Use a Vec instead of a slice in DeconstructedPat

Author: Nadrieril

compiler/rustc_pattern_analysis/src/lib.rs

@@ -111,7 +111,7 @@ pub trait TypeCx: Sized + fmt::Debug {
     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;
+    fn debug_pat(f: &mut fmt::Formatter<'_>, pat: &DeconstructedPat<Self>) -> fmt::Result;
 
     /// Raise a bug.
     fn bug(&self, fmt: fmt::Arguments<'_>) -> !;
@@ -121,9 +121,9 @@ pub trait TypeCx: Sized + fmt::Debug {
     /// The default implementation does nothing.
     fn lint_overlapping_range_endpoints(
         &self,
-        _pat: &DeconstructedPat<'_, Self>,
+        _pat: &DeconstructedPat<Self>,
         _overlaps_on: IntRange,
-        _overlaps_with: &[&DeconstructedPat<'_, Self>],
+        _overlaps_with: &[&DeconstructedPat<Self>],
     ) {
     }
 }
@@ -133,7 +133,7 @@ pub trait TypeCx: Sized + fmt::Debug {
 #[derive(derivative::Derivative)]
 #[derivative(Clone(bound = ""), Copy(bound = ""))]
 pub struct MatchArm<'p, Cx: TypeCx> {
-    pub pat: &'p DeconstructedPat<'p, Cx>,
+    pub pat: &'p DeconstructedPat<Cx>,
     pub has_guard: bool,
     pub arm_data: Cx::ArmData,
 }

compiler/rustc_pattern_analysis/src/pat.rs

@@ -6,7 +6,7 @@ use std::fmt;
 use smallvec::{smallvec, SmallVec};
 
 use crate::constructor::{Constructor, Slice, SliceKind};
-use crate::{Captures, TypeCx};
+use crate::TypeCx;
 
 use self::Constructor::*;
 
@@ -21,9 +21,9 @@ use self::Constructor::*;
 /// This happens if a private or `non_exhaustive` field is uninhabited, because the code mustn't
 /// observe that it is uninhabited. In that case that field is not included in `fields`. Care must
 /// be taken when converting to/from `thir::Pat`.
-pub struct DeconstructedPat<'p, Cx: TypeCx> {
+pub struct DeconstructedPat<Cx: TypeCx> {
     ctor: Constructor<Cx>,
-    fields: &'p [DeconstructedPat<'p, Cx>],
+    fields: Vec<DeconstructedPat<Cx>>,
     ty: Cx::Ty,
     /// Extra data to store in a pattern. `None` if the pattern is a wildcard that does not
     /// correspond to a user-supplied pattern.
@@ -32,14 +32,20 @@ pub struct DeconstructedPat<'p, Cx: TypeCx> {
     useful: Cell<bool>,
 }
 
-impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
+impl<Cx: TypeCx> DeconstructedPat<Cx> {
     pub fn wildcard(ty: Cx::Ty) -> Self {
-        DeconstructedPat { ctor: Wildcard, fields: &[], ty, data: None, useful: Cell::new(false) }
+        DeconstructedPat {
+            ctor: Wildcard,
+            fields: Vec::new(),
+            ty,
+            data: None,
+            useful: Cell::new(false),
+        }
     }
 
     pub fn new(
         ctor: Constructor<Cx>,
-        fields: &'p [DeconstructedPat<'p, Cx>],
+        fields: Vec<DeconstructedPat<Cx>>,
         ty: Cx::Ty,
         data: Cx::PatData,
     ) -> Self {
@@ -62,17 +68,17 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
         self.data.as_ref()
     }
 
-    pub fn iter_fields(&self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'_> {
+    pub fn iter_fields<'a>(&'a self) -> impl Iterator<Item = &'a DeconstructedPat<Cx>> {
         self.fields.iter()
     }
 
     /// Specialize this pattern with a constructor.
     /// `other_ctor` can be different from `self.ctor`, but must be covered by it.
-    pub(crate) fn specialize(
-        &self,
+    pub(crate) fn specialize<'a>(
+        &'a self,
         other_ctor: &Constructor<Cx>,
         ctor_arity: usize,
-    ) -> SmallVec<[PatOrWild<'p, Cx>; 2]> {
+    ) -> SmallVec<[PatOrWild<'a, Cx>; 2]> {
         let wildcard_sub_tys = || (0..ctor_arity).map(|_| PatOrWild::Wild).collect();
         match (&self.ctor, other_ctor) {
             // Return a wildcard for each field of `other_ctor`.
@@ -139,7 +145,7 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
 }
 
 /// This is best effort and not good enough for a `Display` impl.
-impl<'p, Cx: TypeCx> fmt::Debug for DeconstructedPat<'p, Cx> {
+impl<Cx: TypeCx> fmt::Debug for DeconstructedPat<Cx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         Cx::debug_pat(f, self)
     }
@@ -155,11 +161,11 @@ pub(crate) enum PatOrWild<'p, Cx: TypeCx> {
     /// A non-user-provided wildcard, created during specialization.
     Wild,
     /// A user-provided pattern.
-    Pat(&'p DeconstructedPat<'p, Cx>),
+    Pat(&'p DeconstructedPat<Cx>),
 }
 
 impl<'p, Cx: TypeCx> PatOrWild<'p, Cx> {
-    pub(crate) fn as_pat(&self) -> Option<&'p DeconstructedPat<'p, Cx>> {
+    pub(crate) fn as_pat(&self) -> Option<&'p DeconstructedPat<Cx>> {
         match self {
             PatOrWild::Wild => None,
             PatOrWild::Pat(pat) => Some(pat),

compiler/rustc_pattern_analysis/src/pat_column.rs

@@ -13,7 +13,7 @@ use crate::{Captures, MatchArm, TypeCx};
 #[derive(Debug)]
 pub struct PatternColumn<'p, Cx: TypeCx> {
     /// This must not contain an or-pattern. `expand_and_push` takes care to expand them.
-    patterns: Vec<&'p DeconstructedPat<'p, Cx>>,
+    patterns: Vec<&'p DeconstructedPat<Cx>>,
 }
 
 impl<'p, Cx: TypeCx> PatternColumn<'p, Cx> {
@@ -41,7 +41,7 @@ impl<'p, Cx: TypeCx> PatternColumn<'p, Cx> {
     pub fn head_ty(&self) -> Option<&Cx::Ty> {
         self.patterns.first().map(|pat| pat.ty())
     }
-    pub fn iter<'a>(&'a self) -> impl Iterator<Item = &'p DeconstructedPat<'p, Cx>> + Captures<'a> {
+    pub fn iter<'a>(&'a self) -> impl Iterator<Item = &'p DeconstructedPat<Cx>> + Captures<'a> {
         self.patterns.iter().copied()
     }
 

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -1,4 +1,3 @@
-use smallvec::SmallVec;
 use std::fmt;
 use std::iter::once;
 
@@ -28,8 +27,7 @@ use crate::constructor::Constructor::*;
 pub type Constructor<'p, 'tcx> = crate::constructor::Constructor<RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type ConstructorSet<'p, 'tcx> =
     crate::constructor::ConstructorSet<RustcMatchCheckCtxt<'p, 'tcx>>;
-pub type DeconstructedPat<'p, 'tcx> =
-    crate::pat::DeconstructedPat<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
+pub type DeconstructedPat<'p, 'tcx> = crate::pat::DeconstructedPat<RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type MatchArm<'p, 'tcx> = crate::MatchArm<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type Usefulness<'p, 'tcx> = crate::usefulness::Usefulness<'p, RustcMatchCheckCtxt<'p, 'tcx>>;
 pub type UsefulnessReport<'p, 'tcx> =
@@ -452,21 +450,20 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
     /// Note: the input patterns must have been lowered through
     /// `rustc_mir_build::thir::pattern::check_match::MatchVisitor::lower_pattern`.
     pub fn lower_pat(&self, pat: &'p Pat<'tcx>) -> DeconstructedPat<'p, 'tcx> {
-        let singleton = |pat| std::slice::from_ref(self.pattern_arena.alloc(pat));
         let cx = self;
         let ty = cx.reveal_opaque_ty(pat.ty);
         let ctor;
-        let fields: &[_];
+        let mut fields: Vec<_>;
         match &pat.kind {
             PatKind::AscribeUserType { subpattern, .. }
             | PatKind::InlineConstant { subpattern, .. } => return self.lower_pat(subpattern),
             PatKind::Binding { subpattern: Some(subpat), .. } => return self.lower_pat(subpat),
             PatKind::Binding { subpattern: None, .. } | PatKind::Wild => {
                 ctor = Wildcard;
-                fields = &[];
+                fields = vec![];
             }
             PatKind::Deref { subpattern } => {
-                fields = singleton(self.lower_pat(subpattern));
+                fields = vec![self.lower_pat(subpattern)];
                 ctor = match ty.kind() {
                     // This is a box pattern.
                     ty::Adt(adt, ..) if adt.is_box() => Struct,
@@ -478,15 +475,14 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                 match ty.kind() {
                     ty::Tuple(fs) => {
                         ctor = Struct;
-                        let mut wilds: SmallVec<[_; 2]> = fs
+                        fields = fs
                             .iter()
                             .map(|ty| cx.reveal_opaque_ty(ty))
                             .map(|ty| DeconstructedPat::wildcard(ty))
                             .collect();
                         for pat in subpatterns {
-                            wilds[pat.field.index()] = self.lower_pat(&pat.pattern);
+                            fields[pat.field.index()] = self.lower_pat(&pat.pattern);
                         }
-                        fields = cx.pattern_arena.alloc_from_iter(wilds);
                     }
                     ty::Adt(adt, args) if adt.is_box() => {
                         // The only legal patterns of type `Box` (outside `std`) are `_` and box
@@ -508,7 +504,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                             DeconstructedPat::wildcard(self.reveal_opaque_ty(args.type_at(0)))
                         };
                         ctor = Struct;
-                        fields = singleton(pat);
+                        fields = vec![pat];
                     }
                     ty::Adt(adt, _) => {
                         ctor = match pat.kind {
@@ -528,14 +524,12 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                                 ty
                             },
                         );
-                        let mut wilds: SmallVec<[_; 2]> =
-                            tys.map(|ty| DeconstructedPat::wildcard(ty)).collect();
+                        fields = tys.map(|ty| DeconstructedPat::wildcard(ty)).collect();
                         for pat in subpatterns {
                             if let Some(i) = field_id_to_id[pat.field.index()] {
-                                wilds[i] = self.lower_pat(&pat.pattern);
+                                fields[i] = self.lower_pat(&pat.pattern);
                             }
                         }
-                        fields = cx.pattern_arena.alloc_from_iter(wilds);
                     }
                     _ => bug!("pattern has unexpected type: pat: {:?}, ty: {:?}", pat, ty),
                 }
@@ -547,7 +541,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                             Some(b) => Bool(b),
                             None => Opaque(OpaqueId::new()),
                         };
-                        fields = &[];
+                        fields = vec![];
                     }
                     ty::Char | ty::Int(_) | ty::Uint(_) => {
                         ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
@@ -563,7 +557,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                             }
                             None => Opaque(OpaqueId::new()),
                         };
-                        fields = &[];
+                        fields = vec![];
                     }
                     ty::Float(ty::FloatTy::F32) => {
                         ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
@@ -574,7 +568,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                             }
                             None => Opaque(OpaqueId::new()),
                         };
-                        fields = &[];
+                        fields = vec![];
                     }
                     ty::Float(ty::FloatTy::F64) => {
                         ctor = match value.try_eval_bits(cx.tcx, cx.param_env) {
@@ -585,7 +579,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                             }
                             None => Opaque(OpaqueId::new()),
                         };
-                        fields = &[];
+                        fields = vec![];
                     }
                     ty::Ref(_, t, _) if t.is_str() => {
                         // We want a `&str` constant to behave like a `Deref` pattern, to be compatible
@@ -596,16 +590,16 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                         // subfields.
                         // Note: `t` is `str`, not `&str`.
                         let ty = self.reveal_opaque_ty(*t);
-                        let subpattern = DeconstructedPat::new(Str(*value), &[], ty, pat);
+                        let subpattern = DeconstructedPat::new(Str(*value), Vec::new(), ty, pat);
                         ctor = Ref;
-                        fields = singleton(subpattern)
+                        fields = vec![subpattern]
                     }
                     // All constants that can be structurally matched have already been expanded
                     // into the corresponding `Pat`s by `const_to_pat`. Constants that remain are
                     // opaque.
                     _ => {
                         ctor = Opaque(OpaqueId::new());
-                        fields = &[];
+                        fields = vec![];
                     }
                 }
             }
@@ -642,7 +636,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                     }
                     _ => bug!("invalid type for range pattern: {}", ty.inner()),
                 };
-                fields = &[];
+                fields = vec![];
             }
             PatKind::Array { prefix, slice, suffix } | PatKind::Slice { prefix, slice, suffix } => {
                 let array_len = match ty.kind() {
@@ -658,25 +652,22 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                     SliceKind::FixedLen(prefix.len() + suffix.len())
                 };
                 ctor = Slice(Slice::new(array_len, kind));
-                fields = cx.pattern_arena.alloc_from_iter(
-                    prefix.iter().chain(suffix.iter()).map(|p| self.lower_pat(&*p)),
-                )
+                fields = prefix.iter().chain(suffix.iter()).map(|p| self.lower_pat(&*p)).collect();
             }
             PatKind::Or { .. } => {
                 ctor = Or;
                 let pats = expand_or_pat(pat);
-                fields =
-                    cx.pattern_arena.alloc_from_iter(pats.into_iter().map(|p| self.lower_pat(p)))
+                fields = pats.into_iter().map(|p| self.lower_pat(p)).collect();
             }
             PatKind::Never => {
                 // FIXME(never_patterns): handle `!` in exhaustiveness. This is a sane default
                 // in the meantime.
                 ctor = Wildcard;
-                fields = &[];
+                fields = vec![];
             }
             PatKind::Error(_) => {
                 ctor = Opaque(OpaqueId::new());
-                fields = &[];
+                fields = vec![];
             }
         }
         DeconstructedPat::new(ctor, fields, ty, pat)
@@ -849,7 +840,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
     /// Best-effort `Debug` implementation.
     pub(crate) fn debug_pat(
         f: &mut fmt::Formatter<'_>,
-        pat: &crate::pat::DeconstructedPat<'_, Self>,
+        pat: &crate::pat::DeconstructedPat<Self>,
     ) -> fmt::Result {
         let mut first = true;
         let mut start_or_continue = |s| {
@@ -975,7 +966,7 @@ impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
 
     fn debug_pat(
         f: &mut fmt::Formatter<'_>,
-        pat: &crate::pat::DeconstructedPat<'_, Self>,
+        pat: &crate::pat::DeconstructedPat<Self>,
     ) -> fmt::Result {
         Self::debug_pat(f, pat)
     }
@@ -985,9 +976,9 @@ impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
 
     fn lint_overlapping_range_endpoints(
         &self,
-        pat: &crate::pat::DeconstructedPat<'_, Self>,
+        pat: &crate::pat::DeconstructedPat<Self>,
         overlaps_on: IntRange,
-        overlaps_with: &[&crate::pat::DeconstructedPat<'_, Self>],
+        overlaps_with: &[&crate::pat::DeconstructedPat<Self>],
     ) {
         let overlap_as_pat = self.hoist_pat_range(&overlaps_on, *pat.ty());
         let overlaps: Vec<_> = overlaps_with

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -826,7 +826,7 @@ struct PatStack<'p, Cx: TypeCx> {
 }
 
 impl<'p, Cx: TypeCx> PatStack<'p, Cx> {
-    fn from_pattern(pat: &'p DeconstructedPat<'p, Cx>) -> Self {
+    fn from_pattern(pat: &'p DeconstructedPat<Cx>) -> Self {
         PatStack { pats: smallvec![PatOrWild::Pat(pat)], relevant: true }
     }
 
@@ -1537,7 +1537,7 @@ pub enum Usefulness<'p, Cx: TypeCx> {
     /// The arm is useful. This additionally carries a set of or-pattern branches that have been
     /// found to be redundant despite the overall arm being useful. Used only in the presence of
     /// or-patterns, otherwise it stays empty.
-    Useful(Vec<&'p DeconstructedPat<'p, Cx>>),
+    Useful(Vec<&'p DeconstructedPat<Cx>>),
     /// The arm is redundant and can be removed without changing the behavior of the match
     /// expression.
     Redundant,