feat: Implement traits - first prototype

[yordanmadzhunkov]

Description

Implement traits #527
Add initial prototype implementation of Traits in Noir.

This is very experimental work and needs more feedback, progress and testing before it can be enabled to the users

Problem*

Add trait functionality to Noir language analogous to how traits are implemented in rust

Resolves

Summary*

The goal is to make this simple program compile & execute

trait Default {
    fn default(x: Field, y: Field) -> Self;
}

struct Foo {
    bar: Field,
    array: [Field; 2],
}

impl Default for Foo {
    fn default(x: Field,y: Field) -> Self {
        Self { bar: x, array: [x,y] }
    }
}

fn main(x: Field, y: Field) {
    let first = Foo::default(x,y);
    assert(first.bar == x);
}

The noir compiler emits the following messages. I accept all kind of suggestion how to improve them:

Example 1:

error: duplicate definitions of Default trait found
   ┌─ tests/compile_tests_data/fail/dup_trait_declaration.nr:3:7
   │
 3 │ trait Default {
   │       ------- first trait definition found here
   ·
19 │ trait Default {
   │       ------- second trait definition found here

Example 2:

error: mismatch return type of method with name default that implemetns trait Default
   ┌─ tests/compile_tests_data/fail/trait_wrong_method_return_type.nr:13:8
   │
13 │     fn default(x: Field, y: Field) -> Field {
   │        -------

error: Could not resolve 'default' in path
   ┌─ tests/compile_tests_data/fail/trait_wrong_method_return_type.nr:19:22
   │
19 │     let first = Foo::default(x,y);

Example 3:

error: method with name default_wrong_name is not part of trait Default, therefore it can't be implemented
   ┌─ tests/compile_tests_data/fail/trait_wrong_method_name.nr:14:8
   │
14 │     fn default_wrong_name(x: Field, y: Field) -> Self {
   │        ------------------

error: Could not resolve 'default_wrong_name' in path
   ┌─ tests/compile_tests_data/fail/trait_wrong_method_name.nr:20:22
   │
20 │     let first = Foo::default_wrong_name(x,y);
   │                      ------------------

Example 4

error: Trait Default not found
  ┌─ tests/compile_tests_data/fail/trait_not_exists.nr:9:6
  │
9 │ impl Default for Foo {
  │      -------

error: Could not resolve 'default' in path
   ┌─ tests/compile_tests_data/fail/trait_not_exists.nr:16:22
   │
16 │     let first = Foo::default(x,y);
   │                      -------

Example 5:

error: Mismatch signature [Number of parameters] of method with name `default` that implemetns trait `Default`
   ┌─ tests/compile_tests_data/fail/trait_wrong_parameters_count.nr:13:8
   │
13 │     fn default(x: Field) -> Self {

Example 6:

error: duplicate definitions of default function found
   ┌─ tests/compile_tests_data/fail/dup_trait_implementation.nr:14:8
   │
14 │     fn default(x: Field,y: Field) -> Self {
   │        ------- first function definition found here
   ·
21 │     fn default(x: Field, y: Field) -> Self {
   │        ------- second function definition found here

Example 7:

error: Mismatch signature of method default that implemtns trait Default
   ┌─ tests/compile_tests_data/fail/trait_wrong_parameter.nr:13:26
   │
13 │     fn default(x: Field, y: Foo) -> Self {
   │                          - `y: Field` expected

Example 8:

error: Default is not a trait, therefore it can't be implemented
   ┌─ tests/compile_tests_data/fail/impl_struct_not_trait.nr:14:6
   │
14 │ impl Default for Foo {

Documentation

• This PR requires documentation updates when merged.

  • I will submit a noir-lang/docs PR.
  • I will request for and support Dev Rel's help in documenting this PR.

Additional Context

PR Checklist*

• [*] I have tested the changes locally.
• [*] I have formatted the changes with Prettier and/or cargo fmt on default settings.

[jfecher]

Can you break this up into smaller PRs next time? This one is too large which makes it take longer to review (apologies for the delay) and contain more TODOs and stubs which prevent it from being merged.

We don't need to add name resolution, type checking, and monomorphization of traits in one PR. We can focus on e.g. one pass at a time and just add the minimum amount of features so that we have a clean base to build upon that can be expanded later.

[jfecher]

I don't see why we wouldn't issue this error if the trait has no generics. Lets keep the traits are experimental error. We should probably change it to a warning now that we're iterating on traits so that we continue through proving.

[jfecher]

Suggested change

	.validate(|((name, typ), default_value), _span, _emit| TraitItem::Constant {
	.map(|((name, typ), default_value)| TraitItem::Constant {

[jfecher]

Suggested change

	pub enum TraitItemType {
	pub enum TraitItem {

[yordanmadzhunkov]

Unfortunetly, this conflicts with crates/noirc_frontend/src/ast/traits.rs: pub enum TraitItem

[yordanmadzhunkov]

Can you break this up into smaller PRs next time? This one is too large which makes it take longer to review (apologies for the delay) and contain more TODOs and stubs which prevent it from being merged.

We don't need to add name resolution, type checking, and monomorphization of traits in one PR. We can focus on e.g. one pass at a time and just add the minimum amount of features so that we have a clean base to build upon that can be expanded later.

I also like to submit small PRs. I was not sure what is the correct approach for implementing traits, so I tried to make it work end-to-end in order to validate the correctness. The result is this BIG PR. In the near future, I will aim at smaller changes/PRs

[kevaundray]

Can you break this up into smaller PRs next time? This one is too large which makes it take longer to review (apologies for the delay) and contain more TODOs and stubs which prevent it from being merged.
We don't need to add name resolution, type checking, and monomorphization of traits in one PR. We can focus on e.g. one pass at a time and just add the minimum amount of features so that we have a clean base to build upon that can be expanded later.

I also like to submit small PRs. I was not sure what is the correct approach for implementing traits, so I tried to make it work end-to-end in order to validate the correctness. The result is this BIG PR. In the near future, I will aim at smaller changes/PRs

Since larger PRs take quite a long time to review, I'd suggest that we break this PR down into smaller PRs and open an issue detailing the smaller chunks that are needed for implementing traits.

If this PR is mostly done, then it would be just copying the relevant parts into separate PRs