Trait manyhow::DeriveMacroHandler

pub trait DeriveMacroHandler<Function> {
    type Item;
    type Dummy;
    type Output;

    // Required method
    fn call(
        self,
        item: Self::Item,
        dummy: &mut Self::Dummy,
        emitter: &mut Emitter
    ) -> Self::Output;
}

Input of a derive proc-macro

Note: for TokenStream either proc_macro::TokenStream or proc_macro2::TokenStream can be used.

Trait is implemented for any function, taking in one TokenStream. Additionally, they can take optionally in any order a &mut Emitter which allows emitting errors without returning early. And a &mut TokenStream to return a dummy TokenStream on failure.

When used with derive() it must return a type implementing MacroOutput, with derive! it can accept types implementing Parse and return types implementing ToTokens.

Required Associated Types

type Item

type Dummy

type Output

Required Methods

fn call( self, item: Self::Item, dummy: &mut Self::Dummy, emitter: &mut Emitter ) -> Self::Output

Implementors

impl<Item, Dummy: Clone, Output, Function> DeriveMacroHandler<(Item, &mut Dummy, &mut Emitter, Output)> for Function

where Function: Fn(Item, &mut Dummy, &mut Emitter) -> Output,

type Dummy = Dummy

type Item = Item

type Output = Output

impl<Item, Dummy: Clone, Output, Function> DeriveMacroHandler<(Item, &mut Dummy, Output)> for Function

where Function: Fn(Item, &mut Dummy) -> Output,

type Dummy = Dummy

type Item = Item

type Output = Output

impl<Item, Output, Function> DeriveMacroHandler<(Item, &mut Emitter, Output)> for Function

where Function: Fn(Item, &mut Emitter) -> Output,

type Dummy = TokenStream

type Item = Item

type Output = Output

impl<Item, Output, Function> DeriveMacroHandler<(Item, Output)> for Function

where Function: Fn(Item) -> Output,

type Dummy = TokenStream

type Item = Item

type Output = Output