Rename ValidityConstraint -> PlaceValidity

The old name came from a time where I wanted to reuse it for
differentiating wildcards from bindings. I don't plan to do this
anymore.

compiler/rustc_pattern_analysis/src/lib.rs

@@ -179,10 +179,10 @@ pub fn analyze_match<'p, 'tcx>(
  pattern_complexity_limit: Option<usize>,
 ) -> Result<rustc::UsefulnessReport<'p, 'tcx>, ErrorGuaranteed> {
  use lints::lint_nonexhaustive_missing_variants;
- use usefulness::{compute_match_usefulness, ValidityConstraint};
+ use usefulness::{compute_match_usefulness, PlaceValidity};
 
  let scrut_ty = tycx.reveal_opaque_ty(scrut_ty);
- let scrut_validity = ValidityConstraint::from_bool(tycx.known_valid_scrutinee);
+ let scrut_validity = PlaceValidity::from_bool(tycx.known_valid_scrutinee);
  let report =
  compute_match_usefulness(tycx, arms, scrut_ty, scrut_validity, pattern_complexity_limit)?;
 

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -540,8 +540,8 @@
 //! We track in the algorithm whether a given place is known to contain valid data. This is done
 //! first by inspecting the scrutinee syntactically (which gives us `cx.known_valid_scrutinee`), and
 //! then by tracking validity of each column of the matrix (which correspond to places) as we
-//! recurse into subpatterns. That second part is done through [`ValidityConstraint`], most notably
-//! [`ValidityConstraint::specialize`].
+//! recurse into subpatterns. That second part is done through [`PlaceValidity`], most notably
+//! [`PlaceValidity::specialize`].
 //!
 //! Having said all that, in practice we don't fully follow what's been presented in this section.
 //! Let's call "toplevel exception" the case where the match scrutinee itself has type `!` or
@@ -718,7 +718,7 @@ use crate::constructor::{Constructor, ConstructorSet, IntRange};
 use crate::pat::{DeconstructedPat, PatId, PatOrWild, WitnessPat};
 use crate::{Captures, MatchArm, PrivateUninhabitedField, TypeCx};
 
-use self::ValidityConstraint::*;
+use self::PlaceValidity::*;
 
 #[cfg(feature = "rustc")]
 use rustc_data_structures::stack::ensure_sufficient_stack;
@@ -780,18 +780,14 @@ impl<'a, Cx: TypeCx> PlaceCtxt<'a, Cx> {
  }
 }
 
-/// Serves two purposes:
-/// - in a wildcard, tracks whether the wildcard matches only valid values (i.e. is a binding `_a`)
-/// or also invalid values (i.e. is a true `_` pattern).
-/// - in the matrix, track whether a given place (aka column) is known to contain a valid value or
-/// not.
+/// Track whether a given place (aka column) is known to contain a valid value or not.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
-pub enum ValidityConstraint {
+pub enum PlaceValidity {
  ValidOnly,
  MaybeInvalid,
 }
 
-impl ValidityConstraint {
+impl PlaceValidity {
  pub fn from_bool(is_valid_only: bool) -> Self {
  if is_valid_only { ValidOnly } else { MaybeInvalid }
  }
@@ -817,7 +813,7 @@ impl ValidityConstraint {
  }
 }
 
-impl fmt::Display for ValidityConstraint {
+impl fmt::Display for PlaceValidity {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  let s = match self {
  ValidOnly => "✓",
@@ -836,7 +832,7 @@ struct PlaceInfo<Cx: TypeCx> {
  /// so that we don't observe its emptiness.
  private_uninhabited: bool,
  /// Whether the place is known to contain valid data.
- validity: ValidityConstraint,
+ validity: PlaceValidity,
  /// Whether the place is the scrutinee itself or a subplace of it.
  is_scrutinee: bool,
 }
@@ -1155,11 +1151,7 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
  }
 
  /// Build a new matrix from an iterator of `MatchArm`s.
- fn new(
- arms: &[MatchArm<'p, Cx>],
- scrut_ty: Cx::Ty,
- scrut_validity: ValidityConstraint,
- ) -> Self {
+ fn new(arms: &[MatchArm<'p, Cx>], scrut_ty: Cx::Ty, scrut_validity: PlaceValidity) -> Self {
  let place_info = PlaceInfo {
  ty: scrut_ty,
  private_uninhabited: false,
@@ -1754,7 +1746,7 @@ pub fn compute_match_usefulness<'p, Cx: TypeCx>(
  tycx: &Cx,
  arms: &[MatchArm<'p, Cx>],
  scrut_ty: Cx::Ty,
- scrut_validity: ValidityConstraint,
+ scrut_validity: PlaceValidity,
  complexity_limit: Option<usize>,
 ) -> Result<UsefulnessReport<'p, Cx>, Cx::Error> {
  let mut cx = UsefulnessCtxt {