Rollup merge of #120331 - Nadrieril:no-arena, r=compiler-errors

pattern_analysis: use a plain `Vec` in `DeconstructedPat`

The use of an arena-allocated slice in `DeconstructedPat` dates to when we needed the arena anyway for lifetime reasons. Now that we don't, I'm thinking that if `thir::Pat` can use plain old `Vec`s, maybe so can I.

r? ```@ghost```

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -291,7 +291,7 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
                 err = err.and(check_never_pattern(cx, pat));
             });
             err?;
-            Ok(cx.pattern_arena.alloc(cx.lower_pat(pat)))
+            Ok(self.pattern_arena.alloc(cx.lower_pat(pat)))
         }
     }
 
@@ -388,7 +388,6 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
             typeck_results: self.typeck_results,
             param_env: self.param_env,
             module: self.tcx.parent_module(self.lint_level).to_def_id(),
-            pattern_arena: self.pattern_arena,
             dropless_arena: self.dropless_arena,
             match_lint_level: self.lint_level,
             whole_match_span,

compiler/rustc_pattern_analysis/src/errors.rs

@@ -23,7 +23,10 @@ impl<'tcx> Uncovered<'tcx> {
         span: Span,
         cx: &RustcMatchCheckCtxt<'p, 'tcx>,
         witnesses: Vec<WitnessPat<'p, 'tcx>>,
-    ) -> Self {
+    ) -> Self
+    where
+        'tcx: 'p,
+    {
         let witness_1 = cx.hoist_witness_pat(witnesses.get(0).unwrap());
         Self {
             span,

compiler/rustc_pattern_analysis/src/lib.rs

@@ -119,7 +119,7 @@ pub trait TypeCx: Sized + fmt::Debug {
     /// `DeconstructedPat`. Only invoqued when `pat.ctor()` is `Struct | Variant(_) | UnionField`.
     fn write_variant_name(
         f: &mut fmt::Formatter<'_>,
-        pat: &crate::pat::DeconstructedPat<'_, Self>,
+        pat: &crate::pat::DeconstructedPat<Self>,
     ) -> fmt::Result;
 
     /// Raise a bug.
@@ -130,17 +130,17 @@ 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>],
     ) {
     }
 }
 
 /// The arm of a match expression.
 #[derive(Debug)]
 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 {
         let pat = self;
         let mut first = true;
@@ -221,7 +227,7 @@ 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> Clone for PatOrWild<'p, Cx> {
@@ -236,7 +242,7 @@ impl<'p, Cx: TypeCx> Clone for PatOrWild<'p, Cx> {
 impl<'p, Cx: TypeCx> Copy for PatOrWild<'p, 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()
     }