From be31b6b6cdfd0d614a22214391b91070fe55d89e Mon Sep 17 00:00:00 2001 From: Guillaume Gomez Date: Sat, 2 Mar 2024 22:48:41 +0100 Subject: Add new `pattern_complexity` attribute to add possibility to limit and check recursion in pattern matching --- compiler/rustc_pattern_analysis/src/usefulness.rs | 24 ++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) (limited to 'compiler/rustc_pattern_analysis/src/usefulness.rs') diff --git a/compiler/rustc_pattern_analysis/src/usefulness.rs b/compiler/rustc_pattern_analysis/src/usefulness.rs index bbe02f94c0a..0261768d916 100644 --- a/compiler/rustc_pattern_analysis/src/usefulness.rs +++ b/compiler/rustc_pattern_analysis/src/usefulness.rs @@ -734,6 +734,21 @@ struct UsefulnessCtxt<'a, Cx: TypeCx> { /// Collect the patterns found useful during usefulness checking. This is used to lint /// unreachable (sub)patterns. useful_subpatterns: FxHashSet, + complexity_limit: Option, + complexity_level: usize, +} + +impl<'a, Cx: TypeCx> UsefulnessCtxt<'a, Cx> { + fn increase_complexity_level(&mut self, complexity_add: usize) -> Result<(), Cx::Error> { + self.complexity_level += complexity_add; + if self + .complexity_limit + .is_some_and(|complexity_limit| complexity_limit < self.complexity_level) + { + return self.tycx.complexity_exceeded(); + } + Ok(()) + } } /// Context that provides information local to a place under investigation. @@ -1552,6 +1567,7 @@ fn compute_exhaustiveness_and_usefulness<'a, 'p, Cx: TypeCx>( } let Some(place) = matrix.head_place() else { + mcx.increase_complexity_level(matrix.rows().len())?; // The base case: there are no columns in the matrix. We are morally pattern-matching on (). // A row is useful iff it has no (unguarded) rows above it. let mut useful = true; // Whether the next row is useful. @@ -1690,8 +1706,14 @@ pub fn compute_match_usefulness<'p, Cx: TypeCx>( arms: &[MatchArm<'p, Cx>], scrut_ty: Cx::Ty, scrut_validity: ValidityConstraint, + complexity_limit: Option, ) -> Result, Cx::Error> { - let mut cx = UsefulnessCtxt { tycx, useful_subpatterns: FxHashSet::default() }; + let mut cx = UsefulnessCtxt { + tycx, + useful_subpatterns: FxHashSet::default(), + complexity_limit, + complexity_level: 0, + }; let mut matrix = Matrix::new(arms, scrut_ty, scrut_validity); let non_exhaustiveness_witnesses = compute_exhaustiveness_and_usefulness(&mut cx, &mut matrix)?; -- cgit 1.4.1-3-g733a5