Auto merge of #44818 - petrochenkov:astymac2, r=jseyfried

Improve resolution of associated types in declarative macros 2.0

Make various identifier comparisons for associated types (and sometimes other associated items) hygienic.
Now declarative macros 2.0 can use `Self::AssocTy`, `TyParam::AssocTy`, `Trait<AssocTy = u8>` where `AssocTy` is an associated type of a trait `Trait` visible from the macro. Also, `Trait` can now be implemented inside the macro and specialization should work properly (fixes https://github.com/rust-lang/rust/pull/40847#issuecomment-310867299).

r? @jseyfried or @eddyb

src/librustc/traits/project.rs

@@ -29,7 +29,6 @@ use infer::{InferCtxt, InferOk};
 use infer::type_variable::TypeVariableOrigin;
 use middle::const_val::ConstVal;
 use rustc_data_structures::snapshot_map::{Snapshot, SnapshotMap};
-use syntax::ast;
 use syntax::symbol::Symbol;
 use ty::subst::{Subst, Substs};
 use ty::{self, ToPredicate, ToPolyTraitRef, Ty, TyCtxt};
@@ -1044,10 +1043,9 @@ fn assemble_candidates_from_impls<'cx, 'gcx, 'tcx>(
                 // In either case, we handle this by not adding a
                 // candidate for an impl if it contains a `default`
                 // type.
-                let item_name = selcx.tcx().associated_item(obligation.predicate.item_def_id).name;
                 let node_item = assoc_ty_def(selcx,
                                              impl_data.impl_def_id,
-                                             item_name);
+                                             obligation.predicate.item_def_id);
 
                 let is_default = if node_item.node.is_from_trait() {
                     // If true, the impl inherited a `type Foo = Bar`
@@ -1441,8 +1439,7 @@ fn confirm_impl_candidate<'cx, 'gcx, 'tcx>(
 
     let tcx = selcx.tcx();
     let param_env = obligation.param_env;
-    let assoc_ty = assoc_ty_def(selcx, impl_def_id,
-        tcx.associated_item(obligation.predicate.item_def_id).name);
+    let assoc_ty = assoc_ty_def(selcx, impl_def_id, obligation.predicate.item_def_id);
 
     let ty = if !assoc_ty.item.defaultness.has_value() {
         // This means that the impl is missing a definition for the
@@ -1471,10 +1468,11 @@ fn confirm_impl_candidate<'cx, 'gcx, 'tcx>(
 fn assoc_ty_def<'cx, 'gcx, 'tcx>(
     selcx: &SelectionContext<'cx, 'gcx, 'tcx>,
     impl_def_id: DefId,
-    assoc_ty_name: ast::Name)
+    assoc_ty_def_id: DefId)
     -> specialization_graph::NodeItem<ty::AssociatedItem>
 {
     let tcx = selcx.tcx();
+    let assoc_ty_name = tcx.associated_item(assoc_ty_def_id).name;
     let trait_def_id = tcx.impl_trait_ref(impl_def_id).unwrap().def_id;
     let trait_def = tcx.trait_def(trait_def_id);
 
@@ -1486,7 +1484,8 @@ fn assoc_ty_def<'cx, 'gcx, 'tcx>(
     // cycle error if the specialization graph is currently being built.
     let impl_node = specialization_graph::Node::Impl(impl_def_id);
     for item in impl_node.items(tcx) {
-        if item.kind == ty::AssociatedKind::Type && item.name == assoc_ty_name {
+        if item.kind == ty::AssociatedKind::Type &&
+                tcx.hygienic_eq(item.name, assoc_ty_name, trait_def_id) {
             return specialization_graph::NodeItem {
                 node: specialization_graph::Node::Impl(impl_def_id),
                 item,
@@ -1496,7 +1495,7 @@ fn assoc_ty_def<'cx, 'gcx, 'tcx>(
 
     if let Some(assoc_item) = trait_def
         .ancestors(tcx, impl_def_id)
-        .defs(tcx, assoc_ty_name, ty::AssociatedKind::Type)
+        .defs(tcx, assoc_ty_name, ty::AssociatedKind::Type, trait_def_id)
         .next() {
         assoc_item
     } else {

src/librustc/traits/specialize/mod.rs

@@ -125,7 +125,7 @@ pub fn find_associated_item<'a, 'tcx>(
     let trait_def = tcx.trait_def(trait_def_id);
 
     let ancestors = trait_def.ancestors(tcx, impl_data.impl_def_id);
-    match ancestors.defs(tcx, item.name, item.kind).next() {
+    match ancestors.defs(tcx, item.name, item.kind, trait_def_id).next() {
         Some(node_item) => {
             let substs = tcx.infer_ctxt().enter(|infcx| {
                 let param_env = ty::ParamEnv::empty(Reveal::All);

src/librustc/traits/specialize/specialization_graph.rs

@@ -346,11 +346,14 @@ impl<'a, 'gcx, 'tcx> Ancestors {
     /// Search the items from the given ancestors, returning each definition
     /// with the given name and the given kind.
     #[inline] // FIXME(#35870) Avoid closures being unexported due to impl Trait.
-    pub fn defs(self, tcx: TyCtxt<'a, 'gcx, 'tcx>, name: Name, kind: ty::AssociatedKind)
+    pub fn defs(self, tcx: TyCtxt<'a, 'gcx, 'tcx>, trait_item_name: Name,
+                trait_item_kind: ty::AssociatedKind, trait_def_id: DefId)
                 -> impl Iterator<Item = NodeItem<ty::AssociatedItem>> + 'a {
         self.flat_map(move |node| {
-            node.items(tcx).filter(move |item| item.kind == kind && item.name == name)
-                           .map(move |item| NodeItem { node: node, item: item })
+            node.items(tcx).filter(move |impl_item| {
+                impl_item.kind == trait_item_kind &&
+                tcx.hygienic_eq(impl_item.name, trait_item_name, trait_def_id)
+            }).map(move |item| NodeItem { node: node, item: item })
         })
     }
 }

src/librustc/ty/mod.rs

@@ -2345,6 +2345,13 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
+    // Hygienically compare a use-site name (`use_name`) for a field or an associated item with its
+    // supposed definition name (`def_name`). The method also needs `DefId` of the supposed
+    // definition's parent/scope to perform comparison.
+    pub fn hygienic_eq(self, use_name: Name, def_name: Name, def_parent_def_id: DefId) -> bool {
+        self.adjust(use_name, def_parent_def_id, DUMMY_NODE_ID).0 == def_name.to_ident()
+    }
+
     pub fn adjust(self, name: Name, scope: DefId, block: NodeId) -> (Ident, DefId) {
         self.adjust_ident(name.to_ident(), scope, block)
     }
@@ -2356,6 +2363,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         };
         let scope = match ident.ctxt.adjust(expansion) {
             Some(macro_def) => self.hir.definitions().macro_def_scope(macro_def),
+            None if block == DUMMY_NODE_ID => DefId::local(CRATE_DEF_INDEX), // Dummy DefId
             None => self.hir.get_module_parent(block),
         };
         (ident, scope)

src/librustc/ty/sty.rs

@@ -596,9 +596,10 @@ impl<'a, 'tcx> ProjectionTy<'tcx> {
     pub fn from_ref_and_name(
         tcx: TyCtxt, trait_ref: ty::TraitRef<'tcx>, item_name: Name
     ) -> ProjectionTy<'tcx> {
-        let item_def_id = tcx.associated_items(trait_ref.def_id).find(
-            |item| item.name == item_name && item.kind == ty::AssociatedKind::Type
-        ).unwrap().def_id;
+        let item_def_id = tcx.associated_items(trait_ref.def_id).find(|item| {
+            item.kind == ty::AssociatedKind::Type &&
+            tcx.hygienic_eq(item_name, item.name, trait_ref.def_id)
+        }).unwrap().def_id;
 
         ProjectionTy {
             substs: trait_ref.substs,

src/librustc_typeck/astconv.rs

@@ -356,9 +356,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
             // specify type to assert that error was already reported in Err case:
             let predicate: Result<_, ErrorReported> =
-                self.ast_type_binding_to_poly_projection_predicate(trait_ref.ref_id,
-                                                                   poly_trait_ref,
-                                                                   binding);
+                self.ast_type_binding_to_poly_projection_predicate(poly_trait_ref, binding);
             predicate.ok() // ok to ignore Err() because ErrorReported (see above)
         }));
 
@@ -423,13 +421,13 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                                            -> bool
     {
         self.tcx().associated_items(trait_def_id).any(|item| {
-            item.kind == ty::AssociatedKind::Type && item.name == assoc_name
+            item.kind == ty::AssociatedKind::Type &&
+            self.tcx().hygienic_eq(assoc_name, item.name, trait_def_id)
         })
     }
 
     fn ast_type_binding_to_poly_projection_predicate(
         &self,
-        _path_id: ast::NodeId,
         trait_ref: ty::PolyTraitRef<'tcx>,
         binding: &ConvertedBinding<'tcx>)
         -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
@@ -504,7 +502,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
 
         let candidate = self.one_bound_for_assoc_type(candidates,
                                                       &trait_ref.to_string(),
-                                                      &binding.item_name.as_str(),
+                                                      binding.item_name,
                                                       binding.span)?;
 
         Ok(candidate.map_bound(|trait_ref| {
@@ -702,7 +700,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         let param_name = tcx.hir.ty_param_name(param_node_id);
         self.one_bound_for_assoc_type(suitable_bounds,
                                       &param_name.as_str(),
-                                      &assoc_name.as_str(),
+                                      assoc_name,
                                       span)
     }
 
@@ -712,7 +710,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
     fn one_bound_for_assoc_type<I>(&self,
                                 mut bounds: I,
                                 ty_param_name: &str,
-                                assoc_name: &str,
+                                assoc_name: ast::Name,
                                 span: Span)
         -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
         where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
@@ -741,7 +739,8 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
 
             for bound in bounds {
                 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
-                    item.kind == ty::AssociatedKind::Type && item.name == assoc_name
+                    item.kind == ty::AssociatedKind::Type &&
+                    self.tcx().hygienic_eq(assoc_name, item.name, bound.def_id())
                 })
                 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
 
@@ -802,10 +801,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                     .filter(|r| self.trait_defines_associated_type_named(r.def_id(),
                                                                          assoc_name));
 
-                match self.one_bound_for_assoc_type(candidates,
-                                                    "Self",
-                                                    &assoc_name.as_str(),
-                                                    span) {
+                match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
                     Ok(bound) => bound,
                     Err(ErrorReported) => return (tcx.types.err, Def::Err),
                 }
@@ -830,14 +826,14 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         };
 
         let trait_did = bound.0.def_id;
-        let item = tcx.associated_items(trait_did).find(|i| i.name == assoc_name)
+        let (assoc_ident, def_scope) = tcx.adjust(assoc_name, trait_did, ref_id);
+        let item = tcx.associated_items(trait_did).find(|i| i.name.to_ident() == assoc_ident)
                                                   .expect("missing associated type");
 
         let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
         let ty = self.normalize_ty(span, ty);
 
         let def = Def::AssociatedTy(item.def_id);
-        let def_scope = tcx.adjust(assoc_name, item.container.id(), ref_id).1;
         if !item.vis.is_accessible_from(def_scope, tcx) {
             let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
             tcx.sess.span_err(span, &msg);

src/librustc_typeck/check/method/mod.rs

@@ -373,7 +373,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     /// and return it, or `None`, if no such item was defined there.
     pub fn associated_item(&self, def_id: DefId, item_name: ast::Name)
                            -> Option<ty::AssociatedItem> {
-        let ident = self.tcx.adjust(item_name, def_id, self.body_id).0;
-        self.tcx.associated_items(def_id).find(|item| item.name.to_ident() == ident)
+        self.tcx.associated_items(def_id)
+                .find(|item| self.tcx.hygienic_eq(item_name, item.name, def_id))
+
     }
 }

src/librustc_typeck/check/mod.rs

@@ -1248,6 +1248,7 @@ fn report_forbidden_specialization<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
 fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                            trait_def: &ty::TraitDef,
+                                           trait_item: &ty::AssociatedItem,
                                            impl_id: DefId,
                                            impl_item: &hir::ImplItem)
 {
@@ -1258,7 +1259,8 @@ fn check_specialization_validity<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         hir::ImplItemKind::Method(..) => ty::AssociatedKind::Method,
         hir::ImplItemKind::Type(_) => ty::AssociatedKind::Type
     };
-    let parent = ancestors.defs(tcx, impl_item.name, kind).skip(1).next()
+
+    let parent = ancestors.defs(tcx, trait_item.name, kind, trait_def.def_id).skip(1).next()
         .map(|node_item| node_item.map(|parent| parent.defaultness));
 
     if let Some(parent) = parent {
@@ -1290,7 +1292,7 @@ fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     for impl_item in impl_items() {
         let ty_impl_item = tcx.associated_item(tcx.hir.local_def_id(impl_item.id));
         let ty_trait_item = tcx.associated_items(impl_trait_ref.def_id)
-            .find(|ac| ac.name == ty_impl_item.name);
+            .find(|ac| tcx.hygienic_eq(ty_impl_item.name, ac.name, impl_trait_ref.def_id));
 
         // Check that impl definition matches trait definition
         if let Some(ty_trait_item) = ty_trait_item {
@@ -1371,9 +1373,9 @@ fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                     }
                 }
             }
-        }
 
-        check_specialization_validity(tcx, trait_def, impl_id, impl_item);
+            check_specialization_validity(tcx, trait_def, &ty_trait_item, impl_id, impl_item);
+        }
     }
 
     // Check for missing items from trait
@@ -1382,7 +1384,7 @@ fn check_impl_items_against_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let associated_type_overridden = overridden_associated_type.is_some();
     for trait_item in tcx.associated_items(impl_trait_ref.def_id) {
         let is_implemented = trait_def.ancestors(tcx, impl_id)
-            .defs(tcx, trait_item.name, trait_item.kind)
+            .defs(tcx, trait_item.name, trait_item.kind, impl_trait_ref.def_id)
             .next()
             .map(|node_item| !node_item.node.is_from_trait())
             .unwrap_or(false);

src/test/compile-fail/hygiene/assoc_item_ctxt.rs

@@ -0,0 +1,52 @@
+// 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.
+
+// ignore-pretty pretty-printing is unhygienic
+
+#![feature(decl_macro)]
+#![allow(unused)]
+
+mod ok {
+    macro mac_trait_item($method: ident) {
+        fn $method();
+    }
+
+    trait Tr {
+        mac_trait_item!(method);
+    }
+
+    macro mac_trait_impl() {
+        impl Tr for u8 { // OK
+            fn method() {} // OK
+        }
+    }
+
+    mac_trait_impl!();
+}
+
+mod error {
+    macro mac_trait_item() {
+        fn method();
+    }
+
+    trait Tr {
+        mac_trait_item!();
+    }
+
+    macro mac_trait_impl() {
+        impl Tr for u8 { //~ ERROR not all trait items implemented, missing: `method`
+            fn method() {} //~ ERROR method `method` is not a member of trait `Tr`
+        }
+    }
+
+    mac_trait_impl!();
+}
+
+fn main() {}

src/test/compile-fail/hygiene/assoc_ty_bindings.rs

@@ -0,0 +1,49 @@
+// 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.
+
+// ignore-pretty pretty-printing is unhygienic
+
+#![feature(decl_macro, associated_type_defaults)]
+#![feature(rustc_attrs)]
+
+trait Base {
+    type AssocTy;
+    fn f();
+}
+trait Derived: Base {
+    fn g();
+}
+
+macro mac() {
+    type A = Base<AssocTy = u8>;
+    type B = Derived<AssocTy = u8>;
+
+    impl Base for u8 {
+        type AssocTy = u8;
+        fn f() {
+            let _: Self::AssocTy;
+        }
+    }
+    impl Derived for u8 {
+        fn g() {
+            let _: Self::AssocTy;
+        }
+    }
+
+    fn h<T: Base, U: Derived>() {
+        let _: T::AssocTy;
+        let _: U::AssocTy;
+    }
+}
+
+mac!();
+
+#[rustc_error]
+fn main() {} //~ ERROR compilation successful

src/test/run-pass/hygiene/specialization.rs

@@ -0,0 +1,34 @@
+// 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.
+
+// ignore-pretty pretty-printing is unhygienic
+
+#![feature(decl_macro)]
+
+trait Tr {
+    fn f(&self) -> &'static str {
+        "This shouldn't happen"
+    }
+}
+
+pub macro m($t:ty) {
+    impl Tr for $t {
+        fn f(&self) -> &'static str {
+            "Run me"
+        }
+    }
+}
+
+struct S;
+m!(S);
+
+fn main() {
+    assert_eq!(S.f(), "Run me");
+}