| //! This calculates the types which has storage which lives across a suspension point in a |
| //! generator from the perspective of typeck. The actual types used at runtime |
| //! is calculated in `rustc_mir::transform::generator` and may be a subset of the |
| //! types computed here. |
| |
| use rustc::hir::def_id::DefId; |
| use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap}; |
| use rustc::hir::{self, Pat, PatKind, Expr}; |
| use rustc::middle::region::{self, YieldData}; |
| use rustc::ty::{self, Ty}; |
| use syntax_pos::Span; |
| use super::FnCtxt; |
| use crate::util::nodemap::FxHashMap; |
| |
| struct InteriorVisitor<'a, 'tcx> { |
| fcx: &'a FnCtxt<'a, 'tcx>, |
| types: FxHashMap<Ty<'tcx>, usize>, |
| region_scope_tree: &'tcx region::ScopeTree, |
| expr_count: usize, |
| kind: hir::GeneratorKind, |
| } |
| |
| impl<'a, 'tcx> InteriorVisitor<'a, 'tcx> { |
| fn record(&mut self, |
| ty: Ty<'tcx>, |
| scope: Option<region::Scope>, |
| expr: Option<&'tcx Expr>, |
| source_span: Span) { |
| use syntax_pos::DUMMY_SP; |
| |
| debug!("generator_interior: attempting to record type {:?} {:?} {:?} {:?}", |
| ty, scope, expr, source_span); |
| |
| |
| let live_across_yield = scope.map(|s| { |
| self.region_scope_tree.yield_in_scope(s).and_then(|yield_data| { |
| // If we are recording an expression that is the last yield |
| // in the scope, or that has a postorder CFG index larger |
| // than the one of all of the yields, then its value can't |
| // be storage-live (and therefore live) at any of the yields. |
| // |
| // See the mega-comment at `yield_in_scope` for a proof. |
| |
| debug!("comparing counts yield: {} self: {}, source_span = {:?}", |
| yield_data.expr_and_pat_count, self.expr_count, source_span); |
| |
| if yield_data.expr_and_pat_count >= self.expr_count { |
| Some(yield_data) |
| } else { |
| None |
| } |
| }) |
| }).unwrap_or_else(|| Some(YieldData { |
| span: DUMMY_SP, |
| expr_and_pat_count: 0, |
| source: match self.kind { // Guess based on the kind of the current generator. |
| hir::GeneratorKind::Gen => hir::YieldSource::Yield, |
| hir::GeneratorKind::Async => hir::YieldSource::Await, |
| }, |
| })); |
| |
| if let Some(yield_data) = live_across_yield { |
| let ty = self.fcx.resolve_vars_if_possible(&ty); |
| |
| debug!("type in expr = {:?}, scope = {:?}, type = {:?}, count = {}, yield_span = {:?}", |
| expr, scope, ty, self.expr_count, yield_data.span); |
| |
| if let Some((unresolved_type, unresolved_type_span)) = |
| self.fcx.unresolved_type_vars(&ty) |
| { |
| let note = format!("the type is part of the {} because of this {}", |
| self.kind, |
| yield_data.source); |
| |
| // If unresolved type isn't a ty_var then unresolved_type_span is None |
| self.fcx.need_type_info_err_in_generator( |
| self.kind, |
| unresolved_type_span.unwrap_or(source_span), |
| unresolved_type, |
| ) |
| .span_note(yield_data.span, &*note) |
| .emit(); |
| } else { |
| // Map the type to the number of types added before it |
| let entries = self.types.len(); |
| self.types.entry(&ty).or_insert(entries); |
| } |
| } else { |
| debug!("no type in expr = {:?}, count = {:?}, span = {:?}", |
| expr, self.expr_count, expr.map(|e| e.span)); |
| } |
| } |
| } |
| |
| pub fn resolve_interior<'a, 'tcx>( |
| fcx: &'a FnCtxt<'a, 'tcx>, |
| def_id: DefId, |
| body_id: hir::BodyId, |
| interior: Ty<'tcx>, |
| kind: hir::GeneratorKind, |
| ) { |
| let body = fcx.tcx.hir().body(body_id); |
| let mut visitor = InteriorVisitor { |
| fcx, |
| types: FxHashMap::default(), |
| region_scope_tree: fcx.tcx.region_scope_tree(def_id), |
| expr_count: 0, |
| kind, |
| }; |
| intravisit::walk_body(&mut visitor, body); |
| |
| // Check that we visited the same amount of expressions and the RegionResolutionVisitor |
| let region_expr_count = visitor.region_scope_tree.body_expr_count(body_id).unwrap(); |
| assert_eq!(region_expr_count, visitor.expr_count); |
| |
| let mut types: Vec<_> = visitor.types.drain().collect(); |
| |
| // Sort types by insertion order |
| types.sort_by_key(|t| t.1); |
| |
| // Extract type components |
| let type_list = fcx.tcx.mk_type_list(types.into_iter().map(|t| t.0)); |
| |
| // The types in the generator interior contain lifetimes local to the generator itself, |
| // which should not be exposed outside of the generator. Therefore, we replace these |
| // lifetimes with existentially-bound lifetimes, which reflect the exact value of the |
| // lifetimes not being known by users. |
| // |
| // These lifetimes are used in auto trait impl checking (for example, |
| // if a Sync generator contains an &'α T, we need to check whether &'α T: Sync), |
| // so knowledge of the exact relationships between them isn't particularly important. |
| |
| debug!("types in generator {:?}, span = {:?}", type_list, body.value.span); |
| |
| // Replace all regions inside the generator interior with late bound regions |
| // Note that each region slot in the types gets a new fresh late bound region, |
| // which means that none of the regions inside relate to any other, even if |
| // typeck had previously found constraints that would cause them to be related. |
| let mut counter = 0; |
| let type_list = fcx.tcx.fold_regions(&type_list, &mut false, |_, current_depth| { |
| counter += 1; |
| fcx.tcx.mk_region(ty::ReLateBound(current_depth, ty::BrAnon(counter))) |
| }); |
| |
| let witness = fcx.tcx.mk_generator_witness(ty::Binder::bind(type_list)); |
| |
| debug!("types in generator after region replacement {:?}, span = {:?}", |
| witness, body.value.span); |
| |
| // Unify the type variable inside the generator with the new witness |
| match fcx.at(&fcx.misc(body.value.span), fcx.param_env).eq(interior, witness) { |
| Ok(ok) => fcx.register_infer_ok_obligations(ok), |
| _ => bug!(), |
| } |
| } |
| |
| // This visitor has to have the same visit_expr calls as RegionResolutionVisitor in |
| // librustc/middle/region.rs since `expr_count` is compared against the results |
| // there. |
| impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> { |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| |
| fn visit_pat(&mut self, pat: &'tcx Pat) { |
| intravisit::walk_pat(self, pat); |
| |
| self.expr_count += 1; |
| |
| if let PatKind::Binding(..) = pat.node { |
| let scope = self.region_scope_tree.var_scope(pat.hir_id.local_id); |
| let ty = self.fcx.tables.borrow().pat_ty(pat); |
| self.record(ty, Some(scope), None, pat.span); |
| } |
| } |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr) { |
| intravisit::walk_expr(self, expr); |
| |
| self.expr_count += 1; |
| |
| let scope = self.region_scope_tree.temporary_scope(expr.hir_id.local_id); |
| |
| // Record the unadjusted type |
| let ty = self.fcx.tables.borrow().expr_ty(expr); |
| self.record(ty, scope, Some(expr), expr.span); |
| |
| // Also include the adjusted types, since these can result in MIR locals |
| for adjustment in self.fcx.tables.borrow().expr_adjustments(expr) { |
| self.record(adjustment.target, scope, Some(expr), expr.span); |
| } |
| } |
| } |