Nika Layzell efda49712b proc_macro/bridge: use the cross-thread executor for nested proc-macros ... While working on some other changes in the bridge, I noticed that when running a nested proc-macro (which is currently only possible using the unstable `TokenStream::expand_expr`), any symbols held by the proc-macro client would be invalidated, as the same thread would be used for the nested macro by default, and the interner doesn't handle nested use. After discussing with @eddyb, we decided the best approach might be to force the use of the cross-thread executor for nested invocations, as it will never re-use thread-local storage, avoiding the issue. This shouldn't impact performance, as expand_expr is still unstable, and infrequently used. This was chosen rather than making the client symbol interner handle nested invocations, as that would require replacing the internal interner `Vec` with a `BTreeMap` (as valid symbol id ranges could now be disjoint), and the symbol interner is known to be fairly perf-sensitive. This patch adds checks to the execution strategy to use the cross-thread executor when doing nested invocations. An alternative implementation strategy could be to track this information in the `ExtCtxt`, however a thread-local in the `proc_macro` crate was chosen to add an assertion so that `rust-analyzer` is aware of the issue if it implements `expand_expr` in the future. r? @eddyb		2022-09-04 14:06:26 -04:00
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src	proc_macro/bridge: use the cross-thread executor for nested proc-macros	2022-09-04 14:06:26 -04:00
Cargo.toml	proc_macro: Add a workaround for rustdoc	2022-04-19 22:49:27 +03:00