delegate

New features

• Implement support for delegating to fields (#88 from JRRudy1).

Internal

• Start using release-plz for releases, together with crates.io Trusted Publishing.

• Do not explicitly forward lifetime arguments when calling delegated functions (https://github.com/Kobzol/rust-delegate/issues/85).

• Add #[const(path::to::Trait::CONST)] attribute to delegate associated constants via a getter (implemented by @vic1707).
• Add #[expr(<$ template>)] attribute to modify delegated call using custom code (implemented by @vic1707).

• Correctly parse attributes with segmented paths (e.g. #[a::b::c]) (https://github.com/Kobzol/rust-delegate/issues/77).

• Correctly pass generic method type and lifetime arguments to the delegated method.

• Generalize match arms handling. You can now combine a match expression target with annotations like #[into] and others:

struct A;

impl A {
    pub fn callable(self) -> Self {
        self
    }
}

struct B;

impl B {
    pub fn callable(self) -> Self {
        self
    }
}

enum Common {
    A(A),
    B(B),
}

impl From<A> for Common {
    fn from(inner: A) -> Self {
        Self::A(inner)
    }
}

impl From<B> for Common {
    fn from(inner: B) -> Self {
        Self::B(inner)
    }
}

impl Common {
    delegate! {
        to match self {
        // ---------- `match` arms have incompatible types
            Common::A(inner) => inner;
            Common::B(inner) => inner;
        } {
            #[into]
            pub fn callable(self) -> Self;
        }
    }

    // Generates
    // pub fn callable(self) -> Self {
    //     match self {
    //         Common::A(inner) => inner.callable().into(),
    //         Common::B(inner) => inner.callable().into(),
    //     }
    // }
}

• The crate should be #[no_std] compatible again (https://github.com/Kobzol/rust-delegate/pull/74).

• Add new #[newtype] function parameter modifier (#64). Implemented by Techassi

• Allow passing arbitrary attributes to delegation segments:

impl Foo {
    delegate! {
    #[inline(always)]
    to self.0 { ... }
  }
}

• Change the default inlining mode from #[inline(always)] to #[inline] (https://github.com/Kobzol/rust-delegate/issues/61).

• Allow delegating an associated function (not just a method).

struct A {}

impl A {
    fn foo(a: u32) -> u32 {
        a + 1
    }
}

struct B;

impl B {
    delegate! {
        to A {
            fn foo(a: u32) -> u32;
        }
    }
}

• Allow specifying certain attributes (e.g. #[into] or #[unwrap]) on delegated segments. The attribute will then be applied to all methods in that segment (unless it is overwritten on the method itself).

delegate! {
  #[unwrap]
  to self.inner {
    fn foo(&self) -> u32; // calls self.inner.foo().unwrap()
    fn bar(&self) -> u32; // calls self.inner.bar().unwrap()
  }
}

• Add new #[unwrap] method modifier. Adding it on top of a delegated method will cause the generated code to .unwrap() the result.

#[unwrap]
fn foo(&self) -> u32;  // foo().unwrap()

• Add new #[through(<trait>)] method modifier. Adding it on top of a delegated method will cause the generated code to call the method through the provided trait using UFCS.

#[through(MyTrait)]
delegate! {
  to &self.inner {
    #[through(MyTrait)]
    fn foo(&self) -> u32;  // MyTrait::foo(&self.inner)
  }
}

• Removed #[try_into(unwrap)]. It can now be replaced with the combination of #[try_into] and #[unwrap]:

#[try_into]
#[unwrap]
fn foo(&self) -> u32;  // TryInto::try_into(foo()).unwrap()

• Add the option to specify explicit type path to the #[into] expression modifier:

#[into(u64)]
fn foo(&self) -> u64; // Into::<u64>::into(foo())

• Expression modifiers #[into], #[try_into] and #[unwrap] can now be used multiple times. The order of their usage dictates in what order they will be applied:

#[into]
#[unwrap]
fn foo(&self) -> u32;  // Into::into(foo()).unwrap()

#[unwrap]
#[into]
fn foo(&self) -> u32;  // Into::into(foo().unwrap())

• Add new #[as_ref] function parameter modifier (#47). Implemented by trueegorletov.

• Allow simple delegation to enum variants (#45). Implemented by gfreezy.

• Add new #[into] attribute for delegated function parameters. If specified, the parameter will be converted using the From trait before being passed as an argument to the called function.
• Add new #[try_from] attribute to delegated functions. You can use it to convert the delegated expression using the TryFrom trait. You can also use #[try_from(unwrap)] to unwrap the result of the conversion.

• Add new #[await(true/false)] attribute to delegated functions. You can use it to control whether .await will be appended to the delegated expression. It will be generated by default if the delegation method signature is async.

• add support for async functions. The delegated call will now use .await.

• add the option to specify inline expressions that will be used as arguments for the delegated call (https://github.com/kobzol/rust-delegate/pull/34)
• removed append_args attribute, which is superseded by the mentioned expression in signature support

• add the append_args attribute to append attributes to delegated calls (https://github.com/kobzol/rust-delegate/pull/31)

• fix breaking change caused by using syn private API (https://github.com/kobzol/rust-delegate/issues/28)

• self can now be used as the delegation target
• Rust 1.46 introduced a change that makes it a bit difficult to use rust-delegate implementations generated by macros. If you have this use case, please use this workaround.