Rollup of 12 pull requests

compiler/rustc_borrowck/src/type_check/canonical.rs

@@ -7,6 +7,7 @@ use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, Upcast};
 use rustc_span::Span;
 use rustc_span::def_id::DefId;
+use rustc_trait_selection::solve::NoSolution;
 use rustc_trait_selection::traits::ObligationCause;
 use rustc_trait_selection::traits::query::type_op::custom::CustomTypeOp;
 use rustc_trait_selection::traits::query::type_op::{self, TypeOpOutput};
@@ -177,6 +178,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         if self.infcx.next_trait_solver() {
             let body = self.body;
             let param_env = self.infcx.param_env;
+            // FIXME: Make this into a real type op?
             self.fully_perform_op(
                 location.to_locations(),
                 ConstraintCategory::Boring,
@@ -213,6 +215,40 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         }
     }
 
+    #[instrument(skip(self), level = "debug")]
+    pub(super) fn structurally_resolve(
+        &mut self,
+        ty: Ty<'tcx>,
+        location: impl NormalizeLocation,
+    ) -> Ty<'tcx> {
+        if self.infcx.next_trait_solver() {
+            let body = self.body;
+            let param_env = self.infcx.param_env;
+            // FIXME: Make this into a real type op?
+            self.fully_perform_op(
+                location.to_locations(),
+                ConstraintCategory::Boring,
+                CustomTypeOp::new(
+                    |ocx| {
+                        ocx.structurally_normalize(
+                            &ObligationCause::misc(
+                                location.to_locations().span(body),
+                                body.source.def_id().expect_local(),
+                            ),
+                            param_env,
+                            ty,
+                        )
+                        .map_err(|_| NoSolution)
+                    },
+                    "normalizing struct tail",
+                ),
+            )
+            .unwrap_or_else(|guar| Ty::new_error(self.tcx(), guar))
+        } else {
+            self.normalize(ty, location)
+        }
+    }
+
     #[instrument(skip(self), level = "debug")]
     pub(super) fn ascribe_user_type(
         &mut self,

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1064,7 +1064,9 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         let tcx = self.infcx.tcx;
 
         for proj in &user_ty.projs {
-            if let ty::Alias(ty::Opaque, ..) = curr_projected_ty.ty.kind() {
+            if !self.infcx.next_trait_solver()
+                && let ty::Alias(ty::Opaque, ..) = curr_projected_ty.ty.kind()
+            {
                 // There is nothing that we can compare here if we go through an opaque type.
                 // We're always in its defining scope as we can otherwise not project through
                 // it, so we're constraining it anyways.
@@ -1075,7 +1077,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 proj,
                 |this, field, ()| {
                     let ty = this.field_ty(tcx, field);
-                    self.normalize(ty, locations)
+                    self.structurally_resolve(ty, locations)
                 },
                 |_, _| unreachable!(),
             );

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -523,8 +523,9 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     let impl_sig = ocx.normalize(
         &misc_cause,
         param_env,
-        tcx.liberate_late_bound_regions(
-            impl_m.def_id,
+        infcx.instantiate_binder_with_fresh_vars(
+            return_span,
+            infer::HigherRankedType,
             tcx.fn_sig(impl_m.def_id).instantiate_identity(),
         ),
     );
@@ -536,10 +537,9 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     // them with inference variables.
     // We will use these inference variables to collect the hidden types of RPITITs.
     let mut collector = ImplTraitInTraitCollector::new(&ocx, return_span, param_env, impl_m_def_id);
-    let unnormalized_trait_sig = infcx
-        .instantiate_binder_with_fresh_vars(
-            return_span,
-            infer::HigherRankedType,
+    let unnormalized_trait_sig = tcx
+        .liberate_late_bound_regions(
+            impl_m.def_id,
             tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_to_impl_args),
         )
         .fold_with(&mut collector);
@@ -702,8 +702,8 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
 
     let mut remapped_types = DefIdMap::default();
     for (def_id, (ty, args)) in collected_types {
-        match infcx.fully_resolve((ty, args)) {
-            Ok((ty, args)) => {
+        match infcx.fully_resolve(ty) {
+            Ok(ty) => {
                 // `ty` contains free regions that we created earlier while liberating the
                 // trait fn signature. However, projection normalization expects `ty` to
                 // contains `def_id`'s early-bound regions.
@@ -883,33 +883,27 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
         self.tcx
     }
 
-    fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
-        if let ty::Alias(ty::Opaque, ty::AliasTy { args, def_id, .. }) = *t.kind() {
-            let mut mapped_args = Vec::with_capacity(args.len());
-            for (arg, v) in std::iter::zip(args, self.tcx.variances_of(def_id)) {
-                mapped_args.push(match (arg.unpack(), v) {
-                    // Skip uncaptured opaque args
-                    (ty::GenericArgKind::Lifetime(_), ty::Bivariant) => arg,
-                    _ => arg.try_fold_with(self)?,
-                });
-            }
-            Ok(Ty::new_opaque(self.tcx, def_id, self.tcx.mk_args(&mapped_args)))
-        } else {
-            t.try_super_fold_with(self)
-        }
-    }
-
     fn try_fold_region(
         &mut self,
         region: ty::Region<'tcx>,
     ) -> Result<ty::Region<'tcx>, Self::Error> {
         match region.kind() {
-            // Remap late-bound regions from the function.
+            // Never remap bound regions or `'static`
+            ty::ReBound(..) | ty::ReStatic | ty::ReError(_) => return Ok(region),
+            // We always remap liberated late-bound regions from the function.
             ty::ReLateParam(_) => {}
             // Remap early-bound regions as long as they don't come from the `impl` itself,
             // in which case we don't really need to renumber them.
-            ty::ReEarlyParam(ebr) if ebr.index as usize >= self.num_impl_args => {}
-            _ => return Ok(region),
+            ty::ReEarlyParam(ebr) => {
+                if ebr.index as usize >= self.num_impl_args {
+                    // Remap
+                } else {
+                    return Ok(region);
+                }
+            }
+            ty::ReVar(_) | ty::RePlaceholder(_) | ty::ReErased => unreachable!(
+                "should not have leaked vars or placeholders into hidden type of RPITIT"
+            ),
         }
 
         let e = if let Some(id_region) = self.map.get(&region) {

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1642,6 +1642,28 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 }
             }
 
+            // FIXME(-Znext-solver): See the linked issue below.
+            // <https://github.com/rust-lang/trait-system-refactor-initiative/issues/134>
+            //
+            // In the new solver, check the well-formedness of the return type.
+            // This emulates, in a way, the predicates that fall out of
+            // normalizing the return type in the old solver.
+            //
+            // We alternatively could check the predicates of the method itself hold,
+            // but we intentionally do not do this in the old solver b/c of cycles,
+            // and doing it in the new solver would be stronger. This should be fixed
+            // in the future, since it likely leads to much better method winnowing.
+            if let Some(xform_ret_ty) = xform_ret_ty
+                && self.infcx.next_trait_solver()
+            {
+                ocx.register_obligation(traits::Obligation::new(
+                    self.tcx,
+                    cause.clone(),
+                    self.param_env,
+                    ty::ClauseKind::WellFormed(xform_ret_ty.into()),
+                ));
+            }
+
             // Evaluate those obligations to see if they might possibly hold.
             for error in ocx.select_where_possible() {
                 result = ProbeResult::NoMatch;

compiler/rustc_span/src/hygiene.rs

@@ -26,6 +26,7 @@
 
 use std::cell::RefCell;
 use std::collections::hash_map::Entry;
+use std::collections::hash_set::Entry as SetEntry;
 use std::fmt;
 use std::hash::Hash;
 
@@ -1270,7 +1271,7 @@ pub struct HygieneDecodeContext {
     inner: Lock<HygieneDecodeContextInner>,
 
     /// A set of serialized `SyntaxContext` ids that are currently being decoded on each thread.
-    local_in_progress: WorkerLocal<RefCell<FxHashMap<u32, ()>>>,
+    local_in_progress: WorkerLocal<RefCell<FxHashSet<u32>>>,
 }
 
 /// Register an expansion which has been decoded from the on-disk-cache for the local crate.
@@ -1364,14 +1365,14 @@ pub fn decode_syntax_context<D: Decoder, F: FnOnce(&mut D, u32) -> SyntaxContext
         match inner.decoding.entry(raw_id) {
             Entry::Occupied(ctxt_entry) => {
                 match context.local_in_progress.borrow_mut().entry(raw_id) {
-                    Entry::Occupied(..) => {
+                    SetEntry::Occupied(..) => {
                         // We're decoding this already on the current thread. Return here
                         // and let the function higher up the stack finish decoding to handle
                         // recursive cases.
                         return *ctxt_entry.get();
                     }
-                    Entry::Vacant(entry) => {
-                        entry.insert(());
+                    SetEntry::Vacant(entry) => {
+                        entry.insert();
 
                         // Some other thread is current decoding this. Race with it.
                         *ctxt_entry.get()
@@ -1380,7 +1381,7 @@ pub fn decode_syntax_context<D: Decoder, F: FnOnce(&mut D, u32) -> SyntaxContext
             }
             Entry::Vacant(entry) => {
                 // We are the first thread to start decoding. Mark the current thread as being progress.
-                context.local_in_progress.borrow_mut().insert(raw_id, ());
+                context.local_in_progress.borrow_mut().insert(raw_id);
 
                 // Allocate and store SyntaxContext id *before* calling the decoder function,
                 // as the SyntaxContextData may reference itself.

compiler/rustc_span/src/lib.rs

@@ -22,6 +22,7 @@
 #![feature(array_windows)]
 #![feature(cfg_match)]
 #![feature(core_io_borrowed_buf)]
+#![feature(hash_set_entry)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
 #![feature(min_specialization)]

compiler/rustc_traits/src/codegen.rs

@@ -74,12 +74,21 @@ pub(crate) fn codegen_select_candidate<'tcx>(
     }
 
     let impl_source = infcx.resolve_vars_if_possible(impl_source);
-    let impl_source = infcx.tcx.erase_regions(impl_source);
-    if impl_source.has_infer() {
-        // Unused lifetimes on an impl get replaced with inference vars, but never resolved,
-        // causing the return value of a query to contain inference vars. We do not have a concept
-        // for this and will in fact ICE in stable hashing of the return value. So bail out instead.
-        infcx.tcx.dcx().has_errors().unwrap();
+    let impl_source = tcx.erase_regions(impl_source);
+    if impl_source.has_non_region_infer() {
+        // Unused generic types or consts on an impl get replaced with inference vars,
+        // but never resolved, causing the return value of a query to contain inference
+        // vars. We do not have a concept for this and will in fact ICE in stable hashing
+        // of the return value. So bail out instead.
+        match impl_source {
+            ImplSource::UserDefined(impl_) => {
+                tcx.dcx().span_delayed_bug(
+                    tcx.def_span(impl_.impl_def_id),
+                    "this impl has unconstrained generic parameters",
+                );
+            }
+            _ => unreachable!(),
+        }
         return Err(CodegenObligationError::FulfillmentError);
     }
 

library/core/src/array/mod.rs

@@ -214,8 +214,8 @@ impl<T, const N: usize> BorrowMut<[T]> for [T; N] {
     }
 }
 
-/// Tries to create an array `[T; N]` by copying from a slice `&[T]`. Succeeds if
-/// `slice.len() == N`.
+/// Tries to create an array `[T; N]` by copying from a slice `&[T]`.
+/// Succeeds if `slice.len() == N`.
 ///
 /// ```
 /// let bytes: [u8; 3] = [1, 0, 2];
@@ -282,13 +282,7 @@ impl<'a, T, const N: usize> TryFrom<&'a [T]> for &'a [T; N] {
 
     #[inline]
     fn try_from(slice: &'a [T]) -> Result<&'a [T; N], TryFromSliceError> {
-        if slice.len() == N {
-            let ptr = slice.as_ptr() as *const [T; N];
-            // SAFETY: ok because we just checked that the length fits
-            unsafe { Ok(&*ptr) }
-        } else {
-            Err(TryFromSliceError(()))
-        }
+        slice.as_array().ok_or(TryFromSliceError(()))
     }
 }
 
@@ -310,13 +304,7 @@ impl<'a, T, const N: usize> TryFrom<&'a mut [T]> for &'a mut [T; N] {
 
     #[inline]
     fn try_from(slice: &'a mut [T]) -> Result<&'a mut [T; N], TryFromSliceError> {
-        if slice.len() == N {
-            let ptr = slice.as_mut_ptr() as *mut [T; N];
-            // SAFETY: ok because we just checked that the length fits
-            unsafe { Ok(&mut *ptr) }
-        } else {
-            Err(TryFromSliceError(()))
-        }
+        slice.as_mut_array().ok_or(TryFromSliceError(()))
     }
 }
 

library/core/src/lib.rs

@@ -144,6 +144,7 @@
 #![feature(ptr_alignment_type)]
 #![feature(ptr_metadata)]
 #![feature(set_ptr_value)]
+#![feature(slice_as_array)]
 #![feature(slice_as_chunks)]
 #![feature(slice_ptr_get)]
 #![feature(str_internals)]

library/core/src/ptr/const_ptr.rs

@@ -1526,6 +1526,22 @@ impl<T> *const [T] {
         self as *const T
     }
 
+    /// Gets a raw pointer to the underlying array.
+    ///
+    /// If `N` is not exactly equal to the length of `self`, then this method returns `None`.
+    #[unstable(feature = "slice_as_array", issue = "133508")]
+    #[rustc_const_unstable(feature = "slice_as_array", issue = "133508")]
+    #[inline]
+    #[must_use]
+    pub const fn as_array<const N: usize>(self) -> Option<*const [T; N]> {
+        if self.len() == N {
+            let me = self.as_ptr() as *const [T; N];
+            Some(me)
+        } else {
+            None
+        }
+    }
+
     /// Returns a raw pointer to an element or subslice, without doing bounds
     /// checking.
     ///

library/core/src/ptr/mut_ptr.rs

@@ -1760,6 +1760,22 @@ impl<T> *mut [T] {
         self.len() == 0
     }
 
+    /// Gets a raw, mutable pointer to the underlying array.
+    ///
+    /// If `N` is not exactly equal to the length of `self`, then this method returns `None`.
+    #[unstable(feature = "slice_as_array", issue = "133508")]
+    #[rustc_const_unstable(feature = "slice_as_array", issue = "133508")]
+    #[inline]
+    #[must_use]
+    pub const fn as_mut_array<const N: usize>(self) -> Option<*mut [T; N]> {
+        if self.len() == N {
+            let me = self.as_mut_ptr() as *mut [T; N];
+            Some(me)
+        } else {
+            None
+        }
+    }
+
     /// Divides one mutable raw slice into two at an index.
     ///
     /// The first will contain all indices from `[0, mid)` (excluding