diff options
Diffstat (limited to 'compiler/rustc_typeck/src/check/writeback.rs')
| -rw-r--r-- | compiler/rustc_typeck/src/check/writeback.rs | 783 |
1 files changed, 783 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/check/writeback.rs b/compiler/rustc_typeck/src/check/writeback.rs new file mode 100644 index 000000000..f549807c3 --- /dev/null +++ b/compiler/rustc_typeck/src/check/writeback.rs @@ -0,0 +1,783 @@ +// Type resolution: the phase that finds all the types in the AST with +// unresolved type variables and replaces "ty_var" types with their +// substitutions. + +use crate::check::FnCtxt; + +use hir::def_id::LocalDefId; +use rustc_data_structures::fx::FxHashMap; +use rustc_errors::ErrorGuaranteed; +use rustc_hir as hir; +use rustc_hir::intravisit::{self, Visitor}; +use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282; +use rustc_infer::infer::InferCtxt; +use rustc_middle::hir::place::Place as HirPlace; +use rustc_middle::mir::FakeReadCause; +use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCast}; +use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable}; +use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable}; +use rustc_middle::ty::{self, ClosureSizeProfileData, Ty, TyCtxt}; +use rustc_span::symbol::sym; +use rustc_span::Span; + +use std::mem; +use std::ops::ControlFlow; + +/////////////////////////////////////////////////////////////////////////// +// Entry point + +// During type inference, partially inferred types are +// represented using Type variables (ty::Infer). These don't appear in +// the final TypeckResults since all of the types should have been +// inferred once typeck is done. +// When type inference is running however, having to update the typeck +// typeck results every time a new type is inferred would be unreasonably slow, +// so instead all of the replacement happens at the end in +// resolve_type_vars_in_body, which creates a new TypeTables which +// doesn't contain any inference types. +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub fn resolve_type_vars_in_body( + &self, + body: &'tcx hir::Body<'tcx>, + ) -> &'tcx ty::TypeckResults<'tcx> { + let item_id = self.tcx.hir().body_owner(body.id()); + let item_def_id = self.tcx.hir().local_def_id(item_id); + + // This attribute causes us to dump some writeback information + // in the form of errors, which is used for unit tests. + let rustc_dump_user_substs = + self.tcx.has_attr(item_def_id.to_def_id(), sym::rustc_dump_user_substs); + + let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs); + for param in body.params { + wbcx.visit_node_id(param.pat.span, param.hir_id); + } + // Type only exists for constants and statics, not functions. + match self.tcx.hir().body_owner_kind(item_def_id) { + hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => { + wbcx.visit_node_id(body.value.span, item_id); + } + hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => (), + } + wbcx.visit_body(body); + wbcx.visit_min_capture_map(); + wbcx.eval_closure_size(); + wbcx.visit_fake_reads_map(); + wbcx.visit_closures(); + wbcx.visit_liberated_fn_sigs(); + wbcx.visit_fru_field_types(); + wbcx.visit_opaque_types(); + wbcx.visit_coercion_casts(); + wbcx.visit_user_provided_tys(); + wbcx.visit_user_provided_sigs(); + wbcx.visit_generator_interior_types(); + + wbcx.typeck_results.rvalue_scopes = + mem::take(&mut self.typeck_results.borrow_mut().rvalue_scopes); + + let used_trait_imports = + mem::take(&mut self.typeck_results.borrow_mut().used_trait_imports); + debug!("used_trait_imports({:?}) = {:?}", item_def_id, used_trait_imports); + wbcx.typeck_results.used_trait_imports = used_trait_imports; + + wbcx.typeck_results.treat_byte_string_as_slice = + mem::take(&mut self.typeck_results.borrow_mut().treat_byte_string_as_slice); + + if self.is_tainted_by_errors() { + // FIXME(eddyb) keep track of `ErrorGuaranteed` from where the error was emitted. + wbcx.typeck_results.tainted_by_errors = + Some(ErrorGuaranteed::unchecked_claim_error_was_emitted()); + } + + debug!("writeback: typeck results for {:?} are {:#?}", item_def_id, wbcx.typeck_results); + + self.tcx.arena.alloc(wbcx.typeck_results) + } +} + +/////////////////////////////////////////////////////////////////////////// +// The Writeback context. This visitor walks the HIR, checking the +// fn-specific typeck results to find references to types or regions. It +// resolves those regions to remove inference variables and writes the +// final result back into the master typeck results in the tcx. Here and +// there, it applies a few ad-hoc checks that were not convenient to +// do elsewhere. + +struct WritebackCx<'cx, 'tcx> { + fcx: &'cx FnCtxt<'cx, 'tcx>, + + typeck_results: ty::TypeckResults<'tcx>, + + body: &'tcx hir::Body<'tcx>, + + rustc_dump_user_substs: bool, +} + +impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> { + fn new( + fcx: &'cx FnCtxt<'cx, 'tcx>, + body: &'tcx hir::Body<'tcx>, + rustc_dump_user_substs: bool, + ) -> WritebackCx<'cx, 'tcx> { + let owner = body.id().hir_id.owner; + + WritebackCx { + fcx, + typeck_results: ty::TypeckResults::new(owner), + body, + rustc_dump_user_substs, + } + } + + fn tcx(&self) -> TyCtxt<'tcx> { + self.fcx.tcx + } + + fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) { + debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty); + assert!(!ty.needs_infer() && !ty.has_placeholders() && !ty.has_free_regions()); + self.typeck_results.node_types_mut().insert(hir_id, ty); + } + + // Hacky hack: During type-checking, we treat *all* operators + // as potentially overloaded. But then, during writeback, if + // we observe that something like `a+b` is (known to be) + // operating on scalars, we clear the overload. + fn fix_scalar_builtin_expr(&mut self, e: &hir::Expr<'_>) { + match e.kind { + hir::ExprKind::Unary(hir::UnOp::Neg | hir::UnOp::Not, inner) => { + let inner_ty = self.fcx.node_ty(inner.hir_id); + let inner_ty = self.fcx.resolve_vars_if_possible(inner_ty); + + if inner_ty.is_scalar() { + let mut typeck_results = self.fcx.typeck_results.borrow_mut(); + typeck_results.type_dependent_defs_mut().remove(e.hir_id); + typeck_results.node_substs_mut().remove(e.hir_id); + } + } + hir::ExprKind::Binary(ref op, lhs, rhs) | hir::ExprKind::AssignOp(ref op, lhs, rhs) => { + let lhs_ty = self.fcx.node_ty(lhs.hir_id); + let lhs_ty = self.fcx.resolve_vars_if_possible(lhs_ty); + + let rhs_ty = self.fcx.node_ty(rhs.hir_id); + let rhs_ty = self.fcx.resolve_vars_if_possible(rhs_ty); + + if lhs_ty.is_scalar() && rhs_ty.is_scalar() { + let mut typeck_results = self.fcx.typeck_results.borrow_mut(); + typeck_results.type_dependent_defs_mut().remove(e.hir_id); + typeck_results.node_substs_mut().remove(e.hir_id); + + match e.kind { + hir::ExprKind::Binary(..) => { + if !op.node.is_by_value() { + let mut adjustments = typeck_results.adjustments_mut(); + if let Some(a) = adjustments.get_mut(lhs.hir_id) { + a.pop(); + } + if let Some(a) = adjustments.get_mut(rhs.hir_id) { + a.pop(); + } + } + } + hir::ExprKind::AssignOp(..) + if let Some(a) = typeck_results.adjustments_mut().get_mut(lhs.hir_id) => + { + a.pop(); + } + _ => {} + } + } + } + _ => {} + } + } + + // Similar to operators, indexing is always assumed to be overloaded + // Here, correct cases where an indexing expression can be simplified + // to use builtin indexing because the index type is known to be + // usize-ish + fn fix_index_builtin_expr(&mut self, e: &hir::Expr<'_>) { + if let hir::ExprKind::Index(ref base, ref index) = e.kind { + let mut typeck_results = self.fcx.typeck_results.borrow_mut(); + + // All valid indexing looks like this; might encounter non-valid indexes at this point. + let base_ty = typeck_results + .expr_ty_adjusted_opt(base) + .map(|t| self.fcx.resolve_vars_if_possible(t).kind()); + if base_ty.is_none() { + // When encountering `return [0][0]` outside of a `fn` body we can encounter a base + // that isn't in the type table. We assume more relevant errors have already been + // emitted, so we delay an ICE if none have. (#64638) + self.tcx().sess.delay_span_bug(e.span, &format!("bad base: `{:?}`", base)); + } + if let Some(ty::Ref(_, base_ty, _)) = base_ty { + let index_ty = typeck_results.expr_ty_adjusted_opt(index).unwrap_or_else(|| { + // When encountering `return [0][0]` outside of a `fn` body we would attempt + // to access an nonexistent index. We assume that more relevant errors will + // already have been emitted, so we only gate on this with an ICE if no + // error has been emitted. (#64638) + self.fcx.tcx.ty_error_with_message( + e.span, + &format!("bad index {:?} for base: `{:?}`", index, base), + ) + }); + let index_ty = self.fcx.resolve_vars_if_possible(index_ty); + + if base_ty.builtin_index().is_some() && index_ty == self.fcx.tcx.types.usize { + // Remove the method call record + typeck_results.type_dependent_defs_mut().remove(e.hir_id); + typeck_results.node_substs_mut().remove(e.hir_id); + + if let Some(a) = typeck_results.adjustments_mut().get_mut(base.hir_id) { + // Discard the need for a mutable borrow + + // Extra adjustment made when indexing causes a drop + // of size information - we need to get rid of it + // Since this is "after" the other adjustment to be + // discarded, we do an extra `pop()` + if let Some(Adjustment { + kind: Adjust::Pointer(PointerCast::Unsize), .. + }) = a.pop() + { + // So the borrow discard actually happens here + a.pop(); + } + } + } + } + } + } +} + +/////////////////////////////////////////////////////////////////////////// +// Impl of Visitor for Resolver +// +// This is the master code which walks the AST. It delegates most of +// the heavy lifting to the generic visit and resolve functions +// below. In general, a function is made into a `visitor` if it must +// traffic in node-ids or update typeck results in the type context etc. + +impl<'cx, 'tcx> Visitor<'tcx> for WritebackCx<'cx, 'tcx> { + fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) { + self.fix_scalar_builtin_expr(e); + self.fix_index_builtin_expr(e); + + match e.kind { + hir::ExprKind::Closure(&hir::Closure { body, .. }) => { + let body = self.fcx.tcx.hir().body(body); + for param in body.params { + self.visit_node_id(e.span, param.hir_id); + } + + self.visit_body(body); + } + hir::ExprKind::Struct(_, fields, _) => { + for field in fields { + self.visit_field_id(field.hir_id); + } + } + hir::ExprKind::Field(..) => { + self.visit_field_id(e.hir_id); + } + hir::ExprKind::ConstBlock(anon_const) => { + self.visit_node_id(e.span, anon_const.hir_id); + + let body = self.tcx().hir().body(anon_const.body); + self.visit_body(body); + } + _ => {} + } + + self.visit_node_id(e.span, e.hir_id); + intravisit::walk_expr(self, e); + } + + fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) { + self.visit_node_id(b.span, b.hir_id); + intravisit::walk_block(self, b); + } + + fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) { + match p.kind { + hir::PatKind::Binding(..) => { + let typeck_results = self.fcx.typeck_results.borrow(); + if let Some(bm) = + typeck_results.extract_binding_mode(self.tcx().sess, p.hir_id, p.span) + { + self.typeck_results.pat_binding_modes_mut().insert(p.hir_id, bm); + } + } + hir::PatKind::Struct(_, fields, _) => { + for field in fields { + self.visit_field_id(field.hir_id); + } + } + _ => {} + }; + + self.visit_pat_adjustments(p.span, p.hir_id); + + self.visit_node_id(p.span, p.hir_id); + intravisit::walk_pat(self, p); + } + + fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) { + intravisit::walk_local(self, l); + let var_ty = self.fcx.local_ty(l.span, l.hir_id).decl_ty; + let var_ty = self.resolve(var_ty, &l.span); + self.write_ty_to_typeck_results(l.hir_id, var_ty); + } + + fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'tcx>) { + intravisit::walk_ty(self, hir_ty); + let ty = self.fcx.node_ty(hir_ty.hir_id); + let ty = self.resolve(ty, &hir_ty.span); + self.write_ty_to_typeck_results(hir_ty.hir_id, ty); + } + + fn visit_infer(&mut self, inf: &'tcx hir::InferArg) { + intravisit::walk_inf(self, inf); + // Ignore cases where the inference is a const. + if let Some(ty) = self.fcx.node_ty_opt(inf.hir_id) { + let ty = self.resolve(ty, &inf.span); + self.write_ty_to_typeck_results(inf.hir_id, ty); + } + } +} + +impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> { + fn eval_closure_size(&mut self) { + let mut res: FxHashMap<LocalDefId, ClosureSizeProfileData<'tcx>> = Default::default(); + for (&closure_def_id, data) in self.fcx.typeck_results.borrow().closure_size_eval.iter() { + let closure_hir_id = self.tcx().hir().local_def_id_to_hir_id(closure_def_id); + + let data = self.resolve(*data, &closure_hir_id); + + res.insert(closure_def_id, data); + } + + self.typeck_results.closure_size_eval = res; + } + fn visit_min_capture_map(&mut self) { + let mut min_captures_wb = ty::MinCaptureInformationMap::with_capacity_and_hasher( + self.fcx.typeck_results.borrow().closure_min_captures.len(), + Default::default(), + ); + for (&closure_def_id, root_min_captures) in + self.fcx.typeck_results.borrow().closure_min_captures.iter() + { + let mut root_var_map_wb = ty::RootVariableMinCaptureList::with_capacity_and_hasher( + root_min_captures.len(), + Default::default(), + ); + for (var_hir_id, min_list) in root_min_captures.iter() { + let min_list_wb = min_list + .iter() + .map(|captured_place| { + let locatable = captured_place.info.path_expr_id.unwrap_or_else(|| { + self.tcx().hir().local_def_id_to_hir_id(closure_def_id) + }); + + self.resolve(captured_place.clone(), &locatable) + }) + .collect(); + root_var_map_wb.insert(*var_hir_id, min_list_wb); + } + min_captures_wb.insert(closure_def_id, root_var_map_wb); + } + + self.typeck_results.closure_min_captures = min_captures_wb; + } + + fn visit_fake_reads_map(&mut self) { + let mut resolved_closure_fake_reads: FxHashMap< + LocalDefId, + Vec<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>, + > = Default::default(); + for (&closure_def_id, fake_reads) in + self.fcx.typeck_results.borrow().closure_fake_reads.iter() + { + let mut resolved_fake_reads = Vec::<(HirPlace<'tcx>, FakeReadCause, hir::HirId)>::new(); + for (place, cause, hir_id) in fake_reads.iter() { + let locatable = self.tcx().hir().local_def_id_to_hir_id(closure_def_id); + + let resolved_fake_read = self.resolve(place.clone(), &locatable); + resolved_fake_reads.push((resolved_fake_read, *cause, *hir_id)); + } + resolved_closure_fake_reads.insert(closure_def_id, resolved_fake_reads); + } + self.typeck_results.closure_fake_reads = resolved_closure_fake_reads; + } + + fn visit_closures(&mut self) { + let fcx_typeck_results = self.fcx.typeck_results.borrow(); + assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner); + let common_hir_owner = fcx_typeck_results.hir_owner; + + for (id, origin) in fcx_typeck_results.closure_kind_origins().iter() { + let hir_id = hir::HirId { owner: common_hir_owner, local_id: *id }; + let place_span = origin.0; + let place = self.resolve(origin.1.clone(), &place_span); + self.typeck_results.closure_kind_origins_mut().insert(hir_id, (place_span, place)); + } + } + + fn visit_coercion_casts(&mut self) { + let fcx_typeck_results = self.fcx.typeck_results.borrow(); + let fcx_coercion_casts = fcx_typeck_results.coercion_casts(); + assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner); + + for local_id in fcx_coercion_casts { + self.typeck_results.set_coercion_cast(*local_id); + } + } + + fn visit_user_provided_tys(&mut self) { + let fcx_typeck_results = self.fcx.typeck_results.borrow(); + assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner); + let common_hir_owner = fcx_typeck_results.hir_owner; + + let mut errors_buffer = Vec::new(); + for (&local_id, c_ty) in fcx_typeck_results.user_provided_types().iter() { + let hir_id = hir::HirId { owner: common_hir_owner, local_id }; + + if cfg!(debug_assertions) && c_ty.needs_infer() { + span_bug!( + hir_id.to_span(self.fcx.tcx), + "writeback: `{:?}` has inference variables", + c_ty + ); + }; + + self.typeck_results.user_provided_types_mut().insert(hir_id, *c_ty); + + if let ty::UserType::TypeOf(_, user_substs) = c_ty.value { + if self.rustc_dump_user_substs { + // This is a unit-testing mechanism. + let span = self.tcx().hir().span(hir_id); + // We need to buffer the errors in order to guarantee a consistent + // order when emitting them. + let err = self + .tcx() + .sess + .struct_span_err(span, &format!("user substs: {:?}", user_substs)); + err.buffer(&mut errors_buffer); + } + } + } + + if !errors_buffer.is_empty() { + errors_buffer.sort_by_key(|diag| diag.span.primary_span()); + for mut diag in errors_buffer.drain(..) { + self.tcx().sess.diagnostic().emit_diagnostic(&mut diag); + } + } + } + + fn visit_user_provided_sigs(&mut self) { + let fcx_typeck_results = self.fcx.typeck_results.borrow(); + assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner); + + for (&def_id, c_sig) in fcx_typeck_results.user_provided_sigs.iter() { + if cfg!(debug_assertions) && c_sig.needs_infer() { + span_bug!( + self.fcx.tcx.hir().span_if_local(def_id).unwrap(), + "writeback: `{:?}` has inference variables", + c_sig + ); + }; + + self.typeck_results.user_provided_sigs.insert(def_id, *c_sig); + } + } + + fn visit_generator_interior_types(&mut self) { + let fcx_typeck_results = self.fcx.typeck_results.borrow(); + assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner); + self.typeck_results.generator_interior_types = + fcx_typeck_results.generator_interior_types.clone(); + } + + #[instrument(skip(self), level = "debug")] + fn visit_opaque_types(&mut self) { + let opaque_types = + self.fcx.infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types(); + for (opaque_type_key, decl) in opaque_types { + let hidden_type = match decl.origin { + hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_) => { + let ty = self.resolve(decl.hidden_type.ty, &decl.hidden_type.span); + struct RecursionChecker { + def_id: LocalDefId, + } + impl<'tcx> ty::TypeVisitor<'tcx> for RecursionChecker { + type BreakTy = (); + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + if let ty::Opaque(def_id, _) = *t.kind() { + if def_id == self.def_id.to_def_id() { + return ControlFlow::Break(()); + } + } + t.super_visit_with(self) + } + } + if ty + .visit_with(&mut RecursionChecker { def_id: opaque_type_key.def_id }) + .is_break() + { + return; + } + Some(ty) + } + hir::OpaqueTyOrigin::TyAlias => None, + }; + self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id, hidden_type); + } + } + + fn visit_field_id(&mut self, hir_id: hir::HirId) { + if let Some(index) = self.fcx.typeck_results.borrow_mut().field_indices_mut().remove(hir_id) + { + self.typeck_results.field_indices_mut().insert(hir_id, index); + } + } + + #[instrument(skip(self, span), level = "debug")] + fn visit_node_id(&mut self, span: Span, hir_id: hir::HirId) { + // Export associated path extensions and method resolutions. + if let Some(def) = + self.fcx.typeck_results.borrow_mut().type_dependent_defs_mut().remove(hir_id) + { + self.typeck_results.type_dependent_defs_mut().insert(hir_id, def); + } + + // Resolve any borrowings for the node with id `node_id` + self.visit_adjustments(span, hir_id); + + // Resolve the type of the node with id `node_id` + let n_ty = self.fcx.node_ty(hir_id); + let n_ty = self.resolve(n_ty, &span); + self.write_ty_to_typeck_results(hir_id, n_ty); + debug!(?n_ty); + + // Resolve any substitutions + if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) { + let substs = self.resolve(substs, &span); + debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs); + assert!(!substs.needs_infer() && !substs.has_placeholders()); + self.typeck_results.node_substs_mut().insert(hir_id, substs); + } + } + + #[instrument(skip(self, span), level = "debug")] + fn visit_adjustments(&mut self, span: Span, hir_id: hir::HirId) { + let adjustment = self.fcx.typeck_results.borrow_mut().adjustments_mut().remove(hir_id); + match adjustment { + None => { + debug!("no adjustments for node"); + } + + Some(adjustment) => { + let resolved_adjustment = self.resolve(adjustment, &span); + debug!(?resolved_adjustment); + self.typeck_results.adjustments_mut().insert(hir_id, resolved_adjustment); + } + } + } + + #[instrument(skip(self, span), level = "debug")] + fn visit_pat_adjustments(&mut self, span: Span, hir_id: hir::HirId) { + let adjustment = self.fcx.typeck_results.borrow_mut().pat_adjustments_mut().remove(hir_id); + match adjustment { + None => { + debug!("no pat_adjustments for node"); + } + + Some(adjustment) => { + let resolved_adjustment = self.resolve(adjustment, &span); + debug!(?resolved_adjustment); + self.typeck_results.pat_adjustments_mut().insert(hir_id, resolved_adjustment); + } + } + } + + fn visit_liberated_fn_sigs(&mut self) { + let fcx_typeck_results = self.fcx.typeck_results.borrow(); + assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner); + let common_hir_owner = fcx_typeck_results.hir_owner; + + for (&local_id, &fn_sig) in fcx_typeck_results.liberated_fn_sigs().iter() { + let hir_id = hir::HirId { owner: common_hir_owner, local_id }; + let fn_sig = self.resolve(fn_sig, &hir_id); + self.typeck_results.liberated_fn_sigs_mut().insert(hir_id, fn_sig); + } + } + + fn visit_fru_field_types(&mut self) { + let fcx_typeck_results = self.fcx.typeck_results.borrow(); + assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner); + let common_hir_owner = fcx_typeck_results.hir_owner; + + for (&local_id, ftys) in fcx_typeck_results.fru_field_types().iter() { + let hir_id = hir::HirId { owner: common_hir_owner, local_id }; + let ftys = self.resolve(ftys.clone(), &hir_id); + self.typeck_results.fru_field_types_mut().insert(hir_id, ftys); + } + } + + fn resolve<T>(&mut self, x: T, span: &dyn Locatable) -> T + where + T: TypeFoldable<'tcx>, + { + let mut resolver = Resolver::new(self.fcx, span, self.body); + let x = x.fold_with(&mut resolver); + if cfg!(debug_assertions) && x.needs_infer() { + span_bug!(span.to_span(self.fcx.tcx), "writeback: `{:?}` has inference variables", x); + } + + // We may have introduced e.g. `ty::Error`, if inference failed, make sure + // to mark the `TypeckResults` as tainted in that case, so that downstream + // users of the typeck results don't produce extra errors, or worse, ICEs. + if resolver.replaced_with_error { + // FIXME(eddyb) keep track of `ErrorGuaranteed` from where the error was emitted. + self.typeck_results.tainted_by_errors = + Some(ErrorGuaranteed::unchecked_claim_error_was_emitted()); + } + + x + } +} + +pub(crate) trait Locatable { + fn to_span(&self, tcx: TyCtxt<'_>) -> Span; +} + +impl Locatable for Span { + fn to_span(&self, _: TyCtxt<'_>) -> Span { + *self + } +} + +impl Locatable for hir::HirId { + fn to_span(&self, tcx: TyCtxt<'_>) -> Span { + tcx.hir().span(*self) + } +} + +/// The Resolver. This is the type folding engine that detects +/// unresolved types and so forth. +struct Resolver<'cx, 'tcx> { + tcx: TyCtxt<'tcx>, + infcx: &'cx InferCtxt<'cx, 'tcx>, + span: &'cx dyn Locatable, + body: &'tcx hir::Body<'tcx>, + + /// Set to `true` if any `Ty` or `ty::Const` had to be replaced with an `Error`. + replaced_with_error: bool, +} + +impl<'cx, 'tcx> Resolver<'cx, 'tcx> { + fn new( + fcx: &'cx FnCtxt<'cx, 'tcx>, + span: &'cx dyn Locatable, + body: &'tcx hir::Body<'tcx>, + ) -> Resolver<'cx, 'tcx> { + Resolver { tcx: fcx.tcx, infcx: fcx, span, body, replaced_with_error: false } + } + + fn report_type_error(&self, t: Ty<'tcx>) { + if !self.tcx.sess.has_errors().is_some() { + self.infcx + .emit_inference_failure_err( + Some(self.body.id()), + self.span.to_span(self.tcx), + t.into(), + E0282, + false, + ) + .emit(); + } + } + + fn report_const_error(&self, c: ty::Const<'tcx>) { + if self.tcx.sess.has_errors().is_none() { + self.infcx + .emit_inference_failure_err( + Some(self.body.id()), + self.span.to_span(self.tcx), + c.into(), + E0282, + false, + ) + .emit(); + } + } +} + +struct EraseEarlyRegions<'tcx> { + tcx: TyCtxt<'tcx>, +} + +impl<'tcx> TypeFolder<'tcx> for EraseEarlyRegions<'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { + self.tcx + } + fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { + if ty.has_type_flags(ty::TypeFlags::HAS_FREE_REGIONS) { + ty.super_fold_with(self) + } else { + ty + } + } + fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { + if r.is_late_bound() { r } else { self.tcx.lifetimes.re_erased } + } +} + +impl<'cx, 'tcx> TypeFolder<'tcx> for Resolver<'cx, 'tcx> { + fn tcx<'a>(&'a self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + match self.infcx.fully_resolve(t) { + Ok(t) => { + // Do not anonymize late-bound regions + // (e.g. keep `for<'a>` named `for<'a>`). + // This allows NLL to generate error messages that + // refer to the higher-ranked lifetime names written by the user. + EraseEarlyRegions { tcx: self.tcx }.fold_ty(t) + } + Err(_) => { + debug!("Resolver::fold_ty: input type `{:?}` not fully resolvable", t); + self.report_type_error(t); + self.replaced_with_error = true; + self.tcx().ty_error() + } + } + } + + fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { + debug_assert!(!r.is_late_bound(), "Should not be resolving bound region."); + self.tcx.lifetimes.re_erased + } + + fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { + match self.infcx.fully_resolve(ct) { + Ok(ct) => self.tcx.erase_regions(ct), + Err(_) => { + debug!("Resolver::fold_const: input const `{:?}` not fully resolvable", ct); + self.report_const_error(ct); + self.replaced_with_error = true; + self.tcx().const_error(ct.ty()) + } + } + } +} + +/////////////////////////////////////////////////////////////////////////// +// During type check, we store promises with the result of trait +// lookup rather than the actual results (because the results are not +// necessarily available immediately). These routines unwind the +// promises. It is expected that we will have already reported any +// errors that may be encountered, so if the promises store an error, +// a dummy result is returned. |