Filter lifetimes from impl trait parent generics

src/librustc/ich/impls_ty.rs

@@ -345,6 +345,7 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for ty::Ge
             // Reverse map to each `TypeParameterDef`'s `index` field, from
             // `def_id.index` (`def_id.krate` is the same as the item's).
             type_param_to_index: _, // Don't hash this
+            region_param_to_index: _, // Don't hash this either
             has_self,
             has_late_bound_regions,
         } = *self;

src/librustc/ty/mod.rs

@@ -716,6 +716,10 @@ pub struct Generics {
     pub regions: Vec<RegionParameterDef>,
     pub types: Vec<TypeParameterDef>,
 
+    /// Reverse map to each `RegionParameterDef`'s `index` field.
+    /// Currently only appears for an `impl Trait` type's `ty::Generics`
+    pub region_param_to_index: Option<BTreeMap<DefIndex, u32>>,
+
     /// Reverse map to each `TypeParameterDef`'s `index` field, from
     /// `def_id.index` (`def_id.krate` is the same as the item's).
     pub type_param_to_index: BTreeMap<DefIndex, u32>,

src/librustc_typeck/astconv.rs

@@ -1078,6 +1078,54 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         }
     }
 
+    fn impl_trait_to_ty(&self, impl_trait_node: ast::NodeId) -> Ty<'tcx> {
+        let tcx = self.tcx();
+        let def_id = tcx.hir.local_def_id(impl_trait_node);
+        let generics = tcx.generics_of(def_id);
+        let type_param_to_index = &generics.type_param_to_index;
+        let region_param_to_index = if let Some(ref x) = generics.region_param_to_index {
+            x
+        } else {
+            bug!("missing region_param_to_index for `impl Trait` generics")
+        };
+        let param_count = type_param_to_index.len() + region_param_to_index.len();
+
+        // Filter the parent substs into just the ones that are relevant to us
+        let parent = tcx.hir.local_def_id(tcx.hir.get_parent(impl_trait_node));
+        let parent_substs = Substs::identity_for_item(tcx, parent);
+        let mut opt_substs: Vec<Option<Kind>> =
+            ::std::iter::repeat(None).take(param_count).collect();
+
+        let mut parent_id = Some(parent);
+        while let Some(cur_gen_id) = parent_id {
+            let cur_generics = tcx.generics_of(cur_gen_id);
+
+            for region in &cur_generics.regions {
+                if let Some(&new_index) = region_param_to_index.get(&region.def_id.index) {
+                    opt_substs[new_index as usize] = Some(parent_substs[region.index as usize]);
+                }
+            }
+            for type_ in &cur_generics.types {
+                if let Some(&new_index) = type_param_to_index.get(&type_.def_id.index) {
+                    opt_substs[new_index as usize] = Some(parent_substs[type_.index as usize]);
+                }
+            }
+
+            parent_id = cur_generics.parent;
+        }
+
+        let mut substs = Vec::with_capacity(param_count);
+        for opt_subst in opt_substs {
+            if let Some(subst) = opt_subst {
+                substs.push(subst);
+            } else {
+                bug!("missing `impl Trait` subst");
+            }
+        }
+
+        tcx.mk_anon(def_id, tcx.intern_substs(&substs))
+    }
+
     /// Parses the programmer's textual representation of a type into our
     /// internal notion of a type.
     pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
@@ -1154,8 +1202,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
 
                 // Create the anonymized type.
                 if allow {
-                    let def_id = tcx.hir.local_def_id(ast_ty.id);
-                    tcx.mk_anon(def_id, Substs::identity_for_item(tcx, def_id))
+                    self.impl_trait_to_ty(ast_ty.id)
                 } else {
                     span_err!(tcx.sess, ast_ty.span, E0562,
                               "`impl Trait` not allowed outside of function \

src/librustc_typeck/collect.rs

@@ -65,7 +65,7 @@ use rustc::ty::{ToPredicate, ReprOptions};
 use rustc::ty::{self, AdtKind, ToPolyTraitRef, Ty, TyCtxt};
 use rustc::ty::maps::Providers;
 use rustc::ty::util::IntTypeExt;
-use util::nodemap::FxHashMap;
+use util::nodemap::{DefIdSet, FxHashMap};
 
 use rustc_const_math::ConstInt;
 
@@ -76,7 +76,7 @@ use syntax::codemap::Spanned;
 use syntax::symbol::{Symbol, keywords};
 use syntax_pos::{Span, DUMMY_SP};
 
-use rustc::hir::{self, map as hir_map};
+use rustc::hir::{self, map as hir_map, Lifetime};
 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
 use rustc::hir::def::{Def, CtorKind};
 use rustc::hir::def_id::DefId;
@@ -863,6 +863,35 @@ fn has_late_bound_regions<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     }
 }
 
+struct ImplTraitRegionBoundsCollector<'a, 'tcx: 'a, 'b> {
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    region_bounds: &'b mut DefIdSet,
+}
+
+impl<'a, 'tcx: 'a, 'b> Visitor<'tcx> for ImplTraitRegionBoundsCollector<'a, 'tcx, 'b> {
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+        NestedVisitorMap::None
+    }
+
+    fn visit_lifetime(&mut self, lifetime: &'tcx Lifetime) {
+        if !lifetime.is_static() { // no need to look up the lifetime if we already know it's static
+            match self.tcx.named_region_map.defs.get(&lifetime.id) {
+                Some(&rl::Region::EarlyBound(_, id)) => {
+                    self.region_bounds.insert(self.tcx.hir.local_def_id(id));
+                }
+                Some(&rl::Region::LateBound(_, _)) |
+                Some(&rl::Region::LateBoundAnon(_, _)) => {
+                    span_bug!(lifetime.span,
+                        "Late-bound lifetimes not yet handed properly in `impl Trait`");
+                }
+                Some(&rl::Region::Static) |
+                Some(&rl::Region::Free(_, _)) |
+                None => {}
+            }
+        }
+    }
+}
+
 fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                          def_id: DefId)
                          -> &'tcx ty::Generics {
@@ -884,18 +913,6 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         NodeExpr(&hir::Expr { node: hir::ExprClosure(..), .. }) => {
             Some(tcx.closure_base_def_id(def_id))
         }
-        NodeTy(&hir::Ty { node: hir::TyImplTrait(..), .. }) => {
-            let mut parent_id = node_id;
-            loop {
-                match tcx.hir.get(parent_id) {
-                    NodeItem(_) | NodeImplItem(_) | NodeTraitItem(_) => break,
-                    _ => {
-                        parent_id = tcx.hir.get_parent_node(parent_id);
-                    }
-                }
-            }
-            Some(tcx.hir.local_def_id(parent_id))
-        }
         _ => None
     };
 
@@ -962,6 +979,67 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             }
         }
 
+        NodeTy(&hir::Ty{ node: hir::TyImplTrait(ref impl_trait_bounds), .. }) => {
+            // Traverse impl_trait_bounds to identify all of the region bounds that appear
+            // so that we can copy them from the environment
+            let mut region_bounds = DefIdSet();
+            {
+                let mut bounds_collector = ImplTraitRegionBoundsCollector {
+                    tcx: tcx,
+                    region_bounds: &mut region_bounds,
+                };
+                for bound in impl_trait_bounds {
+                    bounds_collector.visit_ty_param_bound(bound);
+                }
+            }
+
+            let mut regions = vec![];
+            let mut types = vec![];
+            let mut region_param_to_index = BTreeMap::new();
+            let mut type_param_to_index = BTreeMap::new();
+            let mut has_self = false;
+
+            // Copy generics from parents, filtering out unused region parameters
+            let mut parent_id = Some(tcx.hir.local_def_id(tcx.hir.get_parent(node_id)));
+            while let Some(cur_gen_id) = parent_id {
+                let cur_generics = tcx.generics_of(cur_gen_id);
+
+                has_self |= cur_generics.has_self;
+
+                for region in &cur_generics.regions {
+                    if region_bounds.contains(&region.def_id) {
+                        regions.push(*region);
+                    }
+                }
+
+                types.extend_from_slice(&cur_generics.types);
+
+                parent_id = cur_generics.parent;
+            }
+
+            // Fixup indices
+            for (i, ref mut region) in regions.iter_mut().enumerate() {
+                region.index = i as u32;
+                region_param_to_index.insert(region.def_id.index, region.index);
+            }
+            for (i, ref mut type_) in types.iter_mut().enumerate() {
+                type_.index = (regions.len() + i) as u32;
+                type_param_to_index.insert(type_.def_id.index, type_.index);
+            }
+
+            return tcx.alloc_generics(ty::Generics {
+                parent: None,
+                parent_regions: 0,
+                parent_types: 0,
+                regions: regions,
+                types: types,
+                region_param_to_index: Some(region_param_to_index),
+                type_param_to_index: type_param_to_index,
+                has_self: has_self,
+                has_late_bound_regions: None,
+            });
+        }
+
         _ => &no_generics
     };
 
@@ -1048,6 +1126,7 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         regions: regions,
         types: types,
         type_param_to_index: type_param_to_index,
+        region_param_to_index: None,
         has_self: has_self || parent_has_self,
         has_late_bound_regions: has_late_bound_regions(tcx, node),
     })

src/test/run-pass/impl-trait/example-st.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-test
+
 #![feature(conservative_impl_trait)]
 
 struct State;

src/test/run-pass/impl-trait/lifetime-generic-scoping.rs

@@ -0,0 +1,28 @@
+// Copyright 2017 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.
+
+#![feature(conservative_impl_trait)]
+
+use std::fmt::Debug;
+
+fn foo<'a>(x: &'a u32) -> impl Debug { *x }
+fn foo_elided(x: &u32) -> impl Debug { *x }
+
+fn main() {
+    // Make sure that the lifetime parameter of `foo` isn't included in `foo`'s return type:
+    let _ = {
+        let x = 5;
+        foo(&x)
+    };
+    let _ = {
+        let x = 5;
+        foo_elided(&x)
+    };
+}