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Merge pull request #340 from dtolnay/fallbackscan

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Add infallible expr scanner fallback for scanning invalid code
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David Tolnay 2024-11-02 21:15:52 -07:00 • committed by GitHub
commit b3bc3e722d
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1 changed files with 35 additions and 1 deletions
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36
impl/src/fmt.rs
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@ -1,10 +1,11 @@
use crate::ast::Field;
use crate::attr::{Display, Trait};
use crate::scan_expr;
use proc_macro2::TokenTree;
use proc_macro2::{TokenStream, TokenTree};
use quote::{format_ident, quote, quote_spanned};
use std::collections::{BTreeSet as Set, HashMap as Map};
use syn::ext::IdentExt;
use syn::parse::discouraged::Speculative;
use syn::parse::{ParseStream, Parser};
use syn::{Expr, Ident, Index, LitStr, Member, Result, Token};
@ -118,7 +119,25 @@ impl Display<'_> {
}
}
#[allow(clippy::unnecessary_wraps)]
fn explicit_named_args(input: ParseStream) -> Result<Set<Ident>> {
let ahead = input.fork();
if let Ok(set) = try_explicit_named_args(&ahead) {
input.advance_to(&ahead);
return Ok(set);
}
let ahead = input.fork();
if let Ok(set) = fallback_explicit_named_args(&ahead) {
input.advance_to(&ahead);
return Ok(set);
}
input.parse::<TokenStream>().unwrap();
Ok(Set::new())
}
fn try_explicit_named_args(input: ParseStream) -> Result<Set<Ident>> {
let scan_expr = if is_syn_full() {
|input: ParseStream| input.parse::<Expr>().map(drop)
} else {
@ -143,6 +162,21 @@ fn explicit_named_args(input: ParseStream) -> Result<Set<Ident>> {
Ok(named_args)
}
fn fallback_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);
}
}
Ok(named_args)
}
fn is_syn_full() -> bool {
// Expr::Block contains syn::Block which contains Vec<syn::Stmt>. In the
// current version of Syn, syn::Stmt is exhaustive and could only plausibly