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#![allow(unused_imports, unused_variables)]
use rustc_ast::token;
use rustc_ast::tokenstream::{DelimSpacing, DelimSpan, Spacing, TokenStream, TokenTree};
use rustc_errors::ErrorGuaranteed;
use rustc_expand::base::{AttrProcMacro, ExtCtxt};
use rustc_span::Span;
use rustc_span::symbol::{Ident, Symbol, kw, sym};
pub(crate) struct ExpandRequires;
pub(crate) struct ExpandEnsures;
impl AttrProcMacro for ExpandRequires {
fn expand<'cx>(
&self,
ecx: &'cx mut ExtCtxt<'_>,
span: Span,
annotation: TokenStream,
annotated: TokenStream,
) -> Result<TokenStream, ErrorGuaranteed> {
expand_requires_tts(ecx, span, annotation, annotated)
}
}
impl AttrProcMacro for ExpandEnsures {
fn expand<'cx>(
&self,
ecx: &'cx mut ExtCtxt<'_>,
span: Span,
annotation: TokenStream,
annotated: TokenStream,
) -> Result<TokenStream, ErrorGuaranteed> {
expand_ensures_tts(ecx, span, annotation, annotated)
}
}
fn expand_injecting_circa_where_clause(
_ecx: &mut ExtCtxt<'_>,
attr_span: Span,
annotated: TokenStream,
inject: impl FnOnce(&mut Vec<TokenTree>) -> Result<(), ErrorGuaranteed>,
) -> Result<TokenStream, ErrorGuaranteed> {
let mut new_tts = Vec::with_capacity(annotated.len());
let mut cursor = annotated.into_trees();
// Find the `fn name<G,...>(x:X,...)` and inject the AST contract forms right after
// the formal parameters (and return type if any).
while let Some(tt) = cursor.next_ref() {
new_tts.push(tt.clone());
if let TokenTree::Token(tok, _) = tt
&& tok.is_ident_named(kw::Fn)
{
break;
}
}
// Found the `fn` keyword, now find the formal parameters.
//
// FIXME: can this fail if you have parentheticals in a generics list, like `fn foo<F: Fn(X) -> Y>` ?
while let Some(tt) = cursor.next_ref() {
new_tts.push(tt.clone());
if let TokenTree::Delimited(_, _, token::Delimiter::Parenthesis, _) = tt {
break;
}
if let TokenTree::Token(token::Token { kind: token::TokenKind::Semi, .. }, _) = tt {
panic!("contract attribute applied to fn without parameter list.");
}
}
// There *might* be a return type declaration (and figuring out where that ends would require
// parsing an arbitrary type expression, e.g. `-> Foo<args ...>`
//
// Instead of trying to figure that out, scan ahead and look for the first occurence of a
// `where`, a `{ ... }`, or a `;`.
//
// FIXME: this might still fall into a trap for something like `-> Ctor<T, const { 0 }>`. I
// *think* such cases must be under a Delimited (e.g. `[T; { N }]` or have the braced form
// prefixed by e.g. `const`, so we should still be able to filter them out without having to
// parse the type expression itself. But rather than try to fix things with hacks like that,
// time might be better spent extending the attribute expander to suport tt-annotation atop
// ast-annotated, which would be an elegant way to sidestep all of this.
let mut opt_next_tt = cursor.next_ref();
while let Some(next_tt) = opt_next_tt {
if let TokenTree::Token(tok, _) = next_tt
&& tok.is_ident_named(kw::Where)
{
break;
}
if let TokenTree::Delimited(_, _, token::Delimiter::Brace, _) = next_tt {
break;
}
if let TokenTree::Token(token::Token { kind: token::TokenKind::Semi, .. }, _) = next_tt {
break;
}
// for anything else, transcribe the tt and keep looking.
new_tts.push(next_tt.clone());
opt_next_tt = cursor.next_ref();
continue;
}
// At this point, we've transcribed everything from the `fn` through the formal parameter list
// and return type declaration, (if any), but `tt` itself has *not* been transcribed.
//
// Now inject the AST contract form.
//
// FIXME: this kind of manual token tree munging does not have significant precedent among
// rustc builtin macros, probably because most builtin macros use direct AST manipulation to
// accomplish similar goals. But since our attributes need to take arbitrary expressions, and
// our attribute infrastructure does not yet support mixing a token-tree annotation with an AST
// annotated, we end up doing token tree manipulation.
inject(&mut new_tts)?;
// Above we injected the internal AST requires/ensures contruct. Now copy over all the other
// token trees.
if let Some(tt) = opt_next_tt {
new_tts.push(tt.clone());
}
while let Some(tt) = cursor.next_ref() {
new_tts.push(tt.clone());
}
Ok(TokenStream::new(new_tts))
}
fn expand_requires_tts(
_ecx: &mut ExtCtxt<'_>,
attr_span: Span,
annotation: TokenStream,
annotated: TokenStream,
) -> Result<TokenStream, ErrorGuaranteed> {
expand_injecting_circa_where_clause(_ecx, attr_span, annotated, |new_tts| {
new_tts.push(TokenTree::Token(
token::Token::from_ast_ident(Ident::new(kw::RustcContractRequires, attr_span)),
Spacing::Joint,
));
new_tts.push(TokenTree::Token(
token::Token::new(token::TokenKind::OrOr, attr_span),
Spacing::Alone,
));
new_tts.push(TokenTree::Delimited(
DelimSpan::from_single(attr_span),
DelimSpacing::new(Spacing::JointHidden, Spacing::JointHidden),
token::Delimiter::Parenthesis,
annotation,
));
Ok(())
})
}
fn expand_ensures_tts(
_ecx: &mut ExtCtxt<'_>,
attr_span: Span,
annotation: TokenStream,
annotated: TokenStream,
) -> Result<TokenStream, ErrorGuaranteed> {
expand_injecting_circa_where_clause(_ecx, attr_span, annotated, |new_tts| {
new_tts.push(TokenTree::Token(
token::Token::from_ast_ident(Ident::new(kw::RustcContractEnsures, attr_span)),
Spacing::Joint,
));
new_tts.push(TokenTree::Delimited(
DelimSpan::from_single(attr_span),
DelimSpacing::new(Spacing::JointHidden, Spacing::JointHidden),
token::Delimiter::Parenthesis,
annotation,
));
Ok(())
})
}
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