Auto merge of #87287 - oli-obk:fixup_fixup_fixup_opaque_types, r=spastorino

 Make mir borrowck's use of opaque types independent of the typeck query's result

fixes #87218
fixes #86465

we used to use the typeck results only to generate an obligation for the mir borrowck type to be equal to the typeck result.

When i removed the `fixup_opaque_types` function in #87200, I exposed a bug that showed that mir borrowck can't doesn't get enough information from typeck in order to build the correct lifetime mapping from opaque type usage to the actual concrete type. We therefor now fully compute the information within mir borrowck (we already did that, but we only used it to verify the typeck result) and stop using the typeck information.

We will likely be able to remove most opaque type information from the borrowck results in the future and just have all current callers use the mir borrowck result instead.

r? `@spastorino`

Author: bors

compiler/rustc_data_structures/src/lib.rs

@@ -24,6 +24,7 @@
 #![feature(new_uninit)]
 #![feature(once_cell)]
 #![feature(maybe_uninit_uninit_array)]
+#![feature(min_type_alias_impl_trait)]
 #![allow(rustc::default_hash_types)]
 #![deny(unaligned_references)]
 

compiler/rustc_data_structures/src/vec_map.rs

@@ -1,6 +1,6 @@
 use std::borrow::Borrow;
 use std::iter::FromIterator;
-use std::slice::{Iter, IterMut};
+use std::slice::Iter;
 use std::vec::IntoIter;
 
 use crate::stable_hasher::{HashStable, StableHasher};
@@ -67,9 +67,13 @@ where
         self.into_iter()
     }
 
-    pub fn iter_mut(&mut self) -> IterMut<'_, (K, V)> {
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (&K, &mut V)> {
         self.into_iter()
     }
+
+    pub fn retain(&mut self, f: impl Fn(&(K, V)) -> bool) {
+        self.0.retain(f)
+    }
 }
 
 impl<K, V> Default for VecMap<K, V> {
@@ -108,12 +112,12 @@ impl<'a, K, V> IntoIterator for &'a VecMap<K, V> {
 }
 
 impl<'a, K, V> IntoIterator for &'a mut VecMap<K, V> {
-    type Item = &'a mut (K, V);
-    type IntoIter = IterMut<'a, (K, V)>;
+    type Item = (&'a K, &'a mut V);
+    type IntoIter = impl Iterator<Item = Self::Item>;
 
     #[inline]
     fn into_iter(self) -> Self::IntoIter {
-        self.0.iter_mut()
+        self.0.iter_mut().map(|(k, v)| (&*k, v))
     }
 }
 

compiler/rustc_mir/src/borrow_check/type_check/mod.rs

@@ -26,7 +26,7 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::cast::CastTy;
 use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::subst::{GenericArgKind, Subst, SubstsRef, UserSubsts};
+use rustc_middle::ty::subst::{GenericArgKind, SubstsRef, UserSubsts};
 use rustc_middle::ty::{
     self, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, OpaqueTypeKey, RegionVid,
     ToPredicate, Ty, TyCtxt, UserType, UserTypeAnnotationIndex, WithConstness,
@@ -60,7 +60,6 @@ use crate::borrow_check::{
         LivenessValues, PlaceholderIndex, PlaceholderIndices, RegionValueElements,
     },
     region_infer::{ClosureRegionRequirementsExt, TypeTest},
-    renumber,
     type_check::free_region_relations::{CreateResult, UniversalRegionRelations},
     universal_regions::{DefiningTy, UniversalRegions},
     Upvar,
@@ -180,7 +179,54 @@ pub(crate) fn type_check<'mir, 'tcx>(
             liveness::generate(&mut cx, body, elements, flow_inits, move_data, location_table);
 
             translate_outlives_facts(&mut cx);
-            cx.opaque_type_values
+            let mut opaque_type_values = cx.opaque_type_values;
+
+            for (_, revealed_ty) in &mut opaque_type_values {
+                *revealed_ty = infcx.resolve_vars_if_possible(*revealed_ty);
+                if revealed_ty.has_infer_types_or_consts() {
+                    infcx.tcx.sess.delay_span_bug(
+                        body.span,
+                        &format!("could not resolve {:#?}", revealed_ty.kind()),
+                    );
+                    *revealed_ty = infcx.tcx.ty_error();
+                }
+            }
+
+            opaque_type_values.retain(|(opaque_type_key, resolved_ty)| {
+                let concrete_is_opaque = if let ty::Opaque(def_id, _) = resolved_ty.kind() {
+                    *def_id == opaque_type_key.def_id
+                } else {
+                    false
+                };
+
+                if concrete_is_opaque {
+                    // We're using an opaque `impl Trait` type without
+                    // 'revealing' it. For example, code like this:
+                    //
+                    // type Foo = impl Debug;
+                    // fn foo1() -> Foo { ... }
+                    // fn foo2() -> Foo { foo1() }
+                    //
+                    // In `foo2`, we're not revealing the type of `Foo` - we're
+                    // just treating it as the opaque type.
+                    //
+                    // When this occurs, we do *not* want to try to equate
+                    // the concrete type with the underlying defining type
+                    // of the opaque type - this will always fail, since
+                    // the defining type of an opaque type is always
+                    // some other type (e.g. not itself)
+                    // Essentially, none of the normal obligations apply here -
+                    // we're just passing around some unknown opaque type,
+                    // without actually looking at the underlying type it
+                    // gets 'revealed' into
+                    debug!(
+                        "eq_opaque_type_and_type: non-defining use of {:?}",
+                        opaque_type_key.def_id,
+                    );
+                }
+                !concrete_is_opaque
+            });
+            opaque_type_values
         },
     );
 
@@ -1239,14 +1285,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             return Ok(());
         }
 
-        let infcx = self.infcx;
-        let tcx = infcx.tcx;
         let param_env = self.param_env;
         let body = self.body;
         let mir_def_id = body.source.def_id().expect_local();
 
-        // the "concrete opaque types" maps
-        let concrete_opaque_types = &tcx.typeck(mir_def_id).concrete_opaque_types;
         let mut opaque_type_values = VecMap::new();
 
         debug!("eq_opaque_type_and_type: mir_def_id={:?}", mir_def_id);
@@ -1296,88 +1338,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                             .eq(output_ty, revealed_ty)?,
                     );
 
-                    // For each opaque type `Foo<T>` inferred by this value, we want to equate
-                    // the inference variable `?T` with the revealed type that was computed
-                    // earlier by type check.
                     for &(opaque_type_key, opaque_decl) in &opaque_type_map {
-                        let resolved_ty = infcx.resolve_vars_if_possible(opaque_decl.concrete_ty);
-                        let concrete_is_opaque = if let ty::Opaque(def_id, _) = resolved_ty.kind() {
-                            *def_id == opaque_type_key.def_id
-                        } else {
-                            false
-                        };
-
-                        // The revealed type computed by the earlier phase of type check.
-                        // In our example, this would be `(U, u32)`. Note that this references
-                        // the type parameter `U` from the definition of `Foo`.
-                        let concrete_ty = match concrete_opaque_types
-                            .get_by(|(key, _)| key.def_id == opaque_type_key.def_id)
-                        {
-                            None => {
-                                if !concrete_is_opaque {
-                                    tcx.sess.delay_span_bug(
-                                        body.span,
-                                        &format!(
-                                            "Non-defining use of {:?} with revealed type",
-                                            opaque_type_key.def_id,
-                                        ),
-                                    );
-                                }
-                                continue;
-                            }
-                            Some(concrete_ty) => concrete_ty,
-                        };
-                        debug!("concrete_ty = {:?}", concrete_ty);
-
-                        // Apply the substitution, in this case `[U -> T]`, so that the
-                        // concrete type becomes `Foo<(T, u32)>`
-                        let subst_opaque_defn_ty = concrete_ty.subst(tcx, opaque_type_key.substs);
-
-                        // "Renumber" this, meaning that we replace all the regions
-                        // with fresh inference variables. Not relevant to our example.
-                        let renumbered_opaque_defn_ty =
-                            renumber::renumber_regions(infcx, subst_opaque_defn_ty);
-
-                        debug!(
-                            "eq_opaque_type_and_type: concrete_ty={:?}={:?} opaque_defn_ty={:?}",
-                            concrete_ty, resolved_ty, renumbered_opaque_defn_ty,
-                        );
-
-                        if !concrete_is_opaque {
-                            // Equate the instantiated opaque type `opaque_decl.concrete_ty` (`?T`,
-                            // in our example) with the renumbered version that we took from
-                            // the type check results (`Foo<(T, u32)>`).
-                            obligations.add(
-                                infcx
-                                    .at(&ObligationCause::dummy(), param_env)
-                                    .eq(opaque_decl.concrete_ty, renumbered_opaque_defn_ty)?,
-                            );
-                            opaque_type_values.insert(opaque_type_key, renumbered_opaque_defn_ty);
-                        } else {
-                            // We're using an opaque `impl Trait` type without
-                            // 'revealing' it. For example, code like this:
-                            //
-                            // type Foo = impl Debug;
-                            // fn foo1() -> Foo { ... }
-                            // fn foo2() -> Foo { foo1() }
-                            //
-                            // In `foo2`, we're not revealing the type of `Foo` - we're
-                            // just treating it as the opaque type.
-                            //
-                            // When this occurs, we do *not* want to try to equate
-                            // the concrete type with the underlying defining type
-                            // of the opaque type - this will always fail, since
-                            // the defining type of an opaque type is always
-                            // some other type (e.g. not itself)
-                            // Essentially, none of the normal obligations apply here -
-                            // we're just passing around some unknown opaque type,
-                            // without actually looking at the underlying type it
-                            // gets 'revealed' into
-                            debug!(
-                                "eq_opaque_type_and_type: non-defining use of {:?}",
-                                opaque_type_key.def_id,
-                            );
-                        }
+                        opaque_type_values.insert(opaque_type_key, opaque_decl.concrete_ty);
                     }
 
                     debug!("eq_opaque_type_and_type: equated");
@@ -1405,7 +1367,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     locations,
                     ConstraintCategory::OpaqueType,
                     CustomTypeOp::new(
-                        |_cx| {
+                        |infcx| {
                             infcx.constrain_opaque_type(
                                 opaque_type_key,
                                 &opaque_decl,

compiler/rustc_trait_selection/src/opaque_types.rs

@@ -83,6 +83,7 @@ pub struct OpaqueTypeDecl<'tcx> {
 }
 
 /// Whether member constraints should be generated for all opaque types
+#[derive(Debug)]
 pub enum GenerateMemberConstraints {
     /// The default, used by typeck
     WhenRequired,
@@ -354,8 +355,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         opaque_types: &OpaqueTypeMap<'tcx>,
         free_region_relations: &FRR,
     ) {
-        debug!("constrain_opaque_types()");
-
         for &(opaque_type_key, opaque_defn) in opaque_types {
             self.constrain_opaque_type(
                 opaque_type_key,
@@ -367,6 +366,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
     }
 
     /// See `constrain_opaque_types` for documentation.
+    #[instrument(level = "debug", skip(self, free_region_relations))]
     fn constrain_opaque_type<FRR: FreeRegionRelations<'tcx>>(
         &self,
         opaque_type_key: OpaqueTypeKey<'tcx>,
@@ -376,15 +376,11 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
     ) {
         let def_id = opaque_type_key.def_id;
 
-        debug!("constrain_opaque_type()");
-        debug!("constrain_opaque_type: def_id={:?}", def_id);
-        debug!("constrain_opaque_type: opaque_defn={:#?}", opaque_defn);
-
         let tcx = self.tcx;
 
         let concrete_ty = self.resolve_vars_if_possible(opaque_defn.concrete_ty);
 
-        debug!("constrain_opaque_type: concrete_ty={:?}", concrete_ty);
+        debug!(?concrete_ty);
 
         let first_own_region = match opaque_defn.origin {
             hir::OpaqueTyOrigin::FnReturn | hir::OpaqueTyOrigin::AsyncFn => {
@@ -397,7 +393,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                 // type foo::<'p0..'pn>::Foo<'q0..'qm>
                 // fn foo<l0..'ln>() -> foo::<'static..'static>::Foo<'l0..'lm>.
                 //
-                // For these types we onlt iterate over `'l0..lm` below.
+                // For these types we only iterate over `'l0..lm` below.
                 tcx.generics_of(def_id).parent_count
             }
             // These opaque type inherit all lifetime parameters from their
@@ -410,10 +406,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         // If there are required region bounds, we can use them.
         if opaque_defn.has_required_region_bounds {
             let bounds = tcx.explicit_item_bounds(def_id);
-            debug!("constrain_opaque_type: predicates: {:#?}", bounds);
+            debug!("{:#?}", bounds);
             let bounds: Vec<_> =
                 bounds.iter().map(|(bound, _)| bound.subst(tcx, opaque_type_key.substs)).collect();
-            debug!("constrain_opaque_type: bounds={:#?}", bounds);
+            debug!("{:#?}", bounds);
             let opaque_type = tcx.mk_opaque(def_id, opaque_type_key.substs);
 
             let required_region_bounds =
@@ -452,8 +448,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             };
 
             // Compute the least upper bound of it with the other regions.
-            debug!("constrain_opaque_types: least_region={:?}", least_region);
-            debug!("constrain_opaque_types: subst_region={:?}", subst_region);
+            debug!(?least_region);
+            debug!(?subst_region);
             match least_region {
                 None => least_region = Some(subst_region),
                 Some(lr) => {
@@ -484,7 +480,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         }
 
         let least_region = least_region.unwrap_or(tcx.lifetimes.re_static);
-        debug!("constrain_opaque_types: least_region={:?}", least_region);
+        debug!(?least_region);
 
         if let GenerateMemberConstraints::IfNoStaticBound = mode {
             if least_region != tcx.lifetimes.re_static {

src/test/ui/associated-type-bounds/assoc-type-eq-with-dyn-atb-fail.rs

@@ -29,7 +29,6 @@ impl Bar for AssocNoCopy {
 impl Thing for AssocNoCopy {
     type Out = Box<dyn Bar<Assoc: Copy>>;
     //~^ ERROR the trait bound `String: Copy` is not satisfied
-    //~| ERROR the trait bound `String: Copy` is not satisfied
 
     fn func() -> Self::Out {
         Box::new(AssocNoCopy)

src/test/ui/associated-type-bounds/assoc-type-eq-with-dyn-atb-fail.stderr

@@ -4,12 +4,6 @@ error[E0277]: the trait bound `String: Copy` is not satisfied
 LL |     type Out = Box<dyn Bar<Assoc: Copy>>;
    |                            ^^^^^^^^^^^ the trait `Copy` is not implemented for `String`
 
-error[E0277]: the trait bound `String: Copy` is not satisfied
-  --> $DIR/assoc-type-eq-with-dyn-atb-fail.rs:30:28
-   |
-LL |     type Out = Box<dyn Bar<Assoc: Copy>>;
-   |                            ^^^^^^^^^^^ the trait `Copy` is not implemented for `String`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.nll.stderr

@@ -1,15 +1,11 @@
 error: lifetime may not live long enough
-  --> $DIR/ret-impl-trait-one.rs:10:80
+  --> $DIR/ret-impl-trait-one.rs:10:65
    |
-LL |   async fn async_ret_impl_trait1<'a, 'b>(a: &'a u8, b: &'b u8) -> impl Trait<'a> {
-   |  ________________________________--__--__________________________________________^
-   | |                                |   |
-   | |                                |   lifetime `'b` defined here
-   | |                                lifetime `'a` defined here
-LL | |
-LL | |     (a, b)
-LL | | }
-   | |_^ function was supposed to return data with lifetime `'a` but it is returning data with lifetime `'b`
+LL | async fn async_ret_impl_trait1<'a, 'b>(a: &'a u8, b: &'b u8) -> impl Trait<'a> {
+   |                                --  --                           ^^^^^^^^^^^^^^ opaque type requires that `'b` must outlive `'a`
+   |                                |   |
+   |                                |   lifetime `'b` defined here
+   |                                lifetime `'a` defined here
    |
    = help: consider adding the following bound: `'b: 'a`
 

src/test/ui/impl-trait/auto-trait-leak.rs

@@ -12,7 +12,6 @@ fn main() {
 fn cycle1() -> impl Clone {
     //~^ ERROR cycle detected
     send(cycle2().clone());
-    //~^ ERROR cannot be sent between threads safely
 
     Rc::new(Cell::new(5))
 }