Rename Skip to PrivateUninhabited

compiler/rustc_pattern_analysis/src/constructor.rs

@@ -688,10 +688,9 @@ pub enum Constructor<Cx: TypeCx> {
     /// Fake extra constructor for constructors that are not seen in the matrix, as explained at the
     /// top of the file.
     Missing,
-    /// Fake extra constructor that indicates that we should skip the column entirely. This is used
+    /// Fake extra constructor that indicates and empty field that is private. When we encounter one
-    /// when a private field is empty, so that we don't observe its emptiness. Only used for
+    /// we skip the column entirely so we don't observe its emptiness. Only used for specialization.
-    /// specialization.
+    PrivateUninhabited,
-    Skip,
 }
 
 impl<Cx: TypeCx> Clone for Constructor<Cx> {
@@ -713,7 +712,7 @@ impl<Cx: TypeCx> Clone for Constructor<Cx> {
             Constructor::NonExhaustive => Constructor::NonExhaustive,
             Constructor::Hidden => Constructor::Hidden,
             Constructor::Missing => Constructor::Missing,
-            Constructor::Skip => Constructor::Skip,
+            Constructor::PrivateUninhabited => Constructor::PrivateUninhabited,
         }
     }
 }
@@ -768,8 +767,8 @@ impl<Cx: TypeCx> Constructor<Cx> {
             }
             // Wildcards cover anything
             (_, Wildcard) => true,
-            // `Skip` skips everything.
+            // `PrivateUninhabited` skips everything.
-            (Skip, _) => true,
+            (PrivateUninhabited, _) => true,
             // Only a wildcard pattern can match these special constructors.
             (Missing { .. } | NonExhaustive | Hidden, _) => false,
 

compiler/rustc_pattern_analysis/src/lib.rs

@@ -82,9 +82,10 @@ use crate::usefulness::{compute_match_usefulness, ValidityConstraint};
 pub trait Captures<'a> {}
 impl<'a, T: ?Sized> Captures<'a> for T {}
 
-/// `bool` newtype that indicates whether we should skip this field during analysis.
+/// `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 SkipField(pub bool);
+pub struct PrivateUninhabitedField(pub bool);
 
 /// Context that provides type information about constructors.
 ///
@@ -114,7 +115,7 @@ pub trait TypeCx: Sized + fmt::Debug {
         &'a self,
         ctor: &'a Constructor<Self>,
         ty: &'a Self::Ty,
-    ) -> impl Iterator<Item = (Self::Ty, SkipField)> + ExactSizeIterator + Captures<'a>;
+    ) -> impl Iterator<Item = (Self::Ty, PrivateUninhabitedField)> + ExactSizeIterator + Captures<'a>;
 
     /// The set of all the constructors for `ty`.
     ///

compiler/rustc_pattern_analysis/src/pat.rs

@@ -5,7 +5,7 @@ use std::fmt;
 use smallvec::{smallvec, SmallVec};
 
 use crate::constructor::{Constructor, Slice, SliceKind};
-use crate::{SkipField, TypeCx};
+use crate::{PrivateUninhabitedField, TypeCx};
 
 use self::Constructor::*;
 
@@ -80,7 +80,7 @@ impl<Cx: TypeCx> DeconstructedPat<Cx> {
             // Return a wildcard for each field of `other_ctor`.
             (Wildcard, _) => wildcard_sub_tys(),
             // Skip this column.
-            (_, Skip) => smallvec![],
+            (_, PrivateUninhabited) => smallvec![],
             // The only non-trivial case: two slices of different arity. `other_slice` is
             // guaranteed to have a larger arity, so we fill the middle part with enough
             // wildcards to reach the length of the new, larger slice.
@@ -189,7 +189,9 @@ impl<Cx: TypeCx> fmt::Debug for DeconstructedPat<Cx> {
                 }
                 Ok(())
             }
-            Wildcard | Missing | NonExhaustive | Hidden | Skip => write!(f, "_ : {:?}", pat.ty()),
+            Wildcard | Missing | NonExhaustive | Hidden | PrivateUninhabited => {
+                write!(f, "_ : {:?}", pat.ty())
+            }
         }
     }
 }
@@ -299,7 +301,7 @@ impl<Cx: TypeCx> WitnessPat<Cx> {
     pub(crate) fn wild_from_ctor(cx: &Cx, ctor: Constructor<Cx>, ty: Cx::Ty) -> Self {
         let fields = cx
             .ctor_sub_tys(&ctor, &ty)
-            .filter(|(_, SkipField(skip))| !skip)
+            .filter(|(_, PrivateUninhabitedField(skip))| !skip)
             .map(|(ty, _)| Self::wildcard(ty))
             .collect();
         Self::new(ctor, fields, ty)

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -18,7 +18,7 @@ use rustc_target::abi::{FieldIdx, Integer, VariantIdx, FIRST_VARIANT};
 use crate::constructor::{
     IntRange, MaybeInfiniteInt, OpaqueId, RangeEnd, Slice, SliceKind, VariantVisibility,
 };
-use crate::{errors, Captures, SkipField, TypeCx};
+use crate::{errors, Captures, PrivateUninhabitedField, TypeCx};
 
 use crate::constructor::Constructor::*;
 
@@ -195,14 +195,16 @@ impl<'p, 'tcx: 'p> RustcMatchCheckCtxt<'p, 'tcx> {
         &'a self,
         ctor: &'a Constructor<'p, 'tcx>,
         ty: RevealedTy<'tcx>,
-    ) -> impl Iterator<Item = (RevealedTy<'tcx>, SkipField)> + ExactSizeIterator + Captures<'a>
+    ) -> impl Iterator<Item = (RevealedTy<'tcx>, PrivateUninhabitedField)>
-    {
+    + ExactSizeIterator
+    + Captures<'a> {
         fn reveal_and_alloc<'a, 'tcx>(
             cx: &'a RustcMatchCheckCtxt<'_, 'tcx>,
             iter: impl Iterator<Item = Ty<'tcx>>,
-        ) -> &'a [(RevealedTy<'tcx>, SkipField)] {
+        ) -> &'a [(RevealedTy<'tcx>, PrivateUninhabitedField)] {
             cx.dropless_arena.alloc_from_iter(
-                iter.map(|ty| cx.reveal_opaque_ty(ty)).map(|ty| (ty, SkipField(false))),
+                iter.map(|ty| cx.reveal_opaque_ty(ty))
+                    .map(|ty| (ty, PrivateUninhabitedField(false))),
             )
         }
         let cx = self;
@@ -230,7 +232,7 @@ impl<'p, 'tcx: 'p> RustcMatchCheckCtxt<'p, 'tcx> {
                                 || cx.tcx.features().min_exhaustive_patterns)
                                 && cx.is_uninhabited(*ty);
                             let skip = is_uninhabited && (!is_visible || is_non_exhaustive);
-                            (ty, SkipField(skip))
+                            (ty, PrivateUninhabitedField(skip))
                         });
                         cx.dropless_arena.alloc_from_iter(tys)
                     }
@@ -249,7 +251,7 @@ impl<'p, 'tcx: 'p> RustcMatchCheckCtxt<'p, 'tcx> {
                 _ => bug!("bad slice pattern {:?} {:?}", ctor, ty),
             },
             Bool(..) | IntRange(..) | F32Range(..) | F64Range(..) | Str(..) | Opaque(..)
-            | NonExhaustive | Hidden | Missing | Skip | Wildcard => &[],
+            | NonExhaustive | Hidden | Missing | PrivateUninhabited | Wildcard => &[],
             Or => {
                 bug!("called `Fields::wildcards` on an `Or` ctor")
             }
@@ -277,7 +279,7 @@ impl<'p, 'tcx: 'p> RustcMatchCheckCtxt<'p, 'tcx> {
             Ref => 1,
             Slice(slice) => slice.arity(),
             Bool(..) | IntRange(..) | F32Range(..) | F64Range(..) | Str(..) | Opaque(..)
-            | NonExhaustive | Hidden | Missing | Skip | Wildcard => 0,
+            | NonExhaustive | Hidden | Missing | PrivateUninhabited | Wildcard => 0,
             Or => bug!("The `Or` constructor doesn't have a fixed arity"),
         }
     }
@@ -805,7 +807,7 @@ impl<'p, 'tcx: 'p> RustcMatchCheckCtxt<'p, 'tcx> {
                 }
             }
             &Str(value) => PatKind::Constant { value },
-            Wildcard | NonExhaustive | Hidden | Skip => PatKind::Wild,
+            Wildcard | NonExhaustive | Hidden | PrivateUninhabited => PatKind::Wild,
             Missing { .. } => bug!(
                 "trying to convert a `Missing` constructor into a `Pat`; this is probably a bug,
                 `Missing` should have been processed in `apply_constructors`"
@@ -841,7 +843,8 @@ impl<'p, 'tcx: 'p> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
         &'a self,
         ctor: &'a crate::constructor::Constructor<Self>,
         ty: &'a Self::Ty,
-    ) -> impl Iterator<Item = (Self::Ty, SkipField)> + ExactSizeIterator + Captures<'a> {
+    ) -> impl Iterator<Item = (Self::Ty, PrivateUninhabitedField)> + ExactSizeIterator + Captures<'a>
+    {
         self.ctor_sub_tys(ctor, *ty)
     }
     fn ctors_for_ty(

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -716,7 +716,7 @@ use std::fmt;
 
 use crate::constructor::{Constructor, ConstructorSet, IntRange};
 use crate::pat::{DeconstructedPat, PatId, PatOrWild, WitnessPat};
-use crate::{Captures, MatchArm, SkipField, TypeCx};
+use crate::{Captures, MatchArm, PrivateUninhabitedField, TypeCx};
 
 use self::ValidityConstraint::*;
 
@@ -817,9 +817,9 @@ impl fmt::Display for ValidityConstraint {
 struct PlaceInfo<Cx: TypeCx> {
     /// The type of the place.
     ty: Cx::Ty,
-    /// Whether we must skip this field during analysis. This is used when a private field is empty,
+    /// Whether the place is a private uninhabited field. If so we skip this field during analysis
     /// so that we don't observe its emptiness.
-    skip: SkipField,
+    private_uninhabited: bool,
     /// Whether the place is known to contain valid data.
     validity: ValidityConstraint,
     /// Whether the place is the scrutinee itself or a subplace of it.
@@ -836,9 +836,9 @@ impl<Cx: TypeCx> PlaceInfo<Cx> {
     ) -> impl Iterator<Item = Self> + ExactSizeIterator + Captures<'a> {
         let ctor_sub_tys = cx.ctor_sub_tys(ctor, &self.ty);
         let ctor_sub_validity = self.validity.specialize(ctor);
-        ctor_sub_tys.map(move |(ty, skip)| PlaceInfo {
+        ctor_sub_tys.map(move |(ty, PrivateUninhabitedField(private_uninhabited))| PlaceInfo {
             ty,
-            skip,
+            private_uninhabited,
             validity: ctor_sub_validity,
             is_scrutinee: false,
         })
@@ -860,9 +860,9 @@ impl<Cx: TypeCx> PlaceInfo<Cx> {
     where
         Cx: 'a,
     {
-        if matches!(self.skip, SkipField(true)) {
+        if self.private_uninhabited {
             // Skip the whole column
-            return Ok((smallvec![Constructor::Skip], vec![]));
+            return Ok((smallvec![Constructor::PrivateUninhabited], vec![]));
         }
 
         let ctors_for_ty = cx.ctors_for_ty(&self.ty)?;
@@ -925,7 +925,7 @@ impl<Cx: TypeCx> Clone for PlaceInfo<Cx> {
     fn clone(&self) -> Self {
         Self {
             ty: self.ty.clone(),
-            skip: self.skip,
+            private_uninhabited: self.private_uninhabited,
             validity: self.validity,
             is_scrutinee: self.is_scrutinee,
         }
@@ -1137,7 +1137,7 @@ impl<'p, Cx: TypeCx> Matrix<'p, Cx> {
     ) -> Self {
         let place_info = PlaceInfo {
             ty: scrut_ty,
-            skip: SkipField(false),
+            private_uninhabited: false,
             validity: scrut_validity,
             is_scrutinee: true,
         };