Struct FormatArgs 

pub struct FormatArgs { /* private fields */ }

A format specification: A format string followed by arguments to be formatted in accordance with that string.

This type can only be built inside of a macro context since it performs constant evaluation.

Both the format string and the arguments are held as the tokens they were written as rather than as a syntax tree, so nothing here recurses over what a macro was handed - see MacroContext::exprs.

Implementations

impl FormatArgs

pub fn parse( cx: &mut MacroContext<'_, '_, '_>, stream: &TokenStream, ) -> Result<Self>

Parse format arguments out of the whole input of a macro.

Examples

use rune::macros::{self, quote, FormatArgs};

macros::test(|cx| {
    let stream = quote!("Hello {}", 42).into_token_stream(cx)?;
    let args = FormatArgs::parse(cx, &stream)?;
    let expanded = args.expand(cx)?.into_token_stream(cx)?;
    assert!(expanded.kinds().count() > 0);
    Ok(())
})?;

pub fn from_exprs<I>( cx: &mut MacroContext<'_, '_, '_>, exprs: I, ) -> Result<Self>

where I: IntoIterator<Item = TokenStream>,

Build format arguments out of expressions which have already been split out of the input of a macro with MacroContext::exprs.

This is what a macro whose format specification is preceded by arguments of its own uses, assert! being one.

pub fn expand(&self, cx: &mut MacroContext<'_, '_, '_>) -> Result<Quote<'_>>

Expand the format specification.