cb56a4420c
Cache pretty-print/retokenize result to avoid compile time blowup Fixes #79242 If a `macro_rules!` recursively builds up a nested nonterminal (passing it to a proc-macro at each step), we will end up repeatedly pretty-printing/retokenizing the same nonterminals. Unfortunately, the 'probable equality' check we do has a non-trivial cost, which leads to a blowup in compilation time. As a workaround, we cache the result of the 'probable equality' check, which eliminates the compilation time blowup for the linked issue. This commit only touches a single file (other than adding tests), so it should be easy to backport. The proper solution is to remove the pretty-print/retokenize hack entirely. However, this will almost certainly break a large number of crates that were relying on hygiene bugs created by using the reparsed `TokenStream`. As a result, we will definitely not want to backport such a change. |
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Cargo.toml |