Port existing callers of evaluate_obligation to the new canonical trait query

Except the one in coherence, which needs support for intercrate mode.

Author: aravind-pg

src/librustc/traits/coherence.rs

@@ -155,6 +155,9 @@ fn overlap<'cx, 'gcx, 'tcx>(selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
                                            predicate: p })
                      .chain(obligations)
                      .find(|o| !selcx.evaluate_obligation(o));
+    // FIXME: the call to `selcx.evaluate_obligation` above should be ported
+    // to the canonical trait query form, `infcx.predicate_may_hold`, once
+    // the new system supports intercrate mode (which coherence needs).
 
     if let Some(failing_obligation) = opt_failing_obligation {
         debug!("overlap: obligation unsatisfiable {:?}", failing_obligation);

src/librustc/traits/error_reporting.rs

@@ -660,8 +660,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                 predicate: ty::Predicate::Trait(predicate),
                                 .. obligation.clone()
                             };
-                            let mut selcx = SelectionContext::new(self);
-                            if selcx.evaluate_obligation(&unit_obligation) {
+                            if self.predicate_may_hold(&unit_obligation) {
                                 err.note("the trait is implemented for `()`. \
                                          Possibly this error has been caused by changes to \
                                          Rust's type-inference algorithm \
@@ -877,7 +876,6 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 .count();
 
             let mut trait_type = trait_ref.self_ty();
-            let mut selcx = SelectionContext::new(self);
 
             for refs_remaining in 0..refs_number {
                 if let ty::TypeVariants::TyRef(_, ty::TypeAndMut{ ty: t_type, mutbl: _ }) =
@@ -891,7 +889,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                                          obligation.param_env,
                                                          new_trait_ref.to_predicate());
 
-                    if selcx.evaluate_obligation(&new_obligation) {
+                    if self.predicate_may_hold(&new_obligation) {
                         let sp = self.tcx.sess.codemap()
                             .span_take_while(span, |c| c.is_whitespace() || *c == '&');
 
@@ -1327,7 +1325,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 cleaned_pred.to_predicate()
             );
 
-            selcx.evaluate_obligation(&obligation)
+            self.predicate_may_hold(&obligation)
         })
     }
 

src/librustc/traits/fulfill.rs

@@ -333,7 +333,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
             if data.is_global() {
                 // no type variables present, can use evaluation for better caching.
                 // FIXME: consider caching errors too.
-                if selcx.evaluate_obligation_conservatively(&obligation) {
+                if selcx.infcx().predicate_must_hold(&obligation) {
                     debug!("selecting trait `{:?}` at depth {} evaluated to holds",
                            data, obligation.recursion_depth);
                     return Ok(Some(vec![]))

src/librustc/traits/mod.rs

@@ -552,8 +552,7 @@ pub fn type_known_to_meet_bound<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx
         predicate: trait_ref.to_predicate(),
     };
 
-    let result = SelectionContext::new(infcx)
-        .evaluate_obligation_conservatively(&obligation);
+    let result = infcx.predicate_must_hold(&obligation);
     debug!("type_known_to_meet_ty={:?} bound={} => {:?}",
            ty, infcx.tcx.item_path_str(def_id), result);
 

src/librustc_typeck/check/autoderef.rs

@@ -120,15 +120,15 @@ impl<'a, 'gcx, 'tcx> Autoderef<'a, 'gcx, 'tcx> {
 
         let cause = traits::ObligationCause::misc(self.span, self.fcx.body_id);
 
-        let mut selcx = traits::SelectionContext::new(self.fcx);
         let obligation = traits::Obligation::new(cause.clone(),
                                                  self.fcx.param_env,
                                                  trait_ref.to_predicate());
-        if !selcx.evaluate_obligation(&obligation) {
+        if !self.fcx.predicate_may_hold(&obligation) {
             debug!("overloaded_deref_ty: cannot match obligation");
             return None;
         }
 
+        let mut selcx = traits::SelectionContext::new(self.fcx);
         let normalized = traits::normalize_projection_type(&mut selcx,
                                                            self.fcx.param_env,
                                                            ty::ProjectionTy::from_ref_and_name(

src/librustc_typeck/check/method/mod.rs

@@ -277,8 +277,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                      poly_trait_ref.to_predicate());
 
         // Now we want to know if this can be matched
-        let mut selcx = traits::SelectionContext::new(self);
-        if !selcx.evaluate_obligation(&obligation) {
+        if !self.predicate_may_hold(&obligation) {
             debug!("--> Cannot match obligation");
             return None; // Cannot be matched, no such method resolution is possible.
         }

src/librustc_typeck/check/method/probe.rs

@@ -1173,7 +1173,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                     let predicate = trait_ref.to_predicate();
                     let obligation =
                         traits::Obligation::new(cause.clone(), self.param_env, predicate);
-                    if !selcx.evaluate_obligation(&obligation) {
+                    if !self.predicate_may_hold(&obligation) {
                         if self.probe(|_| self.select_trait_candidate(trait_ref).is_err()) {
                             // This candidate's primary obligation doesn't even
                             // select - don't bother registering anything in
@@ -1201,7 +1201,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             // Evaluate those obligations to see if they might possibly hold.
             for o in candidate_obligations.into_iter().chain(sub_obligations) {
                 let o = self.resolve_type_vars_if_possible(&o);
-                if !selcx.evaluate_obligation(&o) {
+                if !self.predicate_may_hold(&o) {
                     result = ProbeResult::NoMatch;
                     if let &ty::Predicate::Trait(ref pred) = &o.predicate {
                         possibly_unsatisfied_predicates.push(pred.skip_binder().trait_ref);

src/librustc_typeck/check/method/suggest.rs

@@ -19,7 +19,7 @@ use hir::def::Def;
 use hir::def_id::{CRATE_DEF_INDEX, DefId};
 use middle::lang_items::FnOnceTraitLangItem;
 use namespace::Namespace;
-use rustc::traits::{Obligation, SelectionContext};
+use rustc::traits::Obligation;
 use util::nodemap::FxHashSet;
 
 use syntax::ast;
@@ -65,7 +65,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                              self.body_id,
                                              self.param_env,
                                              poly_trait_ref.to_predicate());
-                        SelectionContext::new(self).evaluate_obligation(&obligation)
+                        self.predicate_may_hold(&obligation)
                     })
                 })
             }

src/test/ui/impl-trait/auto-trait-leak.stderr

@@ -34,6 +34,7 @@ error[E0391]: cycle detected when processing `cycle1`
 LL | fn cycle1() -> impl Clone {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
 note: ...which requires processing `cycle2::{{impl-Trait}}`...
   --> $DIR/auto-trait-leak.rs:49:16
    |
@@ -44,6 +45,7 @@ note: ...which requires processing `cycle2`...
    |
 LL | fn cycle2() -> impl Clone {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^
+note: ...which requires evaluating trait selection obligation `impl std::clone::Clone: std::marker::Send`...
 note: ...which requires processing `cycle1::{{impl-Trait}}`...
   --> $DIR/auto-trait-leak.rs:42:16
    |