else ensure that it can be implemented with a simple Noir macro.

Workaround

Yes

Workaround Description

trait Baz: Foo + Bar {} can currently be defined, but currently needs an explicit impl Baz for MyStruct for each type

Additional Context

No response

Project Impact

None

Blocker Context

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response

[michaeljklein]

After discussing with Tom and Jake, we'd prefer to implement Rust-style trait aliases with the following notes:

1. The error messages when a trait is missing should be clear
2. Error messages when the trait alias is used in other places than intended should be clear
3. ^ If these error messages are tricky, use a first-order enum variant for trait aliases