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Diffstat (limited to 'third_party/rust/rustversion/src/expand.rs')
-rw-r--r-- | third_party/rust/rustversion/src/expand.rs | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/third_party/rust/rustversion/src/expand.rs b/third_party/rust/rustversion/src/expand.rs new file mode 100644 index 0000000000..813ba85d7d --- /dev/null +++ b/third_party/rust/rustversion/src/expand.rs @@ -0,0 +1,72 @@ +use crate::attr::{self, Then}; +use crate::error::{Error, Result}; +use crate::{constfn, expr, iter, token}; +use proc_macro::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree}; +use std::iter::FromIterator; + +pub fn cfg(introducer: &str, args: TokenStream, input: TokenStream) -> TokenStream { + try_cfg(introducer, args, input).unwrap_or_else(Error::into_compile_error) +} + +fn try_cfg(introducer: &str, args: TokenStream, input: TokenStream) -> Result<TokenStream> { + let introducer = Ident::new(introducer, Span::call_site()); + + let mut full_args = TokenStream::from(TokenTree::Ident(introducer)); + if !args.is_empty() { + full_args.extend(std::iter::once(TokenTree::Group(Group::new( + Delimiter::Parenthesis, + args, + )))); + } + + let ref mut full_args = iter::new(full_args); + let expr = expr::parse(full_args)?; + token::parse_end(full_args)?; + + if expr.eval(crate::RUSTVERSION) { + Ok(input) + } else { + Ok(TokenStream::new()) + } +} + +pub fn try_attr(args: attr::Args, input: TokenStream) -> Result<TokenStream> { + if !args.condition.eval(crate::RUSTVERSION) { + return Ok(input); + } + + match args.then { + Then::Const(const_token) => constfn::insert_const(input, const_token), + Then::Attribute(then) => { + // #[cfg_attr(all(), #then)] + Ok(TokenStream::from_iter( + vec![ + TokenTree::Punct(Punct::new('#', Spacing::Alone)), + TokenTree::Group(Group::new( + Delimiter::Bracket, + TokenStream::from_iter(vec![ + TokenTree::Ident(Ident::new("cfg_attr", Span::call_site())), + TokenTree::Group(Group::new( + Delimiter::Parenthesis, + TokenStream::from_iter( + vec![ + TokenTree::Ident(Ident::new("all", Span::call_site())), + TokenTree::Group(Group::new( + Delimiter::Parenthesis, + TokenStream::new(), + )), + TokenTree::Punct(Punct::new(',', Spacing::Alone)), + ] + .into_iter() + .chain(then), + ), + )), + ]), + )), + ] + .into_iter() + .chain(input), + )) + } + } +} |