Exhaustiveness: clean up after librarification

Cargo.lock

@@ -4340,6 +4340,7 @@ dependencies = [
 name = "rustc_pattern_analysis"
 version = "0.0.0"
 dependencies = [
+ "derivative",
  "rustc_apfloat",
  "rustc_arena",
  "rustc_data_structures",

compiler/rustc_index/src/bit_set.rs

@@ -502,6 +502,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                     };
                     #[cfg(not(feature = "nightly"))]
                     let mut words = {
+                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#63291).
                         let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
                         // SAFETY: `words` can safely be all zeroes.
                         let words = unsafe { words.assume_init() };
@@ -567,6 +568,7 @@ impl<T: Idx> ChunkedBitSet<T> {
                     };
                     #[cfg(not(feature = "nightly"))]
                     let mut words = {
+                        // FIXME: unconditionally use `Rc::new_zeroed` once it is stable (#63291).
                         let words = mem::MaybeUninit::<[Word; CHUNK_WORDS]>::zeroed();
                         // SAFETY: `words` can safely be all zeroes.
                         let words = unsafe { words.assume_init() };

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

@@ -860,7 +860,7 @@ fn report_arm_reachability<'p, 'tcx>(
     for (arm, is_useful) in report.arm_usefulness.iter() {
         match is_useful {
             Usefulness::Redundant => {
-                report_unreachable_pattern(*arm.pat.data(), arm.arm_data, catchall)
+                report_unreachable_pattern(*arm.pat.data().unwrap(), arm.arm_data, catchall)
             }
             Usefulness::Useful(redundant_subpats) if redundant_subpats.is_empty() => {}
             // The arm is reachable, but contains redundant subpatterns (from or-patterns).
@@ -869,12 +869,12 @@ fn report_arm_reachability<'p, 'tcx>(
                 // Emit lints in the order in which they occur in the file.
                 redundant_subpats.sort_unstable_by_key(|pat| pat.data());
                 for pat in redundant_subpats {
-                    report_unreachable_pattern(*pat.data(), arm.arm_data, None);
+                    report_unreachable_pattern(*pat.data().unwrap(), arm.arm_data, None);
                 }
             }
         }
         if !arm.has_guard && catchall.is_none() && pat_is_catchall(arm.pat) {
-            catchall = Some(*arm.pat.data());
+            catchall = Some(*arm.pat.data().unwrap());
         }
     }
 }

compiler/rustc_pattern_analysis/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2021"
 
 [dependencies]
 # tidy-alphabetical-start
+derivative = "2.2.0"
 rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena", optional = true }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }

compiler/rustc_pattern_analysis/src/constructor.rs

@@ -642,7 +642,8 @@ impl OpaqueId {
 /// `specialize_constructor` returns the list of fields corresponding to a pattern, given a
 /// constructor. `Constructor::apply` reconstructs the pattern from a pair of `Constructor` and
 /// `Fields`.
-#[derive(Clone, Debug, PartialEq)]
+#[derive(derivative::Derivative)]
+#[derivative(Debug(bound = ""), Clone(bound = ""), PartialEq(bound = ""))]
 pub enum Constructor<Cx: TypeCx> {
     /// Tuples and structs.
     Struct,

compiler/rustc_pattern_analysis/src/lib.rs

@@ -49,7 +49,7 @@ 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 TypeCx: Sized + Clone + fmt::Debug {
+pub trait TypeCx: Sized + fmt::Debug {
     /// The type of a pattern.
     type Ty: Copy + Clone + fmt::Debug; // FIXME: remove Copy
     /// The index of an enum variant.
@@ -58,9 +58,8 @@ pub trait TypeCx: Sized + Clone + fmt::Debug {
     type StrLit: Clone + PartialEq + fmt::Debug;
     /// Extra data to store in a match arm.
     type ArmData: Copy + Clone + fmt::Debug;
-    /// Extra data to store in a pattern. `Default` needed when we create fictitious wildcard
-    /// patterns during analysis.
-    type PatData: Clone + Default;
+    /// Extra data to store in a pattern.
+    type PatData: Clone;
 
     /// FIXME(Nadrieril): `Cx` should only give us revealed types.
     fn reveal_opaque_ty(&self, ty: Self::Ty) -> Self::Ty;
@@ -86,26 +85,25 @@ pub trait TypeCx: Sized + Clone + fmt::Debug {
 }
 
 /// Context that provides information global to a match.
-#[derive(Clone)]
+#[derive(derivative::Derivative)]
+#[derivative(Clone(bound = ""), Copy(bound = ""))]
 pub struct MatchCtxt<'a, 'p, Cx: TypeCx> {
     /// 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: TypeCx> Copy for MatchCtxt<'a, 'p, Cx> {}
-
 /// The arm of a match expression.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
+#[derive(derivative::Derivative)]
+#[derivative(Clone(bound = ""), Copy(bound = ""))]
 pub struct MatchArm<'p, Cx: TypeCx> {
     pub pat: &'p DeconstructedPat<'p, Cx>,
     pub has_guard: bool,
     pub arm_data: Cx::ArmData,
 }
 
-impl<'p, Cx: TypeCx> Copy for MatchArm<'p, Cx> {}
-
 /// 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")]

compiler/rustc_pattern_analysis/src/lints.rs

@@ -203,7 +203,7 @@ pub(crate) fn lint_nonexhaustive_missing_variants<'a, 'p, 'tcx>(
                 };
 
                 use rustc_errors::DecorateLint;
-                let mut err = rcx.tcx.sess.struct_span_warn(*arm.pat.data(), "");
+                let mut err = rcx.tcx.sess.struct_span_warn(*arm.pat.data().unwrap(), "");
                 err.set_primary_message(decorator.msg());
                 decorator.decorate_lint(&mut err);
                 err.emit();
@@ -253,8 +253,8 @@ pub(crate) fn lint_overlapping_range_endpoints<'a, 'p, 'tcx>(
                 let mut suffixes: SmallVec<[_; 1]> = Default::default();
                 // Iterate on patterns that contained `overlap`.
                 for pat in column.iter() {
-                    let this_span = *pat.data();
                     let Constructor::IntRange(this_range) = pat.ctor() else { continue };
+                    let this_span = *pat.data().unwrap();
                     if this_range.is_singleton() {
                         // Don't lint when one of the ranges is a singleton.
                         continue;

compiler/rustc_pattern_analysis/src/pat.rs

@@ -26,14 +26,16 @@ pub struct DeconstructedPat<'p, Cx: TypeCx> {
     ctor: Constructor<Cx>,
     fields: &'p [DeconstructedPat<'p, Cx>],
     ty: Cx::Ty,
-    data: Cx::PatData,
+    /// Extra data to store in a pattern. `None` if the pattern is a wildcard that does not
+    /// correspond to a user-supplied pattern.
+    data: Option<Cx::PatData>,
     /// Whether removing this arm would change the behavior of the match expression.
     useful: Cell<bool>,
 }
 
 impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
-    pub fn wildcard(ty: Cx::Ty, data: Cx::PatData) -> Self {
-        Self::new(Wildcard, &[], ty, data)
+    pub fn wildcard(ty: Cx::Ty) -> Self {
+        DeconstructedPat { ctor: Wildcard, fields: &[], ty, data: None, useful: Cell::new(false) }
     }
 
     pub fn new(
@@ -42,7 +44,7 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
         ty: Cx::Ty,
         data: Cx::PatData,
     ) -> Self {
-        DeconstructedPat { ctor, fields, ty, data, useful: Cell::new(false) }
+        DeconstructedPat { ctor, fields, ty, data: Some(data), useful: Cell::new(false) }
     }
 
     pub(crate) fn is_or_pat(&self) -> bool {
@@ -63,8 +65,10 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
     pub fn ty(&self) -> Cx::Ty {
         self.ty
     }
-    pub fn data(&self) -> &Cx::PatData {
-        &self.data
+    /// Returns the extra data stored in a pattern. Returns `None` if the pattern is a wildcard that
+    /// does not correspond to a user-supplied pattern.
+    pub fn data(&self) -> Option<&Cx::PatData> {
+        self.data.as_ref()
     }
 
     pub fn iter_fields<'a>(
@@ -83,7 +87,7 @@ impl<'p, Cx: TypeCx> DeconstructedPat<'p, Cx> {
         let wildcard_sub_tys = || {
             let tys = pcx.ctor_sub_tys(other_ctor);
             tys.iter()
-                .map(|ty| DeconstructedPat::wildcard(*ty, Cx::PatData::default()))
+                .map(|ty| DeconstructedPat::wildcard(*ty))
                 .map(|pat| pcx.mcx.wildcard_arena.alloc(pat) as &_)
                 .collect()
         };
@@ -160,7 +164,8 @@ impl<'p, Cx: TypeCx> fmt::Debug for DeconstructedPat<'p, Cx> {
 
 /// Same idea as `DeconstructedPat`, except this is a fictitious pattern built up for diagnostics
 /// purposes. As such they don't use interning and can be cloned.
-#[derive(Debug, Clone)]
+#[derive(derivative::Derivative)]
+#[derivative(Debug(bound = ""), Clone(bound = ""))]
 pub struct WitnessPat<Cx: TypeCx> {
     ctor: Constructor<Cx>,
     pub(crate) fields: Vec<WitnessPat<Cx>>,

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -416,7 +416,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                     ty::Tuple(fs) => {
                         ctor = Struct;
                         let mut wilds: SmallVec<[_; 2]> =
-                            fs.iter().map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
+                            fs.iter().map(|ty| DeconstructedPat::wildcard(ty)).collect();
                         for pat in subpatterns {
                             wilds[pat.field.index()] = self.lower_pat(&pat.pattern);
                         }
@@ -439,7 +439,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                         let pat = if let Some(pat) = pattern {
                             self.lower_pat(&pat.pattern)
                         } else {
-                            DeconstructedPat::wildcard(args.type_at(0), pat.span)
+                            DeconstructedPat::wildcard(args.type_at(0))
                         };
                         ctor = Struct;
                         fields = singleton(pat);
@@ -464,7 +464,7 @@ impl<'p, 'tcx> RustcMatchCheckCtxt<'p, 'tcx> {
                                 ty
                             });
                         let mut wilds: SmallVec<[_; 2]> =
-                            tys.map(|ty| DeconstructedPat::wildcard(ty, pat.span)).collect();
+                            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);

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -569,8 +569,10 @@ pub fn ensure_sufficient_stack<R>(f: impl FnOnce() -> R) -> R {
 }
 
 /// Context that provides information local to a place under investigation.
-#[derive(Clone)]
+#[derive(derivative::Derivative)]
+#[derivative(Debug(bound = ""), Clone(bound = ""), Copy(bound = ""))]
 pub(crate) struct PlaceCtxt<'a, 'p, Cx: TypeCx> {
+    #[derivative(Debug = "ignore")]
     pub(crate) mcx: MatchCtxt<'a, 'p, Cx>,
     /// Type of the place under investigation.
     pub(crate) ty: Cx::Ty,
@@ -596,14 +598,6 @@ impl<'a, 'p, Cx: TypeCx> PlaceCtxt<'a, 'p, Cx> {
     }
 }
 
-impl<'a, 'p, Cx: TypeCx> Copy for PlaceCtxt<'a, 'p, Cx> {}
-
-impl<'a, 'p, Cx: TypeCx> fmt::Debug for PlaceCtxt<'a, 'p, Cx> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("PlaceCtxt").field("ty", &self.ty).finish()
-    }
-}
-
 /// 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).
@@ -670,7 +664,8 @@ impl fmt::Display for ValidityConstraint {
 // - 'a allocated by us
 // - 'p coming from the input
 // - Cx global compilation context
-#[derive(Clone)]
+#[derive(derivative::Derivative)]
+#[derivative(Clone(bound = ""))]
 struct PatStack<'a, 'p, Cx: TypeCx> {
     // Rows of len 1 are very common, which is why `SmallVec[_; 2]` works well.
     pats: SmallVec<[&'a DeconstructedPat<'p, Cx>; 2]>,
@@ -845,8 +840,7 @@ impl<'a, 'p, Cx: TypeCx> Matrix<'a, 'p, Cx> {
         scrut_ty: Cx::Ty,
         scrut_validity: ValidityConstraint,
     ) -> Self {
-        let wild_pattern =
-            wildcard_arena.alloc(DeconstructedPat::wildcard(scrut_ty, Default::default()));
+        let wild_pattern = wildcard_arena.alloc(DeconstructedPat::wildcard(scrut_ty));
         let wildcard_row = PatStack::from_pattern(wild_pattern);
         let mut matrix = Matrix {
             rows: Vec::with_capacity(arms.len()),
@@ -1022,7 +1016,8 @@ impl<'a, 'p, Cx: TypeCx> fmt::Debug for Matrix<'a, 'p, Cx> {
 /// The final `Pair(Some(_), true)` is then the resulting witness.
 ///
 /// See the top of the file for more detailed explanations and examples.
-#[derive(Debug, Clone)]
+#[derive(derivative::Derivative)]
+#[derivative(Debug(bound = ""), Clone(bound = ""))]
 struct WitnessStack<Cx: TypeCx>(Vec<WitnessPat<Cx>>);
 
 impl<Cx: TypeCx> WitnessStack<Cx> {
@@ -1069,7 +1064,8 @@ impl<Cx: TypeCx> WitnessStack<Cx> {
 ///
 /// Just as the `Matrix` starts with a single column, by the end of the algorithm, this has a single
 /// column, which contains the patterns that are missing for the match to be exhaustive.
-#[derive(Debug, Clone)]
+#[derive(derivative::Derivative)]
+#[derivative(Debug(bound = ""), Clone(bound = ""))]
 struct WitnessMatrix<Cx: TypeCx>(Vec<WitnessStack<Cx>>);
 
 impl<Cx: TypeCx> WitnessMatrix<Cx> {