bjoernager/rust
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Introduce MatchCtxt

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This commit is contained in:
Nadrieril 2023-12-15 16:53:29 +01:00
parent 60ea14bfaa
commit 4bcf66f875
6 changed files with 93 additions and 77 deletions
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46
compiler/rustc_pattern_analysis/src/lib.rs
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@ -36,6 +36,19 @@ use crate::rustc::RustcMatchCheckCtxt;
#[cfg(feature = "rustc")]
use crate::usefulness::{compute_match_usefulness, ValidityConstraint};
// It's not possible to only enable the `typed_arena` dependency when the `rustc` feature is off, so
// we use another feature instead. The crate won't compile if one of these isn't enabled.
#[cfg(feature = "rustc")]
pub(crate) use rustc_arena::TypedArena;
#[cfg(feature = "stable")]
pub(crate) use typed_arena::Arena as TypedArena;
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 MatchCx: Sized + Clone + fmt::Debug {
/// The type of a pattern.
type Ty: Copy + Clone + fmt::Debug; // FIXME: remove Copy
@ -71,10 +84,20 @@ pub trait MatchCx: Sized + Clone + fmt::Debug {
fn bug(&self, fmt: fmt::Arguments<'_>) -> !;
}
/// Context that provides information global to a match.
#[derive(Clone)]
pub struct MatchCtxt<'a, 'p, Cx: MatchCx> {
/// The context for type information.
pub tycx: &'a Cx,
/// An arena to store the wildcards we produce during analysis.
pub wildcard_arena: &'a TypedArena<DeconstructedPat<'p, Cx>>,
}
impl<'a, 'p, Cx: MatchCx> Copy for MatchCtxt<'a, 'p, Cx> {}
/// The arm of a match expression.
#[derive(Clone, Debug)]
pub struct MatchArm<'p, Cx: MatchCx> {
/// The pattern must have been lowered through `check_match::MatchVisitor::lower_pattern`.
pub pat: &'p DeconstructedPat<'p, Cx>,
pub has_guard: bool,
pub arm_data: Cx::ArmData,
@ -82,31 +105,30 @@ pub struct MatchArm<'p, Cx: MatchCx> {
impl<'p, Cx: MatchCx> Copy for MatchArm<'p, Cx> {}
pub trait Captures<'a> {}
impl<'a, T: ?Sized> Captures<'a> for T {}
/// 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>(
cx: &RustcMatchCheckCtxt<'p, 'tcx>,
tycx: &RustcMatchCheckCtxt<'p, 'tcx>,
arms: &[rustc::MatchArm<'p, 'tcx>],
scrut_ty: Ty<'tcx>,
) -> rustc::UsefulnessReport<'p, 'tcx> {
// Arena to store the extra wildcards we construct during analysis.
let wildcard_arena = cx.pattern_arena;
let wildcard_arena = tycx.pattern_arena;
let scrut_validity = ValidityConstraint::from_bool(tycx.known_valid_scrutinee);
let cx = MatchCtxt { tycx, wildcard_arena };
let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity);
let pat_column = PatternColumn::new(arms);
let scrut_validity = ValidityConstraint::from_bool(cx.known_valid_scrutinee);
let report = compute_match_usefulness(cx, arms, scrut_ty, scrut_validity, wildcard_arena);
// Lint on ranges that overlap on their endpoints, which is likely a mistake.
lint_overlapping_range_endpoints(cx, &pat_column, wildcard_arena);
lint_overlapping_range_endpoints(cx, &pat_column);
// 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 cx.refutable && report.non_exhaustiveness_witnesses.is_empty() {
lint_nonexhaustive_missing_variants(cx, arms, &pat_column, scrut_ty, wildcard_arena)
if tycx.refutable && report.non_exhaustiveness_witnesses.is_empty() {
lint_nonexhaustive_missing_variants(cx, arms, &pat_column, scrut_ty)
}
report