attr.rs - source
Description: Source of the Rust file `/Users/erlendbasso/.cargo/registry/src/github.com-1ecc6299db9ec823/paste-1.0.11/src/attr.rs`.
Keywords: rust, rustlang, rust-lang

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    use crate::error::Result;
    use crate::segment::{self, Segment};
    use proc_macro::{Delimiter, Group, Spacing, Span, TokenStream, TokenTree};
    use std::iter;
    use std::mem;
    use std::str::FromStr;

    pub fn expand_attr(
        attr: TokenStream,
        span: Span,
        contains_paste: &mut bool,
    ) -> Result<TokenStream> {
        let mut tokens = attr.clone().into_iter();
        let mut leading_colons = 0; // $(::)?
        let mut leading_path = 0; // $($ident)::+

        let mut token;
        let group = loop {
            token = tokens.next();
            match token {
                // colon after `$(:)?`
                Some(TokenTree::Punct(ref punct))
                    if punct.as_char() == ':' && leading_colons < 2 && leading_path == 0 =>
                {
                    leading_colons += 1;
                }
                // ident after `$(::)? $($ident ::)*`
                Some(TokenTree::Ident(_)) if leading_colons != 1 && leading_path % 3 == 0 => {
                    leading_path += 1;
                }
                // colon after `$(::)? $($ident ::)* $ident $(:)?`
                Some(TokenTree::Punct(ref punct)) if punct.as_char() == ':' && leading_path % 3 > 0 => {
                    leading_path += 1;
                }
                // eq+value after `$(::)? $($ident)::+`
                Some(TokenTree::Punct(ref punct))
                    if punct.as_char() == '=' && leading_path % 3 == 1 =>
                {
                    let mut count = 0;
                    if tokens.inspect(|_| count += 1).all(|tt| is_stringlike(&tt)) && count > 1 {
                        *contains_paste = true;
                        let leading = leading_colons + leading_path;
                        return do_paste_name_value_attr(attr, span, leading);
                    }
                    return Ok(attr);
                }
                // parens after `$(::)? $($ident)::+`
                Some(TokenTree::Group(ref group))
                    if group.delimiter() == Delimiter::Parenthesis && leading_path % 3 == 1 =>
                {
                    break group;
                }
                // bail out
                _ => return Ok(attr),
            }
        };

        // There can't be anything else after the first group in a valid attribute.
        if tokens.next().is_some() {
            return Ok(attr);
        }

        let mut group_contains_paste = false;
        let mut expanded = TokenStream::new();
        let mut nested_attr = TokenStream::new();
        for tt in group.stream() {
            match &tt {
                TokenTree::Punct(punct) if punct.as_char() == ',' => {
                    expanded.extend(expand_attr(
                        nested_attr,
                        group.span(),
                        &mut group_contains_paste,
                    )?);
                    expanded.extend(iter::once(tt));
                    nested_attr = TokenStream::new();
                }
                _ => nested_attr.extend(iter::once(tt)),
            }
        }

        if !nested_attr.is_empty() {
            expanded.extend(expand_attr(
                nested_attr,
                group.span(),
                &mut group_contains_paste,
            )?);
        }

        if group_contains_paste {
            *contains_paste = true;
            let mut group = Group::new(Delimiter::Parenthesis, expanded);
            group.set_span(span);
            Ok(attr
                .into_iter()
                // Just keep the initial ident in `#[ident(...)]`.
                .take(leading_colons + leading_path)
                .chain(iter::once(TokenTree::Group(group)))
                .collect())
        } else {
            Ok(attr)
        }
    }

    fn do_paste_name_value_attr(attr: TokenStream, span: Span, leading: usize) -> Result<TokenStream> {
        let mut expanded = TokenStream::new();
        let mut tokens = attr.into_iter().peekable();
        expanded.extend(tokens.by_ref().take(leading + 1)); // `doc =`

        let mut segments = segment::parse(&mut tokens)?;

        for segment in &mut segments {
            if let Segment::String(string) = segment {
                if let Some(open_quote) = string.value.find('"') {
                    if open_quote == 0 {
                        string.value.truncate(string.value.len() - 1);
                        string.value.remove(0);
                    } else {
                        let begin = open_quote + 1;
                        let end = string.value.rfind('"').unwrap();
                        let raw_string = mem::replace(&mut string.value, String::new());
                        for ch in raw_string[begin..end].chars() {
                            string.value.extend(ch.escape_default());
                        }
                    }
                }
            }
        }

        let mut lit = segment::paste(&segments)?;
        lit.insert(0, '"');
        lit.push('"');

        let mut lit = TokenStream::from_str(&lit)
            .unwrap()
            .into_iter()
            .next()
            .unwrap();
        lit.set_span(span);
        expanded.extend(iter::once(lit));
        Ok(expanded)
    }

    fn is_stringlike(token: &TokenTree) -> bool {
        match token {
            TokenTree::Ident(_) => true,
            TokenTree::Literal(literal) => {
                let repr = literal.to_string();
                !repr.starts_with('b') && !repr.starts_with('\'')
            }
            TokenTree::Group(group) => {
                if group.delimiter() != Delimiter::None {
                    return false;
                }
                let mut inner = group.stream().into_iter();
                match inner.next() {
                    Some(first) => inner.next().is_none() && is_stringlike(&first),
                    None => false,
                }
            }
            TokenTree::Punct(punct) => {
                punct.as_char() == '\'' || punct.as_char() == ':' && punct.spacing() == Spacing::Alone
            }
        }
    }