1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147

use crate::ast::Field;
use crate::attr::Display;
use proc_macro2::TokenTree;
use quote::{format_ident, quote_spanned};
use std::collections::HashSet as Set;
use syn::ext::IdentExt;
use syn::parse::{ParseStream, Parser};
use syn::{Ident, Index, LitStr, Member, Result, Token};

impl Display<'_> {
    // Transform `"error {var}"` to `"error {}", var`.
    pub fn expand_shorthand(&mut self, fields: &[Field]) {
        let raw_args = self.args.clone();
        let mut named_args = explicit_named_args.parse2(raw_args).unwrap();
        let fields: Set<Member> = fields.iter().map(|f| f.member.clone()).collect();

        let span = self.fmt.span();
        let fmt = self.fmt.value();
        let mut read = fmt.as_str();
        let mut out = String::new();
        let mut args = self.args.clone();
        let mut has_bonus_display = false;

        let mut has_trailing_comma = false;
        if let Some(TokenTree::Punct(punct)) = args.clone().into_iter().last() {
            if punct.as_char() == ',' {
                has_trailing_comma = true;
            }
        }

        while let Some(brace) = read.find('{') {
            out += &read[..brace + 1];
            read = &read[brace + 1..];
            if read.starts_with('{') {
                out.push('{');
                read = &read[1..];
                continue;
            }
            let next = match read.chars().next() {
                Some(next) => next,
                None => return,
            };
            let member = match next {
                '0'..='9' => {
                    let int = take_int(&mut read);
                    let member = match int.parse::<u32>() {
                        Ok(index) => Member::Unnamed(Index { index, span }),
                        Err(_) => return,
                    };
                    if !fields.contains(&member) {
                        out += &int;
                        continue;
                    }
                    member
                }
                'a'..='z' | 'A'..='Z' | '_' => {
                    let mut ident = take_ident(&mut read);
                    ident.set_span(span);
                    Member::Named(ident)
                }
                _ => continue,
            };
            let local = match &member {
                Member::Unnamed(index) => format_ident!("_{}", index),
                Member::Named(ident) => ident.clone(),
            };
            let mut formatvar = local.clone();
            if formatvar.to_string().starts_with("r#") {
                formatvar = format_ident!("r_{}", formatvar);
            }
            if formatvar.to_string().starts_with('_') {
                // Work around leading underscore being rejected by 1.40 and
                // older compilers. https://github.com/rust-lang/rust/pull/66847
                formatvar = format_ident!("field_{}", formatvar);
            }
            out += &formatvar.to_string();
            if !named_args.insert(formatvar.clone()) {
                // Already specified in the format argument list.
                continue;
            }
            if !has_trailing_comma {
                args.extend(quote_spanned!(span=> ,));
            }
            args.extend(quote_spanned!(span=> #formatvar = #local));
            if read.starts_with('}') && fields.contains(&member) {
                has_bonus_display = true;
                args.extend(quote_spanned!(span=> .as_display()));
            }
            has_trailing_comma = false;
        }

        out += read;
        self.fmt = LitStr::new(&out, self.fmt.span());
        self.args = args;
        self.has_bonus_display = has_bonus_display;
    }
}

fn explicit_named_args(input: ParseStream) -> Result<Set<Ident>> {
    let mut named_args = Set::new();

    while !input.is_empty() {
        if input.peek(Token![,]) && input.peek2(Ident::peek_any) && input.peek3(Token![=]) {
            input.parse::<Token![,]>()?;
            let ident = input.call(Ident::parse_any)?;
            input.parse::<Token![=]>()?;
            named_args.insert(ident);
        } else {
            input.parse::<TokenTree>()?;
        }
    }

    Ok(named_args)
}

fn take_int(read: &mut &str) -> String {
    let mut int = String::new();
    for (i, ch) in read.char_indices() {
        match ch {
            '0'..='9' => int.push(ch),
            _ => {
                *read = &read[i..];
                break;
            }
        }
    }
    int
}

fn take_ident(read: &mut &str) -> Ident {
    let mut ident = String::new();
    let raw = read.starts_with("r#");
    if raw {
        ident.push_str("r#");
        *read = &read[2..];
    }
    for (i, ch) in read.char_indices() {
        match ch {
            'a'..='z' | 'A'..='Z' | '0'..='9' | '_' => ident.push(ch),
            _ => {
                *read = &read[i..];
                break;
            }
        }
    }
    Ident::parse_any.parse_str(&ident).unwrap()
}