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-rw-r--r--third_party/rust/rustversion/src/expand.rs72
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),
+ ))
+ }
+ }
+}