make no_late_bound_regions a method on Binder<T>

Author: nikomatsakis

src/librustc/infer/outlives/implied_bounds.rs

@@ -126,7 +126,7 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
                     }
 
                     ty::Predicate::RegionOutlives(ref data) => {
-                        match tcx.no_late_bound_regions(data) {
+                        match data.no_late_bound_regions() {
                             None => vec![],
                             Some(ty::OutlivesPredicate(r_a, r_b)) => {
                                 vec![ImpliedBound::RegionSubRegion(r_b, r_a)]
@@ -135,7 +135,7 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
                     }
 
                     ty::Predicate::TypeOutlives(ref data) => {
-                        match tcx.no_late_bound_regions(data) {
+                        match data.no_late_bound_regions() {
                             None => vec![],
                             Some(ty::OutlivesPredicate(ty_a, r_b)) => {
                                 let ty_a = self.resolve_type_vars_if_possible(&ty_a);

src/librustc/infer/outlives/obligations.rs

@@ -604,7 +604,7 @@ impl<'cx, 'gcx, 'tcx> TypeOutlives<'cx, 'gcx, 'tcx> {
         predicates
             .into_iter()
             .filter_map(|p| p.as_ref().to_opt_type_outlives())
-            .filter_map(|p| self.tcx().no_late_bound_regions(&p))
+            .filter_map(|p| p.no_late_bound_regions())
             .filter(|p| p.0 == ty)
             .map(|p| p.1)
             .collect()

src/librustc/traits/fulfill.rs

@@ -400,14 +400,14 @@ fn process_predicate<'a, 'gcx, 'tcx>(
 
         ty::Predicate::TypeOutlives(ref binder) => {
             // Check if there are higher-ranked regions.
-            match selcx.tcx().no_late_bound_regions(binder) {
+            match binder.no_late_bound_regions() {
                 // If there are, inspect the underlying type further.
                 None => {
                     // Convert from `Binder<OutlivesPredicate<Ty, Region>>` to `Binder<Ty>`.
                     let binder = binder.map_bound_ref(|pred| pred.0);
 
                     // Check if the type has any bound regions.
-                    match selcx.tcx().no_late_bound_regions(&binder) {
+                    match binder.no_late_bound_regions() {
                         // If so, this obligation is an error (for now). Eventually we should be
                         // able to support additional cases here, like `for<'a> &'a str: 'a`.
                         None => {

src/librustc/traits/project.rs

@@ -1559,7 +1559,7 @@ impl<'cx, 'gcx, 'tcx> ProjectionCacheKey<'tcx> {
         let infcx = selcx.infcx();
         // We don't do cross-snapshot caching of obligations with escaping regions,
         // so there's no cache key to use
-        infcx.tcx.no_late_bound_regions(&predicate)
+        predicate.no_late_bound_regions()
             .map(|predicate| ProjectionCacheKey {
                 // We don't attempt to match up with a specific type-variable state
                 // from a specific call to `opt_normalize_projection_type` - if

src/librustc/traits/select.rs

@@ -1834,7 +1834,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         //     T: Trait
         // so it seems ok if we (conservatively) fail to accept that `Unsize`
         // obligation above. Should be possible to extend this in the future.
-        let source = match self.tcx().no_late_bound_regions(&obligation.self_ty()) {
+        let source = match obligation.self_ty().no_late_bound_regions() {
             Some(t) => t,
             None => {
                 // Don't add any candidates if there are bound regions.
@@ -2784,7 +2784,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         // assemble_candidates_for_unsizing should ensure there are no late bound
         // regions here. See the comment there for more details.
         let source = self.infcx.shallow_resolve(
-            tcx.no_late_bound_regions(&obligation.self_ty()).unwrap());
+            obligation.self_ty().no_late_bound_regions().unwrap());
         let target = obligation.predicate.skip_binder().trait_ref.substs.type_at(1);
         let target = self.infcx.shallow_resolve(target);
 

src/librustc/ty/fold.rs

@@ -364,16 +364,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         Binder(value)
     }
 
-    pub fn no_late_bound_regions<T>(self, value: &Binder<T>) -> Option<T>
-        where T : TypeFoldable<'tcx>
-    {
-        if value.0.has_escaping_regions() {
-            None
-        } else {
-            Some(value.0.clone())
-        }
-    }
-
     /// Returns a set of all late-bound regions that are constrained
     /// by `value`, meaning that if we instantiate those LBR with
     /// variables and equate `value` with something else, those

src/librustc/ty/sty.rs

@@ -680,6 +680,26 @@ impl<T> Binder<T> {
     {
         ty::Binder(f(self.0))
     }
+
+    /// Unwraps and returns the value within, but only if it contains
+    /// no bound regions at all. (In other words, if this binder --
+    /// and indeed any enclosing binder -- doesn't bind anything at
+    /// all.) Otherwise, returns `None`.
+    ///
+    /// (One could imagine having a method that just unwraps a single
+    /// binder, but permits late-bound regions bound by enclosing
+    /// binders, but that would require adjusting the debruijn
+    /// indices, and given the shallow binding structure we often use,
+    /// would not be that useful.)
+    pub fn no_late_bound_regions<'tcx>(self) -> Option<T>
+        where T : TypeFoldable<'tcx>
+    {
+        if self.skip_binder().has_escaping_regions() {
+            None
+        } else {
+            Some(self.skip_binder().clone())
+        }
+    }
 }
 
 /// Represents the projection of an associated type. In explicit UFCS

src/librustc_mir/shim.rs

@@ -833,7 +833,7 @@ pub fn build_adt_ctor<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
     let tcx = infcx.tcx;
     let gcx = tcx.global_tcx();
     let def_id = tcx.hir.local_def_id(ctor_id);
-    let sig = gcx.no_late_bound_regions(&gcx.fn_sig(def_id))
+    let sig = gcx.fn_sig(def_id).no_late_bound_regions()
         .expect("LBR in ADT constructor signature");
     let sig = gcx.erase_regions(&sig);
     let param_env = gcx.param_env(def_id);

src/librustc_mir/transform/lower_128bit.rs

@@ -144,7 +144,7 @@ fn check_lang_item_type<'a, 'tcx, D>(
 {
     let did = tcx.require_lang_item(lang_item);
     let poly_sig = tcx.fn_sig(did);
-    let sig = tcx.no_late_bound_regions(&poly_sig).unwrap();
+    let sig = poly_sig.no_late_bound_regions().unwrap();
     let lhs_ty = lhs.ty(local_decls, tcx);
     let rhs_ty = rhs.ty(local_decls, tcx);
     let place_ty = place.ty(local_decls, tcx).to_ty(tcx);

src/librustc_typeck/check/_match.rs

@@ -800,7 +800,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         let pat_ty = self.instantiate_value_path(segments, opt_ty, def, pat.span, pat.id);
         // Replace constructor type with constructed type for tuple struct patterns.
         let pat_ty = pat_ty.fn_sig(tcx).output();
-        let pat_ty = tcx.no_late_bound_regions(&pat_ty).expect("expected fn type");
+        let pat_ty = pat_ty.no_late_bound_regions().expect("expected fn type");
 
         self.demand_eqtype(pat.span, expected, pat_ty);