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8121958fda
It's very useful. There are some false positives involving integration tests in `rustc_pattern_analysis` and `rustc_serialize`. There is also a false positive involving `rustc_driver_impl`'s `rustc_randomized_layouts` feature. And I removed a `rustc_span` mention in a doc comment in `rustc_log` because it wasn't integral to the comment but caused a dev-dependency.
128 lines
4.3 KiB
Rust
128 lines
4.3 KiB
Rust
//! Analysis of patterns, notably match exhaustiveness checking. The main entrypoint for this crate
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//! is [`usefulness::compute_match_usefulness`]. For rustc-specific types and entrypoints, see the
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//! [`rustc`] module.
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// tidy-alphabetical-start
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#![allow(rustc::diagnostic_outside_of_impl)]
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#![allow(rustc::untranslatable_diagnostic)]
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#![allow(unused_crate_dependencies)]
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#![cfg_attr(feature = "rustc", feature(let_chains))]
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// tidy-alphabetical-end
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pub mod constructor;
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#[cfg(feature = "rustc")]
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pub mod errors;
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#[cfg(feature = "rustc")]
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pub(crate) mod lints;
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pub mod pat;
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pub mod pat_column;
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#[cfg(feature = "rustc")]
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pub mod rustc;
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pub mod usefulness;
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#[cfg(feature = "rustc")]
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rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
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use std::fmt;
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pub use rustc_index::{Idx, IndexVec}; // re-exported to avoid rustc_index version issues
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use crate::constructor::{Constructor, ConstructorSet, IntRange};
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use crate::pat::DeconstructedPat;
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pub trait Captures<'a> {}
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impl<'a, T: ?Sized> Captures<'a> for T {}
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/// `bool` newtype that indicates whether this is a privately uninhabited field that we should skip
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/// during analysis.
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#[derive(Copy, Clone, Debug, PartialEq, Eq)]
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pub struct PrivateUninhabitedField(pub bool);
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/// Context that provides type information about constructors.
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///
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/// Most of the crate is parameterized on a type that implements this trait.
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pub trait PatCx: Sized + fmt::Debug {
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/// The type of a pattern.
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type Ty: Clone + fmt::Debug;
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/// Errors that can abort analysis.
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type Error: fmt::Debug;
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/// The index of an enum variant.
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type VariantIdx: Clone + Idx + fmt::Debug;
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/// A string literal
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type StrLit: Clone + PartialEq + fmt::Debug;
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/// Extra data to store in a match arm.
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type ArmData: Copy + Clone + fmt::Debug;
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/// Extra data to store in a pattern.
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type PatData: Clone;
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fn is_exhaustive_patterns_feature_on(&self) -> bool;
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/// The number of fields for this constructor.
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fn ctor_arity(&self, ctor: &Constructor<Self>, ty: &Self::Ty) -> usize;
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/// The types of the fields for this constructor. The result must contain `ctor_arity()` fields.
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fn ctor_sub_tys(
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&self,
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ctor: &Constructor<Self>,
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ty: &Self::Ty,
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) -> impl Iterator<Item = (Self::Ty, PrivateUninhabitedField)> + ExactSizeIterator;
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/// The set of all the constructors for `ty`.
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///
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/// This must follow the invariants of `ConstructorSet`
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fn ctors_for_ty(&self, ty: &Self::Ty) -> Result<ConstructorSet<Self>, Self::Error>;
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/// Write the name of the variant represented by `pat`. Used for the best-effort `Debug` impl of
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/// `DeconstructedPat`. Only invoqued when `pat.ctor()` is `Struct | Variant(_) | UnionField`.
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fn write_variant_name(
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f: &mut fmt::Formatter<'_>,
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ctor: &crate::constructor::Constructor<Self>,
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ty: &Self::Ty,
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) -> fmt::Result;
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/// Raise a bug.
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fn bug(&self, fmt: fmt::Arguments<'_>) -> Self::Error;
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/// Lint that the range `pat` overlapped with all the ranges in `overlaps_with`, where the range
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/// they overlapped over is `overlaps_on`. We only detect singleton overlaps.
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/// The default implementation does nothing.
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fn lint_overlapping_range_endpoints(
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&self,
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_pat: &DeconstructedPat<Self>,
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_overlaps_on: IntRange,
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_overlaps_with: &[&DeconstructedPat<Self>],
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) {
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}
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/// The maximum pattern complexity limit was reached.
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fn complexity_exceeded(&self) -> Result<(), Self::Error>;
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/// Lint that there is a gap `gap` between `pat` and all of `gapped_with` such that the gap is
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/// not matched by another range. If `gapped_with` is empty, then `gap` is `T::MAX`. We only
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/// detect singleton gaps.
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/// The default implementation does nothing.
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fn lint_non_contiguous_range_endpoints(
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&self,
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_pat: &DeconstructedPat<Self>,
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_gap: IntRange,
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_gapped_with: &[&DeconstructedPat<Self>],
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) {
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}
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}
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/// The arm of a match expression.
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#[derive(Debug)]
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pub struct MatchArm<'p, Cx: PatCx> {
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pub pat: &'p DeconstructedPat<Cx>,
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pub has_guard: bool,
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pub arm_data: Cx::ArmData,
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}
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impl<'p, Cx: PatCx> Clone for MatchArm<'p, Cx> {
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fn clone(&self) -> Self {
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Self { pat: self.pat, has_guard: self.has_guard, arm_data: self.arm_data }
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}
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}
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impl<'p, Cx: PatCx> Copy for MatchArm<'p, Cx> {}
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