Live demo (code)

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A library to generate syntax ("railroad") diagrams for Rust's macro_rules!().

Diagrams are generated as Scalable Vector Graphics, with layout-details controlled by customizable CSS.

As an example, given the definition of nom's method

macro_rules! method {
    ($name:ident<$a:ty>( $i:ty ) -> $o:ty, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty,$i:ty,$o:ty,$e:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty,$i:ty,$o:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty,$o:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty>( $i:ty ) -> $o:ty, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty,$i:ty,$o:ty,$e:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty,$i:ty,$o:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty,$o:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty>, $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty>( $i:ty ) -> $o:ty, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty,$i:ty,$o:ty,$e:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty,$i:ty,$o:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty,$o:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    ($name:ident<$a:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty>( $i:ty ) -> $o:ty, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty,$i:ty,$o:ty,$e:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty,$i:ty,$o:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty,$o:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
    (pub $name:ident<$a:ty>, mut $self_:ident, $submac:ident!( $($args:tt)* )) => { ... };
}

... the library generates an SVG which renders (using default CSS) as

The library is currently mostly a tech-demo. Pull requests are most welcome.

To generate the examples shown here, run

cargo run --example various

which will output some html-files to /examples; Feel free to hack on the demos in /examples/various.rs.

Examples

• Live demo (code)
• The macros from nom-4.1.1 as diagrams
• Some of the macros from the standard library as diagrams
• The macros from syn-0.14 as diagrams
• Some macros from various crates, including bitflags, quickcheck and cfg-if, as diagrams