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//! Analysis of patterns, notably match exhaustiveness checking.
pub mod constructor;
#[cfg(feature = "rustc")]
pub mod errors;
#[cfg(feature = "rustc")]
pub(crate) mod lints;
pub mod pat;
#[cfg(feature = "rustc")]
pub mod rustc;
pub mod usefulness;
#[macro_use]
extern crate tracing;
#[cfg(feature = "rustc")]
#[macro_use]
extern crate rustc_middle;
#[cfg(feature = "rustc")]
rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
use std::fmt;
use rustc_index::Idx;
#[cfg(feature = "rustc")]
use rustc_middle::ty::Ty;
#[cfg(feature = "rustc")]
use rustc_span::ErrorGuaranteed;
use crate::constructor::{Constructor, ConstructorSet};
#[cfg(feature = "rustc")]
use crate::lints::{
lint_nonexhaustive_missing_variants, lint_overlapping_range_endpoints, PatternColumn,
};
use crate::pat::DeconstructedPat;
#[cfg(feature = "rustc")]
use crate::rustc::RustcMatchCheckCtxt;
#[cfg(feature = "rustc")]
use crate::usefulness::{compute_match_usefulness, ValidityConstraint};
pub trait Captures<'a> {}
impl<'a, T: ?Sized> Captures<'a> for T {}
/// Context that provides type information about constructors.
///
/// Most of the crate is parameterized on a type that implements this trait.
pub trait TypeCx: Sized + fmt::Debug {
/// The type of a pattern.
type Ty: Copy + Clone + fmt::Debug; // FIXME: remove Copy
/// Errors that can abort analysis.
type Error: fmt::Debug;
/// The index of an enum variant.
type VariantIdx: Clone + Idx;
/// 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 have a length of
/// `ctor_arity()`.
fn ctor_sub_tys(&self, ctor: &Constructor<Self>, ty: Self::Ty) -> &[Self::Ty];
/// 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>;
/// Best-effort `Debug` implementation.
fn debug_pat(f: &mut fmt::Formatter<'_>, pat: &DeconstructedPat<'_, Self>) -> fmt::Result;
/// Raise a bug.
fn bug(&self, fmt: fmt::Arguments<'_>) -> !;
}
/// Context that provides information global to a match.
#[derive(derivative::Derivative)]
#[derivative(Clone(bound = ""), Copy(bound = ""))]
pub struct MatchCtxt<'a, Cx: TypeCx> {
/// The context for type information.
pub tycx: &'a Cx,
}
/// The arm of a match expression.
#[derive(Debug)]
#[derive(derivative::Derivative)]
#[derivative(Clone(bound = ""), Copy(bound = ""))]
pub struct MatchArm<'p, Cx: TypeCx> {
pub pat: &'p DeconstructedPat<'p, Cx>,
pub has_guard: bool,
pub arm_data: Cx::ArmData,
}
/// The entrypoint for this crate. Computes whether a match is exhaustive and which of its arms are
/// useful, and runs some lints.
#[cfg(feature = "rustc")]
pub fn analyze_match<'p, 'tcx>(
tycx: &RustcMatchCheckCtxt<'p, 'tcx>,
arms: &[rustc::MatchArm<'p, 'tcx>],
scrut_ty: Ty<'tcx>,
) -> Result<rustc::UsefulnessReport<'p, 'tcx>, ErrorGuaranteed> {
let scrut_ty = tycx.reveal_opaque_ty(scrut_ty);
let scrut_validity = ValidityConstraint::from_bool(tycx.known_valid_scrutinee);
let cx = MatchCtxt { tycx };
let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity)?;
let pat_column = PatternColumn::new(arms);
// Lint ranges that overlap on their endpoints, which is likely a mistake.
if !report.overlapping_range_endpoints.is_empty() {
lint_overlapping_range_endpoints(cx, &report.overlapping_range_endpoints);
}
// Run the non_exhaustive_omitted_patterns lint. Only run on refutable patterns to avoid hitting
// `if let`s. Only run if the match is exhaustive otherwise the error is redundant.
if tycx.refutable && report.non_exhaustiveness_witnesses.is_empty() {
lint_nonexhaustive_missing_variants(cx, arms, &pat_column, scrut_ty)?;
}
Ok(report)
}
|
