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Use desc as a doc-comment if none exist yet

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- Replace {} with the stringified expr

  Giant thank you to `@danielhenrymantilla` for figuring out how to make
  this work ❤️

- Note that this is just an approximation and it would be better to add
  a doc-comment
This commit is contained in:
Joshua Nelson 2020-12-23 11:45:30 -05:00
parent 50a90975c0
commit e67f9d3105
1 changed files with 36 additions and 2 deletions
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38
compiler/rustc_macros/src/query.rs
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@ -5,8 +5,8 @@
use syn::punctuated::Punctuated;
use syn::spanned::Spanned;
use syn::{
braced, parenthesized, parse_macro_input, AttrStyle, Attribute, Block, Error, Expr, Ident,
ReturnType, Token, Type,
braced, parenthesized, parse_macro_input, parse_quote, AttrStyle, Attribute, Block, Error,
Expr, Ident, ReturnType, Token, Type,
};
mod kw {
@ -272,6 +272,40 @@ fn process_modifiers(query: &mut Query) -> QueryModifiers {
if desc.is_some() {
panic!("duplicate modifier `desc` for query `{}`", query.name);
}
// If there are no doc-comments, give at least some idea of what
// it does by showing the query description.
if query.doc_comments.is_empty() {
use ::syn::*;
let mut list = list.iter();
let format_str: String = match list.next() {
Some(&Expr::Lit(ExprLit { lit: Lit::Str(ref lit_str), .. })) => {
lit_str.value().replace("`{}`", "{}") // We add them later anyways for consistency
}
_ => panic!("Expected a string literal"),
};
let mut fmt_fragments = format_str.split("{}");
let mut doc_string = fmt_fragments.next().unwrap().to_string();
list.map(::quote::ToTokens::to_token_stream).zip(fmt_fragments).for_each(
|(tts, next_fmt_fragment)| {
use ::core::fmt::Write;
write!(
&mut doc_string,
" `{}` {}",
tts.to_string().replace(" . ", "."),
next_fmt_fragment,
)
.unwrap();
},
);
let doc_string = format!(
"[query description - consider adding a doc-comment!] {}",
doc_string
);
let comment = parse_quote! {
#[doc = #doc_string]
};
query.doc_comments.push(comment);
}
desc = Some((tcx, list));
}
QueryModifier::FatalCycle => {