Add deprecated versions of the old markers and integrate them back into the variance analysis.

Author: nikomatsakis

src/libcore/marker.rs

@@ -383,3 +383,40 @@ mod impls {
     unsafe impl<'a, T: Sync + ?Sized> Send for &'a T {}
     unsafe impl<'a, T: Send + ?Sized> Send for &'a mut T {}
 }
+
+/// Old-style marker trait. Deprecated.
+#[unstable(feature = "core", reason = "deprecated")]
+#[deprecated(since = "1.0.0", reason = "Replace with `PhantomData<&'a ()>`")]
+#[lang="contravariant_lifetime"]
+pub struct ContravariantLifetime<'a>;
+
+/// Old-style marker trait. Deprecated.
+#[unstable(feature = "core", reason = "deprecated")]
+#[deprecated(since = "1.0.0", reason = "Replace with `PhantomData<fn(&'a ())>`")]
+#[lang="covariant_lifetime"]
+pub struct CovariantLifetime<'a>;
+
+/// Old-style marker trait. Deprecated.
+#[unstable(feature = "core", reason = "deprecated")]
+#[deprecated(since = "1.0.0", reason = "Replace with `PhantomData<Cell<&'a ()>>`")]
+#[lang="invariant_lifetime"]
+pub struct InvariantLifetime<'a>;
+
+/// Old-style marker trait. Deprecated.
+#[unstable(feature = "core", reason = "deprecated")]
+#[deprecated(since = "1.0.0", reason = "Replace with `PhantomData<fn(T)>`")]
+#[lang="contravariant_type"]
+pub struct ContravariantType<T>;
+
+/// Old-style marker trait. Deprecated.
+#[unstable(feature = "core", reason = "deprecated")]
+#[deprecated(since = "1.0.0", reason = "Replace with `PhantomData<T>`")]
+#[lang="covariant_type"]
+#[cfg(not(stage0))]
+pub struct CovariantType<T>;
+
+/// Old-style marker trait. Deprecated.
+#[unstable(feature = "core", reason = "deprecated")]
+#[deprecated(since = "1.0.0", reason = "Replace with `PhantomData<Cell<T>>`")]
+#[lang="invariant_type"]
+pub struct InvariantType<T>;

src/librustc/middle/lang_items.rs

@@ -315,6 +315,14 @@ lets_do_this! {
     PhantomFnItem,                   "phantom_fn",              phantom_fn;
     PhantomDataItem,                 "phantom_data",            phantom_data;
 
+    // Deprecated:
+    CovariantTypeItem,               "covariant_type",          covariant_type;
+    ContravariantTypeItem,           "contravariant_type",      contravariant_type;
+    InvariantTypeItem,               "invariant_type",          invariant_type;
+    CovariantLifetimeItem,           "covariant_lifetime",      covariant_lifetime;
+    ContravariantLifetimeItem,       "contravariant_lifetime",  contravariant_lifetime;
+    InvariantLifetimeItem,           "invariant_lifetime",      invariant_lifetime;
+
     NoCopyItem,                      "no_copy_bound",           no_copy_bound;
     ManagedItem,                     "managed_bound",           managed_bound;
 

src/librustc_typeck/variance.rs

@@ -335,7 +335,17 @@ fn lang_items(tcx: &ty::ctxt) -> Vec<(ast::NodeId,Vec<ty::Variance>)> {
     let all = vec![
         (tcx.lang_items.phantom_fn(), vec![ty::Contravariant, ty::Covariant]),
         (tcx.lang_items.phantom_data(), vec![ty::Covariant]),
-        (tcx.lang_items.unsafe_cell_type(), vec![ty::Invariant])];
+        (tcx.lang_items.unsafe_cell_type(), vec![ty::Invariant]),
+
+        // Deprecated:
+        (tcx.lang_items.covariant_type(), vec![ty::Covariant]),
+        (tcx.lang_items.contravariant_type(), vec![ty::Contravariant]),
+        (tcx.lang_items.invariant_type(), vec![ty::Invariant]),
+        (tcx.lang_items.covariant_lifetime(), vec![ty::Covariant]),
+        (tcx.lang_items.contravariant_lifetime(), vec![ty::Contravariant]),
+        (tcx.lang_items.invariant_lifetime(), vec![ty::Invariant]),
+
+        ];
 
     all.into_iter()
        .filter(|&(ref d,_)| d.is_some())

src/test/compile-fail/variance-deprecated-markers.rs

@@ -0,0 +1,35 @@
+// 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 the deprecated markers still have their old effect.
+
+#![feature(rustc_attrs)]
+
+use std::marker;
+
+#[rustc_variance]
+struct A<T>(marker::CovariantType<T>); //~ ERROR types=[[+];[];[]]
+
+#[rustc_variance]
+struct B<T>(marker::ContravariantType<T>); //~ ERROR types=[[-];[];[]]
+
+#[rustc_variance]
+struct C<T>(marker::InvariantType<T>); //~ ERROR types=[[o];[];[]]
+
+#[rustc_variance]
+struct D<'a>(marker::CovariantLifetime<'a>); //~ ERROR regions=[[+];[];[]]
+
+#[rustc_variance]
+struct E<'a>(marker::ContravariantLifetime<'a>); //~ ERROR regions=[[-];[];[]]
+
+#[rustc_variance]
+struct F<'a>(marker::InvariantLifetime<'a>); //~ ERROR regions=[[o];[];[]]
+
+fn main() { }