Normalize associated types in the type_is_newtype_immediate pass. Fixes #21010.

Author: nikomatsakis

src/librustc_trans/trans/common.rs

@@ -217,12 +217,15 @@ pub fn type_needs_drop<'tcx>(cx: &ty::ctxt<'tcx>,
     ty::type_contents(cx, ty).needs_drop(cx)
 }
 
-fn type_is_newtype_immediate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
-                                   ty: Ty<'tcx>) -> bool {
+fn type_is_newtype_immediate<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>, ty: Ty<'tcx>) -> bool {
     match ty.sty {
         ty::ty_struct(def_id, substs) => {
-            let fields = ty::struct_fields(ccx.tcx(), def_id, substs);
-            fields.len() == 1 && type_is_immediate(ccx, fields[0].mt.ty)
+            let fields = ty::lookup_struct_fields(ccx.tcx(), def_id);
+            fields.len() == 1 && {
+                let ty = ty::lookup_field_type(ccx.tcx(), def_id, fields[0].id, substs);
+                let ty = monomorphize::normalize_associated_type(ccx.tcx(), &ty);
+                type_is_immediate(ccx, ty)
+            }
         }
         _ => false
     }

src/test/run-pass/associated-types-normalize-unifield-struct.rs

@@ -0,0 +1,32 @@
+// 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.
+
+// Regression test for issue #21010: Normalize associated types in
+// various special paths in the `type_is_immediate` function.
+
+#![allow(unstable)]
+
+pub trait OffsetState: Sized {}
+pub trait Offset { type State: OffsetState; }
+
+#[derive(Copy)] pub struct X;
+impl Offset for X { type State = Y; }
+
+#[derive(Copy)] pub struct Y;
+impl OffsetState for Y {}
+
+pub fn now() -> DateTime<X> { from_utc(Y) }
+
+pub struct DateTime<Off: Offset> { pub offset: Off::State }
+pub fn from_utc<Off: Offset>(offset: Off::State) -> DateTime<Off> { DateTime { offset: offset } }
+
+pub fn main() {
+    let _x = now();
+}