-// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
//! Code for type-checking closure expressions.
-use super::{check_fn, Expectation, FnCtxt};
-
-use astconv::AstConv;
-use rustc::infer::type_variable::TypeVariableOrigin;
-use rustc::ty::{self, ToPolyTraitRef, Ty};
-use rustc::ty::subst::Substs;
+use super::{check_fn, Expectation, FnCtxt, GeneratorTypes};
+
+use crate::astconv::AstConv;
+use crate::middle::{lang_items, region};
+use rustc::hir::def_id::DefId;
+use rustc::infer::{InferOk, InferResult};
+use rustc::infer::LateBoundRegionConversionTime;
+use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc::traits::Obligation;
+use rustc::traits::error_reporting::ArgKind;
+use rustc::ty::{self, Ty, GenericParamDefKind};
+use rustc::ty::fold::TypeFoldable;
+use rustc::ty::subst::InternalSubsts;
use std::cmp;
use std::iter;
-use syntax::abi::Abi;
+use rustc_target::spec::abi::Abi;
+use syntax::source_map::Span;
use rustc::hir;
-impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
- pub fn check_expr_closure(&self,
- expr: &hir::Expr,
- _capture: hir::CaptureClause,
- decl: &'gcx hir::FnDecl,
- body_id: hir::BodyId,
- expected: Expectation<'tcx>)
- -> Ty<'tcx> {
- debug!("check_expr_closure(expr={:?},expected={:?})",
- expr,
- expected);
+/// What signature do we *expect* the closure to have from context?
+#[derive(Debug)]
+struct ExpectedSig<'tcx> {
+ /// Span that gave us this expectation, if we know that.
+ cause_span: Option<Span>,
+ sig: ty::FnSig<'tcx>,
+}
+
+struct ClosureSignatures<'tcx> {
+ bound_sig: ty::PolyFnSig<'tcx>,
+ liberated_sig: ty::FnSig<'tcx>,
+}
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+ pub fn check_expr_closure(
+ &self,
+ expr: &hir::Expr,
+ _capture: hir::CaptureBy,
+ decl: &'tcx hir::FnDecl,
+ body_id: hir::BodyId,
+ gen: Option<hir::Movability>,
+ expected: Expectation<'tcx>,
+ ) -> Ty<'tcx> {
+ debug!(
+ "check_expr_closure(expr={:?},expected={:?})",
+ expr, expected
+ );
// It's always helpful for inference if we know the kind of
// closure sooner rather than later, so first examine the expected
Some(ty) => self.deduce_expectations_from_expected_type(ty),
None => (None, None),
};
- let body = self.tcx.hir.body(body_id);
- self.check_closure(expr, expected_kind, decl, body, expected_sig)
+ let body = self.tcx.hir().body(body_id);
+ self.check_closure(expr, expected_kind, decl, body, gen, expected_sig)
}
- fn check_closure(&self,
- expr: &hir::Expr,
- opt_kind: Option<ty::ClosureKind>,
- decl: &'gcx hir::FnDecl,
- body: &'gcx hir::Body,
- expected_sig: Option<ty::FnSig<'tcx>>)
- -> Ty<'tcx> {
- debug!("check_closure opt_kind={:?} expected_sig={:?}",
- opt_kind,
- expected_sig);
-
- let expr_def_id = self.tcx.hir.local_def_id(expr.id);
- let sig = AstConv::ty_of_closure(self,
- hir::Unsafety::Normal,
- decl,
- Abi::RustCall,
- expected_sig);
- // `deduce_expectations_from_expected_type` introduces late-bound
- // lifetimes defined elsewhere, which we need to anonymize away.
- let sig = self.tcx.anonymize_late_bound_regions(&sig);
+ fn check_closure(
+ &self,
+ expr: &hir::Expr,
+ opt_kind: Option<ty::ClosureKind>,
+ decl: &'tcx hir::FnDecl,
+ body: &'tcx hir::Body,
+ gen: Option<hir::Movability>,
+ expected_sig: Option<ExpectedSig<'tcx>>,
+ ) -> Ty<'tcx> {
+ debug!(
+ "check_closure(opt_kind={:?}, expected_sig={:?})",
+ opt_kind, expected_sig
+ );
+
+ let expr_def_id = self.tcx.hir().local_def_id(expr.hir_id);
+
+ let ClosureSignatures {
+ bound_sig,
+ liberated_sig,
+ } = self.sig_of_closure(expr_def_id, decl, body, expected_sig);
+
+ debug!("check_closure: ty_of_closure returns {:?}", liberated_sig);
+
+ let generator_types = check_fn(
+ self,
+ self.param_env,
+ liberated_sig,
+ decl,
+ expr.hir_id,
+ body,
+ gen,
+ ).1;
// Create type variables (for now) to represent the transformed
// types of upvars. These will be unified during the upvar
// inference phase (`upvar.rs`).
- let base_substs = Substs::identity_for_item(self.tcx,
- self.tcx.closure_base_def_id(expr_def_id));
- let closure_type = self.tcx.mk_closure(expr_def_id,
- base_substs.extend_to(self.tcx, expr_def_id,
- |_, _| span_bug!(expr.span, "closure has region param"),
- |_, _| self.infcx.next_ty_var(TypeVariableOrigin::TransformedUpvar(expr.span))
- )
- );
-
- debug!("check_closure: expr.id={:?} closure_type={:?}", expr.id, closure_type);
+ let base_substs =
+ InternalSubsts::identity_for_item(self.tcx, self.tcx.closure_base_def_id(expr_def_id));
+ let substs = base_substs.extend_to(self.tcx,expr_def_id, |param, _| {
+ match param.kind {
+ GenericParamDefKind::Lifetime => {
+ span_bug!(expr.span, "closure has lifetime param")
+ }
+ GenericParamDefKind::Type { .. } => {
+ self.infcx.next_ty_var(TypeVariableOrigin {
+ kind: TypeVariableOriginKind::ClosureSynthetic,
+ span: expr.span,
+ }).into()
+ }
+ GenericParamDefKind::Const => {
+ span_bug!(expr.span, "closure has const param")
+ }
+ }
+ });
+ if let Some(GeneratorTypes { yield_ty, interior, movability }) = generator_types {
+ let generator_substs = substs.as_generator();
+ self.demand_eqtype(
+ expr.span,
+ yield_ty,
+ generator_substs.yield_ty(expr_def_id, self.tcx),
+ );
+ self.demand_eqtype(
+ expr.span,
+ liberated_sig.output(),
+ generator_substs.return_ty(expr_def_id, self.tcx),
+ );
+ self.demand_eqtype(
+ expr.span,
+ interior,
+ generator_substs.witness(expr_def_id, self.tcx),
+ );
+ return self.tcx.mk_generator(expr_def_id, substs, movability);
+ }
- let fn_sig = self.liberate_late_bound_regions(expr_def_id, &sig);
- let fn_sig = self.inh.normalize_associated_types_in(body.value.span,
- body.value.id,
- self.param_env,
- &fn_sig);
+ let closure_type = self.tcx.mk_closure(expr_def_id, substs);
- check_fn(self, self.param_env, fn_sig, decl, expr.id, body);
+ debug!(
+ "check_closure: expr.hir_id={:?} closure_type={:?}",
+ expr.hir_id, closure_type
+ );
// Tuple up the arguments and insert the resulting function type into
// the `closures` table.
- let sig = sig.map_bound(|sig| self.tcx.mk_fn_sig(
- iter::once(self.tcx.intern_tup(sig.inputs(), false)),
- sig.output(),
- sig.variadic,
- sig.unsafety,
- sig.abi
- ));
+ let sig = bound_sig.map_bound(|sig| {
+ self.tcx.mk_fn_sig(
+ iter::once(self.tcx.intern_tup(sig.inputs())),
+ sig.output(),
+ sig.c_variadic,
+ sig.unsafety,
+ sig.abi,
+ )
+ });
- debug!("closure for {:?} --> sig={:?} opt_kind={:?}",
- expr_def_id,
- sig,
- opt_kind);
+ debug!(
+ "check_closure: expr_def_id={:?}, sig={:?}, opt_kind={:?}",
+ expr_def_id, sig, opt_kind
+ );
- self.tables.borrow_mut().closure_tys.insert(expr.id, sig);
- match opt_kind {
- Some(kind) => {
- self.tables.borrow_mut().closure_kinds.insert(expr.id, (kind, None));
- }
- None => {}
+ let sig_fn_ptr_ty = self.tcx.mk_fn_ptr(sig);
+ self.demand_eqtype(
+ expr.span,
+ sig_fn_ptr_ty,
+ substs.as_closure().sig_ty(expr_def_id, self.tcx),
+ );
+
+ if let Some(kind) = opt_kind {
+ self.demand_eqtype(
+ expr.span,
+ kind.to_ty(self.tcx),
+ substs.as_closure().kind_ty(expr_def_id, self.tcx),
+ );
}
closure_type
}
- fn deduce_expectations_from_expected_type
- (&self,
- expected_ty: Ty<'tcx>)
- -> (Option<ty::FnSig<'tcx>>, Option<ty::ClosureKind>) {
- debug!("deduce_expectations_from_expected_type(expected_ty={:?})",
- expected_ty);
+ /// Given the expected type, figures out what it can about this closure we
+ /// are about to type check:
+ fn deduce_expectations_from_expected_type(
+ &self,
+ expected_ty: Ty<'tcx>,
+ ) -> (Option<ExpectedSig<'tcx>>, Option<ty::ClosureKind>) {
+ debug!(
+ "deduce_expectations_from_expected_type(expected_ty={:?})",
+ expected_ty
+ );
- match expected_ty.sty {
- ty::TyDynamic(ref object_type, ..) => {
- let sig = object_type.projection_bounds()
+ match expected_ty.kind {
+ ty::Dynamic(ref object_type, ..) => {
+ let sig = object_type
+ .projection_bounds()
.filter_map(|pb| {
let pb = pb.with_self_ty(self.tcx, self.tcx.types.err);
- self.deduce_sig_from_projection(&pb)
+ self.deduce_sig_from_projection(None, &pb)
})
.next();
- let kind = object_type.principal()
- .and_then(|p| self.tcx.lang_items.fn_trait_kind(p.def_id()));
+ let kind = object_type.principal_def_id().and_then(|did| {
+ self.tcx.lang_items().fn_trait_kind(did)
+ });
(sig, kind)
}
- ty::TyInfer(ty::TyVar(vid)) => self.deduce_expectations_from_obligations(vid),
- ty::TyFnPtr(sig) => (Some(sig.skip_binder().clone()), Some(ty::ClosureKind::Fn)),
+ ty::Infer(ty::TyVar(vid)) => self.deduce_expectations_from_obligations(vid),
+ ty::FnPtr(sig) => {
+ let expected_sig = ExpectedSig {
+ cause_span: None,
+ sig: sig.skip_binder().clone(),
+ };
+ (Some(expected_sig), Some(ty::ClosureKind::Fn))
+ }
_ => (None, None),
}
}
- fn deduce_expectations_from_obligations
- (&self,
- expected_vid: ty::TyVid)
- -> (Option<ty::FnSig<'tcx>>, Option<ty::ClosureKind>) {
- let fulfillment_cx = self.fulfillment_cx.borrow();
- // Here `expected_ty` is known to be a type inference variable.
-
- let expected_sig = fulfillment_cx.pending_obligations()
- .iter()
- .map(|obligation| &obligation.obligation)
- .filter_map(|obligation| {
- debug!("deduce_expectations_from_obligations: obligation.predicate={:?}",
- obligation.predicate);
-
- match obligation.predicate {
+ fn deduce_expectations_from_obligations(
+ &self,
+ expected_vid: ty::TyVid,
+ ) -> (Option<ExpectedSig<'tcx>>, Option<ty::ClosureKind>) {
+ let expected_sig = self.obligations_for_self_ty(expected_vid)
+ .find_map(|(_, obligation)| {
+ debug!(
+ "deduce_expectations_from_obligations: obligation.predicate={:?}",
+ obligation.predicate
+ );
+
+ if let ty::Predicate::Projection(ref proj_predicate) = obligation.predicate {
// Given a Projection predicate, we can potentially infer
// the complete signature.
- ty::Predicate::Projection(ref proj_predicate) => {
- let trait_ref = proj_predicate.to_poly_trait_ref();
- self.self_type_matches_expected_vid(trait_ref, expected_vid)
- .and_then(|_| self.deduce_sig_from_projection(proj_predicate))
- }
- _ => None,
+ self.deduce_sig_from_projection(
+ Some(obligation.cause.span),
+ proj_predicate
+ )
+ } else {
+ None
}
- })
- .next();
+ });
// Even if we can't infer the full signature, we may be able to
// infer the kind. This can occur if there is a trait-reference
// like `F : Fn<A>`. Note that due to subtyping we could encounter
// many viable options, so pick the most restrictive.
- let expected_kind = fulfillment_cx.pending_obligations()
- .iter()
- .map(|obligation| &obligation.obligation)
- .filter_map(|obligation| {
- let opt_trait_ref = match obligation.predicate {
- ty::Predicate::Projection(ref data) => Some(data.to_poly_trait_ref()),
- ty::Predicate::Trait(ref data) => Some(data.to_poly_trait_ref()),
- ty::Predicate::Equate(..) => None,
- ty::Predicate::Subtype(..) => None,
- ty::Predicate::RegionOutlives(..) => None,
- ty::Predicate::TypeOutlives(..) => None,
- ty::Predicate::WellFormed(..) => None,
- ty::Predicate::ObjectSafe(..) => None,
-
- // NB: This predicate is created by breaking down a
- // `ClosureType: FnFoo()` predicate, where
- // `ClosureType` represents some `TyClosure`. It can't
- // possibly be referring to the current closure,
- // because we haven't produced the `TyClosure` for
- // this closure yet; this is exactly why the other
- // code is looking for a self type of a unresolved
- // inference variable.
- ty::Predicate::ClosureKind(..) => None,
- };
- opt_trait_ref.and_then(|tr| self.self_type_matches_expected_vid(tr, expected_vid))
- .and_then(|tr| self.tcx.lang_items.fn_trait_kind(tr.def_id()))
- })
- .fold(None,
- |best, cur| Some(best.map_or(cur, |best| cmp::min(best, cur))));
+ let expected_kind = self.obligations_for_self_ty(expected_vid)
+ .filter_map(|(tr, _)| self.tcx.lang_items().fn_trait_kind(tr.def_id()))
+ .fold(None, |best, cur| {
+ Some(best.map_or(cur, |best| cmp::min(best, cur)))
+ });
(expected_sig, expected_kind)
}
/// Given a projection like "<F as Fn(X)>::Result == Y", we can deduce
- /// everything we need to know about a closure.
- fn deduce_sig_from_projection(&self,
- projection: &ty::PolyProjectionPredicate<'tcx>)
- -> Option<ty::FnSig<'tcx>> {
+ /// everything we need to know about a closure or generator.
+ ///
+ /// The `cause_span` should be the span that caused us to
+ /// have this expected signature, or `None` if we can't readily
+ /// know that.
+ fn deduce_sig_from_projection(
+ &self,
+ cause_span: Option<Span>,
+ projection: &ty::PolyProjectionPredicate<'tcx>,
+ ) -> Option<ExpectedSig<'tcx>> {
let tcx = self.tcx;
debug!("deduce_sig_from_projection({:?})", projection);
- let trait_ref = projection.to_poly_trait_ref();
+ let trait_ref = projection.to_poly_trait_ref(tcx);
- if tcx.lang_items.fn_trait_kind(trait_ref.def_id()).is_none() {
+ let is_fn = tcx.lang_items().fn_trait_kind(trait_ref.def_id()).is_some();
+ let gen_trait = tcx.require_lang_item(lang_items::GeneratorTraitLangItem, cause_span);
+ let is_gen = gen_trait == trait_ref.def_id();
+ if !is_fn && !is_gen {
+ debug!("deduce_sig_from_projection: not fn or generator");
return None;
}
- let arg_param_ty = trait_ref.substs().type_at(1);
- let arg_param_ty = self.resolve_type_vars_if_possible(&arg_param_ty);
- debug!("deduce_sig_from_projection: arg_param_ty {:?}",
- arg_param_ty);
-
- let input_tys = match arg_param_ty.sty {
- ty::TyTuple(tys, _) => tys.into_iter(),
- _ => {
+ if is_gen {
+ // Check that we deduce the signature from the `<_ as std::ops::Generator>::Return`
+ // associated item and not yield.
+ let return_assoc_item = self.tcx.associated_items(gen_trait).nth(1).unwrap().def_id;
+ if return_assoc_item != projection.projection_def_id() {
+ debug!("deduce_sig_from_projection: not return assoc item of generator");
return None;
}
+ }
+
+ let input_tys = if is_fn {
+ let arg_param_ty = trait_ref.skip_binder().substs.type_at(1);
+ let arg_param_ty = self.resolve_vars_if_possible(&arg_param_ty);
+ debug!("deduce_sig_from_projection: arg_param_ty={:?}", arg_param_ty);
+
+ match arg_param_ty.kind {
+ ty::Tuple(tys) => tys.into_iter().map(|k| k.expect_ty()).collect::<Vec<_>>(),
+ _ => return None,
+ }
+ } else {
+ // Generators cannot have explicit arguments.
+ vec![]
};
- let ret_param_ty = projection.0.ty;
- let ret_param_ty = self.resolve_type_vars_if_possible(&ret_param_ty);
- debug!("deduce_sig_from_projection: ret_param_ty {:?}", ret_param_ty);
+ let ret_param_ty = projection.skip_binder().ty;
+ let ret_param_ty = self.resolve_vars_if_possible(&ret_param_ty);
+ debug!("deduce_sig_from_projection: ret_param_ty={:?}", ret_param_ty);
- let fn_sig = self.tcx.mk_fn_sig(
- input_tys.cloned(),
- ret_param_ty,
+ let sig = self.tcx.mk_fn_sig(
+ input_tys.iter(),
+ &ret_param_ty,
false,
hir::Unsafety::Normal,
- Abi::Rust
+ Abi::Rust,
+ );
+ debug!("deduce_sig_from_projection: sig={:?}", sig);
+
+ Some(ExpectedSig { cause_span, sig })
+ }
+
+ fn sig_of_closure(
+ &self,
+ expr_def_id: DefId,
+ decl: &hir::FnDecl,
+ body: &hir::Body,
+ expected_sig: Option<ExpectedSig<'tcx>>,
+ ) -> ClosureSignatures<'tcx> {
+ if let Some(e) = expected_sig {
+ self.sig_of_closure_with_expectation(expr_def_id, decl, body, e)
+ } else {
+ self.sig_of_closure_no_expectation(expr_def_id, decl, body)
+ }
+ }
+
+ /// If there is no expected signature, then we will convert the
+ /// types that the user gave into a signature.
+ fn sig_of_closure_no_expectation(
+ &self,
+ expr_def_id: DefId,
+ decl: &hir::FnDecl,
+ body: &hir::Body,
+ ) -> ClosureSignatures<'tcx> {
+ debug!("sig_of_closure_no_expectation()");
+
+ let bound_sig = self.supplied_sig_of_closure(expr_def_id, decl, body);
+
+ self.closure_sigs(expr_def_id, body, bound_sig)
+ }
+
+ /// Invoked to compute the signature of a closure expression. This
+ /// combines any user-provided type annotations (e.g., `|x: u32|
+ /// -> u32 { .. }`) with the expected signature.
+ ///
+ /// The approach is as follows:
+ ///
+ /// - Let `S` be the (higher-ranked) signature that we derive from the user's annotations.
+ /// - Let `E` be the (higher-ranked) signature that we derive from the expectations, if any.
+ /// - If we have no expectation `E`, then the signature of the closure is `S`.
+ /// - Otherwise, the signature of the closure is E. Moreover:
+ /// - Skolemize the late-bound regions in `E`, yielding `E'`.
+ /// - Instantiate all the late-bound regions bound in the closure within `S`
+ /// with fresh (existential) variables, yielding `S'`
+ /// - Require that `E' = S'`
+ /// - We could use some kind of subtyping relationship here,
+ /// I imagine, but equality is easier and works fine for
+ /// our purposes.
+ ///
+ /// The key intuition here is that the user's types must be valid
+ /// from "the inside" of the closure, but the expectation
+ /// ultimately drives the overall signature.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// fn with_closure<F>(_: F)
+ /// where F: Fn(&u32) -> &u32 { .. }
+ ///
+ /// with_closure(|x: &u32| { ... })
+ /// ```
+ ///
+ /// Here:
+ /// - E would be `fn(&u32) -> &u32`.
+ /// - S would be `fn(&u32) ->
+ /// - E' is `&'!0 u32 -> &'!0 u32`
+ /// - S' is `&'?0 u32 -> ?T`
+ ///
+ /// S' can be unified with E' with `['?0 = '!0, ?T = &'!10 u32]`.
+ ///
+ /// # Arguments
+ ///
+ /// - `expr_def_id`: the `DefId` of the closure expression
+ /// - `decl`: the HIR declaration of the closure
+ /// - `body`: the body of the closure
+ /// - `expected_sig`: the expected signature (if any). Note that
+ /// this is missing a binder: that is, there may be late-bound
+ /// regions with depth 1, which are bound then by the closure.
+ fn sig_of_closure_with_expectation(
+ &self,
+ expr_def_id: DefId,
+ decl: &hir::FnDecl,
+ body: &hir::Body,
+ expected_sig: ExpectedSig<'tcx>,
+ ) -> ClosureSignatures<'tcx> {
+ debug!(
+ "sig_of_closure_with_expectation(expected_sig={:?})",
+ expected_sig
+ );
+
+ // Watch out for some surprises and just ignore the
+ // expectation if things don't see to match up with what we
+ // expect.
+ if expected_sig.sig.c_variadic != decl.c_variadic {
+ return self.sig_of_closure_no_expectation(expr_def_id, decl, body);
+ } else if expected_sig.sig.inputs_and_output.len() != decl.inputs.len() + 1 {
+ return self.sig_of_closure_with_mismatched_number_of_arguments(
+ expr_def_id,
+ decl,
+ body,
+ expected_sig,
+ );
+ }
+
+ // Create a `PolyFnSig`. Note the oddity that late bound
+ // regions appearing free in `expected_sig` are now bound up
+ // in this binder we are creating.
+ assert!(!expected_sig.sig.has_vars_bound_above(ty::INNERMOST));
+ let bound_sig = ty::Binder::bind(self.tcx.mk_fn_sig(
+ expected_sig.sig.inputs().iter().cloned(),
+ expected_sig.sig.output(),
+ decl.c_variadic,
+ hir::Unsafety::Normal,
+ Abi::RustCall,
+ ));
+
+ // `deduce_expectations_from_expected_type` introduces
+ // late-bound lifetimes defined elsewhere, which we now
+ // anonymize away, so as not to confuse the user.
+ let bound_sig = self.tcx.anonymize_late_bound_regions(&bound_sig);
+
+ let closure_sigs = self.closure_sigs(expr_def_id, body, bound_sig);
+
+ // Up till this point, we have ignored the annotations that the user
+ // gave. This function will check that they unify successfully.
+ // Along the way, it also writes out entries for types that the user
+ // wrote into our tables, which are then later used by the privacy
+ // check.
+ match self.check_supplied_sig_against_expectation(expr_def_id, decl, body, &closure_sigs) {
+ Ok(infer_ok) => self.register_infer_ok_obligations(infer_ok),
+ Err(_) => return self.sig_of_closure_no_expectation(expr_def_id, decl, body),
+ }
+
+ closure_sigs
+ }
+
+ fn sig_of_closure_with_mismatched_number_of_arguments(
+ &self,
+ expr_def_id: DefId,
+ decl: &hir::FnDecl,
+ body: &hir::Body,
+ expected_sig: ExpectedSig<'tcx>,
+ ) -> ClosureSignatures<'tcx> {
+ let expr_map_node = self.tcx.hir().get_if_local(expr_def_id).unwrap();
+ let expected_args: Vec<_> = expected_sig
+ .sig
+ .inputs()
+ .iter()
+ .map(|ty| ArgKind::from_expected_ty(ty, None))
+ .collect();
+ let (closure_span, found_args) = self.get_fn_like_arguments(expr_map_node);
+ let expected_span = expected_sig.cause_span.unwrap_or(closure_span);
+ self.report_arg_count_mismatch(
+ expected_span,
+ Some(closure_span),
+ expected_args,
+ found_args,
+ true,
+ ).emit();
+
+ let error_sig = self.error_sig_of_closure(decl);
+
+ self.closure_sigs(expr_def_id, body, error_sig)
+ }
+
+ /// Enforce the user's types against the expectation. See
+ /// `sig_of_closure_with_expectation` for details on the overall
+ /// strategy.
+ fn check_supplied_sig_against_expectation(
+ &self,
+ expr_def_id: DefId,
+ decl: &hir::FnDecl,
+ body: &hir::Body,
+ expected_sigs: &ClosureSignatures<'tcx>,
+ ) -> InferResult<'tcx, ()> {
+ // Get the signature S that the user gave.
+ //
+ // (See comment on `sig_of_closure_with_expectation` for the
+ // meaning of these letters.)
+ let supplied_sig = self.supplied_sig_of_closure(expr_def_id, decl, body);
+
+ debug!(
+ "check_supplied_sig_against_expectation: supplied_sig={:?}",
+ supplied_sig
);
- debug!("deduce_sig_from_projection: fn_sig {:?}", fn_sig);
- Some(fn_sig)
+ // FIXME(#45727): As discussed in [this comment][c1], naively
+ // forcing equality here actually results in suboptimal error
+ // messages in some cases. For now, if there would have been
+ // an obvious error, we fallback to declaring the type of the
+ // closure to be the one the user gave, which allows other
+ // error message code to trigger.
+ //
+ // However, I think [there is potential to do even better
+ // here][c2], since in *this* code we have the precise span of
+ // the type parameter in question in hand when we report the
+ // error.
+ //
+ // [c1]: https://github.com/rust-lang/rust/pull/45072#issuecomment-341089706
+ // [c2]: https://github.com/rust-lang/rust/pull/45072#issuecomment-341096796
+ self.infcx.commit_if_ok(|_| {
+ let mut all_obligations = vec![];
+
+ // The liberated version of this signature should be a subtype
+ // of the liberated form of the expectation.
+ for ((hir_ty, &supplied_ty), expected_ty) in decl.inputs.iter()
+ .zip(*supplied_sig.inputs().skip_binder()) // binder moved to (*) below
+ .zip(expected_sigs.liberated_sig.inputs())
+ // `liberated_sig` is E'.
+ {
+ // Instantiate (this part of..) S to S', i.e., with fresh variables.
+ let (supplied_ty, _) = self.infcx.replace_bound_vars_with_fresh_vars(
+ hir_ty.span,
+ LateBoundRegionConversionTime::FnCall,
+ &ty::Binder::bind(supplied_ty),
+ ); // recreated from (*) above
+
+ // Check that E' = S'.
+ let cause = self.misc(hir_ty.span);
+ let InferOk {
+ value: (),
+ obligations,
+ } = self.at(&cause, self.param_env)
+ .eq(*expected_ty, supplied_ty)?;
+ all_obligations.extend(obligations);
+
+ // Also, require that the supplied type must outlive
+ // the closure body.
+ let closure_body_region = self.tcx.mk_region(
+ ty::ReScope(
+ region::Scope {
+ id: body.value.hir_id.local_id,
+ data: region::ScopeData::Node,
+ },
+ ),
+ );
+ all_obligations.push(
+ Obligation::new(
+ cause,
+ self.param_env,
+ ty::Predicate::TypeOutlives(
+ ty::Binder::dummy(
+ ty::OutlivesPredicate(
+ supplied_ty,
+ closure_body_region,
+ ),
+ ),
+ ),
+ ),
+ );
+ }
+
+ let (supplied_output_ty, _) = self.infcx.replace_bound_vars_with_fresh_vars(
+ decl.output.span(),
+ LateBoundRegionConversionTime::FnCall,
+ &supplied_sig.output(),
+ );
+ let cause = &self.misc(decl.output.span());
+ let InferOk {
+ value: (),
+ obligations,
+ } = self.at(cause, self.param_env)
+ .eq(expected_sigs.liberated_sig.output(), supplied_output_ty)?;
+ all_obligations.extend(obligations);
+
+ Ok(InferOk {
+ value: (),
+ obligations: all_obligations,
+ })
+ })
+ }
+
+ /// If there is no expected signature, then we will convert the
+ /// types that the user gave into a signature.
+ ///
+ /// Also, record this closure signature for later.
+ fn supplied_sig_of_closure(
+ &self,
+ expr_def_id: DefId,
+ decl: &hir::FnDecl,
+ body: &hir::Body,
+ ) -> ty::PolyFnSig<'tcx> {
+ let astconv: &dyn AstConv<'_> = self;
+
+ debug!(
+ "supplied_sig_of_closure(decl={:?}, body.generator_kind={:?})",
+ decl,
+ body.generator_kind,
+ );
+
+ // First, convert the types that the user supplied (if any).
+ let supplied_arguments = decl.inputs.iter().map(|a| astconv.ast_ty_to_ty(a));
+ let supplied_return = match decl.output {
+ hir::Return(ref output) => astconv.ast_ty_to_ty(&output),
+ hir::DefaultReturn(_) => match body.generator_kind {
+ // In the case of the async block that we create for a function body,
+ // we expect the return type of the block to match that of the enclosing
+ // function.
+ Some(hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Fn)) => {
+ debug!("supplied_sig_of_closure: closure is async fn body");
+ self.deduce_future_output_from_obligations(expr_def_id)
+ .unwrap_or_else(|| {
+ // AFAIK, deducing the future output
+ // always succeeds *except* in error cases
+ // like #65159. I'd like to return Error
+ // here, but I can't because I can't
+ // easily (and locally) prove that we
+ // *have* reported an
+ // error. --nikomatsakis
+ astconv.ty_infer(None, decl.output.span())
+ })
+ }
+
+ _ => astconv.ty_infer(None, decl.output.span()),
+ }
+ };
+
+ let result = ty::Binder::bind(self.tcx.mk_fn_sig(
+ supplied_arguments,
+ supplied_return,
+ decl.c_variadic,
+ hir::Unsafety::Normal,
+ Abi::RustCall,
+ ));
+
+ debug!("supplied_sig_of_closure: result={:?}", result);
+
+ let c_result = self.inh.infcx.canonicalize_response(&result);
+ self.tables.borrow_mut().user_provided_sigs.insert(
+ expr_def_id,
+ c_result,
+ );
+
+ result
+ }
+
+ /// Invoked when we are translating the generator that results
+ /// from desugaring an `async fn`. Returns the "sugared" return
+ /// type of the `async fn` -- that is, the return type that the
+ /// user specified. The "desugared" return type is a `impl
+ /// Future<Output = T>`, so we do this by searching through the
+ /// obligations to extract the `T`.
+ fn deduce_future_output_from_obligations(
+ &self,
+ expr_def_id: DefId,
+ ) -> Option<Ty<'tcx>> {
+ debug!("deduce_future_output_from_obligations(expr_def_id={:?})", expr_def_id);
+
+ let ret_coercion =
+ self.ret_coercion
+ .as_ref()
+ .unwrap_or_else(|| span_bug!(
+ self.tcx.def_span(expr_def_id),
+ "async fn generator outside of a fn"
+ ));
+
+ // In practice, the return type of the surrounding function is
+ // always a (not yet resolved) inference variable, because it
+ // is the hidden type for an `impl Trait` that we are going to
+ // be inferring.
+ let ret_ty = ret_coercion.borrow().expected_ty();
+ let ret_ty = self.inh.infcx.shallow_resolve(ret_ty);
+ let ret_vid = match ret_ty.kind {
+ ty::Infer(ty::TyVar(ret_vid)) => ret_vid,
+ _ => {
+ span_bug!(
+ self.tcx.def_span(expr_def_id),
+ "async fn generator return type not an inference variable"
+ )
+ }
+ };
+
+ // Search for a pending obligation like
+ //
+ // `<R as Future>::Output = T`
+ //
+ // where R is the return type we are expecting. This type `T`
+ // will be our output.
+ let output_ty = self.obligations_for_self_ty(ret_vid)
+ .find_map(|(_, obligation)| {
+ if let ty::Predicate::Projection(ref proj_predicate) = obligation.predicate {
+ self.deduce_future_output_from_projection(
+ obligation.cause.span,
+ proj_predicate
+ )
+ } else {
+ None
+ }
+ });
+
+ debug!("deduce_future_output_from_obligations: output_ty={:?}", output_ty);
+ output_ty
}
- fn self_type_matches_expected_vid(&self,
- trait_ref: ty::PolyTraitRef<'tcx>,
- expected_vid: ty::TyVid)
- -> Option<ty::PolyTraitRef<'tcx>> {
- let self_ty = self.shallow_resolve(trait_ref.self_ty());
- debug!("self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?})",
- trait_ref,
- self_ty);
- match self_ty.sty {
- ty::TyInfer(ty::TyVar(v)) if expected_vid == v => Some(trait_ref),
- _ => None,
+ /// Given a projection like
+ ///
+ /// `<X as Future>::Output = T`
+ ///
+ /// where `X` is some type that has no late-bound regions, returns
+ /// `Some(T)`. If the projection is for some other trait, returns
+ /// `None`.
+ fn deduce_future_output_from_projection(
+ &self,
+ cause_span: Span,
+ predicate: &ty::PolyProjectionPredicate<'tcx>,
+ ) -> Option<Ty<'tcx>> {
+ debug!("deduce_future_output_from_projection(predicate={:?})", predicate);
+
+ // We do not expect any bound regions in our predicate, so
+ // skip past the bound vars.
+ let predicate = match predicate.no_bound_vars() {
+ Some(p) => p,
+ None => {
+ debug!("deduce_future_output_from_projection: has late-bound regions");
+ return None;
+ }
+ };
+
+ // Check that this is a projection from the `Future` trait.
+ let trait_ref = predicate.projection_ty.trait_ref(self.tcx);
+ let future_trait = self.tcx.lang_items().future_trait().unwrap();
+ if trait_ref.def_id != future_trait {
+ debug!("deduce_future_output_from_projection: not a future");
+ return None;
+ }
+
+ // The `Future` trait has only one associted item, `Output`,
+ // so check that this is what we see.
+ let output_assoc_item = self.tcx.associated_items(future_trait).nth(0).unwrap().def_id;
+ if output_assoc_item != predicate.projection_ty.item_def_id {
+ span_bug!(
+ cause_span,
+ "projecting associated item `{:?}` from future, which is not Output `{:?}`",
+ predicate.projection_ty.item_def_id,
+ output_assoc_item,
+ );
+ }
+
+ // Extract the type from the projection. Note that there can
+ // be no bound variables in this type because the "self type"
+ // does not have any regions in it.
+ let output_ty = self.resolve_vars_if_possible(&predicate.ty);
+ debug!("deduce_future_output_from_projection: output_ty={:?}", output_ty);
+ Some(output_ty)
+ }
+
+ /// Converts the types that the user supplied, in case that doing
+ /// so should yield an error, but returns back a signature where
+ /// all parameters are of type `TyErr`.
+ fn error_sig_of_closure(&self, decl: &hir::FnDecl) -> ty::PolyFnSig<'tcx> {
+ let astconv: &dyn AstConv<'_> = self;
+
+ let supplied_arguments = decl.inputs.iter().map(|a| {
+ // Convert the types that the user supplied (if any), but ignore them.
+ astconv.ast_ty_to_ty(a);
+ self.tcx.types.err
+ });
+
+ if let hir::Return(ref output) = decl.output {
+ astconv.ast_ty_to_ty(&output);
+ }
+
+ let result = ty::Binder::bind(self.tcx.mk_fn_sig(
+ supplied_arguments,
+ self.tcx.types.err,
+ decl.c_variadic,
+ hir::Unsafety::Normal,
+ Abi::RustCall,
+ ));
+
+ debug!("supplied_sig_of_closure: result={:?}", result);
+
+ result
+ }
+
+ fn closure_sigs(
+ &self,
+ expr_def_id: DefId,
+ body: &hir::Body,
+ bound_sig: ty::PolyFnSig<'tcx>,
+ ) -> ClosureSignatures<'tcx> {
+ let liberated_sig = self.tcx()
+ .liberate_late_bound_regions(expr_def_id, &bound_sig);
+ let liberated_sig = self.inh.normalize_associated_types_in(
+ body.value.span,
+ body.value.hir_id,
+ self.param_env,
+ &liberated_sig,
+ );
+ ClosureSignatures {
+ bound_sig,
+ liberated_sig,
}
}
}
projects / rustc.git / blobdiff