Trait proc_macro_assertions::generatable::Generatable

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pub trait Generatable<'a, Assert>where
    Self: TidAble<'a>,
    Assert: 'a + TidAble<'a>,{
    type GeneratableData: 'a;
    type TemplateData: 'a;

    const EMITS_NON_CONSTANT_CODE: bool;

    // Required methods
    fn generatable(
        context: &mut Context<'_>
    ) -> PassedData<Self::GeneratableData>
       where Self: Sized;
    fn template(
        &self,
        context: &mut Context<'_>,
        passed: &Self::GeneratableData
    ) -> PassedData<Self::TemplateData>;
    fn assert(
        &self,
        _context: &mut Context<'_>,
        _passed: (&Self::GeneratableData, &Self::TemplateData),
        _to_assert: &Assert
    ) -> Option<TokenStream>;
}
Expand description

This indicates that some type can be turned into tokens that assert something. Be aware that this only relies on rust’s type checking, the code that is generated is never actually meant to be executed. The generation functions in three distinct “Stages”. See below for more information on that.

The type implementing this must also be TidAble, which is similar to Any but allows for non-’static lifetimes. The easiest way to implement it is to use the derive macro (#[derive(Tid)])

Idents

There is a need to ensure that there are no ident collisions among the generated code. For that purpose in each stage there is a context provided, which contains some IdentGenerator. Other than Idents passed into the methods by either Self or any parameters, use Idents generates by the IdentGenerator exclusively to avoid any collisions.

Generation “Stages”

Stage 1: Generatable

These tokens are generated for each type that implemets this trait once. This is the perfect place to put tokens that are needed as “Setup” for any asserts.

Stage 2: Template

These tokens are generated for each unique instance of Self. You should put any tokens that should be unique for each instance in here.

Stage 3: Assert

These tokens are generated for each unique Assert, which represent some type that is tested against Self. No generation is actually happening until at least one assert is created for Self.

Passed Data

There may be a need to pass data, for example generated idents, between stages. For that purpose this trait provides a way to do so. See PassedData for more information.

Required Associated Types§

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type GeneratableData: 'a

The type of any data passed from the Generatable stage to proceeding stages.

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type TemplateData: 'a

The type of any data passed from the Template stage to proceeding stages.

Required Associated Constants§

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const EMITS_NON_CONSTANT_CODE: bool

Set this to true when any of the emitted code may be non-constant

Required Methods§

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fn generatable(context: &mut Context<'_>) -> PassedData<Self::GeneratableData>where Self: Sized,

This is the method the Generatable stage is composed of. Should return Tokens (if any) generated by this stage, plus optionally any data passed to preceding stages.

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fn template( &self, context: &mut Context<'_>, passed: &Self::GeneratableData ) -> PassedData<Self::TemplateData>

This is the method the Template stage is composed of. Should return Tokens (if any) generated by this stage, plus optionally any data passed to preceding stages.

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fn assert( &self, _context: &mut Context<'_>, _passed: (&Self::GeneratableData, &Self::TemplateData), _to_assert: &Assert ) -> Option<TokenStream>

This is the method the Assert stage is composed of. Should return Tokens generated by this stage.

Object Safety§

This trait is not object safe.

Implementors§