41 lines
1.5 KiB
Rust
41 lines
1.5 KiB
Rust
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// force-host
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// no-prefer-dynamic
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#![crate_type = "proc-macro"]
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extern crate proc_macro;
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use proc_macro::{Group, TokenStream, TokenTree};
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// This macro exists as part of a reproduction of #61963 but without using quote/syn/proc_macro2.
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#[proc_macro_derive(DomObject)]
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pub fn expand_token_stream(input: TokenStream) -> TokenStream {
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// Construct a dummy span - `#0 bytes(0..0)` - which is present in the input because
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// of the specially crafted generated tokens in the `attribute-crate` proc-macro.
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let dummy_span = input.clone().into_iter().nth(0).unwrap().span();
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// Define what the macro would output if constructed properly from the source using syn/quote.
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let output: TokenStream = "impl Bar for ((), Qux<Qux<Baz> >) { }
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impl Bar for ((), Box<Bar>) { }".parse().unwrap();
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let mut tokens: Vec<_> = output.into_iter().collect();
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// Adjust token spans to match the original crate (which would use `quote`). Some of the
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// generated tokens point to the dummy span.
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for token in tokens.iter_mut() {
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if let TokenTree::Group(group) = token {
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let mut tokens: Vec<_> = group.stream().into_iter().collect();
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for token in tokens.iter_mut().skip(2) {
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token.set_span(dummy_span);
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}
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let mut stream = TokenStream::new();
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stream.extend(tokens);
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*group = Group::new(group.delimiter(), stream);
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}
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}
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let mut output = TokenStream::new();
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output.extend(tokens);
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output
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}
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