Replace tuple of infer vars for upvar_tys with single infer var

compiler/rustc_middle/src/ty/outlives.rs

@@ -96,15 +96,25 @@ fn compute_components(
             }
 
             ty::Closure(_, ref substs) => {
-                for upvar_ty in substs.as_closure().upvar_tys() {
-                    compute_components(tcx, upvar_ty, out, visited);
+                if substs.as_closure().is_valid() {
+                    for upvar_ty in substs.as_closure().upvar_tys() {
+                        compute_components(tcx, upvar_ty, out, visited);
+                    }
+                } else {
+                    let tupled_ty = substs.as_closure().tupled_upvars_ty();
+                    compute_components(tcx, tupled_ty, out, visited);
                 }
             }
 
             ty::Generator(_, ref substs, _) => {
                 // Same as the closure case
-                for upvar_ty in substs.as_generator().upvar_tys() {
-                    compute_components(tcx, upvar_ty, out, visited);
+                if substs.as_generator().is_valid() {
+                    for upvar_ty in substs.as_generator().upvar_tys() {
+                        compute_components(tcx, upvar_ty, out, visited);
+                    }
+                } else {
+                    let tupled_ty = substs.as_generator().tupled_upvars_ty();
+                    compute_components(tcx, tupled_ty, out, visited);
                 }
 
                 // We ignore regions in the generator interior as we don't

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -663,18 +663,13 @@ pub trait PrettyPrinter<'tcx>:
                     }
                 } else {
                     p!(print_def_path(did, substs));
-                    if substs.as_generator().is_valid() {
-                        // Search for the first inference variable
-                        p!(" upvar_tys=(");
-                        let mut uninferred_ty =
-                            substs.as_generator().upvar_tys().filter(|ty| ty.is_ty_infer());
-                        if uninferred_ty.next().is_some() {
-                            p!(write("unavailable"));
-                        } else {
-                            self = self.comma_sep(substs.as_generator().upvar_tys())?;
-                        }
-                        p!(")");
+                    p!(" upvar_tys=(");
+                    if !substs.as_generator().is_valid() {
+                        p!("unavailable");
+                    } else {
+                        self = self.comma_sep(substs.as_generator().upvar_tys())?;
                     }
+                    p!(")");
                 }
 
                 if substs.as_generator().is_valid() {
@@ -704,24 +699,17 @@ pub trait PrettyPrinter<'tcx>:
                     }
                 } else {
                     p!(print_def_path(did, substs));
-                    if substs.as_closure().is_valid() {
-                        // Search for the first inference variable
-                        let mut uninferred_ty =
-                            substs.as_closure().upvar_tys().filter(|ty| ty.is_ty_infer());
-                        if uninferred_ty.next().is_some() {
-                            // If the upvar substs contain an inference variable we haven't
-                            // finished capture analysis.
-                            p!(" closure_substs=(unavailable)");
-                        } else {
-                            p!(" closure_kind_ty=", print(substs.as_closure().kind_ty()));
-                            p!(
-                                " closure_sig_as_fn_ptr_ty=",
-                                print(substs.as_closure().sig_as_fn_ptr_ty())
-                            );
-                            p!(" upvar_tys=(");
-                            self = self.comma_sep(substs.as_closure().upvar_tys())?;
-                            p!(")");
-                        }
+                    if !substs.as_closure().is_valid() {
+                        p!(" closure_substs=(unavailable)");
+                    } else {
+                        p!(" closure_kind_ty=", print(substs.as_closure().kind_ty()));
+                        p!(
+                            " closure_sig_as_fn_ptr_ty=",
+                            print(substs.as_closure().sig_as_fn_ptr_ty())
+                        );
+                        p!(" upvar_tys=(");
+                        self = self.comma_sep(substs.as_closure().upvar_tys())?;
+                        p!(")");
                     }
                 }
                 p!("]");

compiler/rustc_middle/src/ty/sty.rs

@@ -656,6 +656,14 @@ impl<'tcx> UpvarSubsts<'tcx> {
         };
         tupled_upvars_ty.expect_ty().tuple_fields()
     }
+
+    #[inline]
+    pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
+        match self {
+            UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
+            UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
+        }
+    }
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, TyEncodable, TyDecodable)]

compiler/rustc_trait_selection/src/opaque_types.rs

@@ -441,6 +441,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
             for required_region in required_region_bounds {
                 concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
+                    infcx: self,
                     op: |r| self.sub_regions(infer::CallReturn(span), required_region, r),
                 });
             }
@@ -509,6 +510,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             }
         }
         concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
+            infcx: self,
             op: |r| self.sub_regions(infer::CallReturn(span), least_region, r),
         });
     }
@@ -543,6 +545,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         );
 
         concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
+            infcx: self,
             op: |r| {
                 self.member_constraint(
                     opaque_type_def_id,
@@ -683,11 +686,12 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 //
 // We ignore any type parameters because impl trait values are assumed to
 // capture all the in-scope type parameters.
-struct ConstrainOpaqueTypeRegionVisitor<OP> {
+struct ConstrainOpaqueTypeRegionVisitor<'cx, 'tcx, OP> {
+    infcx: &'cx InferCtxt<'cx, 'tcx>,
     op: OP,
 }
 
-impl<'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<OP>
+impl<'cx, 'tcx, OP> TypeVisitor<'tcx> for ConstrainOpaqueTypeRegionVisitor<'cx, 'tcx, OP>
 where
     OP: FnMut(ty::Region<'tcx>),
 {
@@ -717,24 +721,36 @@ where
             ty::Closure(_, ref substs) => {
                 // Skip lifetime parameters of the enclosing item(s)
 
-                for upvar_ty in substs.as_closure().upvar_tys() {
-                    upvar_ty.visit_with(self);
-                }
+                let ty = self.infcx.shallow_resolve(substs.as_closure().tupled_upvars_ty());
+                if let ty::Infer(ty::TyVar(_)) = ty.kind() {
+                    // Not yet resolved.
+                    ty.super_visit_with(self);
+                } else {
+                    for upvar_ty in substs.as_closure().upvar_tys() {
+                        upvar_ty.visit_with(self);
+                    }
 
-                substs.as_closure().sig_as_fn_ptr_ty().visit_with(self);
+                    substs.as_closure().sig_as_fn_ptr_ty().visit_with(self);
+                }
             }
 
             ty::Generator(_, ref substs, _) => {
                 // Skip lifetime parameters of the enclosing item(s)
                 // Also skip the witness type, because that has no free regions.
 
-                for upvar_ty in substs.as_generator().upvar_tys() {
-                    upvar_ty.visit_with(self);
-                }
+                let ty = self.infcx.shallow_resolve(substs.as_generator().tupled_upvars_ty());
+                if let ty::Infer(ty::TyVar(_)) = ty.kind() {
+                    // Not yet resolved.
+                    ty.super_visit_with(self);
+                } else {
+                    for upvar_ty in substs.as_generator().upvar_tys() {
+                        upvar_ty.visit_with(self);
+                    }
 
-                substs.as_generator().return_ty().visit_with(self);
-                substs.as_generator().yield_ty().visit_with(self);
-                substs.as_generator().resume_ty().visit_with(self);
+                    substs.as_generator().return_ty().visit_with(self);
+                    substs.as_generator().yield_ty().visit_with(self);
+                    substs.as_generator().resume_ty().visit_with(self);
+                }
             }
             _ => {
                 ty.super_visit_with(self);

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1307,6 +1307,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         let mut generator = None;
         let mut outer_generator = None;
         let mut next_code = Some(&obligation.cause.code);
+
+        let mut seen_upvar_tys_infer_tuple = false;
+
         while let Some(code) = next_code {
             debug!("maybe_note_obligation_cause_for_async_await: code={:?}", code);
             match code {
@@ -1327,6 +1330,13 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             outer_generator = Some(did);
                         }
                         ty::GeneratorWitness(..) => {}
+                        ty::Tuple(_) if !seen_upvar_tys_infer_tuple => {
+                            // By introducing a tuple of upvar types into the chain of obligations
+                            // of a generator, the first non-generator item is now the tuple itself,
+                            // we shall ignore this.
+
+                            seen_upvar_tys_infer_tuple = true;
+                        }
                         _ if generator.is_none() => {
                             trait_ref = Some(derived_obligation.parent_trait_ref.skip_binder());
                             target_ty = Some(ty);

compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs

@@ -110,7 +110,7 @@ pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
         // check if *any* of those are trivial.
         ty::Tuple(ref tys) => tys.iter().all(|t| trivial_dropck_outlives(tcx, t.expect_ty())),
         ty::Closure(_, ref substs) => {
-            substs.as_closure().upvar_tys().all(|t| trivial_dropck_outlives(tcx, t))
+            trivial_dropck_outlives(tcx, substs.as_closure().tupled_upvars_ty())
         }
 
         ty::Adt(def, _) => {

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1631,7 +1631,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
             ty::Closure(_, substs) => {
                 // (*) binder moved here
-                Where(ty::Binder::bind(substs.as_closure().upvar_tys().collect()))
+                let ty = self.infcx.shallow_resolve(substs.as_closure().tupled_upvars_ty());
+                if let ty::Infer(ty::TyVar(_)) = ty.kind() {
+                    // Not yet resolved.
+                    Ambiguous
+                } else {
+                    Where(ty::Binder::bind(substs.as_closure().upvar_tys().collect()))
+                }
             }
 
             ty::Adt(..) | ty::Projection(..) | ty::Param(..) | ty::Opaque(..) => {
@@ -1700,11 +1706,31 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 tys.iter().map(|k| k.expect_ty()).collect()
             }
 
-            ty::Closure(_, ref substs) => substs.as_closure().upvar_tys().collect(),
+            ty::Closure(_, ref substs) => {
+                let ty = self.infcx.shallow_resolve(substs.as_closure().tupled_upvars_ty());
+                if let ty::Infer(ty::TyVar(_)) = ty.kind() {
+                    // The inference variable will be replaced by a tuple once capture analysis
+                    // completes. If the tuple meets a bound, so do all the elements within it.
+                    vec![ty]
+                } else {
+                    substs.as_closure().upvar_tys().collect()
+                }
+            }
 
             ty::Generator(_, ref substs, _) => {
-                let witness = substs.as_generator().witness();
-                substs.as_generator().upvar_tys().chain(iter::once(witness)).collect()
+                let upvar_tys_resolved =
+                    self.infcx.shallow_resolve(substs.as_generator().tupled_upvars_ty());
+
+                if let ty::Infer(ty::TyVar(_)) = upvar_tys_resolved.kind() {
+                    // The inference variable will be replaced by a tuple once capture analysis
+                    // completes, if the tuple meets a bound, so do all the elements within it.
+                    let witness_resolved =
+                        self.infcx.shallow_resolve(substs.as_generator().witness());
+                    vec![upvar_tys_resolved, witness_resolved]
+                } else {
+                    let witness = substs.as_generator().witness();
+                    substs.as_generator().upvar_tys().chain(iter::once(witness)).collect()
+                }
             }
 
             ty::GeneratorWitness(types) => {

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -592,10 +592,8 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // anyway, except via auto trait matching (which
                     // only inspects the upvar types).
                     walker.skip_current_subtree(); // subtree handled below
-                    for upvar_ty in substs.as_closure().upvar_tys() {
-                        // FIXME(eddyb) add the type to `walker` instead of recursing.
-                        self.compute(upvar_ty.into());
-                    }
+                    // FIXME(eddyb) add the type to `walker` instead of recursing.
+                    self.compute(substs.as_closure().tupled_upvars_ty().into());
                 }
 
                 ty::FnPtr(_) => {

compiler/rustc_traits/src/dropck_outlives.rs

@@ -210,12 +210,20 @@ fn dtorck_constraint_for_ty<'tcx>(
             Ok::<_, NoSolution>(())
         })?,
 
-        ty::Closure(_, substs) => rustc_data_structures::stack::ensure_sufficient_stack(|| {
-            for ty in substs.as_closure().upvar_tys() {
-                dtorck_constraint_for_ty(tcx, span, for_ty, depth + 1, ty, constraints)?;
+        ty::Closure(_, substs) => {
+            if !substs.as_closure().is_valid() {
+                // By the time this code runs, all type variables ought to
+                // be fully resolved.
+                return Err(NoSolution);
             }
-            Ok::<_, NoSolution>(())
-        })?,
+
+            rustc_data_structures::stack::ensure_sufficient_stack(|| {
+                for ty in substs.as_closure().upvar_tys() {
+                    dtorck_constraint_for_ty(tcx, span, for_ty, depth + 1, ty, constraints)?;
+                }
+                Ok::<_, NoSolution>(())
+            })?
+        }
 
         ty::Generator(_, substs, _movability) => {
             // rust-lang/rust#49918: types can be constructed, stored
@@ -241,6 +249,12 @@ fn dtorck_constraint_for_ty<'tcx>(
             // derived from lifetimes attached to the upvars and resume
             // argument, and we *do* incorporate those here.
 
+            if !substs.as_generator().is_valid() {
+                // By the time this code runs, all type variables ought to
+                // be fully resolved.
+                return Err(NoSolution);
+            }
+
             constraints.outlives.extend(
                 substs
                     .as_generator()

compiler/rustc_typeck/src/check/closure.rs

@@ -81,19 +81,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.tcx.closure_base_def_id(expr_def_id.to_def_id()),
         );
 
-        let tupled_upvars_ty =
-            self.tcx.mk_tup(self.tcx.upvars_mentioned(expr_def_id).iter().flat_map(|upvars| {
-                upvars.iter().map(|(&var_hir_id, _)| {
-                    // Create type variables (for now) to represent the transformed
-                    // types of upvars. These will be unified during the upvar
-                    // inference phase (`upvar.rs`).
-                    self.infcx.next_ty_var(TypeVariableOrigin {
-                        // FIXME(eddyb) distinguish upvar inference variables from the rest.
-                        kind: TypeVariableOriginKind::ClosureSynthetic,
-                        span: self.tcx.hir().span(var_hir_id),
-                    })
-                })
-            }));
+        let tupled_upvars_ty = self.infcx.next_ty_var(TypeVariableOrigin {
+            kind: TypeVariableOriginKind::ClosureSynthetic,
+            span: self.tcx.hir().span(expr.hir_id),
+        });
 
         if let Some(GeneratorTypes { resume_ty, yield_ty, interior, movability }) = generator_types
         {