Rollup merge of rust-lang#119417 - compiler-errors:closure-checking, r=davidtwco

Uplift some miscellaneous coroutine-specific machinery into `check_closure`

This PR uplifts some of the logic in `check_fn` that is specific to checking coroutines, which always flows through `check_closure`.

This is just some miscellaneous clean up that I've wanted to do, especially because I'm poking around this code to make it work for async closures.

Author: matthiaskrgr

compiler/rustc_hir_typeck/src/check.rs

@@ -28,10 +28,10 @@ use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
 pub(super) fn check_fn<'a, 'tcx>(
     fcx: &mut FnCtxt<'a, 'tcx>,
     fn_sig: ty::FnSig<'tcx>,
+    coroutine_types: Option<CoroutineTypes<'tcx>>,
     decl: &'tcx hir::FnDecl<'tcx>,
     fn_def_id: LocalDefId,
     body: &'tcx hir::Body<'tcx>,
-    closure_kind: Option<hir::ClosureKind>,
     params_can_be_unsized: bool,
 ) -> Option<CoroutineTypes<'tcx>> {
     let fn_id = fcx.tcx.local_def_id_to_hir_id(fn_def_id);
@@ -49,54 +49,13 @@ pub(super) fn check_fn<'a, 'tcx>(
             fcx.param_env,
         ));
 
+    fcx.coroutine_types = coroutine_types;
     fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
 
     let span = body.value.span;
 
     forbid_intrinsic_abi(tcx, span, fn_sig.abi);
 
-    if let Some(hir::ClosureKind::Coroutine(kind)) = closure_kind {
-        let yield_ty = match kind {
-            hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
-            | hir::CoroutineKind::Coroutine(_) => {
-                let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
-                    kind: TypeVariableOriginKind::TypeInference,
-                    span,
-                });
-                fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
-                yield_ty
-            }
-            // HACK(-Ztrait-solver=next): In the *old* trait solver, we must eagerly
-            // guide inference on the yield type so that we can handle `AsyncIterator`
-            // in this block in projection correctly. In the new trait solver, it is
-            // not a problem.
-            hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _) => {
-                let yield_ty = fcx.next_ty_var(TypeVariableOrigin {
-                    kind: TypeVariableOriginKind::TypeInference,
-                    span,
-                });
-                fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
-
-                Ty::new_adt(
-                    tcx,
-                    tcx.adt_def(tcx.require_lang_item(hir::LangItem::Poll, Some(span))),
-                    tcx.mk_args(&[Ty::new_adt(
-                        tcx,
-                        tcx.adt_def(tcx.require_lang_item(hir::LangItem::Option, Some(span))),
-                        tcx.mk_args(&[yield_ty.into()]),
-                    )
-                    .into()]),
-                )
-            }
-            hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _) => Ty::new_unit(tcx),
-        };
-
-        // Resume type defaults to `()` if the coroutine has no argument.
-        let resume_ty = fn_sig.inputs().get(0).copied().unwrap_or_else(|| Ty::new_unit(tcx));
-
-        fcx.resume_yield_tys = Some((resume_ty, yield_ty));
-    }
-
     GatherLocalsVisitor::new(fcx).visit_body(body);
 
     // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
@@ -147,25 +106,6 @@ pub(super) fn check_fn<'a, 'tcx>(
     fcx.require_type_is_sized(declared_ret_ty, return_or_body_span, traits::SizedReturnType);
     fcx.check_return_expr(body.value, false);
 
-    // We insert the deferred_coroutine_interiors entry after visiting the body.
-    // This ensures that all nested coroutines appear before the entry of this coroutine.
-    // resolve_coroutine_interiors relies on this property.
-    let coroutine_ty = if let Some(hir::ClosureKind::Coroutine(coroutine_kind)) = closure_kind {
-        let interior = fcx
-            .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
-        fcx.deferred_coroutine_interiors.borrow_mut().push((
-            fn_def_id,
-            body.id(),
-            interior,
-            coroutine_kind,
-        ));
-
-        let (resume_ty, yield_ty) = fcx.resume_yield_tys.unwrap();
-        Some(CoroutineTypes { resume_ty, yield_ty, interior })
-    } else {
-        None
-    };
-
     // Finalize the return check by taking the LUB of the return types
     // we saw and assigning it to the expected return type. This isn't
     // really expected to fail, since the coercions would have failed
@@ -201,7 +141,7 @@ pub(super) fn check_fn<'a, 'tcx>(
         check_lang_start_fn(tcx, fn_sig, fn_def_id);
     }
 
-    coroutine_ty
+    fcx.coroutine_types
 }
 
 fn check_panic_info_fn(tcx: TyCtxt<'_>, fn_id: LocalDefId, fn_sig: ty::FnSig<'_>) {

compiler/rustc_hir_typeck/src/closure.rs

@@ -72,7 +72,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         opt_kind: Option<ty::ClosureKind>,
         expected_sig: Option<ExpectedSig<'tcx>>,
     ) -> Ty<'tcx> {
-        let body = self.tcx.hir().body(closure.body);
+        let tcx = self.tcx;
+        let body = tcx.hir().body(closure.body);
 
         trace!("decl = {:#?}", closure.fn_decl);
         let expr_def_id = closure.def_id;
@@ -83,81 +84,151 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         debug!(?bound_sig, ?liberated_sig);
 
+        // FIXME: We could probably actually just unify this further --
+        // instead of having a `FnSig` and a `Option<CoroutineTypes>`,
+        // we can have a `ClosureSignature { Coroutine { .. }, Closure { .. } }`,
+        // similar to how `ty::GenSig` is a distinct data structure.
+        let coroutine_types = match closure.kind {
+            hir::ClosureKind::Closure => None,
+            hir::ClosureKind::Coroutine(kind) => {
+                let yield_ty = match kind {
+                    hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
+                    | hir::CoroutineKind::Coroutine(_) => {
+                        let yield_ty = self.next_ty_var(TypeVariableOrigin {
+                            kind: TypeVariableOriginKind::TypeInference,
+                            span: expr_span,
+                        });
+                        self.require_type_is_sized(yield_ty, expr_span, traits::SizedYieldType);
+                        yield_ty
+                    }
+                    // HACK(-Ztrait-solver=next): In the *old* trait solver, we must eagerly
+                    // guide inference on the yield type so that we can handle `AsyncIterator`
+                    // in this block in projection correctly. In the new trait solver, it is
+                    // not a problem.
+                    hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _) => {
+                        let yield_ty = self.next_ty_var(TypeVariableOrigin {
+                            kind: TypeVariableOriginKind::TypeInference,
+                            span: expr_span,
+                        });
+                        self.require_type_is_sized(yield_ty, expr_span, traits::SizedYieldType);
+
+                        Ty::new_adt(
+                            tcx,
+                            tcx.adt_def(
+                                tcx.require_lang_item(hir::LangItem::Poll, Some(expr_span)),
+                            ),
+                            tcx.mk_args(&[Ty::new_adt(
+                                tcx,
+                                tcx.adt_def(
+                                    tcx.require_lang_item(hir::LangItem::Option, Some(expr_span)),
+                                ),
+                                tcx.mk_args(&[yield_ty.into()]),
+                            )
+                            .into()]),
+                        )
+                    }
+                    hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _) => {
+                        tcx.types.unit
+                    }
+                };
+
+                // Resume type defaults to `()` if the coroutine has no argument.
+                let resume_ty = liberated_sig.inputs().get(0).copied().unwrap_or(tcx.types.unit);
+
+                Some(CoroutineTypes { resume_ty, yield_ty })
+            }
+        };
+
         let mut fcx = FnCtxt::new(self, self.param_env, closure.def_id);
-        let coroutine_types = check_fn(
+        check_fn(
             &mut fcx,
             liberated_sig,
+            coroutine_types,
             closure.fn_decl,
             expr_def_id,
             body,
-            Some(closure.kind),
             // Closure "rust-call" ABI doesn't support unsized params
             false,
         );
 
-        let parent_args = GenericArgs::identity_for_item(
-            self.tcx,
-            self.tcx.typeck_root_def_id(expr_def_id.to_def_id()),
-        );
+        let parent_args =
+            GenericArgs::identity_for_item(tcx, tcx.typeck_root_def_id(expr_def_id.to_def_id()));
 
         let tupled_upvars_ty = self.next_root_ty_var(TypeVariableOrigin {
             kind: TypeVariableOriginKind::ClosureSynthetic,
-            span: self.tcx.def_span(expr_def_id),
-        });
-
-        if let Some(CoroutineTypes { resume_ty, yield_ty, interior }) = coroutine_types {
-            let coroutine_args = ty::CoroutineArgs::new(
-                self.tcx,
-                ty::CoroutineArgsParts {
-                    parent_args,
-                    resume_ty,
-                    yield_ty,
-                    return_ty: liberated_sig.output(),
-                    witness: interior,
-                    tupled_upvars_ty,
-                },
-            );
-
-            return Ty::new_coroutine(self.tcx, expr_def_id.to_def_id(), coroutine_args.args);
-        }
-
-        // Tuple up the arguments and insert the resulting function type into
-        // the `closures` table.
-        let sig = bound_sig.map_bound(|sig| {
-            self.tcx.mk_fn_sig(
-                [Ty::new_tup(self.tcx, sig.inputs())],
-                sig.output(),
-                sig.c_variadic,
-                sig.unsafety,
-                sig.abi,
-            )
+            span: expr_span,
         });
 
-        debug!(?sig, ?opt_kind);
-
-        let closure_kind_ty = match opt_kind {
-            Some(kind) => Ty::from_closure_kind(self.tcx, kind),
+        match closure.kind {
+            hir::ClosureKind::Closure => {
+                assert_eq!(coroutine_types, None);
+                // Tuple up the arguments and insert the resulting function type into
+                // the `closures` table.
+                let sig = bound_sig.map_bound(|sig| {
+                    tcx.mk_fn_sig(
+                        [Ty::new_tup(tcx, sig.inputs())],
+                        sig.output(),
+                        sig.c_variadic,
+                        sig.unsafety,
+                        sig.abi,
+                    )
+                });
 
-            // Create a type variable (for now) to represent the closure kind.
-            // It will be unified during the upvar inference phase (`upvar.rs`)
-            None => self.next_root_ty_var(TypeVariableOrigin {
-                // FIXME(eddyb) distinguish closure kind inference variables from the rest.
-                kind: TypeVariableOriginKind::ClosureSynthetic,
-                span: expr_span,
-            }),
-        };
+                debug!(?sig, ?opt_kind);
+
+                let closure_kind_ty = match opt_kind {
+                    Some(kind) => Ty::from_closure_kind(tcx, kind),
+
+                    // Create a type variable (for now) to represent the closure kind.
+                    // It will be unified during the upvar inference phase (`upvar.rs`)
+                    None => self.next_root_ty_var(TypeVariableOrigin {
+                        // FIXME(eddyb) distinguish closure kind inference variables from the rest.
+                        kind: TypeVariableOriginKind::ClosureSynthetic,
+                        span: expr_span,
+                    }),
+                };
+
+                let closure_args = ty::ClosureArgs::new(
+                    tcx,
+                    ty::ClosureArgsParts {
+                        parent_args,
+                        closure_kind_ty,
+                        closure_sig_as_fn_ptr_ty: Ty::new_fn_ptr(tcx, sig),
+                        tupled_upvars_ty,
+                    },
+                );
 
-        let closure_args = ty::ClosureArgs::new(
-            self.tcx,
-            ty::ClosureArgsParts {
-                parent_args,
-                closure_kind_ty,
-                closure_sig_as_fn_ptr_ty: Ty::new_fn_ptr(self.tcx, sig),
-                tupled_upvars_ty,
-            },
-        );
+                Ty::new_closure(tcx, expr_def_id.to_def_id(), closure_args.args)
+            }
+            hir::ClosureKind::Coroutine(_) => {
+                let Some(CoroutineTypes { resume_ty, yield_ty }) = coroutine_types else {
+                    bug!("expected coroutine to have yield/resume types");
+                };
+                let interior = fcx.next_ty_var(TypeVariableOrigin {
+                    kind: TypeVariableOriginKind::MiscVariable,
+                    span: body.value.span,
+                });
+                fcx.deferred_coroutine_interiors.borrow_mut().push((
+                    expr_def_id,
+                    body.id(),
+                    interior,
+                ));
+
+                let coroutine_args = ty::CoroutineArgs::new(
+                    tcx,
+                    ty::CoroutineArgsParts {
+                        parent_args,
+                        resume_ty,
+                        yield_ty,
+                        return_ty: liberated_sig.output(),
+                        witness: interior,
+                        tupled_upvars_ty,
+                    },
+                );
 
-        Ty::new_closure(self.tcx, expr_def_id.to_def_id(), closure_args.args)
+                Ty::new_coroutine(tcx, expr_def_id.to_def_id(), coroutine_args.args)
+            }
+        }
     }
 
     /// Given the expected type, figures out what it can about this closure we

compiler/rustc_hir_typeck/src/expr.rs

@@ -15,6 +15,7 @@ use crate::errors::{
 use crate::fatally_break_rust;
 use crate::method::SelfSource;
 use crate::type_error_struct;
+use crate::CoroutineTypes;
 use crate::Expectation::{self, ExpectCastableToType, ExpectHasType, NoExpectation};
 use crate::{
     report_unexpected_variant_res, BreakableCtxt, Diverges, FnCtxt, Needs,
@@ -3163,8 +3164,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         value: &'tcx hir::Expr<'tcx>,
         expr: &'tcx hir::Expr<'tcx>,
     ) -> Ty<'tcx> {
-        match self.resume_yield_tys {
-            Some((resume_ty, yield_ty)) => {
+        match self.coroutine_types {
+            Some(CoroutineTypes { resume_ty, yield_ty }) => {
                 self.check_expr_coercible_to_type(value, yield_ty, None);
 
                 resume_ty

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -534,7 +534,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let coroutines = std::mem::take(&mut *self.deferred_coroutine_interiors.borrow_mut());
         debug!(?coroutines);
 
-        for &(expr_def_id, body_id, interior, _) in coroutines.iter() {
+        for &(expr_def_id, body_id, interior) in coroutines.iter() {
             debug!(?expr_def_id);
 
             // Create the `CoroutineWitness` type that we will unify with `interior`.

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -5,7 +5,7 @@ mod checks;
 mod suggestions;
 
 use crate::coercion::DynamicCoerceMany;
-use crate::{Diverges, EnclosingBreakables, Inherited};
+use crate::{CoroutineTypes, Diverges, EnclosingBreakables, Inherited};
 use rustc_errors::{DiagCtxt, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -68,7 +68,7 @@ pub struct FnCtxt<'a, 'tcx> {
     /// First span of a return site that we find. Used in error messages.
     pub(super) ret_coercion_span: Cell<Option<Span>>,
 
-    pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
+    pub(super) coroutine_types: Option<CoroutineTypes<'tcx>>,
 
     /// Whether the last checked node generates a divergence (e.g.,
     /// `return` will set this to `Always`). In general, when entering
@@ -122,7 +122,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             err_count_on_creation: inh.tcx.dcx().err_count(),
             ret_coercion: None,
             ret_coercion_span: Cell::new(None),
-            resume_yield_tys: None,
+            coroutine_types: None,
             diverges: Cell::new(Diverges::Maybe),
             enclosing_breakables: RefCell::new(EnclosingBreakables {
                 stack: Vec::new(),

compiler/rustc_hir_typeck/src/inherited.rs

@@ -55,8 +55,7 @@ pub struct Inherited<'tcx> {
 
     pub(super) deferred_asm_checks: RefCell<Vec<(&'tcx hir::InlineAsm<'tcx>, hir::HirId)>>,
 
-    pub(super) deferred_coroutine_interiors:
-        RefCell<Vec<(LocalDefId, hir::BodyId, Ty<'tcx>, hir::CoroutineKind)>>,
+    pub(super) deferred_coroutine_interiors: RefCell<Vec<(LocalDefId, hir::BodyId, Ty<'tcx>)>>,
 
     /// Whenever we introduce an adjustment from `!` into a type variable,
     /// we record that type variable here. This is later used to inform