# Crate proc_macro 1.15.0[−][src]

A support library for macro authors when defining new macros.

This library, provided by the standard distribution, provides the types consumed in the interfaces of procedurally defined macro definitions. Currently the primary use of this crate is to provide the ability to define new custom derive modes through `#[proc_macro_derive]`.

Note that this crate is intentionally very bare-bones currently. The main type, `TokenStream`, only supports `fmt::Display` and `FromStr` implementations, indicating that it can only go to and come from a string. This functionality is intended to be expanded over time as more surface area for macro authors is stabilized.

See the book for more.

## Modules

token_stream | [ Experimental ] Implementation details for the `TokenTree` type, such as iterators.

## Macros

quote | [ Experimental ] `quote!(..)` accepts arbitrary tokens and expands into a `TokenStream` describing the input. For example, `quote!(a + b)` will produce a expression, that, when evaluated, constructs the `TokenStream` `[Word("a"), Op('+', Alone), Word("b")]`.

## Structs

LexError | Error returned from `TokenStream::from_str`.
TokenStream | The main type provided by this crate, representing an abstract stream of tokens.
Diagnostic | [ Experimental ] A structure representing a diagnostic message and associated children messages.
Group | [ Experimental ] A delimited token stream
LineColumn | [ Experimental ] A line-column pair representing the start or end of a `Span`.
Literal | [ Experimental ] A literal character (`'a'`), string (`"hello"`), a number (`2.3`), etc.
Op | [ Experimental ] An `Op` is an operator like `+` or `-`, and only represents one character.
SourceFile | [ Experimental ] The source file of a given `Span`.
Span | [ Experimental ] A region of source code, along with macro expansion information.
Term | [ Experimental ] An interned string.

## Enums

Delimiter | [ Experimental ] Describes how a sequence of token trees is delimited.
Level | [ Experimental ] An enum representing a diagnostic level.
Spacing | [ Experimental ] Whether an `Op` is either followed immediately by another `Op` or followed by whitespace.
TokenTree | [ Experimental ] A single token or a delimited sequence of token trees (e.g. `[1, (), ..]`).

## Functions

quote_span | [ Experimental ] Quote a `Span` into a `TokenStream`. This is needed to implement a custom quoter.

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