introduce infcx.at(..).normalize(..) operation [VIC]

It is backed by the new `normalize_projection_ty` query, which uses
canonicalization.

src/librustc/dep_graph/dep_node.rs

@@ -67,11 +67,12 @@ use hir::{HirId, ItemLocalId};
 
 use ich::{Fingerprint, StableHashingContext};
 use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
-use ty::{TyCtxt, Instance, InstanceDef, ParamEnv, ParamEnvAnd, PolyTraitRef, Ty};
-use ty::subst::Substs;
 use std::fmt;
 use std::hash::Hash;
 use syntax_pos::symbol::InternedString;
+use traits::query::CanonicalProjectionGoal;
+use ty::{TyCtxt, Instance, InstanceDef, ParamEnv, ParamEnvAnd, PolyTraitRef, Ty};
+use ty::subst::Substs;
 
 // erase!() just makes tokens go away. It's used to specify which macro argument
 // is repeated (i.e. which sub-expression of the macro we are in) but don't need
@@ -635,6 +636,7 @@ define_dep_nodes!( <'tcx>
     [] CompileCodegenUnit(InternedString),
     [input] OutputFilenames,
     [anon] NormalizeTy,
+    [] NormalizeProjectionTy(CanonicalProjectionGoal<'tcx>),
 
     [] SubstituteNormalizeAndTestPredicates { key: (DefId, &'tcx Substs<'tcx>) },
 

src/librustc/infer/at.rs

@@ -40,9 +40,9 @@ use super::*;
 use ty::relate::{Relate, TypeRelation};
 
 pub struct At<'a, 'gcx: 'tcx, 'tcx: 'a> {
-    infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
-    cause: &'a ObligationCause<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
+    pub infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+    pub cause: &'a ObligationCause<'tcx>,
+    pub param_env: ty::ParamEnv<'tcx>,
 }
 
 pub struct Trace<'a, 'gcx: 'tcx, 'tcx: 'a> {

src/librustc/infer/mod.rs

@@ -69,6 +69,7 @@ pub mod type_variable;
 pub mod unify_key;
 
 #[must_use]
+#[derive(Debug)]
 pub struct InferOk<'tcx, T> {
     pub value: T,
     pub obligations: PredicateObligations<'tcx>,
@@ -1224,6 +1225,16 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         self.borrow_region_constraints().take_and_reset_data()
     }
 
+    /// Gives temporary access to the region constraint data.
+    #[allow(non_camel_case_types)] // bug with impl trait
+    pub fn with_region_constraints<R>(
+        &self,
+        op: impl FnOnce(&RegionConstraintData<'tcx>) -> R,
+    ) -> R {
+        let region_constraints = self.borrow_region_constraints();
+        op(region_constraints.data())
+    }
+
     /// Takes ownership of the list of variable regions. This implies
     /// that all the region constriants have already been taken, and
     /// hence that `resolve_regions_and_report_errors` can never be

src/librustc/infer/outlives/obligations.rs

@@ -99,6 +99,16 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
             .push((body_id, obligation));
     }
 
+    /// Trait queries just want to pass back type obligations "as is"
+    pub fn take_registered_region_obligations(
+        &self,
+    ) -> Vec<(ast::NodeId, RegionObligation<'tcx>)> {
+        ::std::mem::replace(
+            &mut *self.region_obligations.borrow_mut(),
+            vec![],
+        )
+    }
+
     /// Process the region obligations that must be proven (during
     /// `regionck`) for the given `body_id`, given information about
     /// the region bounds in scope and so forth. This function must be

src/librustc/infer/region_constraints/mod.rs

@@ -350,6 +350,10 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
         mem::replace(data, RegionConstraintData::default())
     }
 
+    pub fn data(&self) -> &RegionConstraintData<'tcx> {
+        &self.data
+    }
+
     fn in_snapshot(&self) -> bool {
         !self.undo_log.is_empty()
     }

src/librustc/session/mod.rs

@@ -175,6 +175,11 @@ pub struct PerfStats {
     pub decode_def_path_tables_time: Cell<Duration>,
     /// Total number of values canonicalized queries constructed.
     pub queries_canonicalized: Cell<usize>,
+    /// Number of times we canonicalized a value and found that the
+    /// result had already been canonicalized.
+    pub canonicalized_values_allocated: Cell<usize>,
+    /// Number of times this query is invoked.
+    pub normalize_projection_ty: Cell<usize>,
 }
 
 /// Enum to support dispatch of one-time diagnostics (in Session.diag_once)
@@ -862,6 +867,10 @@ impl Session {
         );
         println!("Total queries canonicalized:                   {}",
                  self.perf_stats.queries_canonicalized.get());
+        println!("Total canonical values interned:               {}",
+                 self.perf_stats.canonicalized_values_allocated.get());
+        println!("normalize_projection_ty:                       {}",
+                 self.perf_stats.normalize_projection_ty.get());
     }
 
     /// We want to know if we're allowed to do an optimization for crate foo from -z fuel=foo=n.
@@ -1149,6 +1158,8 @@ pub fn build_session_(
             symbol_hash_time: Cell::new(Duration::from_secs(0)),
             decode_def_path_tables_time: Cell::new(Duration::from_secs(0)),
             queries_canonicalized: Cell::new(0),
+            canonicalized_values_allocated: Cell::new(0),
+            normalize_projection_ty: Cell::new(0),
         },
         code_stats: RefCell::new(CodeStats::new()),
         optimization_fuel_crate,

src/librustc/traits/mod.rs

@@ -63,6 +63,8 @@ mod structural_impls;
 pub mod trans;
 mod util;
 
+pub mod query;
+
 // Whether to enable bug compatibility with issue #43355
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub enum IntercrateMode {

src/librustc/traits/query/mod.rs

@@ -0,0 +1,31 @@
+// Copyright 2014 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.
+
+//! Experimental types for the trait query interface. The methods
+//! defined in this module are all based on **canonicalization**,
+//! which makes a canonical query by replacing unbound inference
+//! variables and regions, so that results can be reused more broadly.
+//! The providers for the queries defined here can be found in
+//! `librustc_traits`.
+
+use infer::canonical::Canonical;
+use ty;
+
+pub mod normalize;
+
+pub type CanonicalProjectionGoal<'tcx> =
+    Canonical<'tcx, ty::ParamEnvAnd<'tcx, ty::ProjectionTy<'tcx>>>;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub struct NoSolution;
+
+pub type Fallible<T> = Result<T, NoSolution>;
+
+impl_stable_hash_for!(struct NoSolution { });