Make str into a libcore struct (redux)

compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs

@@ -406,7 +406,6 @@ fn build_slice_type_di_node<'ll, 'tcx>(
 ) -> DINodeCreationResult<'ll> {
     let element_type = match slice_type.kind() {
         ty::Slice(element_type) => *element_type,
-        ty::Str => cx.tcx.types.u8,
         _ => {
             bug!(
                 "Only ty::Slice is valid for build_slice_type_di_node(). Found {:?} instead.",
@@ -440,7 +439,7 @@ pub fn type_di_node<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>) -> &'ll D
         }
         ty::Tuple(elements) if elements.is_empty() => build_basic_type_di_node(cx, t),
         ty::Array(..) => build_fixed_size_array_di_node(cx, unique_type_id, t),
-        ty::Slice(_) | ty::Str => build_slice_type_di_node(cx, t, unique_type_id),
+        ty::Slice(_) => build_slice_type_di_node(cx, t, unique_type_id),
         ty::Dynamic(..) => build_dyn_type_di_node(cx, t, unique_type_id),
         ty::Foreign(..) => build_foreign_type_di_node(cx, t, unique_type_id),
         ty::RawPtr(ty::TypeAndMut { ty: pointee_type, .. }) | ty::Ref(_, pointee_type, _) => {

compiler/rustc_codegen_llvm/src/debuginfo/utils.rs

@@ -77,7 +77,7 @@ pub(crate) fn fat_pointer_kind<'ll, 'tcx>(
     }
 
     match *pointee_tail_ty.kind() {
-        ty::Str | ty::Slice(_) => Some(FatPtrKind::Slice),
+        ty::Slice(_) => Some(FatPtrKind::Slice),
         ty::Dynamic(..) => Some(FatPtrKind::Dyn),
         ty::Foreign(_) => {
             // Assert that pointers to foreign types really are thin:

compiler/rustc_codegen_llvm/src/type_of.rs

@@ -42,7 +42,7 @@ fn uncached_llvm_type<'a, 'tcx>(
         // FIXME(eddyb) producing readable type names for trait objects can result
         // in problematically distinct types due to HRTB and subtyping (see #47638).
         // ty::Dynamic(..) |
-        ty::Adt(..) | ty::Closure(..) | ty::Foreign(..) | ty::Generator(..) | ty::Str
+        ty::Adt(..) | ty::Closure(..) | ty::Foreign(..) | ty::Generator(..)
             // For performance reasons we use names only when emitting LLVM IR. Unless we are on
             // LLVM < 14, where the use of unnamed types resulted in various issues, e.g., #76213,
             // #79564, and #79246.

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -59,7 +59,7 @@ fn push_debuginfo_type_name<'tcx>(
     match *t.kind() {
         ty::Bool => output.push_str("bool"),
         ty::Char => output.push_str("char"),
-        ty::Str => {
+        ty::Adt(def, _) if def.is_str() => {
             if cpp_like_debuginfo {
                 output.push_str("str$")
             } else {

compiler/rustc_codegen_ssa/src/glue.rs

@@ -37,7 +37,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
             (size, align)
         }
-        ty::Slice(_) | ty::Str => {
+        ty::Slice(_) => {
             let unit = layout.field(bx, 0);
             // The info in this case is the length of the str, so the size is that
             // times the unit size.

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -146,7 +146,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
                 return simple();
             }
             _ if field.is_sized() => return simple(),
-            ty::Slice(..) | ty::Str | ty::Foreign(..) => return simple(),
+            ty::Slice(..) | ty::Foreign(..) => return simple(),
             ty::Adt(def, _) => {
                 if def.repr().packed() {
                     // FIXME(eddyb) generalize the adjustment when we

compiler/rustc_codegen_ssa/src/traits/type_.rs

@@ -91,7 +91,7 @@ pub trait DerivedTypeMethods<'tcx>: BaseTypeMethods<'tcx> + MiscMethods<'tcx> {
         let tail = self.tcx().struct_tail_erasing_lifetimes(ty, param_env);
         match tail.kind() {
             ty::Foreign(..) => false,
-            ty::Str | ty::Slice(..) | ty::Dynamic(..) => true,
+            ty::Slice(..) | ty::Dynamic(..) => true,
             _ => bug!("unexpected unsized tail: {:?}", tail),
         }
     }

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -126,7 +126,7 @@ pub(super) fn op_to_const<'tcx>(
         Abi::ScalarPair(..) => match op.layout.ty.kind() {
             ty::Ref(_, inner, _) => match *inner.kind() {
                 ty::Slice(elem) => elem == ecx.tcx.types.u8,
-                ty::Str => true,
+                ty::Adt(def, _) => def.is_str(),
                 _ => false,
             },
             _ => false,

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -154,7 +154,6 @@ pub(crate) fn deref_mir_constant<'tcx>(
         MemPlaceMeta::None => mplace.layout.ty,
         // In case of unsized types, figure out the real type behind.
         MemPlaceMeta::Meta(scalar) => match mplace.layout.ty.kind() {
-            ty::Str => bug!("there's no sized equivalent of a `str`"),
             ty::Slice(elem_ty) => tcx.mk_array(*elem_ty, scalar.to_machine_usize(&tcx).unwrap()),
             _ => bug!(
                 "type {} should not have metadata, but had {:?}",

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -111,9 +111,15 @@ pub(crate) fn const_to_valtree_inner<'tcx>(
             const_to_valtree_inner(ecx, &derefd_place, num_nodes)
         }
 
-        ty::Str | ty::Slice(_) | ty::Array(_, _) => {
+        ty::Slice(_) | ty::Array(_, _) => {
             slice_branches(ecx, place, num_nodes)
         }
+
+        // FIXME(str): Do we need this?
+        ty::Adt(def, _) if def.is_str() => {
+            slice_branches(ecx, place, num_nodes)
+        }
+
         // Trait objects are not allowed in type level constants, as we have no concept for
         // resolving their backing type, even if we can do that at const eval time. We may
         // hypothetically be able to allow `dyn StructuralEq` trait objects in the future,
@@ -187,16 +193,9 @@ fn get_info_on_unsized_field<'tcx>(
     );
     let unsized_inner_ty = match tail.kind() {
         ty::Slice(t) => *t,
-        ty::Str => tail,
         _ => bug!("expected Slice or Str"),
     };
 
-    // Have to adjust type for ty::Str
-    let unsized_inner_ty = match unsized_inner_ty.kind() {
-        ty::Str => tcx.mk_ty(ty::Uint(ty::UintTy::U8)),
-        _ => unsized_inner_ty,
-    };
-
     // Get the number of elements in the unsized field
     let num_elems = last_valtree.unwrap_branch().len();
 
@@ -215,10 +214,6 @@ fn create_pointee_place<'tcx>(
         // We need to create `Allocation`s for custom DSTs
 
         let (unsized_inner_ty, num_elems) = get_info_on_unsized_field(ty, valtree, tcx);
-        let unsized_inner_ty = match unsized_inner_ty.kind() {
-            ty::Str => tcx.mk_ty(ty::Uint(ty::UintTy::U8)),
-            _ => unsized_inner_ty,
-        };
         let unsized_inner_ty_size =
             tcx.layout_of(ty::ParamEnv::empty().and(unsized_inner_ty)).unwrap().layout.size();
         debug!(?unsized_inner_ty, ?unsized_inner_ty_size, ?num_elems);
@@ -317,7 +312,6 @@ pub fn valtree_to_const_value<'tcx>(
         | ty::GeneratorWitnessMIR(..)
         | ty::FnPtr(_)
         | ty::RawPtr(_)
-        | ty::Str
         | ty::Slice(_)
         | ty::Dynamic(..) => bug!("no ValTree should have been created for type {:?}", ty.kind()),
     }
@@ -353,7 +347,16 @@ fn valtree_into_mplace<'tcx>(
             intern_const_alloc_recursive(ecx, InternKind::Constant, &pointee_place).unwrap();
 
             let imm = match inner_ty.kind() {
-                ty::Slice(_) | ty::Str => {
+                ty::Slice(_) => {
+                    let len = valtree.unwrap_branch().len();
+                    let len_scalar = Scalar::from_machine_usize(len as u64, &tcx);
+
+                    Immediate::ScalarPair(
+                        Scalar::from_maybe_pointer((*pointee_place).ptr, &tcx),
+                        len_scalar,
+                    )
+                }
+                ty::Adt(def, _) if def.is_str() => {
                     let len = valtree.unwrap_branch().len();
                     let len_scalar = Scalar::from_machine_usize(len as u64, &tcx);
 
@@ -368,7 +371,7 @@ fn valtree_into_mplace<'tcx>(
 
             ecx.write_immediate(imm, &place.into()).unwrap();
         }
-        ty::Adt(_, _) | ty::Tuple(_) | ty::Array(_, _) | ty::Str | ty::Slice(_) => {
+        ty::Adt(_, _) | ty::Tuple(_) | ty::Array(_, _) | ty::Slice(_) => {
             let branches = valtree.unwrap_branch();
 
             // Need to downcast place for enums
@@ -396,7 +399,8 @@ fn valtree_into_mplace<'tcx>(
                 debug!(?i, ?inner_valtree);
 
                 let mut place_inner = match ty.kind() {
-                    ty::Str | ty::Slice(_) => ecx.mplace_index(&place, i as u64).unwrap(),
+                    ty::Adt(def, _) if def.is_str() => ecx.mplace_index(&place, i as u64).unwrap(),
+                    ty::Slice(_) => ecx.mplace_index(&place, i as u64).unwrap(),
                     _ if !ty.is_sized(*ecx.tcx, ty::ParamEnv::empty())
                         && i == branches.len() - 1 =>
                     {

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -573,6 +573,20 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             return Ok(Some((layout.size, layout.align.abi)));
         }
         match layout.ty.kind() {
+            // FIXME(str): Do we need this?
+            ty::Adt(def, _) if def.is_str() => {
+                let len = metadata.unwrap_meta().to_machine_usize(self)?;
+                let elem = layout.field(self, 0);
+
+                // Make sure the slice is not too big.
+                let size = elem.size.bytes().saturating_mul(len); // we rely on `max_size_of_val` being smaller than `u64::MAX`.
+                let size = Size::from_bytes(size);
+                if size > self.max_size_of_val() {
+                    throw_ub!(InvalidMeta("slice is bigger than largest supported object"));
+                }
+                Ok(Some((size, elem.align.abi)))
+            }
+
             ty::Adt(..) | ty::Tuple(..) => {
                 // First get the size of all statically known fields.
                 // Don't use type_of::sizing_type_of because that expects t to be sized,
@@ -638,7 +652,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 Ok(Some(self.get_vtable_size_and_align(vtable)?))
             }
 
-            ty::Slice(_) | ty::Str => {
+            ty::Slice(_) => {
                 let len = metadata.unwrap_meta().to_machine_usize(self)?;
                 let elem = layout.field(self, 0);
 

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -90,7 +90,6 @@ pub(crate) fn eval_nullary_intrinsic<'tcx>(
             | ty::Uint(_)
             | ty::Float(_)
             | ty::Foreign(_)
-            | ty::Str
             | ty::Array(_, _)
             | ty::Slice(_)
             | ty::RawPtr(_)

compiler/rustc_const_eval/src/interpret/place.rs

@@ -229,7 +229,10 @@ impl<'tcx, Prov: Provenance> MPlaceTy<'tcx, Prov> {
         if self.layout.is_unsized() {
             // We need to consult `meta` metadata
             match self.layout.ty.kind() {
-                ty::Slice(..) | ty::Str => self.mplace.meta.unwrap_meta().to_machine_usize(cx),
+                ty::Slice(..) => self.mplace.meta.unwrap_meta().to_machine_usize(cx),
+                ty::Adt(adt, _) if adt.is_str() => {
+                    self.mplace.meta.unwrap_meta().to_machine_usize(cx)
+                }
                 _ => bug!("len not supported on unsized type {:?}", self.layout.ty),
             }
         } else {

compiler/rustc_const_eval/src/interpret/projection.rs

@@ -200,8 +200,9 @@ where
             }
             _ => span_bug!(
                 self.cur_span(),
-                "`mplace_index` called on non-array type {:?}",
-                base.layout.ty
+                "`mplace_index` called on non-array type {:?} with abi {:?}",
+                base.layout.ty,
+                base.layout.fields
             ),
         }
     }

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -347,7 +347,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
                 );
                 // FIXME: check if the type/trait match what ty::Dynamic says?
             }
-            ty::Slice(..) | ty::Str => {
+            ty::Slice(..) => {
                 let _len = meta.unwrap_meta().to_machine_usize(self.ecx)?;
                 // We do not check that `len * elem_size <= isize::MAX`:
                 // that is only required for references, and there it falls out of the
@@ -590,7 +590,6 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
             | ty::Tuple(..)
             | ty::Array(..)
             | ty::Slice(..)
-            | ty::Str
             | ty::Dynamic(..)
             | ty::Closure(..)
             | ty::Generator(..) => Ok(false),
@@ -813,15 +812,6 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
         fields: impl Iterator<Item = InterpResult<'tcx, Self::V>>,
     ) -> InterpResult<'tcx> {
         match op.layout.ty.kind() {
-            ty::Str => {
-                let mplace = op.assert_mem_place(); // strings are unsized and hence never immediate
-                let len = mplace.len(self.ecx)?;
-                try_validation!(
-                    self.ecx.read_bytes_ptr_strip_provenance(mplace.ptr, Size::from_bytes(len)),
-                    self.path,
-                    InvalidUninitBytes(..) => { "uninitialized data in `str`" },
-                );
-            }
             ty::Array(tys, ..) | ty::Slice(tys)
                 // This optimization applies for types that can hold arbitrary bytes (such as
                 // integer and floating point types) or for structs or tuples with no fields.

compiler/rustc_const_eval/src/util/type_name.rs

@@ -39,7 +39,6 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
             | ty::Int(_)
             | ty::Uint(_)
             | ty::Float(_)
-            | ty::Str
             | ty::Array(_, _)
             | ty::Slice(_)
             | ty::RawPtr(_)

compiler/rustc_hir/src/lang_items.rs

@@ -328,6 +328,7 @@ language_item_table! {
     RangeTo,                 sym::RangeTo,             range_to_struct,            Target::Struct,         GenericRequirement::None;
 
     String,                  sym::String,              string,                     Target::Struct,         GenericRequirement::None;
+    Str,                     sym::str,                 str_type,                   Target::Struct,         GenericRequirement::Exact(0);
 }
 
 pub enum GenericRequirement {

compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs

@@ -213,7 +213,6 @@ impl<'tcx> InherentCollect<'tcx> {
             | ty::Int(_)
             | ty::Uint(_)
             | ty::Float(_)
-            | ty::Str
             | ty::Array(..)
             | ty::Slice(_)
             | ty::RawPtr(_)

compiler/rustc_hir_analysis/src/coherence/orphan.rs

@@ -219,7 +219,6 @@ fn do_orphan_check_impl<'tcx>(
             | ty::Int(..)
             | ty::Uint(..)
             | ty::Float(..)
-            | ty::Str
             | ty::Array(..)
             | ty::Slice(..)
             | ty::RawPtr(..)

compiler/rustc_hir_analysis/src/variance/constraints.rs

@@ -214,7 +214,6 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
             | ty::Int(_)
             | ty::Uint(_)
             | ty::Float(_)
-            | ty::Str
             | ty::Never
             | ty::Foreign(..) => {
                 // leaf type -- noop

compiler/rustc_hir_typeck/src/cast.rs

@@ -101,7 +101,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         Ok(match *t.kind() {
-            ty::Slice(_) | ty::Str => Some(PointerKind::Length),
+            ty::Slice(_) => Some(PointerKind::Length),
             ty::Dynamic(ref tty, _, ty::Dyn) => Some(PointerKind::VTable(tty.principal_def_id())),
             ty::Adt(def, substs) if def.is_struct() => match def.non_enum_variant().fields.last() {
                 None => Some(PointerKind::Thin),
@@ -1101,7 +1101,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
             let derefed = fcx
                 .autoderef(self.expr_span, self.expr_ty)
                 .silence_errors()
-                .find(|t| matches!(t.0.kind(), ty::Str | ty::Slice(..)));
+                .find(|t| matches!(t.0.kind(), ty::Slice(..)) || t.0.is_str());
 
             if let Some((deref_ty, _)) = derefed {
                 // Give a note about what the expr derefs to.

compiler/rustc_hir_typeck/src/demand.rs

@@ -1224,7 +1224,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         match (&expr.kind, expected.kind(), checked_ty.kind()) {
             (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) {
-                (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => {
+                (&ty::Adt(def, _), &ty::Array(arr, _) | &ty::Slice(arr)) if def.is_str() && arr == self.tcx.types.u8 => {
                     if let hir::ExprKind::Lit(_) = expr.kind
                         && let Ok(src) = sm.span_to_snippet(sp)
                         && replace_prefix(&src, "b\"", "\"").is_some()
@@ -1240,7 +1240,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 ));
                             }
                         }
-                (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => {
+                (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Adt(def, _)) if def.is_str() && arr == self.tcx.types.u8 => {
                     if let hir::ExprKind::Lit(_) = expr.kind
                         && let Ok(src) = sm.span_to_snippet(sp)
                         && replace_prefix(&src, "\"", "b\"").is_some()

compiler/rustc_hir_typeck/src/expectation.rs

@@ -74,7 +74,8 @@ impl<'a, 'tcx> Expectation<'tcx> {
     /// for examples of where this comes up,.
     pub(super) fn rvalue_hint(fcx: &FnCtxt<'a, 'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
         match fcx.tcx.struct_tail_without_normalization(ty).kind() {
-            ty::Slice(_) | ty::Str | ty::Dynamic(..) => ExpectRvalueLikeUnsized(ty),
+            ty::Slice(_) | ty::Dynamic(..) => ExpectRvalueLikeUnsized(ty),
+            ty::Adt(def, _) if def.is_str() => ExpectRvalueLikeUnsized(ty),
             _ => ExpectHasType(ty),
         }
     }

compiler/rustc_hir_typeck/src/expr.rs

@@ -2402,7 +2402,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ty::RawPtr(..) => {
                 self.suggest_first_deref_field(&mut err, expr, base, ident);
             }
-            ty::Adt(def, _) if !def.is_enum() => {
+            ty::Adt(def, _) if !def.is_enum() && !def.is_str() => {
                 self.suggest_fields_on_recordish(&mut err, def, ident, expr.span);
             }
             ty::Param(param_ty) => {

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -689,7 +689,6 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             | ty::Int(_)
             | ty::Uint(_)
             | ty::Float(_)
-            | ty::Str
             | ty::Array(..)
             | ty::Slice(_)
             | ty::RawPtr(_)

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -2131,7 +2131,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         | ty::Uint(_)
                         | ty::Float(_)
                         | ty::Adt(_, _)
-                        | ty::Str
                         | ty::Alias(ty::Projection, _)
                         | ty::Param(_) => format!("{deref_ty}"),
                         // we need to test something like  <&[_]>::len or <(&[u32])>::len