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