Rust - derive macro generate struct impl based on another trait (procedurally)

help
1

I have a struct:

struct Foo {
    i: i32,
}

I have a trait:

trait FooTrait {
    fn foo(&self);
}

I want to create a derive macro, which, when attached to the struct, generates an impl like below:

impl FooTrait for Foo {
    fn foo(&self) {
        println!("generated code: {}", self.i);
    }
}

When I attempted to achieve this, I'm facing the blocker that my derive macro doesn't seem to have a way to know the token stream of FooTrait, where I need to iterate through the methods of FooTrait, and generate the implementation for each trait method based on Foo!

How could I possibly achieve that?

NOTE: to make it clearer, this question is not really about how I simply use quote! to quote the trait impl and spell out foo directly - the hard part is that I want to procedurally iterate through the methods of FooTrait, and generate some boilerplate code for each trait method.

2

Looks no way to me. Derive macro handle tokens, not AST. You may need more powerful tool than derive macro, for example rustc drivers.

3

Derive macro doesn't have access to the trait definition, it only receives the struct it is applied on. So what do you want to iterate through?

4

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