Add an intital HIR and lowering step

2 files changed, 1391 insertions, 0 deletions

diff --git a/src/librustc/front/map/blocks.rs b/src/librustc/front/map/blocks.rs
new file mode 100644
index 00000000000..4e16d9e5670
--- /dev/null
+++ b/src/librustc/front/map/blocks.rs
@@ -0,0 +1,255 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! This module provides a simplified abstraction for working with
+//! code blocks identified by their integer node-id.  In particular,
+//! it captures a common set of attributes that all "function-like
+//! things" (represented by `FnLike` instances) share.  For example,
+//! all `FnLike` instances have a type signature (be it explicit or
+//! inferred).  And all `FnLike` instances have a body, i.e. the code
+//! that is run when the function-like thing it represents is invoked.
+//!
+//! With the above abstraction in place, one can treat the program
+//! text as a collection of blocks of code (and most such blocks are
+//! nested within a uniquely determined `FnLike`), and users can ask
+//! for the `Code` associated with a particular NodeId.
+
+pub use self::Code::*;
+
+use front::map::{self, Node};
+use syntax::abi;
+use rustc_front::hir::{Block, FnDecl};
+use syntax::ast::{NodeId, Ident};
+use rustc_front::hir as ast;
+use syntax::codemap::Span;
+use rustc_front::visit::FnKind;
+
+/// An FnLikeNode is a Node that is like a fn, in that it has a decl
+/// and a body (as well as a NodeId, a span, etc).
+///
+/// More specifically, it is one of either:
+///   - A function item,
+///   - A closure expr (i.e. an ExprClosure), or
+///   - The default implementation for a trait method.
+///
+/// To construct one, use the `Code::from_node` function.
+#[derive(Copy, Clone)]
+pub struct FnLikeNode<'a> { node: map::Node<'a> }
+
+/// MaybeFnLike wraps a method that indicates if an object
+/// corresponds to some FnLikeNode.
+pub trait MaybeFnLike { fn is_fn_like(&self) -> bool; }
+
+/// Components shared by fn-like things (fn items, methods, closures).
+pub struct FnParts<'a> {
+    pub decl: &'a FnDecl,
+    pub body: &'a Block,
+    pub kind: FnKind<'a>,
+    pub span: Span,
+    pub id:   NodeId,
+}
+
+impl MaybeFnLike for ast::Item {
+    fn is_fn_like(&self) -> bool {
+        match self.node { ast::ItemFn(..) => true, _ => false, }
+    }
+}
+
+impl MaybeFnLike for ast::TraitItem {
+    fn is_fn_like(&self) -> bool {
+        match self.node { ast::MethodTraitItem(_, Some(_)) => true, _ => false, }
+    }
+}
+
+impl MaybeFnLike for ast::Expr {
+    fn is_fn_like(&self) -> bool {
+        match self.node {
+            ast::ExprClosure(..) => true,
+            _ => false,
+        }
+    }
+}
+
+/// Carries either an FnLikeNode or a Block, as these are the two
+/// constructs that correspond to "code" (as in, something from which
+/// we can construct a control-flow graph).
+#[derive(Copy, Clone)]
+pub enum Code<'a> {
+    FnLikeCode(FnLikeNode<'a>),
+    BlockCode(&'a Block),
+}
+
+impl<'a> Code<'a> {
+    pub fn id(&self) -> NodeId {
+        match *self {
+            FnLikeCode(node) => node.id(),
+            BlockCode(block) => block.id,
+        }
+    }
+
+    /// Attempts to construct a Code from presumed FnLike or Block node input.
+    pub fn from_node(node: Node) -> Option<Code> {
+        if let map::NodeBlock(block) = node {
+            Some(BlockCode(block))
+        } else {
+            FnLikeNode::from_node(node).map(|fn_like| FnLikeCode(fn_like))
+        }
+    }
+}
+
+/// These are all the components one can extract from a fn item for
+/// use when implementing FnLikeNode operations.
+struct ItemFnParts<'a> {
+    ident:    Ident,
+    decl:     &'a ast::FnDecl,
+    unsafety: ast::Unsafety,
+    constness: ast::Constness,
+    abi:      abi::Abi,
+    vis:      ast::Visibility,
+    generics: &'a ast::Generics,
+    body:     &'a Block,
+    id:       NodeId,
+    span:     Span
+}
+
+/// These are all the components one can extract from a closure expr
+/// for use when implementing FnLikeNode operations.
+struct ClosureParts<'a> {
+    decl: &'a FnDecl,
+    body: &'a Block,
+    id: NodeId,
+    span: Span
+}
+
+impl<'a> ClosureParts<'a> {
+    fn new(d: &'a FnDecl, b: &'a Block, id: NodeId, s: Span) -> ClosureParts<'a> {
+        ClosureParts { decl: d, body: b, id: id, span: s }
+    }
+}
+
+impl<'a> FnLikeNode<'a> {
+    /// Attempts to construct a FnLikeNode from presumed FnLike node input.
+    pub fn from_node(node: Node) -> Option<FnLikeNode> {
+        let fn_like = match node {
+            map::NodeItem(item) => item.is_fn_like(),
+            map::NodeTraitItem(tm) => tm.is_fn_like(),
+            map::NodeImplItem(_) => true,
+            map::NodeExpr(e) => e.is_fn_like(),
+            _ => false
+        };
+        if fn_like {
+            Some(FnLikeNode {
+                node: node
+            })
+        } else {
+            None
+        }
+    }
+
+    pub fn to_fn_parts(self) -> FnParts<'a> {
+        FnParts {
+            decl: self.decl(),
+            body: self.body(),
+            kind: self.kind(),
+            span: self.span(),
+            id:   self.id(),
+        }
+    }
+
+    pub fn body(self) -> &'a Block {
+        self.handle(|i: ItemFnParts<'a>|  &*i.body,
+                    |_, _, _: &'a ast::MethodSig, _, body: &'a ast::Block, _|  body,
+                    |c: ClosureParts<'a>| c.body)
+    }
+
+    pub fn decl(self) -> &'a FnDecl {
+        self.handle(|i: ItemFnParts<'a>|  &*i.decl,
+                    |_, _, sig: &'a ast::MethodSig, _, _, _|  &sig.decl,
+                    |c: ClosureParts<'a>| c.decl)
+    }
+
+    pub fn span(self) -> Span {
+        self.handle(|i: ItemFnParts|     i.span,
+                    |_, _, _: &'a ast::MethodSig, _, _, span| span,
+                    |c: ClosureParts|    c.span)
+    }
+
+    pub fn id(self) -> NodeId {
+        self.handle(|i: ItemFnParts|     i.id,
+                    |id, _, _: &'a ast::MethodSig, _, _, _| id,
+                    |c: ClosureParts|    c.id)
+    }
+
+    pub fn kind(self) -> FnKind<'a> {
+        let item = |p: ItemFnParts<'a>| -> FnKind<'a> {
+            FnKind::ItemFn(p.ident, p.generics, p.unsafety, p.constness, p.abi, p.vis)
+        };
+        let closure = |_: ClosureParts| {
+            FnKind::Closure
+        };
+        let method = |_, ident, sig: &'a ast::MethodSig, vis, _, _| {
+            FnKind::Method(ident, sig, vis)
+        };
+        self.handle(item, method, closure)
+    }
+
+    fn handle<A, I, M, C>(self, item_fn: I, method: M, closure: C) -> A where
+        I: FnOnce(ItemFnParts<'a>) -> A,
+        M: FnOnce(NodeId,
+                  Ident,
+                  &'a ast::MethodSig,
+                  Option<ast::Visibility>,
+                  &'a ast::Block,
+                  Span)
+                  -> A,
+        C: FnOnce(ClosureParts<'a>) -> A,
+    {
+        match self.node {
+            map::NodeItem(i) => match i.node {
+                ast::ItemFn(ref decl, unsafety, constness, abi, ref generics, ref block) =>
+                    item_fn(ItemFnParts {
+                        id: i.id,
+                        ident: i.ident,
+                        decl: &**decl,
+                        unsafety: unsafety,
+                        body: &**block,
+                        generics: generics,
+                        abi: abi,
+                        vis: i.vis,
+                        constness: constness,
+                        span: i.span
+                    }),
+                _ => panic!("item FnLikeNode that is not fn-like"),
+            },
+            map::NodeTraitItem(ti) => match ti.node {
+                ast::MethodTraitItem(ref sig, Some(ref body)) => {
+                    method(ti.id, ti.ident, sig, None, body, ti.span)
+                }
+                _ => panic!("trait method FnLikeNode that is not fn-like"),
+            },
+            map::NodeImplItem(ii) => {
+                match ii.node {
+                    ast::MethodImplItem(ref sig, ref body) => {
+                        method(ii.id, ii.ident, sig, Some(ii.vis), body, ii.span)
+                    }
+                    _ => {
+                        panic!("impl method FnLikeNode that is not fn-like")
+                    }
+                }
+            }
+            map::NodeExpr(e) => match e.node {
+                ast::ExprClosure(_, ref decl, ref block) =>
+                    closure(ClosureParts::new(&**decl, &**block, e.id, e.span)),
+                _ => panic!("expr FnLikeNode that is not fn-like"),
+            },
+            _ => panic!("other FnLikeNode that is not fn-like"),
+        }
+    }
+}
diff --git a/src/librustc/front/map/mod.rs b/src/librustc/front/map/mod.rs
new file mode 100644
index 00000000000..764f54ce0f0
--- /dev/null
+++ b/src/librustc/front/map/mod.rs
@@ -0,0 +1,1136 @@
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub use self::Node::*;
+pub use self::PathElem::*;
+use self::MapEntry::*;
+
+use metadata::inline::InlinedItem;
+use metadata::inline::InlinedItem as II;
+use middle::def_id::DefId;
+
+use syntax::abi;
+use syntax::ast::{Name, NodeId, Ident, CRATE_NODE_ID, DUMMY_NODE_ID};
+use syntax::codemap::{Span, Spanned};
+use syntax::parse::token;
+
+use rustc_front::hir::*;
+use rustc_front::fold::Folder;
+use rustc_front::visit::{self, Visitor};
+use rustc_front::util;
+use rustc_front::print::pprust;
+
+use arena::TypedArena;
+use std::cell::RefCell;
+use std::fmt;
+use std::io;
+use std::iter::{self, repeat};
+use std::mem;
+use std::slice;
+
+pub mod blocks;
+
+#[derive(Clone, Copy, PartialEq, Debug)]
+pub enum PathElem {
+    PathMod(Name),
+    PathName(Name)
+}
+
+impl PathElem {
+    pub fn name(&self) -> Name {
+        match *self {
+            PathMod(name) | PathName(name) => name
+        }
+    }
+}
+
+impl fmt::Display for PathElem {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.name())
+    }
+}
+
+#[derive(Clone)]
+pub struct LinkedPathNode<'a> {
+    node: PathElem,
+    next: LinkedPath<'a>,
+}
+
+#[derive(Copy, Clone)]
+pub struct LinkedPath<'a>(Option<&'a LinkedPathNode<'a>>);
+
+impl<'a> LinkedPath<'a> {
+    pub fn empty() -> LinkedPath<'a> {
+        LinkedPath(None)
+    }
+
+    pub fn from(node: &'a LinkedPathNode) -> LinkedPath<'a> {
+        LinkedPath(Some(node))
+    }
+}
+
+impl<'a> Iterator for LinkedPath<'a> {
+    type Item = PathElem;
+
+    fn next(&mut self) -> Option<PathElem> {
+        match self.0 {
+            Some(node) => {
+                *self = node.next;
+                Some(node.node)
+            }
+            None => None
+        }
+    }
+}
+
+/// The type of the iterator used by with_path.
+pub type PathElems<'a, 'b> = iter::Chain<iter::Cloned<slice::Iter<'a, PathElem>>, LinkedPath<'b>>;
+
+pub fn path_to_string<PI: Iterator<Item=PathElem>>(path: PI) -> String {
+    let itr = token::get_ident_interner();
+
+    path.fold(String::new(), |mut s, e| {
+        let e = itr.get(e.name());
+        if !s.is_empty() {
+            s.push_str("::");
+        }
+        s.push_str(&e[..]);
+        s
+    })
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum Node<'ast> {
+    NodeItem(&'ast Item),
+    NodeForeignItem(&'ast ForeignItem),
+    NodeTraitItem(&'ast TraitItem),
+    NodeImplItem(&'ast ImplItem),
+    NodeVariant(&'ast Variant),
+    NodeExpr(&'ast Expr),
+    NodeStmt(&'ast Stmt),
+    NodeArg(&'ast Pat),
+    NodeLocal(&'ast Pat),
+    NodePat(&'ast Pat),
+    NodeBlock(&'ast Block),
+
+    /// NodeStructCtor represents a tuple struct.
+    NodeStructCtor(&'ast StructDef),
+
+    NodeLifetime(&'ast Lifetime),
+    NodeTyParam(&'ast TyParam)
+}
+
+/// Represents an entry and its parent NodeID.
+/// The odd layout is to bring down the total size.
+#[derive(Copy, Debug)]
+enum MapEntry<'ast> {
+    /// Placeholder for holes in the map.
+    NotPresent,
+
+    /// All the node types, with a parent ID.
+    EntryItem(NodeId, &'ast Item),
+    EntryForeignItem(NodeId, &'ast ForeignItem),
+    EntryTraitItem(NodeId, &'ast TraitItem),
+    EntryImplItem(NodeId, &'ast ImplItem),
+    EntryVariant(NodeId, &'ast Variant),
+    EntryExpr(NodeId, &'ast Expr),
+    EntryStmt(NodeId, &'ast Stmt),
+    EntryArg(NodeId, &'ast Pat),
+    EntryLocal(NodeId, &'ast Pat),
+    EntryPat(NodeId, &'ast Pat),
+    EntryBlock(NodeId, &'ast Block),
+    EntryStructCtor(NodeId, &'ast StructDef),
+    EntryLifetime(NodeId, &'ast Lifetime),
+    EntryTyParam(NodeId, &'ast TyParam),
+
+    /// Roots for node trees.
+    RootCrate,
+    RootInlinedParent(&'ast InlinedParent)
+}
+
+impl<'ast> Clone for MapEntry<'ast> {
+    fn clone(&self) -> MapEntry<'ast> {
+        *self
+    }
+}
+
+#[derive(Debug)]
+pub struct InlinedParent {
+    path: Vec<PathElem>,
+    ii: InlinedItem
+}
+
+impl<'ast> MapEntry<'ast> {
+    fn from_node(p: NodeId, node: Node<'ast>) -> MapEntry<'ast> {
+        match node {
+            NodeItem(n) => EntryItem(p, n),
+            NodeForeignItem(n) => EntryForeignItem(p, n),
+            NodeTraitItem(n) => EntryTraitItem(p, n),
+            NodeImplItem(n) => EntryImplItem(p, n),
+            NodeVariant(n) => EntryVariant(p, n),
+            NodeExpr(n) => EntryExpr(p, n),
+            NodeStmt(n) => EntryStmt(p, n),
+            NodeArg(n) => EntryArg(p, n),
+            NodeLocal(n) => EntryLocal(p, n),
+            NodePat(n) => EntryPat(p, n),
+            NodeBlock(n) => EntryBlock(p, n),
+            NodeStructCtor(n) => EntryStructCtor(p, n),
+            NodeLifetime(n) => EntryLifetime(p, n),
+            NodeTyParam(n) => EntryTyParam(p, n),
+        }
+    }
+
+    fn parent_node(self) -> Option<NodeId> {
+        Some(match self {
+            EntryItem(id, _) => id,
+            EntryForeignItem(id, _) => id,
+            EntryTraitItem(id, _) => id,
+            EntryImplItem(id, _) => id,
+            EntryVariant(id, _) => id,
+            EntryExpr(id, _) => id,
+            EntryStmt(id, _) => id,
+            EntryArg(id, _) => id,
+            EntryLocal(id, _) => id,
+            EntryPat(id, _) => id,
+            EntryBlock(id, _) => id,
+            EntryStructCtor(id, _) => id,
+            EntryLifetime(id, _) => id,
+            EntryTyParam(id, _) => id,
+            _ => return None
+        })
+    }
+
+    fn to_node(self) -> Option<Node<'ast>> {
+        Some(match self {
+            EntryItem(_, n) => NodeItem(n),
+            EntryForeignItem(_, n) => NodeForeignItem(n),
+            EntryTraitItem(_, n) => NodeTraitItem(n),
+            EntryImplItem(_, n) => NodeImplItem(n),
+            EntryVariant(_, n) => NodeVariant(n),
+            EntryExpr(_, n) => NodeExpr(n),
+            EntryStmt(_, n) => NodeStmt(n),
+            EntryArg(_, n) => NodeArg(n),
+            EntryLocal(_, n) => NodeLocal(n),
+            EntryPat(_, n) => NodePat(n),
+            EntryBlock(_, n) => NodeBlock(n),
+            EntryStructCtor(_, n) => NodeStructCtor(n),
+            EntryLifetime(_, n) => NodeLifetime(n),
+            EntryTyParam(_, n) => NodeTyParam(n),
+            _ => return None
+        })
+    }
+}
+
+/// Stores a crate and any number of inlined items from other crates.
+pub struct Forest {
+    pub krate: Crate,
+    inlined_items: TypedArena<InlinedParent>
+}
+
+impl Forest {
+    pub fn new(krate: Crate) -> Forest {
+        Forest {
+            krate: krate,
+            inlined_items: TypedArena::new()
+        }
+    }
+
+    pub fn krate<'ast>(&'ast self) -> &'ast Crate {
+        &self.krate
+    }
+}
+
+/// Represents a mapping from Node IDs to AST elements and their parent
+/// Node IDs
+#[derive(Clone)]
+pub struct Map<'ast> {
+    /// The backing storage for all the AST nodes.
+    pub forest: &'ast Forest,
+
+    /// NodeIds are sequential integers from 0, so we can be
+    /// super-compact by storing them in a vector. Not everything with
+    /// a NodeId is in the map, but empirically the occupancy is about
+    /// 75-80%, so there's not too much overhead (certainly less than
+    /// a hashmap, since they (at the time of writing) have a maximum
+    /// of 75% occupancy).
+    ///
+    /// Also, indexing is pretty quick when you've got a vector and
+    /// plain old integers.
+    map: RefCell<Vec<MapEntry<'ast>>>
+}
+
+impl<'ast> Map<'ast> {
+    fn entry_count(&self) -> usize {
+        self.map.borrow().len()
+    }
+
+    fn find_entry(&self, id: NodeId) -> Option<MapEntry<'ast>> {
+        self.map.borrow().get(id as usize).cloned()
+    }
+
+    pub fn krate(&self) -> &'ast Crate {
+        &self.forest.krate
+    }
+
+    /// Retrieve the Node corresponding to `id`, panicking if it cannot
+    /// be found.
+    pub fn get(&self, id: NodeId) -> Node<'ast> {
+        match self.find(id) {
+            Some(node) => node,
+            None => panic!("couldn't find node id {} in the AST map", id)
+        }
+    }
+
+    /// Retrieve the Node corresponding to `id`, returning None if
+    /// cannot be found.
+    pub fn find(&self, id: NodeId) -> Option<Node<'ast>> {
+        self.find_entry(id).and_then(|x| x.to_node())
+    }
+
+    /// Similar to get_parent, returns the parent node id or id if there is no
+    /// parent.
+    /// This function returns the immediate parent in the AST, whereas get_parent
+    /// returns the enclosing item. Note that this might not be the actual parent
+    /// node in the AST - some kinds of nodes are not in the map and these will
+    /// never appear as the parent_node. So you can always walk the parent_nodes
+    /// from a node to the root of the ast (unless you get the same id back here
+    /// that can happen if the id is not in the map itself or is just weird).
+    pub fn get_parent_node(&self, id: NodeId) -> NodeId {
+        self.find_entry(id).and_then(|x| x.parent_node()).unwrap_or(id)
+    }
+
+    /// If there is some error when walking the parents (e.g., a node does not
+    /// have a parent in the map or a node can't be found), then we return the
+    /// last good node id we found. Note that reaching the crate root (id == 0),
+    /// is not an error, since items in the crate module have the crate root as
+    /// parent.
+    fn walk_parent_nodes<F>(&self, start_id: NodeId, found: F) -> Result<NodeId, NodeId>
+        where F: Fn(&Node<'ast>) -> bool
+    {
+        let mut id = start_id;
+        loop {
+            let parent_node = self.get_parent_node(id);
+            if parent_node == 0 {
+                return Ok(0);
+            }
+            if parent_node == id {
+                return Err(id);
+            }
+
+            let node = self.find_entry(parent_node);
+            if node.is_none() {
+                return Err(id);
+            }
+            let node = node.unwrap().to_node();
+            match node {
+                Some(ref node) => {
+                    if found(node) {
+                        return Ok(parent_node);
+                    }
+                }
+                None => {
+                    return Err(parent_node);
+                }
+            }
+            id = parent_node;
+        }
+    }
+
+    /// Retrieve the NodeId for `id`'s parent item, or `id` itself if no
+    /// parent item is in this map. The "parent item" is the closest parent node
+    /// in the AST which is recorded by the map and is an item, either an item
+    /// in a module, trait, or impl.
+    pub fn get_parent(&self, id: NodeId) -> NodeId {
+        match self.walk_parent_nodes(id, |node| match *node {
+            NodeItem(_) |
+            NodeForeignItem(_) |
+            NodeTraitItem(_) |
+            NodeImplItem(_) => true,
+            _ => false,
+        }) {
+            Ok(id) => id,
+            Err(id) => id,
+        }
+    }
+
+    /// Returns the nearest enclosing scope. A scope is an item or block.
+    /// FIXME it is not clear to me that all items qualify as scopes - statics
+    /// and associated types probably shouldn't, for example. Behaviour in this
+    /// regard should be expected to be highly unstable.
+    pub fn get_enclosing_scope(&self, id: NodeId) -> Option<NodeId> {
+        match self.walk_parent_nodes(id, |node| match *node {
+            NodeItem(_) |
+            NodeForeignItem(_) |
+            NodeTraitItem(_) |
+            NodeImplItem(_) |
+            NodeBlock(_) => true,
+            _ => false,
+        }) {
+            Ok(id) => Some(id),
+            Err(_) => None,
+        }
+    }
+
+    pub fn get_parent_did(&self, id: NodeId) -> DefId {
+        let parent = self.get_parent(id);
+        match self.find_entry(parent) {
+            Some(RootInlinedParent(&InlinedParent {ii: II::TraitItem(did, _), ..})) => did,
+            Some(RootInlinedParent(&InlinedParent {ii: II::ImplItem(did, _), ..})) => did,
+            _ => DefId::local(parent)
+        }
+    }
+
+    pub fn get_foreign_abi(&self, id: NodeId) -> abi::Abi {
+        let parent = self.get_parent(id);
+        let abi = match self.find_entry(parent) {
+            Some(EntryItem(_, i)) => {
+                match i.node {
+                    ItemForeignMod(ref nm) => Some(nm.abi),
+                    _ => None
+                }
+            }
+            /// Wrong but OK, because the only inlined foreign items are intrinsics.
+            Some(RootInlinedParent(_)) => Some(abi::RustIntrinsic),
+            _ => None
+        };
+        match abi {
+            Some(abi) => abi,
+            None => panic!("expected foreign mod or inlined parent, found {}",
+                          self.node_to_string(parent))
+        }
+    }
+
+    pub fn get_foreign_vis(&self, id: NodeId) -> Visibility {
+        let vis = self.expect_foreign_item(id).vis;
+        match self.find(self.get_parent(id)) {
+            Some(NodeItem(i)) => vis.inherit_from(i.vis),
+            _ => vis
+        }
+    }
+
+    pub fn expect_item(&self, id: NodeId) -> &'ast Item {
+        match self.find(id) {
+            Some(NodeItem(item)) => item,
+            _ => panic!("expected item, found {}", self.node_to_string(id))
+        }
+    }
+
+    pub fn expect_trait_item(&self, id: NodeId) -> &'ast TraitItem {
+        match self.find(id) {
+            Some(NodeTraitItem(item)) => item,
+            _ => panic!("expected trait item, found {}", self.node_to_string(id))
+        }
+    }
+
+    pub fn expect_struct(&self, id: NodeId) -> &'ast StructDef {
+        match self.find(id) {
+            Some(NodeItem(i)) => {
+                match i.node {
+                    ItemStruct(ref struct_def, _) => &**struct_def,
+                    _ => panic!("struct ID bound to non-struct")
+                }
+            }
+            Some(NodeVariant(variant)) => {
+                match variant.node.kind {
+                    StructVariantKind(ref struct_def) => &**struct_def,
+                    _ => panic!("struct ID bound to enum variant that isn't struct-like"),
+                }
+            }
+            _ => panic!(format!("expected struct, found {}", self.node_to_string(id))),
+        }
+    }
+
+    pub fn expect_variant(&self, id: NodeId) -> &'ast Variant {
+        match self.find(id) {
+            Some(NodeVariant(variant)) => variant,
+            _ => panic!(format!("expected variant, found {}", self.node_to_string(id))),
+        }
+    }
+
+    pub fn expect_foreign_item(&self, id: NodeId) -> &'ast ForeignItem {
+        match self.find(id) {
+            Some(NodeForeignItem(item)) => item,
+            _ => panic!("expected foreign item, found {}", self.node_to_string(id))
+        }
+    }
+
+    pub fn expect_expr(&self, id: NodeId) -> &'ast Expr {
+        match self.find(id) {
+            Some(NodeExpr(expr)) => expr,
+            _ => panic!("expected expr, found {}", self.node_to_string(id))
+        }
+    }
+
+    /// returns the name associated with the given NodeId's AST
+    pub fn get_path_elem(&self, id: NodeId) -> PathElem {
+        let node = self.get(id);
+        match node {
+            NodeItem(item) => {
+                match item.node {
+                    ItemMod(_) | ItemForeignMod(_) => {
+                        PathMod(item.ident.name)
+                    }
+                    _ => PathName(item.ident.name)
+                }
+            }
+            NodeForeignItem(i) => PathName(i.ident.name),
+            NodeImplItem(ii) => PathName(ii.ident.name),
+            NodeTraitItem(ti) => PathName(ti.ident.name),
+            NodeVariant(v) => PathName(v.node.name.name),
+            NodeLifetime(lt) => PathName(lt.name),
+            _ => panic!("no path elem for {:?}", node)
+        }
+    }
+
+    pub fn with_path<T, F>(&self, id: NodeId, f: F) -> T where
+        F: FnOnce(PathElems) -> T,
+    {
+        self.with_path_next(id, LinkedPath::empty(), f)
+    }
+
+    pub fn path_to_string(&self, id: NodeId) -> String {
+        self.with_path(id, |path| path_to_string(path))
+    }
+
+    fn path_to_str_with_ident(&self, id: NodeId, i: Ident) -> String {
+        self.with_path(id, |path| {
+            path_to_string(path.chain(Some(PathName(i.name))))
+        })
+    }
+
+    fn with_path_next<T, F>(&self, id: NodeId, next: LinkedPath, f: F) -> T where
+        F: FnOnce(PathElems) -> T,
+    {
+        let parent = self.get_parent(id);
+        let parent = match self.find_entry(id) {
+            Some(EntryForeignItem(..)) => {
+                // Anonymous extern items go in the parent scope.
+                self.get_parent(parent)
+            }
+            // But tuple struct ctors don't have names, so use the path of its
+            // parent, the struct item. Similarly with closure expressions.
+            Some(EntryStructCtor(..)) | Some(EntryExpr(..)) => {
+                return self.with_path_next(parent, next, f);
+            }
+            _ => parent
+        };
+        if parent == id {
+            match self.find_entry(id) {
+                Some(RootInlinedParent(data)) => {
+                    f(data.path.iter().cloned().chain(next))
+                }
+                _ => f([].iter().cloned().chain(next))
+            }
+        } else {
+            self.with_path_next(parent, LinkedPath::from(&LinkedPathNode {
+                node: self.get_path_elem(id),
+                next: next
+            }), f)
+        }
+    }
+
+    /// Given a node ID, get a list of of attributes associated with the AST
+    /// corresponding to the Node ID
+    pub fn attrs(&self, id: NodeId) -> &'ast [Attribute] {
+        let attrs = match self.find(id) {
+            Some(NodeItem(i)) => Some(&i.attrs[..]),
+            Some(NodeForeignItem(fi)) => Some(&fi.attrs[..]),
+            Some(NodeTraitItem(ref ti)) => Some(&ti.attrs[..]),
+            Some(NodeImplItem(ref ii)) => Some(&ii.attrs[..]),
+            Some(NodeVariant(ref v)) => Some(&v.node.attrs[..]),
+            // unit/tuple structs take the attributes straight from
+            // the struct definition.
+            Some(NodeStructCtor(_)) => {
+                return self.attrs(self.get_parent(id));
+            }
+            _ => None
+        };
+        attrs.unwrap_or(&[])
+    }
+
+    /// Returns an iterator that yields the node id's with paths that
+    /// match `parts`.  (Requires `parts` is non-empty.)
+    ///
+    /// For example, if given `parts` equal to `["bar", "quux"]`, then
+    /// the iterator will produce node id's for items with paths
+    /// such as `foo::bar::quux`, `bar::quux`, `other::bar::quux`, and
+    /// any other such items it can find in the map.
+    pub fn nodes_matching_suffix<'a>(&'a self, parts: &'a [String])
+                                 -> NodesMatchingSuffix<'a, 'ast> {
+        NodesMatchingSuffix {
+            map: self,
+            item_name: parts.last().unwrap(),
+            in_which: &parts[..parts.len() - 1],
+            idx: 0,
+        }
+    }
+
+    pub fn opt_span(&self, id: NodeId) -> Option<Span> {
+        let sp = match self.find(id) {
+            Some(NodeItem(item)) => item.span,
+            Some(NodeForeignItem(foreign_item)) => foreign_item.span,
+            Some(NodeTraitItem(trait_method)) => trait_method.span,
+            Some(NodeImplItem(ref impl_item)) => impl_item.span,
+            Some(NodeVariant(variant)) => variant.span,
+            Some(NodeExpr(expr)) => expr.span,
+            Some(NodeStmt(stmt)) => stmt.span,
+            Some(NodeArg(pat)) | Some(NodeLocal(pat)) => pat.span,
+            Some(NodePat(pat)) => pat.span,
+            Some(NodeBlock(block)) => block.span,
+            Some(NodeStructCtor(_)) => self.expect_item(self.get_parent(id)).span,
+            Some(NodeTyParam(ty_param)) => ty_param.span,
+            _ => return None,
+        };
+        Some(sp)
+    }
+
+    pub fn span(&self, id: NodeId) -> Span {
+        self.opt_span(id)
+            .unwrap_or_else(|| panic!("AstMap.span: could not find span for id {:?}", id))
+    }
+
+    pub fn def_id_span(&self, def_id: DefId, fallback: Span) -> Span {
+        if def_id.is_local() {
+            self.opt_span(def_id.node).unwrap_or(fallback)
+        } else {
+            fallback
+        }
+    }
+
+    pub fn node_to_string(&self, id: NodeId) -> String {
+        node_id_to_string(self, id, true)
+    }
+
+    pub fn node_to_user_string(&self, id: NodeId) -> String {
+        node_id_to_string(self, id, false)
+    }
+}
+
+pub struct NodesMatchingSuffix<'a, 'ast:'a> {
+    map: &'a Map<'ast>,
+    item_name: &'a String,
+    in_which: &'a [String],
+    idx: NodeId,
+}
+
+impl<'a, 'ast> NodesMatchingSuffix<'a, 'ast> {
+    /// Returns true only if some suffix of the module path for parent
+    /// matches `self.in_which`.
+    ///
+    /// In other words: let `[x_0,x_1,...,x_k]` be `self.in_which`;
+    /// returns true if parent's path ends with the suffix
+    /// `x_0::x_1::...::x_k`.
+    fn suffix_matches(&self, parent: NodeId) -> bool {
+        let mut cursor = parent;
+        for part in self.in_which.iter().rev() {
+            let (mod_id, mod_name) = match find_first_mod_parent(self.map, cursor) {
+                None => return false,
+                Some((node_id, name)) => (node_id, name),
+            };
+            if &part[..] != mod_name.as_str() {
+                return false;
+            }
+            cursor = self.map.get_parent(mod_id);
+        }
+        return true;
+
+        // Finds the first mod in parent chain for `id`, along with
+        // that mod's name.
+        //
+        // If `id` itself is a mod named `m` with parent `p`, then
+        // returns `Some(id, m, p)`.  If `id` has no mod in its parent
+        // chain, then returns `None`.
+        fn find_first_mod_parent<'a>(map: &'a Map, mut id: NodeId) -> Option<(NodeId, Name)> {
+            loop {
+                match map.find(id) {
+                    None => return None,
+                    Some(NodeItem(item)) if item_is_mod(&*item) =>
+                        return Some((id, item.ident.name)),
+                    _ => {}
+                }
+                let parent = map.get_parent(id);
+                if parent == id { return None }
+                id = parent;
+            }
+
+            fn item_is_mod(item: &Item) -> bool {
+                match item.node {
+                    ItemMod(_) => true,
+                    _ => false,
+                }
+            }
+        }
+    }
+
+    // We are looking at some node `n` with a given name and parent
+    // id; do their names match what I am seeking?
+    fn matches_names(&self, parent_of_n: NodeId, name: Name) -> bool {
+        name.as_str() == &self.item_name[..] &&
+            self.suffix_matches(parent_of_n)
+    }
+}
+
+impl<'a, 'ast> Iterator for NodesMatchingSuffix<'a, 'ast> {
+    type Item = NodeId;
+
+    fn next(&mut self) -> Option<NodeId> {
+        loop {
+            let idx = self.idx;
+            if idx as usize >= self.map.entry_count() {
+                return None;
+            }
+            self.idx += 1;
+            let name = match self.map.find_entry(idx) {
+                Some(EntryItem(_, n))       => n.name(),
+                Some(EntryForeignItem(_, n))=> n.name(),
+                Some(EntryTraitItem(_, n))  => n.name(),
+                Some(EntryImplItem(_, n))   => n.name(),
+                Some(EntryVariant(_, n))    => n.name(),
+                _ => continue,
+            };
+            if self.matches_names(self.map.get_parent(idx), name) {
+                return Some(idx)
+            }
+        }
+    }
+}
+
+trait Named {
+    fn name(&self) -> Name;
+}
+
+impl<T:Named> Named for Spanned<T> { fn name(&self) -> Name { self.node.name() } }
+
+impl Named for Item { fn name(&self) -> Name { self.ident.name } }
+impl Named for ForeignItem { fn name(&self) -> Name { self.ident.name } }
+impl Named for Variant_ { fn name(&self) -> Name { self.name.name } }
+impl Named for TraitItem { fn name(&self) -> Name { self.ident.name } }
+impl Named for ImplItem { fn name(&self) -> Name { self.ident.name } }
+
+pub trait FoldOps {
+    fn new_id(&self, id: NodeId) -> NodeId {
+        id
+    }
+    fn new_def_id(&self, def_id: DefId) -> DefId {
+        def_id
+    }
+    fn new_span(&self, span: Span) -> Span {
+        span
+    }
+}
+
+/// A Folder that updates IDs and Span's according to fold_ops.
+struct IdAndSpanUpdater<F> {
+    fold_ops: F
+}
+
+impl<F: FoldOps> Folder for IdAndSpanUpdater<F> {
+    fn new_id(&mut self, id: NodeId) -> NodeId {
+        self.fold_ops.new_id(id)
+    }
+
+    fn new_span(&mut self, span: Span) -> Span {
+        self.fold_ops.new_span(span)
+    }
+}
+
+/// A Visitor that walks over an AST and collects Node's into an AST Map.
+struct NodeCollector<'ast> {
+    map: Vec<MapEntry<'ast>>,
+    parent_node: NodeId,
+}
+
+impl<'ast> NodeCollector<'ast> {
+    fn insert_entry(&mut self, id: NodeId, entry: MapEntry<'ast>) {
+        debug!("ast_map: {:?} => {:?}", id, entry);
+        let len = self.map.len();
+        if id as usize >= len {
+            self.map.extend(repeat(NotPresent).take(id as usize - len + 1));
+        }
+        self.map[id as usize] = entry;
+    }
+
+    fn insert(&mut self, id: NodeId, node: Node<'ast>) {
+        let entry = MapEntry::from_node(self.parent_node, node);
+        self.insert_entry(id, entry);
+    }
+
+    fn visit_fn_decl(&mut self, decl: &'ast FnDecl) {
+        for a in &decl.inputs {
+            self.insert(a.id, NodeArg(&*a.pat));
+        }
+    }
+}
+
+impl<'ast> Visitor<'ast> for NodeCollector<'ast> {
+    fn visit_item(&mut self, i: &'ast Item) {
+        self.insert(i.id, NodeItem(i));
+
+        let parent_node = self.parent_node;
+        self.parent_node = i.id;
+
+        match i.node {
+            ItemImpl(_, _, _, _, _, ref impl_items) => {
+                for ii in impl_items {
+                    self.insert(ii.id, NodeImplItem(ii));
+                }
+            }
+            ItemEnum(ref enum_definition, _) => {
+                for v in &enum_definition.variants {
+                    self.insert(v.node.id, NodeVariant(&**v));
+                }
+            }
+            ItemForeignMod(ref nm) => {
+                for nitem in &nm.items {
+                    self.insert(nitem.id, NodeForeignItem(&**nitem));
+                }
+            }
+            ItemStruct(ref struct_def, _) => {
+                // If this is a tuple-like struct, register the constructor.
+                match struct_def.ctor_id {
+                    Some(ctor_id) => {
+                        self.insert(ctor_id, NodeStructCtor(&**struct_def));
+                    }
+                    None => {}
+                }
+            }
+            ItemTrait(_, _, ref bounds, ref trait_items) => {
+                for b in bounds.iter() {
+                    if let TraitTyParamBound(ref t, TraitBoundModifier::None) = *b {
+                        self.insert(t.trait_ref.ref_id, NodeItem(i));
+                    }
+                }
+
+                for ti in trait_items {
+                    self.insert(ti.id, NodeTraitItem(ti));
+                }
+            }
+            ItemUse(ref view_path) => {
+                match view_path.node {
+                    ViewPathList(_, ref paths) => {
+                        for path in paths {
+                            self.insert(path.node.id(), NodeItem(i));
+                        }
+                    }
+                    _ => ()
+                }
+            }
+            _ => {}
+        }
+        visit::walk_item(self, i);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_generics(&mut self, generics: &'ast Generics) {
+        for ty_param in generics.ty_params.iter() {
+            self.insert(ty_param.id, NodeTyParam(ty_param));
+        }
+
+        visit::walk_generics(self, generics);
+    }
+
+    fn visit_trait_item(&mut self, ti: &'ast TraitItem) {
+        let parent_node = self.parent_node;
+        self.parent_node = ti.id;
+        visit::walk_trait_item(self, ti);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_impl_item(&mut self, ii: &'ast ImplItem) {
+        let parent_node = self.parent_node;
+        self.parent_node = ii.id;
+
+        visit::walk_impl_item(self, ii);
+
+        self.parent_node = parent_node;
+    }
+
+    fn visit_pat(&mut self, pat: &'ast Pat) {
+        self.insert(pat.id, match pat.node {
+            // Note: this is at least *potentially* a pattern...
+            PatIdent(..) => NodeLocal(pat),
+            _ => NodePat(pat)
+        });
+
+        let parent_node = self.parent_node;
+        self.parent_node = pat.id;
+        visit::walk_pat(self, pat);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_expr(&mut self, expr: &'ast Expr) {
+        self.insert(expr.id, NodeExpr(expr));
+        let parent_node = self.parent_node;
+        self.parent_node = expr.id;
+        visit::walk_expr(self, expr);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_stmt(&mut self, stmt: &'ast Stmt) {
+        let id = util::stmt_id(stmt);
+        self.insert(id, NodeStmt(stmt));
+        let parent_node = self.parent_node;
+        self.parent_node = id;
+        visit::walk_stmt(self, stmt);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_fn(&mut self, fk: visit::FnKind<'ast>, fd: &'ast FnDecl,
+                b: &'ast Block, s: Span, id: NodeId) {
+        let parent_node = self.parent_node;
+        self.parent_node = id;
+        self.visit_fn_decl(fd);
+        visit::walk_fn(self, fk, fd, b, s);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_ty(&mut self, ty: &'ast Ty) {
+        let parent_node = self.parent_node;
+        self.parent_node = ty.id;
+        match ty.node {
+            TyBareFn(ref fd) => {
+                self.visit_fn_decl(&*fd.decl);
+            }
+            _ => {}
+        }
+        visit::walk_ty(self, ty);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_block(&mut self, block: &'ast Block) {
+        self.insert(block.id, NodeBlock(block));
+        let parent_node = self.parent_node;
+        self.parent_node = block.id;
+        visit::walk_block(self, block);
+        self.parent_node = parent_node;
+    }
+
+    fn visit_lifetime_ref(&mut self, lifetime: &'ast Lifetime) {
+        self.insert(lifetime.id, NodeLifetime(lifetime));
+    }
+
+    fn visit_lifetime_def(&mut self, def: &'ast LifetimeDef) {
+        self.visit_lifetime_ref(&def.lifetime);
+    }
+}
+
+pub fn map_crate<'ast>(forest: &'ast mut Forest) -> Map<'ast> {
+    let mut collector = NodeCollector {
+        map: vec![],
+        parent_node: CRATE_NODE_ID,
+    };
+    collector.insert_entry(CRATE_NODE_ID, RootCrate);
+    visit::walk_crate(&mut collector, &forest.krate);
+    let map = collector.map;
+
+    if log_enabled!(::log::DEBUG) {
+        // This only makes sense for ordered stores; note the
+        // enumerate to count the number of entries.
+        let (entries_less_1, _) = map.iter().filter(|&x| {
+            match *x {
+                NotPresent => false,
+                _ => true
+            }
+        }).enumerate().last().expect("AST map was empty after folding?");
+
+        let entries = entries_less_1 + 1;
+        let vector_length = map.len();
+        debug!("The AST map has {} entries with a maximum of {}: occupancy {:.1}%",
+              entries, vector_length, (entries as f64 / vector_length as f64) * 100.);
+    }
+
+    Map {
+        forest: forest,
+        map: RefCell::new(map)
+    }
+}
+
+/// Used for items loaded from external crate that are being inlined into this
+/// crate.  The `path` should be the path to the item but should not include
+/// the item itself.
+pub fn map_decoded_item<'ast, F: FoldOps>(map: &Map<'ast>,
+                                          path: Vec<PathElem>,
+                                          ii: InlinedItem,
+                                          fold_ops: F)
+                                          -> &'ast InlinedItem {
+    let mut fld = IdAndSpanUpdater { fold_ops: fold_ops };
+    let ii = match ii {
+        II::Item(i) => II::Item(fld.fold_item(i).expect_one("expected one item")),
+        II::TraitItem(d, ti) => {
+            II::TraitItem(fld.fold_ops.new_def_id(d),
+                        fld.fold_trait_item(ti).expect_one("expected one trait item"))
+        }
+        II::ImplItem(d, ii) => {
+            II::ImplItem(fld.fold_ops.new_def_id(d),
+                       fld.fold_impl_item(ii).expect_one("expected one impl item"))
+        }
+        II::Foreign(i) => II::Foreign(fld.fold_foreign_item(i))
+    };
+
+    let ii_parent = map.forest.inlined_items.alloc(InlinedParent {
+        path: path,
+        ii: ii
+    });
+
+    let ii_parent_id = fld.new_id(DUMMY_NODE_ID);
+    let mut collector = NodeCollector {
+        map: mem::replace(&mut *map.map.borrow_mut(), vec![]),
+        parent_node: ii_parent_id,
+    };
+    collector.insert_entry(ii_parent_id, RootInlinedParent(ii_parent));
+    ii_parent.ii.visit(&mut collector);
+
+    // Methods get added to the AST map when their impl is visited.  Since we
+    // don't decode and instantiate the impl, but just the method, we have to
+    // add it to the table now. Likewise with foreign items.
+    match ii_parent.ii {
+        II::Item(_) => {}
+        II::TraitItem(_, ref ti) => {
+            collector.insert(ti.id, NodeTraitItem(ti));
+        }
+        II::ImplItem(_, ref ii) => {
+            collector.insert(ii.id, NodeImplItem(ii));
+        }
+        II::Foreign(ref i) => {
+            collector.insert(i.id, NodeForeignItem(i));
+        }
+    }
+    *map.map.borrow_mut() = collector.map;
+    &ii_parent.ii
+}
+
+pub trait NodePrinter {
+    fn print_node(&mut self, node: &Node) -> io::Result<()>;
+}
+
+impl<'a> NodePrinter for pprust::State<'a> {
+    fn print_node(&mut self, node: &Node) -> io::Result<()> {
+        match *node {
+            NodeItem(a)        => self.print_item(&*a),
+            NodeForeignItem(a) => self.print_foreign_item(&*a),
+            NodeTraitItem(a)   => self.print_trait_item(a),
+            NodeImplItem(a)    => self.print_impl_item(a),
+            NodeVariant(a)     => self.print_variant(&*a),
+            NodeExpr(a)        => self.print_expr(&*a),
+            NodeStmt(a)        => self.print_stmt(&*a),
+            NodePat(a)         => self.print_pat(&*a),
+            NodeBlock(a)       => self.print_block(&*a),
+            NodeLifetime(a)    => self.print_lifetime(&*a),
+            NodeTyParam(_)     => panic!("cannot print TyParam"),
+            // these cases do not carry enough information in the
+            // ast_map to reconstruct their full structure for pretty
+            // printing.
+            NodeLocal(_)       => panic!("cannot print isolated Local"),
+            NodeArg(_)         => panic!("cannot print isolated Arg"),
+            NodeStructCtor(_)  => panic!("cannot print isolated StructCtor"),
+        }
+    }
+}
+
+fn node_id_to_string(map: &Map, id: NodeId, include_id: bool) -> String {
+    let id_str = format!(" (id={})", id);
+    let id_str = if include_id { &id_str[..] } else { "" };
+
+    match map.find(id) {
+        Some(NodeItem(item)) => {
+            let path_str = map.path_to_str_with_ident(id, item.ident);
+            let item_str = match item.node {
+                ItemExternCrate(..) => "extern crate",
+                ItemUse(..) => "use",
+                ItemStatic(..) => "static",
+                ItemConst(..) => "const",
+                ItemFn(..) => "fn",
+                ItemMod(..) => "mod",
+                ItemForeignMod(..) => "foreign mod",
+                ItemTy(..) => "ty",
+                ItemEnum(..) => "enum",
+                ItemStruct(..) => "struct",
+                ItemTrait(..) => "trait",
+                ItemImpl(..) => "impl",
+                ItemDefaultImpl(..) => "default impl",
+            };
+            format!("{} {}{}", item_str, path_str, id_str)
+        }
+        Some(NodeForeignItem(item)) => {
+            let path_str = map.path_to_str_with_ident(id, item.ident);
+            format!("foreign item {}{}", path_str, id_str)
+        }
+        Some(NodeImplItem(ii)) => {
+            match ii.node {
+                ConstImplItem(..) => {
+                    format!("assoc const {} in {}{}",
+                            ii.ident,
+                            map.path_to_string(id),
+                            id_str)
+                }
+                MethodImplItem(..) => {
+                    format!("method {} in {}{}",
+                            ii.ident,
+                            map.path_to_string(id), id_str)
+                }
+                TypeImplItem(_) => {
+                    format!("assoc type {} in {}{}",
+                            ii.ident,
+                            map.path_to_string(id),
+                            id_str)
+                }
+            }
+        }
+        Some(NodeTraitItem(ti)) => {
+            let kind = match ti.node {
+                ConstTraitItem(..) => "assoc constant",
+                MethodTraitItem(..) => "trait method",
+                TypeTraitItem(..) => "assoc type",
+            };
+
+            format!("{} {} in {}{}",
+                    kind,
+                    ti.ident,
+                    map.path_to_string(id),
+                    id_str)
+        }
+        Some(NodeVariant(ref variant)) => {
+            format!("variant {} in {}{}",
+                    variant.node.name,
+                    map.path_to_string(id), id_str)
+        }
+        Some(NodeExpr(ref expr)) => {
+            format!("expr {}{}", pprust::expr_to_string(&**expr), id_str)
+        }
+        Some(NodeStmt(ref stmt)) => {
+            format!("stmt {}{}", pprust::stmt_to_string(&**stmt), id_str)
+        }
+        Some(NodeArg(ref pat)) => {
+            format!("arg {}{}", pprust::pat_to_string(&**pat), id_str)
+        }
+        Some(NodeLocal(ref pat)) => {
+            format!("local {}{}", pprust::pat_to_string(&**pat), id_str)
+        }
+        Some(NodePat(ref pat)) => {
+            format!("pat {}{}", pprust::pat_to_string(&**pat), id_str)
+        }
+        Some(NodeBlock(ref block)) => {
+            format!("block {}{}", pprust::block_to_string(&**block), id_str)
+        }
+        Some(NodeStructCtor(_)) => {
+            format!("struct_ctor {}{}", map.path_to_string(id), id_str)
+        }
+        Some(NodeLifetime(ref l)) => {
+            format!("lifetime {}{}",
+                    pprust::lifetime_to_string(&**l), id_str)
+        }
+        Some(NodeTyParam(ref ty_param)) => {
+            format!("typaram {:?}{}", ty_param, id_str)
+        }
+        None => {
+            format!("unknown node{}", id_str)
+        }
+    }
+}