src/spanned.rs

// Copyright 2018 Syn Developers
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use proc_macro2::{Span, TokenStream};
use quote::{ToTokens, Tokens};

pub trait Spanned {
    /// Returns a `Span` covering the complete contents of this AST node, or
    /// `Span::call_site()` if this node is empty.
    fn span(&self) -> Span;
}

impl<T> Spanned for T
where
    T: ToTokens,
{
    #[cfg(procmacro2_semver_exempt)]
    fn span(&self) -> Span {
        let mut tokens = Tokens::new();
        self.to_tokens(&mut tokens);
        let token_stream = TokenStream::from(tokens);
        let mut iter = token_stream.into_iter();
        let mut span = match iter.next() {
            Some(tt) => tt.span,
            None => {
                return Span::call_site();
            }
        };
        for tt in iter {
            if let Some(joined) = span.join(tt.span) {
                span = joined;
            }
        }
        span
    }

    #[cfg(not(procmacro2_semver_exempt))]
    fn span(&self) -> Span {
        let mut tokens = Tokens::new();
        self.to_tokens(&mut tokens);
        let token_stream = TokenStream::from(tokens);
        let mut iter = token_stream.into_iter();

        // We can't join spans without procmacro2_semver_exempt so just grab the
        // first one.
        match iter.next() {
            Some(tt) => tt.span,
            None => Span::call_site(),
        }
    }
}