More de-abuse of TyKind::Error

src/librustc_mir_build/hair/pattern/_match.rs

@@ -242,7 +242,7 @@ use rustc_hir::{HirId, RangeEnd};
 use rustc_middle::mir::interpret::{truncate, AllocId, ConstValue, Pointer, Scalar};
 use rustc_middle::mir::Field;
 use rustc_middle::ty::layout::IntegerExt;
-use rustc_middle::ty::{self, Const, Ty, TyCtxt, TypeFoldable, VariantDef};
+use rustc_middle::ty::{self, Const, FieldDef, Ty, TyCtxt, TypeFoldable, VariantDef};
 use rustc_session::lint;
 use rustc_span::{Span, DUMMY_SP};
 use rustc_target::abi::{Integer, Size, VariantIdx};
@@ -602,7 +602,7 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
         }
     }
 
-    // Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`.
+    /// Returns whether the given type is an enum from another crate declared `#[non_exhaustive]`.
     crate fn is_foreign_non_exhaustive_enum(&self, ty: Ty<'tcx>) -> bool {
         match ty.kind {
             ty::Adt(def, ..) => {
@@ -612,14 +612,35 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
         }
     }
 
-    // Returns whether the given variant is from another crate and has its fields declared
-    // `#[non_exhaustive]`.
+    /// Returns whether the given variant is from another crate and has its fields declared
+    /// `#[non_exhaustive]`.
     fn is_foreign_non_exhaustive_variant(&self, ty: Ty<'tcx>, variant: &VariantDef) -> bool {
         match ty.kind {
             ty::Adt(def, ..) => variant.is_field_list_non_exhaustive() && !def.did.is_local(),
             _ => false,
         }
     }
+
+    /// In the cases of either a `#[non_exhaustive]` field list or a non-public field, we hide
+    /// uninhabited fields in order not to reveal the uninhabitedness of the whole variant.
+    fn hide_uninhabited_field(
+        &self,
+        adt_ty: Ty<'tcx>,
+        variant: &VariantDef,
+        field: &FieldDef,
+    ) -> bool {
+        match adt_ty.kind {
+            ty::Adt(adt, substs) => {
+                let is_non_exhaustive = self.is_foreign_non_exhaustive_variant(adt_ty, variant);
+                let field_ty = field.ty(self.tcx, substs);
+                let is_visible =
+                    adt.is_enum() || field.vis.is_accessible_from(self.module, self.tcx);
+                let is_uninhabited = self.is_uninhabited(field_ty);
+                is_uninhabited && (!is_visible || is_non_exhaustive)
+            }
+            _ => false,
+        }
+    }
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -733,8 +754,8 @@ impl Slice {
 
 #[derive(Clone, Debug, PartialEq)]
 enum Constructor<'tcx> {
-    /// The constructor of all patterns that don't vary by constructor,
-    /// e.g., struct patterns and fixed-length arrays.
+    /// The constructor for patterns that have a single constructor, like tuples, struct patterns
+    /// and fixed-length arrays.
     Single,
     /// Enum variants.
     Variant(DefId),
@@ -881,38 +902,16 @@ impl<'tcx> Constructor<'tcx> {
                         vec![Pat::wildcard_from_ty(substs.type_at(0))]
                     } else {
                         let variant = &adt.variants[self.variant_index_for_adt(cx, adt)];
-                        let is_non_exhaustive = cx.is_foreign_non_exhaustive_variant(ty, variant);
                         variant
                             .fields
                             .iter()
                             .map(|field| {
-                                let is_visible = adt.is_enum()
-                                    || field.vis.is_accessible_from(cx.module, cx.tcx);
-                                let is_uninhabited = cx.is_uninhabited(field.ty(cx.tcx, substs));
-                                match (is_visible, is_non_exhaustive, is_uninhabited) {
-                                    // Treat all uninhabited types in non-exhaustive variants as
-                                    // `TyErr`.
-                                    (_, true, true) => cx.tcx.types.err,
-                                    // Treat all non-visible fields as `TyErr`. They can't appear
-                                    // in any other pattern from this match (because they are
-                                    // private), so their type does not matter - but we don't want
-                                    // to know they are uninhabited.
-                                    (false, ..) => cx.tcx.types.err,
-                                    (true, ..) => {
-                                        let ty = field.ty(cx.tcx, substs);
-                                        match ty.kind {
-                                            // If the field type returned is an array of an unknown
-                                            // size return an TyErr.
-                                            ty::Array(_, len)
-                                                if len
-                                                    .try_eval_usize(cx.tcx, cx.param_env)
-                                                    .is_none() =>
-                                            {
-                                                cx.tcx.types.err
-                                            }
-                                            _ => ty,
-                                        }
-                                    }
+                                // Treat hidden fields as TyErr so we don't know they are
+                                // uninhabited.
+                                if cx.hide_uninhabited_field(ty, variant, field) {
+                                    cx.tcx.types.err
+                                } else {
+                                    field.ty(cx.tcx, substs)
                                 }
                             })
                             .map(Pat::wildcard_from_ty)
@@ -2360,12 +2359,17 @@ fn specialize_one_pattern<'p, 'tcx>(
 
         PatKind::Variant { adt_def, variant_index, ref subpatterns, .. } => {
             let variant = &adt_def.variants[variant_index];
-            let is_non_exhaustive = cx.is_foreign_non_exhaustive_variant(pat.ty, variant);
-            Some(Variant(variant.def_id))
-                .filter(|variant_constructor| variant_constructor == constructor)
-                .map(|_| {
-                    patterns_for_variant(cx, subpatterns, ctor_wild_subpatterns, is_non_exhaustive)
-                })
+            if constructor == &Variant(variant.def_id) {
+                let is_non_exhaustive = cx.is_foreign_non_exhaustive_variant(pat.ty, variant);
+                Some(patterns_for_variant(
+                    cx,
+                    subpatterns,
+                    ctor_wild_subpatterns,
+                    is_non_exhaustive,
+                ))
+            } else {
+                None
+            }
         }
 
         PatKind::Leaf { ref subpatterns } => {

src/librustc_typeck/check/closure.rs

@@ -178,7 +178,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         match expected_ty.kind {
             ty::Dynamic(ref object_type, ..) => {
                 let sig = object_type.projection_bounds().find_map(|pb| {
-                    let pb = pb.with_self_ty(self.tcx, self.tcx.types.err);
+                    let pb = pb.with_self_ty(self.tcx, self.tcx.types.trait_object_dummy_self);
                     self.deduce_sig_from_projection(None, &pb)
                 });
                 let kind = object_type