Add new `pattern_complexity` attribute to add possibility to limit and check recursion in pattern matching #121917

GuillaumeGomez · 2024-03-02T21:51:06Z

Needed for rust-lang/rust-analyzer#9528.

This PR adds a new attribute only available when running rust testsuite called pattern_complexity which allows to set the maximum recursion for the pattern matching. It is quite useful to ensure the complexity doesn't grow, like in tests/ui/pattern/usefulness/issue-118437-exponential-time-on-diagonal-match.rs.

r? @Nadrieril

rustbot · 2024-03-02T21:51:14Z

Some changes occurred in match checking

cc @Nadrieril

Some changes occurred in exhaustiveness checking

cc @Nadrieril

compiler/rustc_pattern_analysis/src/rustc.rs

tests/ui/pattern/complexity_limit.rs

Nadrieril · 2024-03-02T22:07:24Z

Could you add a test that ensures the new attribute is internal-only? Like we do for feature gates:

#![pattern_complexity = "60"]
//~^ ERROR: internal attribute
fn main() {}

GuillaumeGomez · 2024-03-02T22:17:38Z

Could you add a test that ensures the new attribute is internal-only? Like we do for feature gates:
#![pattern_complexity = "60"]
//~^ ERROR: internal attribute
fn main() {}

CI caught this one but good catch! ;)

compiler/rustc_feature/src/unstable.rs

compiler/rustc_pattern_analysis/src/rustc.rs

Nadrieril · 2024-03-03T11:53:33Z

compiler/rustc_pattern_analysis/src/usefulness.rs

+            .map(|complexity_limit| complexity_limit < self.complexity_level)
+            .unwrap_or(false)


Suggested change

.map(|complexity_limit| complexity_limit < self.complexity_level)

.unwrap_or(false)

.is_some_and(|complexity_limit| complexity_limit < self.complexity_level)

I'll make a new clippy lint for this if it doesn't exist. :o

Nadrieril · 2024-03-03T11:55:00Z

Amazing, thank you! r=me with or without the last suggestion

…d check recursion in pattern matching

GuillaumeGomez · 2024-03-03T13:06:17Z

@bors r=Nadrieril rollup

bors · 2024-03-03T13:06:19Z

📌 Commit f04c5c5 has been approved by Nadrieril

It is now in the queue for this repository.

…llaumeGomez Rollup of 3 pull requests Successful merges: - rust-lang#121917 (Add new `pattern_complexity` attribute to add possibility to limit and check recursion in pattern matching) - rust-lang#121933 (Add missing get_name for wasm::thread.) - rust-lang#121934 (rustc_log: expose tracing-tree "wraparound" in an env var) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#121917 - GuillaumeGomez:pattern-complexity_limit.rs, r=Nadrieril Add new `pattern_complexity` attribute to add possibility to limit and check recursion in pattern matching Needed for rust-lang/rust-analyzer#9528. This PR adds a new attribute only available when running rust testsuite called `pattern_complexity` which allows to set the maximum recursion for the pattern matching. It is quite useful to ensure the complexity doesn't grow, like in `tests/ui/pattern/usefulness/issue-118437-exponential-time-on-diagonal-match.rs`. r? `@Nadrieril`

rustbot assigned Nadrieril Mar 2, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Mar 2, 2024

GuillaumeGomez force-pushed the pattern-complexity_limit.rs branch from 22ae31c to f759c8b Compare March 2, 2024 21:52