Abstract away differences between Vec and ptr::P in HIR

17 files changed, 214 insertions, 184 deletions

diff --git a/src/librustc/middle/check_match.rs b/src/librustc/middle/check_match.rs
index ba4bdccb20b..cab7e45ee62 100644
--- a/src/librustc/middle/check_match.rs
+++ b/src/librustc/middle/check_match.rs
@@ -517,7 +517,7 @@ fn construct_witness<'a,'tcx>(cx: &MatchCheckCtxt<'a,'tcx>, ctor: &Constructor,
         ty::TyEnum(adt, _) | ty::TyStruct(adt, _)  => {
             let v = adt.variant_of_ctor(ctor);
             if let VariantKind::Struct = v.kind() {
-                let field_pats: Vec<_> = v.fields.iter()
+                let field_pats: hir::HirVec<_> = v.fields.iter()
                     .zip(pats)
                     .filter(|&(_, ref pat)| pat.node != hir::PatWild)
                     .map(|(field, pat)| Spanned {
@@ -540,14 +540,14 @@ fn construct_witness<'a,'tcx>(cx: &MatchCheckCtxt<'a,'tcx>, ctor: &Constructor,
                ty::TyArray(_, n) => match ctor {
                     &Single => {
                         assert_eq!(pats_len, n);
-                        hir::PatVec(pats.collect(), None, vec!())
+                        hir::PatVec(pats.collect(), None, hir::HirVec::new())
                     },
                     _ => unreachable!()
                 },
                 ty::TySlice(_) => match ctor {
                     &Slice(n) => {
                         assert_eq!(pats_len, n);
-                        hir::PatVec(pats.collect(), None, vec!())
+                        hir::PatVec(pats.collect(), None, hir::HirVec::new())
                     },
                     _ => unreachable!()
                 },
@@ -562,7 +562,7 @@ fn construct_witness<'a,'tcx>(cx: &MatchCheckCtxt<'a,'tcx>, ctor: &Constructor,
 
         ty::TyArray(_, len) => {
             assert_eq!(pats_len, len);
-            hir::PatVec(pats.collect(), None, vec![])
+            hir::PatVec(pats.collect(), None, hir::HirVec::new())
         }
 
         _ => {
diff --git a/src/librustc/middle/const_eval.rs b/src/librustc/middle/const_eval.rs
index f0cfd900fd7..fb471fb6aaa 100644
--- a/src/librustc/middle/const_eval.rs
+++ b/src/librustc/middle/const_eval.rs
@@ -357,14 +357,14 @@ pub fn const_expr_to_pat(tcx: &ty::ctxt, expr: &Expr, span: Span) -> P<hir::Pat>
 
         hir::ExprVec(ref exprs) => {
             let pats = exprs.iter().map(|expr| const_expr_to_pat(tcx, &**expr, span)).collect();
-            hir::PatVec(pats, None, vec![])
+            hir::PatVec(pats, None, hir::HirVec::new())
         }
 
         hir::ExprPath(_, ref path) => {
             let opt_def = tcx.def_map.borrow().get(&expr.id).map(|d| d.full_def());
             match opt_def {
                 Some(def::DefStruct(..)) =>
-                    hir::PatStruct(path.clone(), vec![], false),
+                    hir::PatStruct(path.clone(), hir::HirVec::new(), false),
                 Some(def::DefVariant(..)) =>
                     hir::PatEnum(path.clone(), None),
                 _ => {
diff --git a/src/librustc/middle/expr_use_visitor.rs b/src/librustc/middle/expr_use_visitor.rs
index 4861f0a6b64..73776304bc8 100644
--- a/src/librustc/middle/expr_use_visitor.rs
+++ b/src/librustc/middle/expr_use_visitor.rs
@@ -324,7 +324,7 @@ impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
         self.delegate.consume(consume_id, consume_span, cmt, mode);
     }
 
-    fn consume_exprs(&mut self, exprs: &Vec<P<hir::Expr>>) {
+    fn consume_exprs(&mut self, exprs: &[P<hir::Expr>]) {
         for expr in exprs {
             self.consume_expr(&**expr);
         }
@@ -651,7 +651,7 @@ impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
 
     fn walk_struct_expr(&mut self,
                         _expr: &hir::Expr,
-                        fields: &Vec<hir::Field>,
+                        fields: &[hir::Field],
                         opt_with: &Option<P<hir::Expr>>) {
         // Consume the expressions supplying values for each field.
         for field in fields {
@@ -697,7 +697,7 @@ impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
         self.walk_expr(with_expr);
 
         fn contains_field_named(field: ty::FieldDef,
-                                fields: &Vec<hir::Field>)
+                                fields: &[hir::Field])
                                 -> bool
         {
             fields.iter().any(
diff --git a/src/librustc/middle/infer/error_reporting.rs b/src/librustc/middle/infer/error_reporting.rs
index d5ecb3f2e86..2abf4991856 100644
--- a/src/librustc/middle/infer/error_reporting.rs
+++ b/src/librustc/middle/infer/error_reporting.rs
@@ -1254,7 +1254,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
         let mut lifetimes = Vec::new();
         for lt in add {
             lifetimes.push(hir::LifetimeDef { lifetime: *lt,
-                                              bounds: Vec::new() });
+                                              bounds: hir::HirVec::new() });
         }
         for lt in &generics.lifetimes {
             if keep.contains(&lt.lifetime.name) ||
@@ -1263,7 +1263,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
             }
         }
         hir::Generics {
-            lifetimes: lifetimes,
+            lifetimes: lifetimes.into(),
             ty_params: ty_params,
             where_clause: where_clause,
         }
@@ -1274,7 +1274,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
                        lifetime: hir::Lifetime,
                        anon_nums: &HashSet<u32>,
                        region_names: &HashSet<ast::Name>)
-                       -> Vec<hir::Arg> {
+                       -> hir::HirVec<hir::Arg> {
         let mut new_inputs = Vec::new();
         for arg in inputs {
             let new_ty = self.rebuild_arg_ty_or_output(&*arg.ty, lifetime,
@@ -1286,7 +1286,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
             };
             new_inputs.push(possibly_new_arg);
         }
-        new_inputs
+        new_inputs.into()
     }
 
     fn rebuild_output(&self, ty: &hir::FunctionRetTy,
@@ -1513,7 +1513,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
                     }
                 });
                 hir::AngleBracketedParameters(hir::AngleBracketedParameterData {
-                    lifetimes: new_lts,
+                    lifetimes: new_lts.into(),
                     types: new_types,
                     bindings: new_bindings,
                })
@@ -1529,7 +1529,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
         hir::Path {
             span: path.span,
             global: path.global,
-            segments: new_segs
+            segments: new_segs.into()
         }
     }
 }
diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs
index 89fa76f2fa7..9b133c54015 100644
--- a/src/librustc/middle/resolve_lifetime.rs
+++ b/src/librustc/middle/resolve_lifetime.rs
@@ -79,10 +79,10 @@ struct LifetimeContext<'a> {
 enum ScopeChain<'a> {
     /// EarlyScope(i, ['a, 'b, ...], s) extends s with early-bound
     /// lifetimes, assigning indexes 'a => i, 'b => i+1, ... etc.
-    EarlyScope(subst::ParamSpace, &'a Vec<hir::LifetimeDef>, Scope<'a>),
+    EarlyScope(subst::ParamSpace, &'a [hir::LifetimeDef], Scope<'a>),
     /// LateScope(['a, 'b, ...], s) extends s with late-bound
     /// lifetimes introduced by the declaration binder_id.
-    LateScope(&'a Vec<hir::LifetimeDef>, Scope<'a>),
+    LateScope(&'a [hir::LifetimeDef], Scope<'a>),
 
     /// lifetimes introduced by a fn are scoped to the call-site for that fn.
     FnScope { fn_id: ast::NodeId, body_id: ast::NodeId, s: Scope<'a> },
@@ -206,7 +206,7 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
                 // a trait ref, which introduces a binding scope.
                 match self.def_map.get(&ty.id).map(|d| (d.base_def, d.depth)) {
                     Some((def::DefTrait(..), 0)) => {
-                        self.with(LateScope(&Vec::new(), self.scope), |_, this| {
+                        self.with(LateScope(&[], self.scope), |_, this| {
                             this.visit_path(path, ty.id);
                         });
                     }
@@ -661,7 +661,7 @@ impl<'a> LifetimeContext<'a> {
                     lifetime_ref.name);
     }
 
-    fn check_lifetime_defs(&mut self, old_scope: Scope, lifetimes: &Vec<hir::LifetimeDef>) {
+    fn check_lifetime_defs(&mut self, old_scope: Scope, lifetimes: &[hir::LifetimeDef]) {
         for i in 0..lifetimes.len() {
             let lifetime_i = &lifetimes[i];
 
@@ -753,7 +753,7 @@ impl<'a> LifetimeContext<'a> {
     }
 }
 
-fn search_lifetimes<'a>(lifetimes: &'a Vec<hir::LifetimeDef>,
+fn search_lifetimes<'a>(lifetimes: &'a [hir::LifetimeDef],
                     lifetime_ref: &hir::Lifetime)
                     -> Option<(u32, &'a hir::Lifetime)> {
     for (i, lifetime_decl) in lifetimes.iter().enumerate() {
diff --git a/src/librustc/middle/stability.rs b/src/librustc/middle/stability.rs
index 8104d53fc93..a41ee51fb55 100644
--- a/src/librustc/middle/stability.rs
+++ b/src/librustc/middle/stability.rs
@@ -82,7 +82,7 @@ struct Annotator<'a, 'tcx: 'a> {
 impl<'a, 'tcx: 'a> Annotator<'a, 'tcx> {
     // Determine the stability for a node based on its attributes and inherited
     // stability. The stability is recorded in the index and used as the parent.
-    fn annotate<F>(&mut self, id: NodeId, attrs: &Vec<Attribute>,
+    fn annotate<F>(&mut self, id: NodeId, attrs: &[Attribute],
                    item_sp: Span, kind: AnnotationKind, visit_children: F)
         where F: FnOnce(&mut Annotator)
     {
diff --git a/src/librustc_front/fold.rs b/src/librustc_front/fold.rs
index 0978c3f78e8..784428cc114 100644
--- a/src/librustc_front/fold.rs
+++ b/src/librustc_front/fold.rs
@@ -34,7 +34,7 @@ pub trait Folder : Sized {
         noop_fold_crate(c, self)
     }
 
-    fn fold_meta_items(&mut self, meta_items: Vec<P<MetaItem>>) -> Vec<P<MetaItem>> {
+    fn fold_meta_items(&mut self, meta_items: HirVec<P<MetaItem>>) -> HirVec<P<MetaItem>> {
         noop_fold_meta_items(meta_items, self)
     }
 
@@ -198,11 +198,11 @@ pub trait Folder : Sized {
         noop_fold_variant_data(vdata, self)
     }
 
-    fn fold_lifetimes(&mut self, lts: Vec<Lifetime>) -> Vec<Lifetime> {
+    fn fold_lifetimes(&mut self, lts: HirVec<Lifetime>) -> HirVec<Lifetime> {
         noop_fold_lifetimes(lts, self)
     }
 
-    fn fold_lifetime_defs(&mut self, lts: Vec<LifetimeDef>) -> Vec<LifetimeDef> {
+    fn fold_lifetime_defs(&mut self, lts: HirVec<LifetimeDef>) -> HirVec<LifetimeDef> {
         noop_fold_lifetime_defs(lts, self)
     }
 
@@ -263,9 +263,9 @@ pub trait Folder : Sized {
     }
 }
 
-pub fn noop_fold_meta_items<T: Folder>(meta_items: Vec<P<MetaItem>>,
+pub fn noop_fold_meta_items<T: Folder>(meta_items: HirVec<P<MetaItem>>,
                                        fld: &mut T)
-                                       -> Vec<P<MetaItem>> {
+                                       -> HirVec<P<MetaItem>> {
     meta_items.move_map(|x| fld.fold_meta_item(x))
 }
 
@@ -304,7 +304,7 @@ pub fn noop_fold_view_path<T: Folder>(view_path: P<ViewPath>, fld: &mut T) -> P<
     })
 }
 
-pub fn fold_attrs<T: Folder>(attrs: Vec<Attribute>, fld: &mut T) -> Vec<Attribute> {
+pub fn fold_attrs<T: Folder>(attrs: HirVec<Attribute>, fld: &mut T) -> HirVec<Attribute> {
     attrs.move_flat_map(|x| fld.fold_attribute(x))
 }
 
@@ -477,7 +477,7 @@ pub fn noop_fold_local<T: Folder>(l: P<Local>, fld: &mut T) -> P<Local> {
             pat: fld.fold_pat(pat),
             init: init.map(|e| fld.fold_expr(e)),
             span: fld.new_span(span),
-            attrs: attrs.map_thin_attrs(|attrs| fold_attrs(attrs, fld)),
+            attrs: attrs.map_thin_attrs(|attrs| fold_attrs(attrs.into(), fld).into()),
         }
     })
 }
@@ -596,11 +596,13 @@ pub fn noop_fold_lifetime_def<T: Folder>(l: LifetimeDef, fld: &mut T) -> Lifetim
     }
 }
 
-pub fn noop_fold_lifetimes<T: Folder>(lts: Vec<Lifetime>, fld: &mut T) -> Vec<Lifetime> {
+pub fn noop_fold_lifetimes<T: Folder>(lts: HirVec<Lifetime>, fld: &mut T) -> HirVec<Lifetime> {
     lts.move_map(|l| fld.fold_lifetime(l))
 }
 
-pub fn noop_fold_lifetime_defs<T: Folder>(lts: Vec<LifetimeDef>, fld: &mut T) -> Vec<LifetimeDef> {
+pub fn noop_fold_lifetime_defs<T: Folder>(lts: HirVec<LifetimeDef>,
+                                          fld: &mut T)
+                                          -> HirVec<LifetimeDef> {
     lts.move_map(|l| fld.fold_lifetime_def(l))
 }
 
@@ -1139,7 +1141,7 @@ pub fn noop_fold_expr<T: Folder>(Expr { id, node, span, attrs }: Expr, folder: &
             }
         },
         span: folder.new_span(span),
-        attrs: attrs.map_thin_attrs(|attrs| fold_attrs(attrs, folder)),
+        attrs: attrs.map_thin_attrs(|attrs| fold_attrs(attrs.into(), folder).into()),
     }
 }
 
diff --git a/src/librustc_front/hir.rs b/src/librustc_front/hir.rs
index 1491ecc89af..6b2664af60b 100644
--- a/src/librustc_front/hir.rs
+++ b/src/librustc_front/hir.rs
@@ -40,7 +40,7 @@ use std::collections::BTreeMap;
 use syntax::codemap::{self, Span, Spanned, DUMMY_SP, ExpnId};
 use syntax::abi::Abi;
 use syntax::ast::{Name, NodeId, DUMMY_NODE_ID, TokenTree, AsmDialect};
-use syntax::ast::{Attribute, Lit, StrStyle, FloatTy, IntTy, UintTy, CrateConfig};
+use syntax::ast::{Attribute, Lit, StrStyle, FloatTy, IntTy, UintTy, MetaItem};
 use syntax::attr::ThinAttributes;
 use syntax::parse::token::InternedString;
 use syntax::ptr::P;
@@ -52,6 +52,22 @@ use std::fmt;
 use std::hash::{Hash, Hasher};
 use serialize::{Encodable, Decodable, Encoder, Decoder};
 
+/// HIR doesn't commit to a concrete storage type and have its own alias for a vector.
+/// It can be `Vec`, `P<[T]>` or potentially `Box<[T]>`, or some other container with similar
+/// behavior. Unlike AST, HIR is mostly a static structure, so we can use an owned slice instead
+/// of `Vec` to avoid keeping extra capacity.
+pub type HirVec<T> = Vec<T>;
+
+macro_rules! hir_vec {
+    ($elem:expr; $n:expr) => (
+        $crate::hir::HirVec::from(vec![$elem; $n])
+    );
+    ($($x:expr),*) => (
+        $crate::hir::HirVec::from(vec![$($x),*])
+    );
+    ($($x:expr,)*) => (vec![$($x),*])
+}
+
 /// Identifier in HIR
 #[derive(Clone, Copy, Eq)]
 pub struct Ident {
@@ -129,7 +145,7 @@ impl fmt::Debug for Lifetime {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct LifetimeDef {
     pub lifetime: Lifetime,
-    pub bounds: Vec<Lifetime>,
+    pub bounds: HirVec<Lifetime>,
 }
 
 /// A "Path" is essentially Rust's notion of a name; for instance:
@@ -142,7 +158,7 @@ pub struct Path {
     /// module (like paths in an import).
     pub global: bool,
     /// The segments in the path: the things separated by `::`.
-    pub segments: Vec<PathSegment>,
+    pub segments: HirVec<PathSegment>,
 }
 
 impl fmt::Debug for Path {
@@ -191,7 +207,7 @@ pub enum PathParameters {
 impl PathParameters {
     pub fn none() -> PathParameters {
         AngleBracketedParameters(AngleBracketedParameterData {
-            lifetimes: Vec::new(),
+            lifetimes: HirVec::new(),
             types: P::empty(),
             bindings: P::empty(),
         })
@@ -223,7 +239,7 @@ impl PathParameters {
 
     /// Returns the types that the user wrote. Note that these do not necessarily map to the type
     /// parameters in the parenthesized case.
-    pub fn types(&self) -> Vec<&P<Ty>> {
+    pub fn types(&self) -> HirVec<&P<Ty>> {
         match *self {
             AngleBracketedParameters(ref data) => {
                 data.types.iter().collect()
@@ -237,24 +253,24 @@ impl PathParameters {
         }
     }
 
-    pub fn lifetimes(&self) -> Vec<&Lifetime> {
+    pub fn lifetimes(&self) -> HirVec<&Lifetime> {
         match *self {
             AngleBracketedParameters(ref data) => {
                 data.lifetimes.iter().collect()
             }
             ParenthesizedParameters(_) => {
-                Vec::new()
+                HirVec::new()
             }
         }
     }
 
-    pub fn bindings(&self) -> Vec<&TypeBinding> {
+    pub fn bindings(&self) -> HirVec<&TypeBinding> {
         match *self {
             AngleBracketedParameters(ref data) => {
                 data.bindings.iter().collect()
             }
             ParenthesizedParameters(_) => {
-                Vec::new()
+                HirVec::new()
             }
         }
     }
@@ -264,7 +280,7 @@ impl PathParameters {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct AngleBracketedParameterData {
     /// The lifetime parameters for this path segment.
-    pub lifetimes: Vec<Lifetime>,
+    pub lifetimes: HirVec<Lifetime>,
     /// The type parameters for this path segment, if present.
     pub types: P<[P<Ty>]>,
     /// Bindings (equality constraints) on associated types, if present.
@@ -285,7 +301,7 @@ pub struct ParenthesizedParameterData {
     pub span: Span,
 
     /// `(A,B)`
-    pub inputs: Vec<P<Ty>>,
+    pub inputs: HirVec<P<Ty>>,
 
     /// `C`
     pub output: Option<P<Ty>>,
@@ -324,7 +340,7 @@ pub struct TyParam {
 /// of a function, enum, trait, etc.
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct Generics {
-    pub lifetimes: Vec<LifetimeDef>,
+    pub lifetimes: HirVec<LifetimeDef>,
     pub ty_params: P<[TyParam]>,
     pub where_clause: WhereClause,
 }
@@ -345,7 +361,7 @@ impl Generics {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct WhereClause {
     pub id: NodeId,
-    pub predicates: Vec<WherePredicate>,
+    pub predicates: HirVec<WherePredicate>,
 }
 
 /// A single predicate in a `where` clause
@@ -364,7 +380,7 @@ pub enum WherePredicate {
 pub struct WhereBoundPredicate {
     pub span: Span,
     /// Any lifetimes from a `for` binding
-    pub bound_lifetimes: Vec<LifetimeDef>,
+    pub bound_lifetimes: HirVec<LifetimeDef>,
     /// The type being bounded
     pub bounded_ty: P<Ty>,
     /// Trait and lifetime bounds (`Clone+Send+'static`)
@@ -376,7 +392,7 @@ pub struct WhereBoundPredicate {
 pub struct WhereRegionPredicate {
     pub span: Span,
     pub lifetime: Lifetime,
-    pub bounds: Vec<Lifetime>,
+    pub bounds: HirVec<Lifetime>,
 }
 
 /// An equality predicate (unsupported), e.g. `T=int`
@@ -388,13 +404,15 @@ pub struct WhereEqPredicate {
     pub ty: P<Ty>,
 }
 
+pub type CrateConfig = HirVec<P<MetaItem>>;
+
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug)]
 pub struct Crate {
     pub module: Mod,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
     pub config: CrateConfig,
     pub span: Span,
-    pub exported_macros: Vec<MacroDef>,
+    pub exported_macros: HirVec<MacroDef>,
 
     // NB: We use a BTreeMap here so that `visit_all_items` iterates
     // over the ids in increasing order. In principle it should not
@@ -431,20 +449,20 @@ impl Crate {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct MacroDef {
     pub name: Name,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
     pub id: NodeId,
     pub span: Span,
     pub imported_from: Option<Name>,
     pub export: bool,
     pub use_locally: bool,
     pub allow_internal_unstable: bool,
-    pub body: Vec<TokenTree>,
+    pub body: HirVec<TokenTree>,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct Block {
     /// Statements in a block
-    pub stmts: Vec<Stmt>,
+    pub stmts: HirVec<Stmt>,
     /// An expression at the end of the block
     /// without a semicolon, if any
     pub expr: Option<P<Expr>>,
@@ -503,7 +521,7 @@ pub enum Pat_ {
     PatIdent(BindingMode, Spanned<Ident>, Option<P<Pat>>),
 
     /// "None" means a `Variant(..)` pattern where we don't bind the fields to names.
-    PatEnum(Path, Option<Vec<P<Pat>>>),
+    PatEnum(Path, Option<HirVec<P<Pat>>>),
 
     /// An associated const named using the qualified path `<T>::CONST` or
     /// `<T as Trait>::CONST`. Associated consts from inherent impls can be
@@ -513,9 +531,9 @@ pub enum Pat_ {
 
     /// Destructuring of a struct, e.g. `Foo {x, y, ..}`
     /// The `bool` is `true` in the presence of a `..`
-    PatStruct(Path, Vec<Spanned<FieldPat>>, bool),
+    PatStruct(Path, HirVec<Spanned<FieldPat>>, bool),
     /// A tuple pattern `(a, b)`
-    PatTup(Vec<P<Pat>>),
+    PatTup(HirVec<P<Pat>>),
     /// A `box` pattern
     PatBox(P<Pat>),
     /// A reference pattern, e.g. `&mut (a, b)`
@@ -526,7 +544,7 @@ pub enum Pat_ {
     PatRange(P<Expr>, P<Expr>),
     /// `[a, b, ..i, y, z]` is represented as:
     ///     `PatVec(box [a, b], Some(i), box [y, z])`
-    PatVec(Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>),
+    PatVec(HirVec<P<Pat>>, Option<P<Pat>>, HirVec<P<Pat>>),
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
@@ -640,8 +658,8 @@ pub enum Decl_ {
 /// represents one arm of a 'match'
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct Arm {
-    pub attrs: Vec<Attribute>,
-    pub pats: Vec<P<Pat>>,
+    pub attrs: HirVec<Attribute>,
+    pub pats: HirVec<P<Pat>>,
     pub guard: Option<P<Expr>>,
     pub body: P<Expr>,
 }
@@ -690,12 +708,12 @@ pub enum Expr_ {
     /// A `box x` expression.
     ExprBox(P<Expr>),
     /// An array (`[a, b, c, d]`)
-    ExprVec(Vec<P<Expr>>),
+    ExprVec(HirVec<P<Expr>>),
     /// A function call
     ///
     /// The first field resolves to the function itself,
     /// and the second field is the list of arguments
-    ExprCall(P<Expr>, Vec<P<Expr>>),
+    ExprCall(P<Expr>, HirVec<P<Expr>>),
     /// A method call (`x.foo::<Bar, Baz>(a, b, c, d)`)
     ///
     /// The `Spanned<Name>` is the identifier for the method name.
@@ -708,9 +726,9 @@ pub enum Expr_ {
     ///
     /// Thus, `x.foo::<Bar, Baz>(a, b, c, d)` is represented as
     /// `ExprMethodCall(foo, [Bar, Baz], [x, a, b, c, d])`.
-    ExprMethodCall(Spanned<Name>, Vec<P<Ty>>, Vec<P<Expr>>),
+    ExprMethodCall(Spanned<Name>, HirVec<P<Ty>>, HirVec<P<Expr>>),
     /// A tuple (`(a, b, c ,d)`)
-    ExprTup(Vec<P<Expr>>),
+    ExprTup(HirVec<P<Expr>>),
     /// A binary operation (For example: `a + b`, `a * b`)
     ExprBinary(BinOp, P<Expr>, P<Expr>),
     /// A unary operation (For example: `!x`, `*x`)
@@ -733,7 +751,7 @@ pub enum Expr_ {
     ExprLoop(P<Block>, Option<Ident>),
     /// A `match` block, with a source that indicates whether or not it is
     /// the result of a desugaring, and if so, which kind.
-    ExprMatch(P<Expr>, Vec<Arm>, MatchSource),
+    ExprMatch(P<Expr>, HirVec<Arm>, MatchSource),
     /// A closure (for example, `move |a, b, c| {a + b + c}`)
     ExprClosure(CaptureClause, P<FnDecl>, P<Block>),
     /// A block (`{ ... }`)
@@ -760,7 +778,7 @@ pub enum Expr_ {
     /// parameters, e.g. foo::bar::<baz>.
     ///
     /// Optionally "qualified",
-    /// e.g. `<Vec<T> as SomeTrait>::SomeType`.
+    /// e.g. `<HirVec<T> as SomeTrait>::SomeType`.
     ExprPath(Option<QSelf>, Path),
 
     /// A referencing operation (`&a` or `&mut a`)
@@ -779,7 +797,7 @@ pub enum Expr_ {
     ///
     /// For example, `Foo {x: 1, y: 2}`, or
     /// `Foo {x: 1, .. base}`, where `base` is the `Option<Expr>`.
-    ExprStruct(Path, Vec<Field>, Option<P<Expr>>),
+    ExprStruct(Path, HirVec<Field>, Option<P<Expr>>),
 
     /// A vector literal constructed from one repeated element.
     ///
@@ -793,11 +811,11 @@ pub enum Expr_ {
 /// separately. `position` represents the index of the associated
 /// item qualified with this Self type.
 ///
-///     <Vec<T> as a::b::Trait>::AssociatedItem
+///     <HirVec<T> as a::b::Trait>::AssociatedItem
 ///      ^~~~~     ~~~~~~~~~~~~~~^
 ///      ty        position = 3
 ///
-///     <Vec<T>>::AssociatedItem
+///     <HirVec<T>>::AssociatedItem
 ///      ^~~~~    ^
 ///      ty       position = 0
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
@@ -850,7 +868,7 @@ pub struct MethodSig {
 pub struct TraitItem {
     pub id: NodeId,
     pub name: Name,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
     pub node: TraitItem_,
     pub span: Span,
 }
@@ -867,7 +885,7 @@ pub struct ImplItem {
     pub id: NodeId,
     pub name: Name,
     pub vis: Visibility,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
     pub node: ImplItemKind,
     pub span: Span,
 }
@@ -918,7 +936,7 @@ pub enum PrimTy {
 pub struct BareFnTy {
     pub unsafety: Unsafety,
     pub abi: Abi,
-    pub lifetimes: Vec<LifetimeDef>,
+    pub lifetimes: HirVec<LifetimeDef>,
     pub decl: P<FnDecl>,
 }
 
@@ -935,9 +953,9 @@ pub enum Ty_ {
     /// A bare function (e.g. `fn(usize) -> bool`)
     TyBareFn(P<BareFnTy>),
     /// A tuple (`(A, B, C, D,...)`)
-    TyTup(Vec<P<Ty>>),
+    TyTup(HirVec<P<Ty>>),
     /// A path (`module::module::...::Type`), optionally
-    /// "qualified", e.g. `<Vec<T> as SomeTrait>::SomeType`.
+    /// "qualified", e.g. `<HirVec<T> as SomeTrait>::SomeType`.
     ///
     /// Type parameters are stored in the Path itself
     TyPath(Option<QSelf>, Path),
@@ -964,9 +982,9 @@ pub struct InlineAsmOutput {
 pub struct InlineAsm {
     pub asm: InternedString,
     pub asm_str_style: StrStyle,
-    pub outputs: Vec<InlineAsmOutput>,
-    pub inputs: Vec<(InternedString, P<Expr>)>,
-    pub clobbers: Vec<InternedString>,
+    pub outputs: HirVec<InlineAsmOutput>,
+    pub inputs: HirVec<(InternedString, P<Expr>)>,
+    pub clobbers: HirVec<InternedString>,
     pub volatile: bool,
     pub alignstack: bool,
     pub dialect: AsmDialect,
@@ -1007,7 +1025,7 @@ impl Arg {
 /// Represents the header (not the body) of a function declaration
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct FnDecl {
-    pub inputs: Vec<Arg>,
+    pub inputs: HirVec<Arg>,
     pub output: FunctionRetTy,
     pub variadic: bool,
 }
@@ -1098,24 +1116,24 @@ pub struct Mod {
     /// For `mod foo;`, the inner span ranges from the first token
     /// to the last token in the external file.
     pub inner: Span,
-    pub item_ids: Vec<ItemId>,
+    pub item_ids: HirVec<ItemId>,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct ForeignMod {
     pub abi: Abi,
-    pub items: Vec<ForeignItem>,
+    pub items: HirVec<ForeignItem>,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct EnumDef {
-    pub variants: Vec<Variant>,
+    pub variants: HirVec<Variant>,
 }
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct Variant_ {
     pub name: Name,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
     pub data: VariantData,
     /// Explicit discriminant, eg `Foo = 1`
     pub disr_expr: Option<P<Expr>>,
@@ -1176,7 +1194,7 @@ pub enum ViewPath_ {
     ViewPathGlob(Path),
 
     /// `foo::bar::{a,b,c}`
-    ViewPathList(Path, Vec<PathListItem>),
+    ViewPathList(Path, HirVec<PathListItem>),
 }
 
 /// TraitRef's appear in impls.
@@ -1194,7 +1212,7 @@ pub struct TraitRef {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct PolyTraitRef {
     /// The `'a` in `<'a> Foo<&'a T>`
-    pub bound_lifetimes: Vec<LifetimeDef>,
+    pub bound_lifetimes: HirVec<LifetimeDef>,
 
     /// The `Foo<&'a T>` in `<'a> Foo<&'a T>`
     pub trait_ref: TraitRef,
@@ -1222,7 +1240,7 @@ pub struct StructField_ {
     pub kind: StructFieldKind,
     pub id: NodeId,
     pub ty: P<Ty>,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
 }
 
 impl StructField_ {
@@ -1271,8 +1289,8 @@ impl StructFieldKind {
 /// Id of the whole struct lives in `Item`.
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum VariantData {
-    Struct(Vec<StructField>, NodeId),
-    Tuple(Vec<StructField>, NodeId),
+    Struct(HirVec<StructField>, NodeId),
+    Tuple(HirVec<StructField>, NodeId),
     Unit(NodeId),
 }
 
@@ -1327,7 +1345,7 @@ pub struct ItemId {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct Item {
     pub name: Name,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
     pub id: NodeId,
     pub node: Item_,
     pub vis: Visibility,
@@ -1360,7 +1378,7 @@ pub enum Item_ {
     /// A struct definition, e.g. `struct Foo<A> {x: A}`
     ItemStruct(VariantData, Generics),
     /// Represents a Trait Declaration
-    ItemTrait(Unsafety, Generics, TyParamBounds, Vec<TraitItem>),
+    ItemTrait(Unsafety, Generics, TyParamBounds, HirVec<TraitItem>),
 
     // Default trait implementations
     ///
@@ -1372,7 +1390,7 @@ pub enum Item_ {
              Generics,
              Option<TraitRef>, // (optional) trait this impl implements
              P<Ty>, // self
-             Vec<ImplItem>),
+             HirVec<ImplItem>),
 }
 
 impl Item_ {
@@ -1398,7 +1416,7 @@ impl Item_ {
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct ForeignItem {
     pub name: Name,
-    pub attrs: Vec<Attribute>,
+    pub attrs: HirVec<Attribute>,
     pub node: ForeignItem_,
     pub id: NodeId,
     pub span: Span,
diff --git a/src/librustc_front/lib.rs b/src/librustc_front/lib.rs
index 3bfa645afc7..60080854a6f 100644
--- a/src/librustc_front/lib.rs
+++ b/src/librustc_front/lib.rs
@@ -47,6 +47,7 @@ extern crate rustc_bitflags;
 
 extern crate serialize as rustc_serialize; // used by deriving
 
+#[macro_use]
 pub mod hir;
 pub mod lowering;
 pub mod fold;
diff --git a/src/librustc_front/lowering.rs b/src/librustc_front/lowering.rs
index 614f6f0bd36..db30ee9a5d2 100644
--- a/src/librustc_front/lowering.rs
+++ b/src/librustc_front/lowering.rs
@@ -147,6 +147,10 @@ pub fn lower_ident(_lctx: &LoweringContext, ident: Ident) -> hir::Ident {
     }
 }
 
+pub fn lower_attrs(_lctx: &LoweringContext, attrs: &Vec<Attribute>) -> hir::HirVec<Attribute> {
+    attrs.clone().into()
+}
+
 pub fn lower_view_path(lctx: &LoweringContext, view_path: &ViewPath) -> P<hir::ViewPath> {
     P(Spanned {
         node: match view_path.node {
@@ -186,7 +190,7 @@ pub fn lower_view_path(lctx: &LoweringContext, view_path: &ViewPath) -> P<hir::V
 
 pub fn lower_arm(lctx: &LoweringContext, arm: &Arm) -> hir::Arm {
     hir::Arm {
-        attrs: arm.attrs.clone(),
+        attrs: lower_attrs(lctx, &arm.attrs),
         pats: arm.pats.iter().map(|x| lower_pat(lctx, x)).collect(),
         guard: arm.guard.as_ref().map(|ref x| lower_expr(lctx, x)),
         body: lower_expr(lctx, &arm.body),
@@ -275,7 +279,7 @@ pub fn lower_variant(lctx: &LoweringContext, v: &Variant) -> hir::Variant {
     Spanned {
         node: hir::Variant_ {
             name: v.node.name.name,
-            attrs: v.node.attrs.clone(),
+            attrs: lower_attrs(lctx, &v.node.attrs),
             data: lower_variant_data(lctx, &v.node.data),
             disr_expr: v.node.disr_expr.as_ref().map(|e| lower_expr(lctx, e)),
         },
@@ -449,13 +453,13 @@ pub fn lower_lifetime_def(lctx: &LoweringContext, l: &LifetimeDef) -> hir::Lifet
     }
 }
 
-pub fn lower_lifetimes(lctx: &LoweringContext, lts: &Vec<Lifetime>) -> Vec<hir::Lifetime> {
+pub fn lower_lifetimes(lctx: &LoweringContext, lts: &Vec<Lifetime>) -> hir::HirVec<hir::Lifetime> {
     lts.iter().map(|l| lower_lifetime(lctx, l)).collect()
 }
 
 pub fn lower_lifetime_defs(lctx: &LoweringContext,
                            lts: &Vec<LifetimeDef>)
-                           -> Vec<hir::LifetimeDef> {
+                           -> hir::HirVec<hir::LifetimeDef> {
     lts.iter().map(|l| lower_lifetime_def(lctx, l)).collect()
 }
 
@@ -560,7 +564,7 @@ pub fn lower_struct_field(lctx: &LoweringContext, f: &StructField) -> hir::Struc
             id: f.node.id,
             kind: lower_struct_field_kind(lctx, &f.node.kind),
             ty: lower_ty(lctx, &f.node.ty),
-            attrs: f.node.attrs.clone(),
+            attrs: lower_attrs(lctx, &f.node.attrs),
         },
         span: f.span,
     }
@@ -673,7 +677,7 @@ pub fn lower_trait_item(lctx: &LoweringContext, i: &TraitItem) -> hir::TraitItem
     hir::TraitItem {
         id: i.id,
         name: i.ident.name,
-        attrs: i.attrs.clone(),
+        attrs: lower_attrs(lctx, &i.attrs),
         node: match i.node {
             ConstTraitItem(ref ty, ref default) => {
                 hir::ConstTraitItem(lower_ty(lctx, ty),
@@ -696,7 +700,7 @@ pub fn lower_impl_item(lctx: &LoweringContext, i: &ImplItem) -> hir::ImplItem {
     hir::ImplItem {
         id: i.id,
         name: i.ident.name,
-        attrs: i.attrs.clone(),
+        attrs: lower_attrs(lctx, &i.attrs),
         vis: lower_visibility(lctx, i.vis),
         node: match i.node {
             ImplItemKind::Const(ref ty, ref expr) => {
@@ -740,25 +744,25 @@ pub fn lower_crate(lctx: &LoweringContext, c: &Crate) -> hir::Crate {
 
     hir::Crate {
         module: lower_mod(lctx, &c.module),
-        attrs: c.attrs.clone(),
-        config: c.config.clone(),
+        attrs: lower_attrs(lctx, &c.attrs),
+        config: c.config.clone().into(),
         span: c.span,
         exported_macros: c.exported_macros.iter().map(|m| lower_macro_def(lctx, m)).collect(),
         items: items,
     }
 }
 
-pub fn lower_macro_def(_lctx: &LoweringContext, m: &MacroDef) -> hir::MacroDef {
+pub fn lower_macro_def(lctx: &LoweringContext, m: &MacroDef) -> hir::MacroDef {
     hir::MacroDef {
         name: m.ident.name,
-        attrs: m.attrs.clone(),
+        attrs: lower_attrs(lctx, &m.attrs),
         id: m.id,
         span: m.span,
         imported_from: m.imported_from.map(|x| x.name),
         export: m.export,
         use_locally: m.use_locally,
         allow_internal_unstable: m.allow_internal_unstable,
-        body: m.body.clone(),
+        body: m.body.clone().into(),
     }
 }
 
@@ -772,7 +776,7 @@ pub fn lower_item(lctx: &LoweringContext, i: &Item) -> hir::Item {
     hir::Item {
         id: i.id,
         name: i.ident.name,
-        attrs: i.attrs.clone(),
+        attrs: lower_attrs(lctx, &i.attrs),
         node: node,
         vis: lower_visibility(lctx, i.vis),
         span: i.span,
@@ -783,7 +787,7 @@ pub fn lower_foreign_item(lctx: &LoweringContext, i: &ForeignItem) -> hir::Forei
     hir::ForeignItem {
         id: i.id,
         name: i.ident.name,
-        attrs: i.attrs.clone(),
+        attrs: lower_attrs(lctx, &i.attrs),
         node: match i.node {
             ForeignItemFn(ref fdec, ref generics) => {
                 hir::ForeignItemFn(lower_fn_decl(lctx, fdec), lower_generics(lctx, generics))
@@ -1020,7 +1024,7 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                     // let placer = <placer_expr> ;
                     let s1 = {
                         let placer_expr = signal_block_expr(lctx,
-                                                            vec![],
+                                                            hir_vec![],
                                                             placer_expr,
                                                             e.span,
                                                             hir::PopUnstableBlock,
@@ -1031,14 +1035,14 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                     // let mut place = Placer::make_place(placer);
                     let s2 = {
                         let placer = expr_ident(lctx, e.span, placer_ident, None);
-                        let call = make_call(lctx, &make_place, vec![placer]);
+                        let call = make_call(lctx, &make_place, hir_vec![placer]);
                         mk_stmt_let_mut(lctx, place_ident, call)
                     };
 
                     // let p_ptr = Place::pointer(&mut place);
                     let s3 = {
                         let agent = expr_ident(lctx, e.span, place_ident, None);
-                        let args = vec![expr_mut_addr_of(lctx, e.span, agent, None)];
+                        let args = hir_vec![expr_mut_addr_of(lctx, e.span, agent, None)];
                         let call = make_call(lctx, &place_pointer, args);
                         mk_stmt_let(lctx, p_ptr_ident, call)
                     };
@@ -1046,13 +1050,13 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                     // pop_unsafe!(EXPR));
                     let pop_unsafe_expr = {
                         let value_expr = signal_block_expr(lctx,
-                                                           vec![],
+                                                           hir_vec![],
                                                            value_expr,
                                                            e.span,
                                                            hir::PopUnstableBlock,
                                                            None);
                         signal_block_expr(lctx,
-                                          vec![],
+                                          hir_vec![],
                                           value_expr,
                                           e.span,
                                           hir::PopUnsafeBlock(hir::CompilerGenerated), None)
@@ -1066,21 +1070,21 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                         let ptr = expr_ident(lctx, e.span, p_ptr_ident, None);
                         let call_move_val_init =
                             hir::StmtSemi(
-                                make_call(lctx, &move_val_init, vec![ptr, pop_unsafe_expr]),
+                                make_call(lctx, &move_val_init, hir_vec![ptr, pop_unsafe_expr]),
                                 lctx.next_id());
                         let call_move_val_init = respan(e.span, call_move_val_init);
 
                         let place = expr_ident(lctx, e.span, place_ident, None);
-                        let call = make_call(lctx, &inplace_finalize, vec![place]);
+                        let call = make_call(lctx, &inplace_finalize, hir_vec![place]);
                         signal_block_expr(lctx,
-                                          vec![call_move_val_init],
+                                          hir_vec![call_move_val_init],
                                           call,
                                           e.span,
                                           hir::PushUnsafeBlock(hir::CompilerGenerated), None)
                     };
 
                     signal_block_expr(lctx,
-                                      vec![s1, s2, s3],
+                                      hir_vec![s1, s2, s3],
                                       expr,
                                       e.span,
                                       hir::PushUnstableBlock,
@@ -1141,7 +1145,7 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                                 let els = lower_expr(lctx, els);
                                 let id = lctx.next_id();
                                 let blk = P(hir::Block {
-                                    stmts: vec![],
+                                    stmts: hir_vec![],
                                     expr: Some(els),
                                     id: id,
                                     rules: hir::DefaultBlock,
@@ -1238,7 +1242,7 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                                 .collect(),
                 asm: asm.clone(),
                 asm_str_style: asm_str_style,
-                clobbers: clobbers.clone(),
+                clobbers: clobbers.clone().into(),
                 volatile: volatile,
                 alignstack: alignstack,
                 dialect: dialect,
@@ -1275,7 +1279,7 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                     let pat_arm = {
                         let body = lower_block(lctx, body);
                         let body_expr = expr_block(lctx, body, None);
-                        arm(vec![lower_pat(lctx, pat)], body_expr)
+                        arm(hir_vec![lower_pat(lctx, pat)], body_expr)
                     };
 
                     // `[_ if <else_opt_if_cond> => <else_opt_if_body>,]`
@@ -1290,8 +1294,8 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                                         hir::ExprIf(cond, then, else_opt) => {
                                             let pat_under = pat_wild(lctx, e.span);
                                             arms.push(hir::Arm {
-                                                attrs: vec![],
-                                                pats: vec![pat_under],
+                                                attrs: hir_vec![],
+                                                pats: hir_vec![pat_under],
                                                 guard: Some(cond),
                                                 body: expr_block(lctx, then, None),
                                             });
@@ -1325,8 +1329,8 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                         let pat_under = pat_wild(lctx, e.span);
                         let else_expr =
                             else_opt.unwrap_or_else(
-                                || expr_tuple(lctx, e.span, vec![], None));
-                        arm(vec![pat_under], else_expr)
+                                || expr_tuple(lctx, e.span, hir_vec![], None));
+                        arm(hir_vec![pat_under], else_expr)
                     };
 
                     let mut arms = Vec::with_capacity(else_if_arms.len() + 2);
@@ -1339,7 +1343,7 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                     expr(lctx,
                          e.span,
                          hir::ExprMatch(sub_expr,
-                                        arms,
+                                        arms.into(),
                                         hir::MatchSource::IfLetDesugar {
                                             contains_else_clause: contains_else_clause,
                                         }),
@@ -1364,18 +1368,18 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                     let pat_arm = {
                         let body = lower_block(lctx, body);
                         let body_expr = expr_block(lctx, body, None);
-                        arm(vec![lower_pat(lctx, pat)], body_expr)
+                        arm(hir_vec![lower_pat(lctx, pat)], body_expr)
                     };
 
                     // `_ => break`
                     let break_arm = {
                         let pat_under = pat_wild(lctx, e.span);
                         let break_expr = expr_break(lctx, e.span, None);
-                        arm(vec![pat_under], break_expr)
+                        arm(hir_vec![pat_under], break_expr)
                     };
 
                     // `match <sub_expr> { ... }`
-                    let arms = vec![pat_arm, break_arm];
+                    let arms = hir_vec![pat_arm, break_arm];
                     let sub_expr = lower_expr(lctx, sub_expr);
                     let match_expr = expr(lctx,
                                           e.span,
@@ -1431,14 +1435,14 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                         let pat = lower_pat(lctx, pat);
                         let some_pat = pat_some(lctx, e.span, pat);
 
-                        arm(vec![some_pat], body_expr)
+                        arm(hir_vec![some_pat], body_expr)
                     };
 
                     // `::std::option::Option::None => break`
                     let break_arm = {
                         let break_expr = expr_break(lctx, e.span, None);
 
-                        arm(vec![pat_none(lctx, e.span)], break_expr)
+                        arm(hir_vec![pat_none(lctx, e.span)], break_expr)
                     };
 
                     // `match ::std::iter::Iterator::next(&mut iter) { ... }`
@@ -1454,9 +1458,9 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                         let next_expr = expr_call(lctx,
                                                   e.span,
                                                   next_path,
-                                                  vec![ref_mut_iter],
+                                                  hir_vec![ref_mut_iter],
                                                   None);
-                        let arms = vec![pat_arm, break_arm];
+                        let arms = hir_vec![pat_arm, break_arm];
 
                         expr(lctx,
                              e.span,
@@ -1476,7 +1480,7 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                                                               e.span,
                                                               iter,
                                                               hir::BindByValue(hir::MutMutable));
-                        arm(vec![iter_pat], loop_expr)
+                        arm(hir_vec![iter_pat], loop_expr)
                     };
 
                     // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
@@ -1488,13 +1492,13 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                         };
 
                         let into_iter = expr_path(lctx, into_iter_path, None);
-                        expr_call(lctx, e.span, into_iter, vec![head], None)
+                        expr_call(lctx, e.span, into_iter, hir_vec![head], None)
                     };
 
                     let match_expr = expr_match(lctx,
                                                 e.span,
                                                 into_iter_expr,
-                                                vec![iter_arm],
+                                                hir_vec![iter_arm],
                                                 hir::MatchSource::ForLoopDesugar,
                                                 None);
 
@@ -1502,7 +1506,7 @@ pub fn lower_expr(lctx: &LoweringContext, e: &Expr) -> P<hir::Expr> {
                     let result_ident = lctx.str_to_ident("result");
                     let let_stmt = stmt_let(lctx, e.span, false, result_ident, match_expr, None);
                     let result = expr_ident(lctx, e.span, result_ident, None);
-                    let block = block_all(lctx, e.span, vec![let_stmt], Some(result));
+                    let block = block_all(lctx, e.span, hir_vec![let_stmt], Some(result));
                     // add the attributes to the outer returned expr node
                     expr_block(lctx, block, e.attrs.clone())
                 });
@@ -1601,9 +1605,9 @@ pub fn lower_trait_bound_modifier(_lctx: &LoweringContext,
 
 // Helper methods for building HIR.
 
-fn arm(pats: Vec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
+fn arm(pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
     hir::Arm {
-        attrs: vec![],
+        attrs: hir_vec![],
         pats: pats,
         guard: None,
         body: expr,
@@ -1618,7 +1622,7 @@ fn expr_break(lctx: &LoweringContext, span: Span,
 fn expr_call(lctx: &LoweringContext,
              span: Span,
              e: P<hir::Expr>,
-             args: Vec<P<hir::Expr>>,
+             args: hir::HirVec<P<hir::Expr>>,
              attrs: ThinAttributes)
              -> P<hir::Expr> {
     expr(lctx, span, hir::ExprCall(e, args), attrs)
@@ -1642,7 +1646,7 @@ fn expr_path(lctx: &LoweringContext, path: hir::Path,
 fn expr_match(lctx: &LoweringContext,
               span: Span,
               arg: P<hir::Expr>,
-              arms: Vec<hir::Arm>,
+              arms: hir::HirVec<hir::Arm>,
               source: hir::MatchSource,
               attrs: ThinAttributes)
               -> P<hir::Expr> {
@@ -1654,7 +1658,7 @@ fn expr_block(lctx: &LoweringContext, b: P<hir::Block>,
     expr(lctx, b.span, hir::ExprBlock(b), attrs)
 }
 
-fn expr_tuple(lctx: &LoweringContext, sp: Span, exprs: Vec<P<hir::Expr>>,
+fn expr_tuple(lctx: &LoweringContext, sp: Span, exprs: hir::HirVec<P<hir::Expr>>,
               attrs: ThinAttributes) -> P<hir::Expr> {
     expr(lctx, sp, hir::ExprTup(exprs), attrs)
 }
@@ -1694,12 +1698,12 @@ fn stmt_let(lctx: &LoweringContext,
 }
 
 fn block_expr(lctx: &LoweringContext, expr: P<hir::Expr>) -> P<hir::Block> {
-    block_all(lctx, expr.span, Vec::new(), Some(expr))
+    block_all(lctx, expr.span, hir::HirVec::new(), Some(expr))
 }
 
 fn block_all(lctx: &LoweringContext,
              span: Span,
-             stmts: Vec<hir::Stmt>,
+             stmts: hir::HirVec<hir::Stmt>,
              expr: Option<P<hir::Expr>>)
              -> P<hir::Block> {
     P(hir::Block {
@@ -1714,19 +1718,19 @@ fn block_all(lctx: &LoweringContext,
 fn pat_some(lctx: &LoweringContext, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
     let some = std_path(lctx, &["option", "Option", "Some"]);
     let path = path_global(span, some);
-    pat_enum(lctx, span, path, vec![pat])
+    pat_enum(lctx, span, path, hir_vec![pat])
 }
 
 fn pat_none(lctx: &LoweringContext, span: Span) -> P<hir::Pat> {
     let none = std_path(lctx, &["option", "Option", "None"]);
     let path = path_global(span, none);
-    pat_enum(lctx, span, path, vec![])
+    pat_enum(lctx, span, path, hir_vec![])
 }
 
 fn pat_enum(lctx: &LoweringContext,
             span: Span,
             path: hir::Path,
-            subpats: Vec<P<hir::Pat>>)
+            subpats: hir::HirVec<P<hir::Pat>>)
             -> P<hir::Pat> {
     let pt = hir::PatEnum(path, Some(subpats));
     pat(lctx, span, pt)
@@ -1767,17 +1771,17 @@ fn path_ident(span: Span, id: hir::Ident) -> hir::Path {
 }
 
 fn path(span: Span, strs: Vec<hir::Ident>) -> hir::Path {
-    path_all(span, false, strs, Vec::new(), Vec::new(), Vec::new())
+    path_all(span, false, strs, hir::HirVec::new(), Vec::new(), Vec::new())
 }
 
 fn path_global(span: Span, strs: Vec<hir::Ident>) -> hir::Path {
-    path_all(span, true, strs, Vec::new(), Vec::new(), Vec::new())
+    path_all(span, true, strs, hir::HirVec::new(), Vec::new(), Vec::new())
 }
 
 fn path_all(sp: Span,
             global: bool,
             mut idents: Vec<hir::Ident>,
-            lifetimes: Vec<hir::Lifetime>,
+            lifetimes: hir::HirVec<hir::Lifetime>,
             types: Vec<P<hir::Ty>>,
             bindings: Vec<hir::TypeBinding>)
             -> hir::Path {
@@ -1801,7 +1805,7 @@ fn path_all(sp: Span,
     hir::Path {
         span: sp,
         global: global,
-        segments: segments,
+        segments: segments.into(),
     }
 }
 
@@ -1822,7 +1826,7 @@ fn core_path(lctx: &LoweringContext, span: Span, components: &[&str]) -> hir::Pa
 }
 
 fn signal_block_expr(lctx: &LoweringContext,
-                     stmts: Vec<hir::Stmt>,
+                     stmts: hir::HirVec<hir::Stmt>,
                      expr: P<hir::Expr>,
                      span: Span,
                      rule: hir::BlockCheckMode,
diff --git a/src/librustc_front/print/pprust.rs b/src/librustc_front/print/pprust.rs
index a3bb005dfbd..c4c5b9170f6 100644
--- a/src/librustc_front/print/pprust.rs
+++ b/src/librustc_front/print/pprust.rs
@@ -521,7 +521,7 @@ impl<'a> State<'a> {
                     ty_params: P::empty(),
                     where_clause: hir::WhereClause {
                         id: ast::DUMMY_NODE_ID,
-                        predicates: Vec::new(),
+                        predicates: hir::HirVec::new(),
                     },
                 };
                 try!(self.print_ty_fn(f.abi, f.unsafety, &*f.decl, None, &generics, None));
@@ -2256,11 +2256,11 @@ impl<'a> State<'a> {
             try!(self.print_generics(generics));
         }
         let generics = hir::Generics {
-            lifetimes: Vec::new(),
+            lifetimes: hir::HirVec::new(),
             ty_params: P::empty(),
             where_clause: hir::WhereClause {
                 id: ast::DUMMY_NODE_ID,
-                predicates: Vec::new(),
+                predicates: hir::HirVec::new(),
             },
         };
         try!(self.print_fn(decl,
diff --git a/src/librustc_front/util.rs b/src/librustc_front/util.rs
index f85eb2bb401..298904d1e0d 100644
--- a/src/librustc_front/util.rs
+++ b/src/librustc_front/util.rs
@@ -334,11 +334,11 @@ pub fn is_path(e: P<Expr>) -> bool {
 
 pub fn empty_generics() -> Generics {
     Generics {
-        lifetimes: Vec::new(),
+        lifetimes: HirVec::new(),
         ty_params: P::empty(),
         where_clause: WhereClause {
             id: DUMMY_NODE_ID,
-            predicates: Vec::new(),
+            predicates: HirVec::new(),
         },
     }
 }
@@ -349,13 +349,13 @@ pub fn ident_to_path(s: Span, ident: Ident) -> Path {
     hir::Path {
         span: s,
         global: false,
-        segments: vec!(hir::PathSegment {
+        segments: hir_vec![hir::PathSegment {
             identifier: ident,
             parameters: hir::AngleBracketedParameters(hir::AngleBracketedParameterData {
-                lifetimes: Vec::new(),
+                lifetimes: HirVec::new(),
                 types: P::empty(),
                 bindings: P::empty(),
             }),
-        }),
+        }],
     }
 }
diff --git a/src/librustc_mir/hair/cx/pattern.rs b/src/librustc_mir/hair/cx/pattern.rs
index 74fef684006..64a86373ee1 100644
--- a/src/librustc_mir/hair/cx/pattern.rs
+++ b/src/librustc_mir/hair/cx/pattern.rs
@@ -252,7 +252,7 @@ impl<'patcx, 'cx, 'tcx> PatCx<'patcx, 'cx, 'tcx> {
         }
     }
 
-    fn to_pats(&mut self, pats: &'tcx Vec<P<hir::Pat>>) -> Vec<Pattern<'tcx>> {
+    fn to_pats(&mut self, pats: &'tcx [P<hir::Pat>]) -> Vec<Pattern<'tcx>> {
         pats.iter().map(|p| self.to_pat(p)).collect()
     }
 
@@ -263,9 +263,9 @@ impl<'patcx, 'cx, 'tcx> PatCx<'patcx, 'cx, 'tcx> {
     fn slice_or_array_pattern(&mut self,
                               pat: &'tcx hir::Pat,
                               ty: Ty<'tcx>,
-                              prefix: &'tcx Vec<P<hir::Pat>>,
+                              prefix: &'tcx [P<hir::Pat>],
                               slice: &'tcx Option<P<hir::Pat>>,
-                              suffix: &'tcx Vec<P<hir::Pat>>)
+                              suffix: &'tcx [P<hir::Pat>])
                               -> PatternKind<'tcx> {
         match ty.sty {
             ty::TySlice(..) => {
diff --git a/src/librustc_trans/trans/consts.rs b/src/librustc_trans/trans/consts.rs
index 77664f19aac..2a9b675d876 100644
--- a/src/librustc_trans/trans/consts.rs
+++ b/src/librustc_trans/trans/consts.rs
@@ -1038,7 +1038,7 @@ pub fn trans_static(ccx: &CrateContext,
                     m: hir::Mutability,
                     expr: &hir::Expr,
                     id: ast::NodeId,
-                    attrs: &Vec<ast::Attribute>)
+                    attrs: &[ast::Attribute])
                     -> Result<ValueRef, ConstEvalErr> {
     unsafe {
         let _icx = push_ctxt("trans_static");
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index e217e7afad7..675eef637b1 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -1584,8 +1584,13 @@ impl Clean<Type> for hir::Ty {
                 resolve_type(cx, p.clean(cx), self.id)
             }
             TyPath(Some(ref qself), ref p) => {
-                let mut trait_path = p.clone();
-                trait_path.segments.pop();
+                let mut segments: Vec<_> = p.segments.clone().into();
+                segments.pop();
+                let trait_path = hir::Path {
+                    span: p.span,
+                    global: p.global,
+                    segments: segments.into(),
+                };
                 Type::QPath {
                     name: p.segments.last().unwrap().identifier.name.clean(cx),
                     self_type: box qself.ty.clean(cx),
diff --git a/src/librustdoc/doctree.rs b/src/librustdoc/doctree.rs
index d1030a6fcb0..fc0422b3a3f 100644
--- a/src/librustdoc/doctree.rs
+++ b/src/librustdoc/doctree.rs
@@ -24,7 +24,7 @@ use rustc_front::hir;
 
 pub struct Module {
     pub name: Option<Name>,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub where_outer: Span,
     pub where_inner: Span,
     pub extern_crates: Vec<ExternCrate>,
@@ -58,7 +58,7 @@ impl Module {
             depr: None,
             where_outer: syntax::codemap::DUMMY_SP,
             where_inner: syntax::codemap::DUMMY_SP,
-            attrs      : Vec::new(),
+            attrs      : hir::HirVec::new(),
             extern_crates: Vec::new(),
             imports    : Vec::new(),
             structs    : Vec::new(),
@@ -103,8 +103,8 @@ pub struct Struct {
     pub struct_type: StructType,
     pub name: Name,
     pub generics: hir::Generics,
-    pub attrs: Vec<ast::Attribute>,
-    pub fields: Vec<hir::StructField>,
+    pub attrs: hir::HirVec<ast::Attribute>,
+    pub fields: hir::HirVec<hir::StructField>,
     pub whence: Span,
 }
 
@@ -112,9 +112,9 @@ pub struct Enum {
     pub vis: hir::Visibility,
     pub stab: Option<attr::Stability>,
     pub depr: Option<attr::Deprecation>,
-    pub variants: Vec<Variant>,
+    pub variants: hir::HirVec<Variant>,
     pub generics: hir::Generics,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub id: NodeId,
     pub whence: Span,
     pub name: Name,
@@ -122,7 +122,7 @@ pub struct Enum {
 
 pub struct Variant {
     pub name: Name,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub def: hir::VariantData,
     pub stab: Option<attr::Stability>,
     pub depr: Option<attr::Deprecation>,
@@ -131,7 +131,7 @@ pub struct Variant {
 
 pub struct Function {
     pub decl: hir::FnDecl,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub id: NodeId,
     pub name: Name,
     pub vis: hir::Visibility,
@@ -149,7 +149,7 @@ pub struct Typedef {
     pub gen: hir::Generics,
     pub name: Name,
     pub id: ast::NodeId,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub whence: Span,
     pub vis: hir::Visibility,
     pub stab: Option<attr::Stability>,
@@ -162,7 +162,7 @@ pub struct Static {
     pub mutability: hir::Mutability,
     pub expr: P<hir::Expr>,
     pub name: Name,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub vis: hir::Visibility,
     pub stab: Option<attr::Stability>,
     pub depr: Option<attr::Deprecation>,
@@ -174,7 +174,7 @@ pub struct Constant {
     pub type_: P<hir::Ty>,
     pub expr: P<hir::Expr>,
     pub name: Name,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub vis: hir::Visibility,
     pub stab: Option<attr::Stability>,
     pub depr: Option<attr::Deprecation>,
@@ -185,10 +185,10 @@ pub struct Constant {
 pub struct Trait {
     pub unsafety: hir::Unsafety,
     pub name: Name,
-    pub items: Vec<hir::TraitItem>,
+    pub items: hir::HirVec<hir::TraitItem>,
     pub generics: hir::Generics,
-    pub bounds: Vec<hir::TyParamBound>,
-    pub attrs: Vec<ast::Attribute>,
+    pub bounds: hir::HirVec<hir::TyParamBound>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub id: ast::NodeId,
     pub whence: Span,
     pub vis: hir::Visibility,
@@ -202,8 +202,8 @@ pub struct Impl {
     pub generics: hir::Generics,
     pub trait_: Option<hir::TraitRef>,
     pub for_: P<hir::Ty>,
-    pub items: Vec<hir::ImplItem>,
-    pub attrs: Vec<ast::Attribute>,
+    pub items: hir::HirVec<hir::ImplItem>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub whence: Span,
     pub vis: hir::Visibility,
     pub stab: Option<attr::Stability>,
@@ -215,16 +215,16 @@ pub struct DefaultImpl {
     pub unsafety: hir::Unsafety,
     pub trait_: hir::TraitRef,
     pub id: ast::NodeId,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub whence: Span,
 }
 
 pub struct Macro {
     pub name: Name,
     pub id: ast::NodeId,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub whence: Span,
-    pub matchers: Vec<Span>,
+    pub matchers: hir::HirVec<Span>,
     pub stab: Option<attr::Stability>,
     pub depr: Option<attr::Deprecation>,
     pub imported_from: Option<Name>,
@@ -234,14 +234,14 @@ pub struct ExternCrate {
     pub name: Name,
     pub path: Option<String>,
     pub vis: hir::Visibility,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub whence: Span,
 }
 
 pub struct Import {
     pub id: NodeId,
     pub vis: hir::Visibility,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub node: hir::ViewPath_,
     pub whence: Span,
 }
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
index d95a4553bf1..ba389bc42b7 100644
--- a/src/librustdoc/visit_ast.rs
+++ b/src/librustdoc/visit_ast.rs
@@ -38,7 +38,7 @@ use doctree::*;
 
 pub struct RustdocVisitor<'a, 'tcx: 'a> {
     pub module: Module,
-    pub attrs: Vec<ast::Attribute>,
+    pub attrs: hir::HirVec<ast::Attribute>,
     pub cx: &'a core::DocContext<'a, 'tcx>,
     pub analysis: Option<&'a core::CrateAnalysis>,
     view_item_stack: HashSet<ast::NodeId>,
@@ -53,7 +53,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
         stack.insert(ast::CRATE_NODE_ID);
         RustdocVisitor {
             module: Module::new(None),
-            attrs: Vec::new(),
+            attrs: hir::HirVec::new(),
             cx: cx,
             analysis: analysis,
             view_item_stack: stack,
@@ -157,7 +157,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
         }
     }
 
-    pub fn visit_mod_contents(&mut self, span: Span, attrs: Vec<ast::Attribute> ,
+    pub fn visit_mod_contents(&mut self, span: Span, attrs: hir::HirVec<ast::Attribute>,
                               vis: hir::Visibility, id: ast::NodeId,
                               m: &hir::Mod,
                               name: Option<ast::Name>) -> Module {
@@ -192,7 +192,7 @@ impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
                 let mine = paths.into_iter().filter(|path| {
                     !self.resolve_id(path.node.id(), None, false, om,
                                      please_inline)
-                }).collect::<Vec<hir::PathListItem>>();
+                }).collect::<hir::HirVec<hir::PathListItem>>();
 
                 if mine.is_empty() {
                     None