auto merge of #20955 : nikomatsakis/rust/assoc-types-struct-field-access, r=nick29581

Normalize the types of fields we project out of a struct or tuple struct.
Fixes #20954.

r? @nick29581

Author: bors

src/librustc/middle/traits/select.rs

@@ -1186,6 +1186,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                         .is_ok()
                 })
             }
+            (&BuiltinCandidate(_), &ParamCandidate(_)) => {
+                // If we have a where-clause like `Option<K> : Send`,
+                // then we wind up in a situation where there is a
+                // default rule (`Option<K>:Send if K:Send) and the
+                // where-clause that both seem applicable. Just take
+                // the where-clause in that case.
+                true
+            }
             (&ProjectionCandidate, &ParamCandidate(_)) => {
                 // FIXME(#20297) -- this gives where clauses precedent
                 // over projections. Really these are just two means

src/librustc_typeck/check/mod.rs

@@ -2289,6 +2289,34 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         obligations.map_move(|o| self.register_predicate(o));
     }
+
+    // Only for fields! Returns <none> for methods>
+    // Indifferent to privacy flags
+    pub fn lookup_field_ty(&self,
+                           span: Span,
+                           class_id: ast::DefId,
+                           items: &[ty::field_ty],
+                           fieldname: ast::Name,
+                           substs: &subst::Substs<'tcx>)
+                           -> Option<Ty<'tcx>>
+    {
+        let o_field = items.iter().find(|f| f.name == fieldname);
+        o_field.map(|f| ty::lookup_field_type(self.tcx(), class_id, f.id, substs))
+               .map(|t| self.normalize_associated_types_in(span, &t))
+    }
+
+    pub fn lookup_tup_field_ty(&self,
+                               span: Span,
+                               class_id: ast::DefId,
+                               items: &[ty::field_ty],
+                               idx: uint,
+                               substs: &subst::Substs<'tcx>)
+                               -> Option<Ty<'tcx>>
+    {
+        let o_field = if idx < items.len() { Some(&items[idx]) } else { None };
+        o_field.map(|f| ty::lookup_field_type(self.tcx(), class_id, f.id, substs))
+               .map(|t| self.normalize_associated_types_in(span, &t))
+    }
 }
 
 impl<'a, 'tcx> RegionScope for FnCtxt<'a, 'tcx> {
@@ -3043,30 +3071,6 @@ pub fn impl_self_ty<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
     TypeAndSubsts { substs: substs, ty: substd_ty }
 }
 
-// Only for fields! Returns <none> for methods>
-// Indifferent to privacy flags
-pub fn lookup_field_ty<'tcx>(tcx: &ty::ctxt<'tcx>,
-                             class_id: ast::DefId,
-                             items: &[ty::field_ty],
-                             fieldname: ast::Name,
-                             substs: &subst::Substs<'tcx>)
-                             -> Option<Ty<'tcx>> {
-
-    let o_field = items.iter().find(|f| f.name == fieldname);
-    o_field.map(|f| ty::lookup_field_type(tcx, class_id, f.id, substs))
-}
-
-pub fn lookup_tup_field_ty<'tcx>(tcx: &ty::ctxt<'tcx>,
-                                 class_id: ast::DefId,
-                                 items: &[ty::field_ty],
-                                 idx: uint,
-                                 substs: &subst::Substs<'tcx>)
-                                 -> Option<Ty<'tcx>> {
-
-    let o_field = if idx < items.len() { Some(&items[idx]) } else { None };
-    o_field.map(|f| ty::lookup_field_type(tcx, class_id, f.id, substs))
-}
-
 // Controls whether the arguments are automatically referenced. This is useful
 // for overloaded binary and unary operators.
 #[derive(Copy, PartialEq)]
@@ -3530,8 +3534,8 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
                     ty::ty_struct(base_id, substs) => {
                         debug!("struct named {}", ppaux::ty_to_string(tcx, base_t));
                         let fields = ty::lookup_struct_fields(tcx, base_id);
-                        lookup_field_ty(tcx, base_id, &fields[],
-                                        field.node.name, &(*substs))
+                        fcx.lookup_field_ty(expr.span, base_id, &fields[],
+                                            field.node.name, &(*substs))
                     }
                     _ => None
                 }
@@ -3593,8 +3597,8 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
                         if tuple_like {
                             debug!("tuple struct named {}", ppaux::ty_to_string(tcx, base_t));
                             let fields = ty::lookup_struct_fields(tcx, base_id);
-                            lookup_tup_field_ty(tcx, base_id, &fields[],
-                                                idx.node, &(*substs))
+                            fcx.lookup_tup_field_ty(expr.span, base_id, &fields[],
+                                                    idx.node, &(*substs))
                         } else {
                             None
                         }

src/test/run-pass/associated-types-struct-field-named.rs

@@ -0,0 +1,41 @@
+// Copyright 2015 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.
+
+// Test that we correctly normalize the type of a struct field
+// which has an associated type.
+
+pub trait UnifyKey {
+    type Value;
+}
+
+pub struct Node<K:UnifyKey> {
+    pub key: K,
+    pub value: K::Value,
+}
+
+fn foo<K : UnifyKey<Value=Option<V>>,V : Clone>(node: &Node<K>) -> Option<V> {
+    node.value.clone()
+}
+
+impl UnifyKey for i32 {
+    type Value = Option<u32>;
+}
+
+impl UnifyKey for u32 {
+    type Value = Option<i32>;
+}
+
+pub fn main() {
+    let node: Node<i32> = Node { key: 1, value: Some(22) };
+    assert_eq!(foo(&node), Some(22_u32));
+
+    let node: Node<u32> = Node { key: 1, value: Some(22) };
+    assert_eq!(foo(&node), Some(22_i32));
+}

src/test/run-pass/associated-types-struct-field-numbered.rs

@@ -0,0 +1,38 @@
+// Copyright 2015 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.
+
+// Test that we correctly normalize the type of a struct field
+// which has an associated type.
+
+pub trait UnifyKey {
+    type Value;
+}
+
+pub struct Node<K:UnifyKey>(K, K::Value);
+
+fn foo<K : UnifyKey<Value=Option<V>>,V : Clone>(node: &Node<K>) -> Option<V> {
+    node.1.clone()
+}
+
+impl UnifyKey for i32 {
+    type Value = Option<u32>;
+}
+
+impl UnifyKey for u32 {
+    type Value = Option<i32>;
+}
+
+pub fn main() {
+    let node: Node<i32> = Node(1, Some(22));
+    assert_eq!(foo(&node), Some(22_u32));
+
+    let node: Node<u32> = Node(1, Some(22));
+    assert_eq!(foo(&node), Some(22_i32));
+}

src/test/run-pass/trait-false-ambiguity-where-clause-builtin-bound.rs

@@ -0,0 +1,23 @@
+// Copyright 2015 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.
+
+// Test that we do not error out because of a (False) ambiguity
+// between the builtin rules for Sized and the where clause. Issue
+// #20959.
+
+fn foo<K>(x: Option<K>)
+    where Option<K> : Sized
+{
+    let _y = x;
+}
+
+fn main() {
+    foo(Some(22));
+}