Crate proc_macro

1.15.0 · source ·
Expand description

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 such as function-like macros #[proc_macro], macro attributes #[proc_macro_attribute] and custom derive attributes#[proc_macro_derive].

See the book for more.


  • tracked_envExperimental
    Tracked access to environment variables.
  • tracked_pathExperimental
    Tracked access to additional files.
  • Public implementation details for the TokenStream type, such as iterators.


  • quoteExperimental
    quote!(..) accepts arbitrary tokens and expands into a TokenStream describing the input. For example, quote!(a + b) will produce an expression, that, when evaluated, constructs the TokenStream [Ident("a"), Punct('+', Alone), Ident("b")].


  • DiagnosticExperimental
    A structure representing a diagnostic message and associated children messages.
  • ExpandErrorExperimental
    Error returned from TokenStream::expand_expr.
  • LineColumnExperimental
    A line-column pair representing the start or end of a Span.
  • SourceFileExperimental
    The source file of a given Span.
  • A delimited token stream.
  • An identifier (ident).
  • Error returned from TokenStream::from_str.
  • A literal string ("hello"), byte string (b"hello"), character ('a'), byte character (b'a'), an integer or floating point number with or without a suffix (1, 1u8, 2.3, 2.3f32). Boolean literals like true and false do not belong here, they are Idents.
  • A Punct is a single punctuation character such as +, - or #.
  • A region of source code, along with macro expansion information.
  • The main type provided by this crate, representing an abstract stream of tokens, or, more specifically, a sequence of token trees. The type provide interfaces for iterating over those token trees and, conversely, collecting a number of token trees into one stream.


  • LevelExperimental
    An enum representing a diagnostic level.
  • Describes how a sequence of token trees is delimited.
  • Describes whether a Punct is followed immediately by another Punct (Spacing::Joint) or by a different token or whitespace (Spacing::Alone).
  • A single token or a delimited sequence of token trees (e.g., [1, (), ..]).


  • MultiSpanExperimental
    Trait implemented by types that can be converted into a set of Spans.


  • quoteExperimental
    Quote a TokenStream into a TokenStream. This is the actual implementation of the quote!() proc macro.
  • quote_spanExperimental
    Quote a Span into a TokenStream. This is needed to implement a custom quoter.
  • Determines whether proc_macro has been made accessible to the currently running program.