[−][src]Trait synattra::ParseStreamExt

pub trait ParseStreamExt {
    fn try_parse<T: Parse>(&self) -> Result<T>;

    fn parse_as<T, R, F>(&self, f: F) -> Result<R>
    where
        T: Parse,
        F: FnOnce(T) -> R;

    fn try_parse_as<T, R, F>(&self, f: F) -> Result<R>
    where
        T: Parse,
        F: FnOnce(T) -> R,
    { ... }
}

An extension trait for syn's ParseStream

Required methods

fn try_parse<T: Parse>(&self) -> Result<T>

Try parsing a value, but do not consume the stream if it failed

This is a potentially costly method, better used when one knows the parsing will fail early.

fn parse_as<T, R, F>(&self, f: F) -> Result<R> where
    T: Parse,
    F: FnOnce(T) -> R, 

Parse a value and apply a function.

This method is useful when working with enums.

use syn::Result;
use syn::parse::{Parse, ParseStream};
use synattra::types::KVOption;
use synattra::ParseStreamExt;

mod kw {
    syn::custom_keyword!(registry);
    syn::custom_keyword!(registry_expr);
}

pub type MeteredRegistryOption = KVOption<kw::registry, syn::Ident>;

pub type MeteredRegistryExprOption = KVOption<kw::registry_expr, syn::Expr>;

pub enum MeteredOption {
    Registry(MeteredRegistryOption),
    RegistryExpr(MeteredRegistryExprOption),
}

impl Parse for MeteredOption {
    fn parse(input: ParseStream) -> Result<Self> {
        if MeteredRegistryOption::peek(input) {
            Ok(input.parse_as(MeteredOption::Registry)?)
        } else if MeteredRegistryExprOption::peek(input) {
            Ok(input.parse_as(MeteredOption::RegistryExpr)?)
        } else {
            let err = format!("invalid metered option: {}", input);
            Err(input.error(err))
        }
    }
}
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Provided methods

fn try_parse_as<T, R, F>(&self, f: F) -> Result<R> where
    T: Parse,
    F: FnOnce(T) -> R, 

Try parsing a value and apply a function, but do not consume the stream if it failed

This method is useful when working with enums. See parse_as for an example.

This is a potentially costly method, better used when one knows the parsing will fail early.

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Implementations on Foreign Types

impl<'a> ParseStreamExt for ParseStream<'a>[src]

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Implementors

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