Auto merge of #26354 - jroesch:remove-param-bounds-take-n, r=nikomatsakis

This pull request removes `ParamBounds` a old holdover in the type checker that we (@nikomatsakis and I) had wanted to remove. I'm not sure if the current form is the best possible refactor but I figured we can use this as a place to discuss it.

r? @nikomatsakis 

9 files changed, 100 insertions, 226 deletions

diff --git a/src/librustc/metadata/tydecode.rs b/src/librustc/metadata/tydecode.rs
index 693ccc13f1e..3907b0624b4 100644
--- a/src/librustc/metadata/tydecode.rs
+++ b/src/librustc/metadata/tydecode.rs
@@ -195,15 +195,6 @@ pub fn parse_substs_data<'tcx, F>(data: &[u8], crate_num: ast::CrateNum, pos: us
     parse_substs(&mut st, conv)
 }
 
-pub fn parse_bounds_data<'tcx, F>(data: &[u8], crate_num: ast::CrateNum,
-                                  pos: usize, tcx: &ty::ctxt<'tcx>, conv: F)
-                                  -> ty::ParamBounds<'tcx> where
-    F: FnMut(DefIdSource, ast::DefId) -> ast::DefId,
-{
-    let mut st = parse_state_from_data(data, crate_num, pos, tcx);
-    parse_bounds(&mut st, conv)
-}
-
 pub fn parse_existential_bounds_data<'tcx, F>(data: &[u8], crate_num: ast::CrateNum,
                                               pos: usize, tcx: &ty::ctxt<'tcx>, conv: F)
                                               -> ty::ExistentialBounds<'tcx> where
@@ -879,11 +870,23 @@ fn parse_existential_bounds_<'a,'tcx, F>(st: &mut PState<'a,'tcx>,
                                         -> ty::ExistentialBounds<'tcx> where
     F: FnMut(DefIdSource, ast::DefId) -> ast::DefId,
 {
-    let ty::ParamBounds { trait_bounds, mut region_bounds, builtin_bounds, projection_bounds } =
-         parse_bounds_(st, conv);
-    assert_eq!(region_bounds.len(), 1);
-    assert_eq!(trait_bounds.len(), 0);
-    let region_bound = region_bounds.pop().unwrap();
+    let builtin_bounds = parse_builtin_bounds_(st, conv);
+    let region_bound = parse_region_(st, conv);
+    let mut projection_bounds = Vec::new();
+
+    loop {
+        match next(st) {
+            'P' => {
+                projection_bounds.push(
+                    ty::Binder(parse_projection_predicate_(st, conv)));
+                }
+            '.' => { break; }
+            c => {
+                panic!("parse_bounds: bad bounds ('{}')", c)
+            }
+        }
+    }
+
     return ty::ExistentialBounds { region_bound: region_bound,
                                    builtin_bounds: builtin_bounds,
                                    projection_bounds: projection_bounds };
@@ -923,60 +926,3 @@ fn parse_builtin_bounds_<F>(st: &mut PState, _conv: &mut F) -> ty::BuiltinBounds
         }
     }
 }
-
-fn parse_bounds<'a, 'tcx, F>(st: &mut PState<'a, 'tcx>, mut conv: F)
-                             -> ty::ParamBounds<'tcx> where
-    F: FnMut(DefIdSource, ast::DefId) -> ast::DefId,
-{
-    parse_bounds_(st, &mut conv)
-}
-
-fn parse_bounds_<'a, 'tcx, F>(st: &mut PState<'a, 'tcx>, conv: &mut F)
-                              -> ty::ParamBounds<'tcx> where
-    F: FnMut(DefIdSource, ast::DefId) -> ast::DefId,
-{
-    let builtin_bounds = parse_builtin_bounds_(st, conv);
-
-    let region_bounds = parse_region_bounds_(st, conv);
-
-    let mut param_bounds = ty::ParamBounds {
-        region_bounds: region_bounds,
-        builtin_bounds: builtin_bounds,
-        trait_bounds: Vec::new(),
-        projection_bounds: Vec::new(),
-    };
-
-
-    loop {
-        match next(st) {
-            'I' => {
-                param_bounds.trait_bounds.push(
-                    ty::Binder(parse_trait_ref_(st, conv)));
-            }
-            'P' => {
-                param_bounds.projection_bounds.push(
-                    ty::Binder(parse_projection_predicate_(st, conv)));
-            }
-            '.' => {
-                return param_bounds;
-            }
-            c => {
-                panic!("parse_bounds: bad bounds ('{}')", c)
-            }
-        }
-    }
-}
-
-fn parse_region_bounds_<'a, 'tcx, F>(st: &mut PState<'a, 'tcx>, conv: &mut F)
-                              -> Vec<ty::Region> where
-    F: FnMut(DefIdSource, ast::DefId) -> ast::DefId,
-{
-    let mut region_bounds = Vec::new();
-    loop {
-        match next(st) {
-            'R' => { region_bounds.push(parse_region_(st, conv)); }
-            '.' => { return region_bounds; }
-            c => { panic!("parse_bounds: bad bounds ('{}')", c); }
-        }
-    }
-}
diff --git a/src/librustc/metadata/tyencode.rs b/src/librustc/metadata/tyencode.rs
index 72e96121a3a..c078b62dd2d 100644
--- a/src/librustc/metadata/tyencode.rs
+++ b/src/librustc/metadata/tyencode.rs
@@ -380,23 +380,9 @@ pub fn enc_builtin_bounds(w: &mut Encoder, _cx: &ctxt, bs: &ty::BuiltinBounds) {
 pub fn enc_existential_bounds<'a,'tcx>(w: &mut Encoder,
                                        cx: &ctxt<'a,'tcx>,
                                        bs: &ty::ExistentialBounds<'tcx>) {
-    let param_bounds = ty::ParamBounds { trait_bounds: vec!(),
-                                         region_bounds: vec!(bs.region_bound),
-                                         builtin_bounds: bs.builtin_bounds,
-                                         projection_bounds: bs.projection_bounds.clone() };
-    enc_bounds(w, cx, &param_bounds);
-}
-
-pub fn enc_bounds<'a, 'tcx>(w: &mut Encoder, cx: &ctxt<'a, 'tcx>,
-                            bs: &ty::ParamBounds<'tcx>) {
     enc_builtin_bounds(w, cx, &bs.builtin_bounds);
 
-    enc_region_bounds(w, cx, &bs.region_bounds);
-
-    for tp in &bs.trait_bounds {
-        mywrite!(w, "I");
-        enc_trait_ref(w, cx, tp.0);
-    }
+    enc_region(w, cx, bs.region_bound);
 
     for tp in &bs.projection_bounds {
         mywrite!(w, "P");
diff --git a/src/librustc/middle/implicator.rs b/src/librustc/middle/implicator.rs
index d26df43286d..bbfa3c9fdfa 100644
--- a/src/librustc/middle/implicator.rs
+++ b/src/librustc/middle/implicator.rs
@@ -13,7 +13,7 @@
 use middle::infer::{InferCtxt, GenericKind};
 use middle::subst::Substs;
 use middle::traits;
-use middle::ty::{self, RegionEscape, ToPolyTraitRef, Ty};
+use middle::ty::{self, RegionEscape, ToPolyTraitRef, AsPredicate, Ty};
 use middle::ty_fold::{TypeFoldable, TypeFolder};
 
 use syntax::ast;
@@ -444,13 +444,8 @@ pub fn object_region_bounds<'tcx>(
     let substs = tcx.mk_substs(principal.0.substs.with_self_ty(open_ty));
     let trait_refs = vec!(ty::Binder(ty::TraitRef::new(principal.0.def_id, substs)));
 
-    let param_bounds = ty::ParamBounds {
-        region_bounds: Vec::new(),
-        builtin_bounds: others,
-        trait_bounds: trait_refs,
-        projection_bounds: Vec::new(), // not relevant to computing region bounds
-    };
+    let mut predicates = others.to_predicates(tcx, open_ty);
+    predicates.extend(trait_refs.iter().map(|t| t.as_predicate()));
 
-    let predicates = ty::predicates(tcx, open_ty, &param_bounds);
     ty::required_region_bounds(tcx, open_ty, predicates)
 }
diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index 53851d0f2a4..e32da7837ec 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -1847,21 +1847,8 @@ pub enum type_err<'tcx> {
     terr_projection_bounds_length(expected_found<usize>),
 }
 
-/// Bounds suitable for a named type parameter like `A` in `fn foo<A>`
-/// as well as the existential type parameter in an object type.
-#[derive(PartialEq, Eq, Hash, Clone)]
-pub struct ParamBounds<'tcx> {
-    pub region_bounds: Vec<ty::Region>,
-    pub builtin_bounds: BuiltinBounds,
-    pub trait_bounds: Vec<PolyTraitRef<'tcx>>,
-    pub projection_bounds: Vec<PolyProjectionPredicate<'tcx>>,
-}
-
 /// Bounds suitable for an existentially quantified type parameter
-/// such as those that appear in object types or closure types. The
-/// major difference between this case and `ParamBounds` is that
-/// general purpose trait bounds are omitted and there must be
-/// *exactly one* region.
+/// such as those that appear in object types or closure types.
 #[derive(PartialEq, Eq, Hash, Clone)]
 pub struct ExistentialBounds<'tcx> {
     pub region_bound: ty::Region,
@@ -1873,13 +1860,24 @@ pub struct ExistentialBounds<'tcx> {
 pub struct BuiltinBounds(EnumSet<BuiltinBound>);
 
 impl BuiltinBounds {
-    pub fn empty() -> BuiltinBounds {
+       pub fn empty() -> BuiltinBounds {
         BuiltinBounds(EnumSet::new())
     }
 
     pub fn iter(&self) -> enum_set::Iter<BuiltinBound> {
         self.into_iter()
     }
+
+    pub fn to_predicates<'tcx>(&self,
+                               tcx: &ty::ctxt<'tcx>,
+                               self_ty: Ty<'tcx>) -> Vec<Predicate<'tcx>> {
+        self.iter().filter_map(|builtin_bound|
+            match traits::trait_ref_for_builtin_bound(tcx, builtin_bound, self_ty) {
+                Ok(trait_ref) => Some(trait_ref.as_predicate()),
+                Err(ErrorReported) => { None }
+            }
+        ).collect()
+    }
 }
 
 impl ops::Deref for BuiltinBounds {
@@ -3704,17 +3702,6 @@ impl<'tcx> ItemSubsts<'tcx> {
     }
 }
 
-impl<'tcx> ParamBounds<'tcx> {
-    pub fn empty() -> ParamBounds<'tcx> {
-        ParamBounds {
-            builtin_bounds: BuiltinBounds::empty(),
-            trait_bounds: Vec::new(),
-            region_bounds: Vec::new(),
-            projection_bounds: Vec::new(),
-        }
-    }
-}
-
 // Type utilities
 
 pub fn type_is_nil(ty: Ty) -> bool {
@@ -6143,39 +6130,6 @@ pub fn lookup_super_predicates<'tcx>(cx: &ctxt<'tcx>, did: ast::DefId)
         || csearch::get_super_predicates(cx, did))
 }
 
-pub fn predicates<'tcx>(
-    tcx: &ctxt<'tcx>,
-    param_ty: Ty<'tcx>,
-    bounds: &ParamBounds<'tcx>)
-    -> Vec<Predicate<'tcx>>
-{
-    let mut vec = Vec::new();
-
-    for builtin_bound in &bounds.builtin_bounds {
-        match traits::trait_ref_for_builtin_bound(tcx, builtin_bound, param_ty) {
-            Ok(trait_ref) => { vec.push(trait_ref.as_predicate()); }
-            Err(ErrorReported) => { }
-        }
-    }
-
-    for &region_bound in &bounds.region_bounds {
-        // account for the binder being introduced below; no need to shift `param_ty`
-        // because, at present at least, it can only refer to early-bound regions
-        let region_bound = ty_fold::shift_region(region_bound, 1);
-        vec.push(ty::Binder(ty::OutlivesPredicate(param_ty, region_bound)).as_predicate());
-    }
-
-    for bound_trait_ref in &bounds.trait_bounds {
-        vec.push(bound_trait_ref.as_predicate());
-    }
-
-    for projection in &bounds.projection_bounds {
-        vec.push(projection.as_predicate());
-    }
-
-    vec
-}
-
 /// Get the attributes of a definition.
 pub fn get_attrs<'tcx>(tcx: &'tcx ctxt, did: DefId)
                        -> Cow<'tcx, [ast::Attribute]> {
diff --git a/src/librustc/middle/ty_fold.rs b/src/librustc/middle/ty_fold.rs
index 63c46032479..fe89ca751e7 100644
--- a/src/librustc/middle/ty_fold.rs
+++ b/src/librustc/middle/ty_fold.rs
@@ -350,17 +350,6 @@ impl<'tcx> TypeFoldable<'tcx> for ty::ExistentialBounds<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for ty::ParamBounds<'tcx> {
-    fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::ParamBounds<'tcx> {
-        ty::ParamBounds {
-            region_bounds: self.region_bounds.fold_with(folder),
-            builtin_bounds: self.builtin_bounds.fold_with(folder),
-            trait_bounds: self.trait_bounds.fold_with(folder),
-            projection_bounds: self.projection_bounds.fold_with(folder),
-        }
-    }
-}
-
 impl<'tcx> TypeFoldable<'tcx> for ty::TypeParameterDef<'tcx> {
     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> ty::TypeParameterDef<'tcx> {
         ty::TypeParameterDef {
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 485d856ac25..0ae089df50d 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -347,23 +347,6 @@ impl fmt::Debug for subst::RegionSubsts {
     }
 }
 
-
-impl<'tcx> fmt::Debug for ty::ParamBounds<'tcx> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        try!(write!(f, "{:?}", self.builtin_bounds));
-        let mut bounds = self.trait_bounds.iter();
-        if self.builtin_bounds.is_empty() {
-            if let Some(bound) = bounds.next() {
-                try!(write!(f, "{:?}", bound));
-            }
-        }
-        for bound in bounds {
-            try!(write!(f, " + {:?}", bound));
-        }
-        Ok(())
-    }
-}
-
 impl<'tcx> fmt::Debug for ty::TraitRef<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         // when printing out the debug representation, we don't need
@@ -539,22 +522,6 @@ impl<'tcx> fmt::Debug for ty::MethodObject<'tcx> {
     }
 }
 
-impl<'tcx> fmt::Display for ty::ParamBounds<'tcx> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        try!(write!(f, "{}", self.builtin_bounds));
-        let mut bounds = self.trait_bounds.iter();
-        if self.builtin_bounds.is_empty() {
-            if let Some(bound) = bounds.next() {
-                try!(write!(f, "{}", bound));
-            }
-        }
-        for bound in bounds {
-            try!(write!(f, " + {}", bound));
-        }
-        Ok(())
-    }
-}
-
 impl<'tcx> fmt::Debug for ty::ExistentialBounds<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let mut empty = true;
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 5e434eae2b4..643c2273eb2 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -56,7 +56,8 @@ use middle::resolve_lifetime as rl;
 use middle::privacy::{AllPublic, LastMod};
 use middle::subst::{FnSpace, TypeSpace, SelfSpace, Subst, Substs};
 use middle::traits;
-use middle::ty::{self, RegionEscape, Ty};
+use middle::ty::{self, RegionEscape, Ty, AsPredicate};
+use middle::ty_fold;
 use rscope::{self, UnelidableRscope, RegionScope, ElidableRscope, ExplicitRscope,
              ObjectLifetimeDefaultRscope, ShiftedRscope, BindingRscope};
 use util::common::{ErrorReported, FN_OUTPUT_NAME};
@@ -2191,3 +2192,47 @@ fn report_lifetime_number_error(tcx: &ty::ctxt, span: Span, number: usize, expec
               "wrong number of lifetime parameters: expected {}, found {}",
               expected, number);
 }
+
+// A helper struct for conveniently grouping a set of bounds which we pass to
+// and return from functions in multiple places.
+#[derive(PartialEq, Eq, Clone, Debug)]
+pub struct Bounds<'tcx> {
+    pub region_bounds: Vec<ty::Region>,
+    pub builtin_bounds: ty::BuiltinBounds,
+    pub trait_bounds: Vec<ty::PolyTraitRef<'tcx>>,
+    pub projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
+}
+
+impl<'tcx> Bounds<'tcx> {
+    pub fn predicates(&self,
+        tcx: &ty::ctxt<'tcx>,
+        param_ty: Ty<'tcx>)
+        -> Vec<ty::Predicate<'tcx>>
+    {
+        let mut vec = Vec::new();
+
+        for builtin_bound in &self.builtin_bounds {
+            match traits::trait_ref_for_builtin_bound(tcx, builtin_bound, param_ty) {
+                Ok(trait_ref) => { vec.push(trait_ref.as_predicate()); }
+                Err(ErrorReported) => { }
+            }
+        }
+
+        for &region_bound in &self.region_bounds {
+            // account for the binder being introduced below; no need to shift `param_ty`
+            // because, at present at least, it can only refer to early-bound regions
+            let region_bound = ty_fold::shift_region(region_bound, 1);
+            vec.push(ty::Binder(ty::OutlivesPredicate(param_ty, region_bound)).as_predicate());
+        }
+
+        for bound_trait_ref in &self.trait_bounds {
+            vec.push(bound_trait_ref.as_predicate());
+        }
+
+        for projection in &self.projection_bounds {
+            vec.push(projection.as_predicate());
+        }
+
+        vec
+    }
+}
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 13d2cf25e06..22926126f7a 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -1178,9 +1178,13 @@ fn ensure_super_predicates_step(ccx: &CrateCtxt,
 
         // Convert the bounds that follow the colon, e.g. `Bar+Zed` in `trait Foo : Bar+Zed`.
         let self_param_ty = ty::mk_self_type(tcx);
-        let superbounds1 = compute_bounds(&ccx.icx(scope), self_param_ty, bounds,
-                                          SizedByDefault::No, item.span);
-        let superbounds1 = ty::predicates(tcx, self_param_ty, &superbounds1);
+        let superbounds1 = compute_bounds(&ccx.icx(scope),
+                                    self_param_ty,
+                                    bounds,
+                                    SizedByDefault::No,
+                                    item.span);
+
+        let superbounds1 = superbounds1.predicates(tcx, self_param_ty);
 
         // Convert any explicit superbounds in the where clause,
         // e.g. `trait Foo where Self : Bar`:
@@ -1395,7 +1399,7 @@ fn convert_trait_predicates<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>, it: &ast::Item)
                                         SizedByDefault::Yes,
                                         trait_item.span);
 
-            ty::predicates(ccx.tcx, assoc_ty, &bounds).into_iter()
+            bounds.predicates(ccx.tcx, assoc_ty).into_iter()
         }).collect()
     }
 }
@@ -1743,7 +1747,7 @@ fn ty_generic_predicates<'a,'tcx>(ccx: &CrateCtxt<'a,'tcx>,
                                     &param.bounds,
                                     SizedByDefault::Yes,
                                     param.span);
-        let predicates = ty::predicates(ccx.tcx, param_ty, &bounds);
+        let predicates = bounds.predicates(ccx.tcx, param_ty);
         result.predicates.extend(space, predicates.into_iter());
     }
 
@@ -1989,23 +1993,24 @@ fn compute_bounds<'tcx>(astconv: &AstConv<'tcx>,
                         ast_bounds: &[ast::TyParamBound],
                         sized_by_default: SizedByDefault,
                         span: Span)
-                        -> ty::ParamBounds<'tcx>
+                        -> astconv::Bounds<'tcx>
 {
-    let mut param_bounds = conv_param_bounds(astconv,
-                                             span,
-                                             param_ty,
-                                             ast_bounds);
+    let mut bounds =
+        conv_param_bounds(astconv,
+                          span,
+                          param_ty,
+                          ast_bounds);
 
     if let SizedByDefault::Yes = sized_by_default {
         add_unsized_bound(astconv,
-                          &mut param_bounds.builtin_bounds,
+                          &mut bounds.builtin_bounds,
                           ast_bounds,
                           span);
     }
 
-    param_bounds.trait_bounds.sort_by(|a,b| a.def_id().cmp(&b.def_id()));
+    bounds.trait_bounds.sort_by(|a,b| a.def_id().cmp(&b.def_id()));
 
-    param_bounds
+    bounds
 }
 
 /// Converts a specific TyParamBound from the AST into a set of
@@ -2055,7 +2060,7 @@ fn conv_param_bounds<'a,'tcx>(astconv: &AstConv<'tcx>,
                               span: Span,
                               param_ty: ty::Ty<'tcx>,
                               ast_bounds: &[ast::TyParamBound])
-                              -> ty::ParamBounds<'tcx>
+                              -> astconv::Bounds<'tcx>
 {
     let tcx = astconv.tcx();
     let astconv::PartitionedBounds {
@@ -2079,7 +2084,7 @@ fn conv_param_bounds<'a,'tcx>(astconv: &AstConv<'tcx>,
                      .map(|r| ast_region_to_region(tcx, r))
                      .collect();
 
-    ty::ParamBounds {
+    astconv::Bounds {
         region_bounds: region_bounds,
         builtin_bounds: builtin_bounds,
         trait_bounds: trait_bounds,
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index d40a9522f23..8ba4470c3ef 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -716,19 +716,6 @@ impl<'tcx> Clean<TyParamBound> for ty::TraitRef<'tcx> {
     }
 }
 
-impl<'tcx> Clean<Vec<TyParamBound>> for ty::ParamBounds<'tcx> {
-    fn clean(&self, cx: &DocContext) -> Vec<TyParamBound> {
-        let mut v = Vec::new();
-        for t in &self.trait_bounds {
-            v.push(t.clean(cx));
-        }
-        for r in self.region_bounds.iter().filter_map(|r| r.clean(cx)) {
-            v.push(RegionBound(r));
-        }
-        v
-    }
-}
-
 impl<'tcx> Clean<Option<Vec<TyParamBound>>> for subst::Substs<'tcx> {
     fn clean(&self, cx: &DocContext) -> Option<Vec<TyParamBound>> {
         let mut v = Vec::new();