Auto merge of #44857 - toidiu:ak-44493-empty-predicate, r=nikomatsakis

#44493 add structure for inferred_outlives_of

#44493

- add placeholder for the final implementation of inferred_outlives_of
- add some placeholder tests

src/librustc/dep_graph/dep_node.rs

@@ -476,6 +476,7 @@ define_dep_nodes!( <'tcx>
     [] TypeOfItem(DefId),
     [] GenericsOfItem(DefId),
     [] PredicatesOfItem(DefId),
+    [] InferredOutlivesOf(DefId),
     [] SuperPredicatesOfItem(DefId),
     [] TraitDefOfItem(DefId),
     [] AdtDefOfItem(DefId),

src/librustc/ty/maps/mod.rs

@@ -121,6 +121,9 @@ define_maps! { <'tcx>
     /// (inferred) variance.
     [] fn variances_of: ItemVariances(DefId) -> Rc<Vec<ty::Variance>>,
 
+    /// Maps from def-id of a type to its (inferred) outlives.
+    [] fn inferred_outlives_of: InferredOutlivesOf(DefId) -> Vec<ty::Predicate<'tcx>>,
+
     /// Maps from an impl/trait def-id to a list of the def-ids of its items
     [] fn associated_item_def_ids: AssociatedItemDefIds(DefId) -> Rc<Vec<DefId>>,
 

src/librustc/ty/maps/plumbing.rs

@@ -736,6 +736,7 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::TypeOfItem => { force!(type_of, def_id!()); }
         DepKind::GenericsOfItem => { force!(generics_of, def_id!()); }
         DepKind::PredicatesOfItem => { force!(predicates_of, def_id!()); }
+        DepKind::InferredOutlivesOf => { force!(inferred_outlives_of, def_id!()); }
         DepKind::SuperPredicatesOfItem => { force!(super_predicates_of, def_id!()); }
         DepKind::TraitDefOfItem => { force!(trait_def, def_id!()); }
         DepKind::AdtDefOfItem => { force!(adt_def, def_id!()); }

src/librustc_typeck/collect.rs

@@ -1332,7 +1332,11 @@ fn early_bound_lifetimes_from_generics<'a, 'tcx>(
 fn predicates_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                            def_id: DefId)
                            -> ty::GenericPredicates<'tcx> {
-    explicit_predicates_of(tcx, def_id)
+    let explicit = explicit_predicates_of(tcx, def_id);
+    ty::GenericPredicates {
+        parent: explicit.parent,
+        predicates: [&explicit.predicates[..], &tcx.inferred_outlives_of(def_id)[..]].concat()
+    }
 }
 
 fn explicit_predicates_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,

src/librustc_typeck/diagnostics.rs

@@ -4676,6 +4676,7 @@ register_diagnostics! {
     E0588, // packed struct cannot transitively contain a `[repr(align)]` struct
     E0592, // duplicate definitions with name `{}`
 //  E0613, // Removed (merged with E0609)
+    E0640, // infer outlives
     E0627, // yield statement outside of generator literal
     E0632, // cannot provide explicit type parameters when `impl Trait` is used in
            // argument position.

src/librustc_typeck/lib.rs

@@ -50,6 +50,8 @@ independently:
 
 - variance: variance inference
 
+- outlives: outlives inference
+
 - check: walks over function bodies and type checks them, inferring types for
   local variables, type parameters, etc as necessary.
 
@@ -122,6 +124,7 @@ mod collect;
 mod constrained_type_params;
 mod impl_wf_check;
 mod coherence;
+mod outlives;
 mod variance;
 mod namespace;
 
@@ -286,6 +289,7 @@ pub fn provide(providers: &mut Providers) {
     coherence::provide(providers);
     check::provide(providers);
     variance::provide(providers);
+    outlives::provide(providers);
 }
 
 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
@@ -301,6 +305,11 @@ pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
 
     })?;
 
+    tcx.sess.track_errors(|| {
+        time(time_passes, "outlives testing", ||
+            outlives::test::test_inferred_outlives(tcx));
+    })?;
+
     tcx.sess.track_errors(|| {
         time(time_passes, "impl wf inference", ||
              impl_wf_check::impl_wf_check(tcx));

src/librustc_typeck/outlives/mod.rs

@@ -0,0 +1,29 @@
+// Copyright 2013 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.
+
+use rustc::hir::def_id::DefId;
+use rustc::ty::{self, TyCtxt};
+use rustc::ty::maps::Providers;
+
+/// Code to write unit test for outlives.
+pub mod test;
+
+pub fn provide(providers: &mut Providers) {
+    *providers = Providers {
+        inferred_outlives_of,
+        ..*providers
+    };
+}
+
+//todo
+fn inferred_outlives_of<'a, 'tcx>(_tcx: TyCtxt<'a, 'tcx, 'tcx>, _def_id: DefId)
+                                  -> Vec<ty::Predicate<'tcx>> {
+    Vec::new()
+}

src/librustc_typeck/outlives/test.rs

@@ -0,0 +1,41 @@
+// Copyright 2013 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.
+
+use rustc::hir;
+use rustc::hir::itemlikevisit::ItemLikeVisitor;
+use rustc::ty::TyCtxt;
+
+pub fn test_inferred_outlives<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
+    tcx.hir.krate().visit_all_item_likes(&mut OutlivesTest { tcx });
+}
+
+struct OutlivesTest<'a, 'tcx: 'a> {
+    tcx: TyCtxt<'a, 'tcx, 'tcx>
+}
+
+impl<'a, 'tcx> ItemLikeVisitor<'tcx> for OutlivesTest<'a, 'tcx> {
+    fn visit_item(&mut self, item: &'tcx hir::Item) {
+        let item_def_id = self.tcx.hir.local_def_id(item.id);
+
+        // For unit testing: check for a special "rustc_outlives"
+        // attribute and report an error with various results if found.
+        if self.tcx.has_attr(item_def_id, "rustc_outlives") {
+            let inferred_outlives_of = self.tcx.inferred_outlives_of(item_def_id);
+            span_err!(self.tcx.sess,
+                      item.span,
+                      E0640,
+                      "{:?}",
+                      inferred_outlives_of);
+        }
+    }
+
+    fn visit_trait_item(&mut self, _: &'tcx hir::TraitItem) { }
+    fn visit_impl_item(&mut self, _: &'tcx hir::ImplItem) { }
+}

src/test/compile-fail/outlives-associated-types.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 the outlives computation runs for now...
+
+#![feature(rustc_attrs)]
+
+//todo add all the test cases
+// https://github.com/rust-lang/rfcs/blob/master/text/2093-infer-outlives.md#example-1-a-reference
+
+#[rustc_outlives]
+struct Direct<'a, T> { //~ ERROR 19:1: 21:2: [] [E0640]
+    field: &'a T
+}
+
+fn main() { }