Macro Apply 

Apply!() { /* proc-macro */ }

Applies a brand to type arguments.

This macro projects a brand type to its concrete type using the appropriate Kind trait. It uses named parameters syntax.

Modes

The macro supports two modes of operation:

1. Unified Signature Mode (Recommended): Uses a single signature parameter to specify both the schema (for Kind trait name generation) and the concrete values (for projection).
2. Explicit Kind Mode (Advanced): Uses an explicit kind parameter along with separate lifetimes and types parameters.

Parameters

• brand: (Required) The brand type (e.g., OptionBrand).
• signature: (Mode 1) The unified signature containing both schema and values.
• kind: (Mode 2) An explicit Kind trait to use.
• lifetimes: (Mode 2) Lifetime arguments to apply. Required with kind.
• types: (Mode 2) Type arguments to apply. Required with kind.

Unified Signature Syntax

The signature parameter uses a syntax similar to a function signature: (param1, param2, ...) -> OutputBounds

• Lifetimes: Specified as 'a, 'static, etc.
• Types: Specified as Type or Type: Bounds.
  • The Type part is used as the concrete value for projection.
  • The Bounds part (optional) is used for Kind trait name generation.

Examples

Unified Signature Mode (Recommended)

// Applies MyBrand to lifetime 'static and type String.
// The schema is inferred as: 1 lifetime, 1 type parameter (unbounded).
type Concrete = Apply!(
    brand: MyBrand,
    signature: ('static, String)
);

// Applies MyBrand to a generic type T with bounds.
// The schema is inferred as: 1 type parameter with Clone bound.
type Concrete = Apply!(
    brand: MyBrand,
    signature: (T: Clone)
);

// Complex example with lifetimes, types, and output bounds.
type Concrete = Apply!(
    brand: MyBrand,
    signature: ('a, T: Clone + Debug) -> Display
);

Explicit Kind Mode (Advanced)

Use this mode when you need to specify a custom Kind trait directly.

// Applies OptionBrand using an explicit Kind trait.
type Concrete = Apply!(
    brand: OptionBrand,
    kind: SomeKind,
    lifetimes: ('a),
    types: (String)
);