Port to using the newer graph, which offers iterators instead of the

older `each` method, but is otherwise identical.

10 files changed, 320 insertions, 244 deletions

diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 6837483a422..ab5c4e76966 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -104,7 +104,6 @@ pub mod middle {
     pub mod entry;
     pub mod expr_use_visitor;
     pub mod fast_reject;
-    pub mod graph;
     pub mod intrinsicck;
     pub mod infer;
     pub mod lang_items;
diff --git a/src/librustc/middle/cfg/construct.rs b/src/librustc/middle/cfg/construct.rs
index cbc2ef1535e..359a1a486c9 100644
--- a/src/librustc/middle/cfg/construct.rs
+++ b/src/librustc/middle/cfg/construct.rs
@@ -8,9 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use rustc_data_structures::graph;
 use middle::cfg::*;
 use middle::def;
-use middle::graph;
 use middle::pat_util;
 use middle::region::CodeExtent;
 use middle::ty;
diff --git a/src/librustc/middle/cfg/mod.rs b/src/librustc/middle/cfg/mod.rs
index ad4fdcd7b83..3ca221c9630 100644
--- a/src/librustc/middle/cfg/mod.rs
+++ b/src/librustc/middle/cfg/mod.rs
@@ -11,7 +11,7 @@
 //! Module that constructs a control-flow graph representing an item.
 //! Uses `Graph` as the underlying representation.
 
-use middle::graph;
+use rustc_data_structures::graph;
 use middle::ty;
 use syntax::ast;
 
@@ -24,7 +24,7 @@ pub struct CFG {
     pub exit: CFGIndex,
 }
 
-#[derive(Copy, Clone, PartialEq)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub enum CFGNodeData {
     AST(ast::NodeId),
     Entry,
@@ -43,6 +43,7 @@ impl CFGNodeData {
     }
 }
 
+#[derive(Debug)]
 pub struct CFGEdgeData {
     pub exiting_scopes: Vec<ast::NodeId>
 }
diff --git a/src/librustc/middle/dataflow.rs b/src/librustc/middle/dataflow.rs
index 41b4495c5f0..1d5d4f72fc2 100644
--- a/src/librustc/middle/dataflow.rs
+++ b/src/librustc/middle/dataflow.rs
@@ -576,10 +576,9 @@ impl<'a, 'b, 'tcx, O:DataFlowOperator> PropagationContext<'a, 'b, 'tcx, O> {
                                                pred_bits: &[usize],
                                                cfg: &cfg::CFG,
                                                cfgidx: CFGIndex) {
-        cfg.graph.each_outgoing_edge(cfgidx, |_e_idx, edge| {
+        for (_, edge) in cfg.graph.outgoing_edges(cfgidx) {
             self.propagate_bits_into_entry_set_for(pred_bits, edge);
-            true
-        });
+        }
     }
 
     fn propagate_bits_into_entry_set_for(&mut self,
diff --git a/src/librustc/middle/infer/region_inference/mod.rs b/src/librustc/middle/infer/region_inference/mod.rs
index c6be97e6dbe..e76468131e0 100644
--- a/src/librustc/middle/infer/region_inference/mod.rs
+++ b/src/librustc/middle/infer/region_inference/mod.rs
@@ -20,14 +20,13 @@ use self::Classification::*;
 
 use super::{RegionVariableOrigin, SubregionOrigin, TypeTrace, MiscVariable};
 
+use rustc_data_structures::graph::{self, Direction, NodeIndex};
 use middle::region;
 use middle::ty::{self, Ty};
 use middle::ty::{BoundRegion, FreeRegion, Region, RegionVid};
 use middle::ty::{ReEmpty, ReStatic, ReInfer, ReFree, ReEarlyBound};
 use middle::ty::{ReLateBound, ReScope, ReVar, ReSkolemized, BrFresh};
 use middle::ty_relate::RelateResult;
-use middle::graph;
-use middle::graph::{Direction, NodeIndex};
 use util::common::indenter;
 use util::nodemap::{FnvHashMap, FnvHashSet};
 use util::ppaux::{Repr, UserString};
@@ -1325,10 +1324,8 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
         let num_vars = self.num_vars();
 
         let constraints = self.constraints.borrow();
-        let num_edges = constraints.len();
 
-        let mut graph = graph::Graph::with_capacity(num_vars as usize + 1,
-                                                    num_edges);
+        let mut graph = graph::Graph::new();
 
         for _ in 0..num_vars {
             graph.add_node(());
@@ -1370,10 +1367,10 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
         // not contained by an upper-bound.
         let (mut lower_bounds, lower_dup) =
             self.collect_concrete_regions(graph, var_data, node_idx,
-                                          graph::Incoming, dup_vec);
+                                          graph::INCOMING, dup_vec);
         let (mut upper_bounds, upper_dup) =
             self.collect_concrete_regions(graph, var_data, node_idx,
-                                          graph::Outgoing, dup_vec);
+                                          graph::OUTGOING, dup_vec);
 
         if lower_dup || upper_dup {
             return;
@@ -1433,7 +1430,7 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
         // that have no intersection.
         let (upper_bounds, dup_found) =
             self.collect_concrete_regions(graph, var_data, node_idx,
-                                          graph::Outgoing, dup_vec);
+                                          graph::OUTGOING, dup_vec);
 
         if dup_found {
             return;
@@ -1508,8 +1505,8 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
             // figure out the direction from which this node takes its
             // values, and search for concrete regions etc in that direction
             let dir = match classification {
-                Expanding => graph::Incoming,
-                Contracting => graph::Outgoing,
+                Expanding => graph::INCOMING,
+                Contracting => graph::OUTGOING,
             };
 
             process_edges(self, &mut state, graph, node_idx, dir);
@@ -1519,14 +1516,14 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
         return (result, dup_found);
 
         fn process_edges<'a, 'tcx>(this: &RegionVarBindings<'a, 'tcx>,
-                         state: &mut WalkState<'tcx>,
-                         graph: &RegionGraph,
-                         source_vid: RegionVid,
-                         dir: Direction) {
+                                   state: &mut WalkState<'tcx>,
+                                   graph: &RegionGraph,
+                                   source_vid: RegionVid,
+                                   dir: Direction) {
             debug!("process_edges(source_vid={:?}, dir={:?})", source_vid, dir);
 
             let source_node_index = NodeIndex(source_vid.index as usize);
-            graph.each_adjacent_edge(source_node_index, dir, |_, edge| {
+            for (_, edge) in graph.adjacent_edges(source_node_index, dir) {
                 match edge.data {
                     ConstrainVarSubVar(from_vid, to_vid) => {
                         let opp_vid =
@@ -1544,8 +1541,7 @@ impl<'a, 'tcx> RegionVarBindings<'a, 'tcx> {
                         });
                     }
                 }
-                true
-            });
+            }
         }
     }
 
diff --git a/src/librustc_data_structures/bitvec.rs b/src/librustc_data_structures/bitvec.rs
new file mode 100644
index 00000000000..f5924ef5a3f
--- /dev/null
+++ b/src/librustc_data_structures/bitvec.rs
@@ -0,0 +1,32 @@
+use std::iter;
+
+/// A very simple BitVector type.
+pub struct BitVector {
+    data: Vec<u64>
+}
+
+impl BitVector {
+    pub fn new(num_bits: usize) -> BitVector {
+        let num_words = (num_bits + 63) / 64;
+        BitVector { data: iter::repeat(0).take(num_words).collect() }
+    }
+
+    fn word_mask(&self, bit: usize) -> (usize, u64) {
+        let word = bit / 64;
+        let mask = 1 << (bit % 64);
+        (word, mask)
+    }
+
+    pub fn contains(&self, bit: usize) -> bool {
+        let (word, mask) = self.word_mask(bit);
+        (self.data[word] & mask) != 0
+    }
+
+    pub fn insert(&mut self, bit: usize) -> bool {
+        let (word, mask) = self.word_mask(bit);
+        let data = &mut self.data[word];
+        let value = *data;
+        *data = value | mask;
+        (value | mask) != value
+    }
+}
diff --git a/src/librustc/middle/graph.rs b/src/librustc_data_structures/graph/mod.rs
index a9ac61b49ec..5741544fe54 100644
--- a/src/librustc/middle/graph.rs
+++ b/src/librustc_data_structures/graph/mod.rs
@@ -30,15 +30,17 @@
 //! the field `next_edge`). Each of those fields is an array that should
 //! be indexed by the direction (see the type `Direction`).
 
-#![allow(dead_code)] // still WIP
-
+use bitvec::BitVector;
 use std::fmt::{Formatter, Error, Debug};
 use std::usize;
-use std::collections::BitSet;
+use snapshot_vec::{SnapshotVec, SnapshotVecDelegate};
+
+#[cfg(test)]
+mod test;
 
 pub struct Graph<N,E> {
-    nodes: Vec<Node<N>> ,
-    edges: Vec<Edge<E>> ,
+    nodes: SnapshotVec<Node<N>> ,
+    edges: SnapshotVec<Edge<E>> ,
 }
 
 pub struct Node<N> {
@@ -53,6 +55,20 @@ pub struct Edge<E> {
     pub data: E,
 }
 
+impl<N> SnapshotVecDelegate for Node<N> {
+    type Value = Node<N>;
+    type Undo = ();
+
+    fn reverse(_: &mut Vec<Node<N>>, _: ()) {}
+}
+
+impl<N> SnapshotVecDelegate for Edge<N> {
+    type Value = Edge<N>;
+    type Undo = ();
+
+    fn reverse(_: &mut Vec<Edge<N>>, _: ()) {}
+}
+
 impl<E: Debug> Debug for Edge<E> {
     fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
         write!(f, "Edge {{ next_edge: [{:?}, {:?}], source: {:?}, target: {:?}, data: {:?} }}",
@@ -61,49 +77,37 @@ impl<E: Debug> Debug for Edge<E> {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Debug)]
+#[derive(Copy, Clone, PartialEq, Debug)]
 pub struct NodeIndex(pub usize);
-#[allow(non_upper_case_globals)]
-pub const InvalidNodeIndex: NodeIndex = NodeIndex(usize::MAX);
 
 #[derive(Copy, Clone, PartialEq, Debug)]
 pub struct EdgeIndex(pub usize);
-#[allow(non_upper_case_globals)]
-pub const InvalidEdgeIndex: EdgeIndex = EdgeIndex(usize::MAX);
+
+pub const INVALID_EDGE_INDEX: EdgeIndex = EdgeIndex(usize::MAX);
 
 // Use a private field here to guarantee no more instances are created:
 #[derive(Copy, Clone, Debug)]
 pub struct Direction { repr: usize }
-#[allow(non_upper_case_globals)]
-pub const Outgoing: Direction = Direction { repr: 0 };
-#[allow(non_upper_case_globals)]
-pub const Incoming: Direction = Direction { repr: 1 };
+
+pub const OUTGOING: Direction = Direction { repr: 0 };
+
+pub const INCOMING: Direction = Direction { repr: 1 };
 
 impl NodeIndex {
-    fn get(&self) -> usize { let NodeIndex(v) = *self; v }
     /// Returns unique id (unique with respect to the graph holding associated node).
-    pub fn node_id(&self) -> usize { self.get() }
+    pub fn node_id(&self) -> usize { self.0 }
 }
 
 impl EdgeIndex {
-    fn get(&self) -> usize { let EdgeIndex(v) = *self; v }
     /// Returns unique id (unique with respect to the graph holding associated edge).
-    pub fn edge_id(&self) -> usize { self.get() }
+    pub fn edge_id(&self) -> usize { self.0 }
 }
 
-impl<N,E> Graph<N,E> {
+impl<N:Debug,E:Debug> Graph<N,E> {
     pub fn new() -> Graph<N,E> {
         Graph {
-            nodes: Vec::new(),
-            edges: Vec::new(),
-        }
-    }
-
-    pub fn with_capacity(num_nodes: usize,
-                         num_edges: usize) -> Graph<N,E> {
-        Graph {
-            nodes: Vec::with_capacity(num_nodes),
-            edges: Vec::with_capacity(num_edges),
+            nodes: SnapshotVec::new(),
+            edges: SnapshotVec::new(),
         }
     }
 
@@ -130,22 +134,22 @@ impl<N,E> Graph<N,E> {
     pub fn add_node(&mut self, data: N) -> NodeIndex {
         let idx = self.next_node_index();
         self.nodes.push(Node {
-            first_edge: [InvalidEdgeIndex, InvalidEdgeIndex],
+            first_edge: [INVALID_EDGE_INDEX, INVALID_EDGE_INDEX],
             data: data
         });
         idx
     }
 
     pub fn mut_node_data<'a>(&'a mut self, idx: NodeIndex) -> &'a mut N {
-        &mut self.nodes[idx.get()].data
+        &mut self.nodes[idx.0].data
     }
 
     pub fn node_data<'a>(&'a self, idx: NodeIndex) -> &'a N {
-        &self.nodes[idx.get()].data
+        &self.nodes[idx.0].data
     }
 
     pub fn node<'a>(&'a self, idx: NodeIndex) -> &'a Node<N> {
-        &self.nodes[idx.get()]
+        &self.nodes[idx.0]
     }
 
     ///////////////////////////////////////////////////////////////////////////
@@ -159,13 +163,15 @@ impl<N,E> Graph<N,E> {
                     source: NodeIndex,
                     target: NodeIndex,
                     data: E) -> EdgeIndex {
+        debug!("graph: add_edge({:?}, {:?}, {:?})", source, target, data);
+
         let idx = self.next_edge_index();
 
         // read current first of the list of edges from each node
-        let source_first = self.nodes[source.get()]
-                                     .first_edge[Outgoing.repr];
-        let target_first = self.nodes[target.get()]
-                                     .first_edge[Incoming.repr];
+        let source_first = self.nodes[source.0]
+                                     .first_edge[OUTGOING.repr];
+        let target_first = self.nodes[target.0]
+                                     .first_edge[INCOMING.repr];
 
         // create the new edge, with the previous firsts from each node
         // as the next pointers
@@ -177,22 +183,22 @@ impl<N,E> Graph<N,E> {
         });
 
         // adjust the firsts for each node target be the next object.
-        self.nodes[source.get()].first_edge[Outgoing.repr] = idx;
-        self.nodes[target.get()].first_edge[Incoming.repr] = idx;
+        self.nodes[source.0].first_edge[OUTGOING.repr] = idx;
+        self.nodes[target.0].first_edge[INCOMING.repr] = idx;
 
         return idx;
     }
 
     pub fn mut_edge_data<'a>(&'a mut self, idx: EdgeIndex) -> &'a mut E {
-        &mut self.edges[idx.get()].data
+        &mut self.edges[idx.0].data
     }
 
     pub fn edge_data<'a>(&'a self, idx: EdgeIndex) -> &'a E {
-        &self.edges[idx.get()].data
+        &self.edges[idx.0].data
     }
 
     pub fn edge<'a>(&'a self, idx: EdgeIndex) -> &'a Edge<E> {
-        &self.edges[idx.get()]
+        &self.edges[idx.0]
     }
 
     pub fn first_adjacent(&self, node: NodeIndex, dir: Direction) -> EdgeIndex {
@@ -200,7 +206,7 @@ impl<N,E> Graph<N,E> {
         //! This is useful if you wish to modify the graph while walking
         //! the linked list of edges.
 
-        self.nodes[node.get()].first_edge[dir.repr]
+        self.nodes[node.0].first_edge[dir.repr]
     }
 
     pub fn next_adjacent(&self, edge: EdgeIndex, dir: Direction) -> EdgeIndex {
@@ -208,7 +214,7 @@ impl<N,E> Graph<N,E> {
         //! This is useful if you wish to modify the graph while walking
         //! the linked list of edges.
 
-        self.edges[edge.get()].next_edge[dir.repr]
+        self.edges[edge.0].next_edge[dir.repr]
     }
 
     ///////////////////////////////////////////////////////////////////////////
@@ -228,41 +234,25 @@ impl<N,E> Graph<N,E> {
         self.edges.iter().enumerate().all(|(i, edge)| f(EdgeIndex(i), edge))
     }
 
-    pub fn each_outgoing_edge<'a, F>(&'a self, source: NodeIndex, f: F) -> bool where
-        F: FnMut(EdgeIndex, &'a Edge<E>) -> bool,
-    {
-        //! Iterates over all outgoing edges from the node `from`
+    pub fn outgoing_edges(&self, source: NodeIndex) -> AdjacentEdges<N,E> {
+        self.adjacent_edges(source, OUTGOING)
+    }
 
-        self.each_adjacent_edge(source, Outgoing, f)
+    pub fn incoming_edges(&self, source: NodeIndex) -> AdjacentEdges<N,E> {
+        self.adjacent_edges(source, INCOMING)
     }
 
-    pub fn each_incoming_edge<'a, F>(&'a self, target: NodeIndex, f: F) -> bool where
-        F: FnMut(EdgeIndex, &'a Edge<E>) -> bool,
-    {
-        //! Iterates over all incoming edges to the node `target`
+    pub fn adjacent_edges(&self, source: NodeIndex, direction: Direction) -> AdjacentEdges<N,E> {
+        let first_edge = self.node(source).first_edge[direction.repr];
+        AdjacentEdges { graph: self, direction: direction, next: first_edge }
+    }
 
-        self.each_adjacent_edge(target, Incoming, f)
+    pub fn successor_nodes<'a>(&'a self, source: NodeIndex) -> AdjacentTargets<N,E> {
+        self.outgoing_edges(source).targets()
     }
 
-    pub fn each_adjacent_edge<'a, F>(&'a self,
-                                     node: NodeIndex,
-                                     dir: Direction,
-                                     mut f: F)
-                                     -> bool where
-        F: FnMut(EdgeIndex, &'a Edge<E>) -> bool,
-    {
-        //! Iterates over all edges adjacent to the node `node`
-        //! in the direction `dir` (either `Outgoing` or `Incoming)
-
-        let mut edge_idx = self.first_adjacent(node, dir);
-        while edge_idx != InvalidEdgeIndex {
-            let edge = &self.edges[edge_idx.get()];
-            if !f(edge_idx, edge) {
-                return false;
-            }
-            edge_idx = edge.next_edge[dir.repr];
-        }
-        return true;
+    pub fn predecessor_nodes<'a>(&'a self, target: NodeIndex) -> AdjacentSources<N,E> {
+        self.incoming_edges(target).sources()
     }
 
     ///////////////////////////////////////////////////////////////////////////
@@ -292,18 +282,82 @@ impl<N,E> Graph<N,E> {
         DepthFirstTraversal {
             graph: self,
             stack: vec![start],
-            visited: BitSet::new()
+            visited: BitVector::new(self.nodes.len()),
+        }
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////
+// Iterators
+
+pub struct AdjacentEdges<'g,N,E>
+    where N:'g, E:'g
+{
+    graph: &'g Graph<N, E>,
+    direction: Direction,
+    next: EdgeIndex,
+}
+
+impl<'g,N,E> AdjacentEdges<'g,N,E> {
+    fn targets(self) -> AdjacentTargets<'g,N,E> {
+        AdjacentTargets { edges: self }
+    }
+
+    fn sources(self) -> AdjacentSources<'g,N,E> {
+        AdjacentSources { edges: self }
+    }
+}
+
+impl<'g, N:Debug, E:Debug> Iterator for AdjacentEdges<'g, N, E> {
+    type Item = (EdgeIndex, &'g Edge<E>);
+
+    fn next(&mut self) -> Option<(EdgeIndex, &'g Edge<E>)> {
+        let edge_index = self.next;
+        if edge_index == INVALID_EDGE_INDEX {
+            return None;
         }
+
+        let edge = self.graph.edge(edge_index);
+        self.next = edge.next_edge[self.direction.repr];
+        Some((edge_index, edge))
+    }
+}
+
+pub struct AdjacentTargets<'g,N:'g,E:'g>
+    where N:'g, E:'g
+{
+    edges: AdjacentEdges<'g,N,E>,
+}
+
+impl<'g, N:Debug, E:Debug> Iterator for AdjacentTargets<'g, N, E> {
+    type Item = NodeIndex;
+
+    fn next(&mut self) -> Option<NodeIndex> {
+        self.edges.next().map(|(_, edge)| edge.target)
+    }
+}
+
+pub struct AdjacentSources<'g,N:'g,E:'g>
+    where N:'g, E:'g
+{
+    edges: AdjacentEdges<'g,N,E>,
+}
+
+impl<'g, N:Debug, E:Debug> Iterator for AdjacentSources<'g, N, E> {
+    type Item = NodeIndex;
+
+    fn next(&mut self) -> Option<NodeIndex> {
+        self.edges.next().map(|(_, edge)| edge.source)
     }
 }
 
 pub struct DepthFirstTraversal<'g, N:'g, E:'g> {
     graph: &'g Graph<N, E>,
     stack: Vec<NodeIndex>,
-    visited: BitSet
+    visited: BitVector
 }
 
-impl<'g, N, E> Iterator for DepthFirstTraversal<'g, N, E> {
+impl<'g, N:Debug, E:Debug> Iterator for DepthFirstTraversal<'g, N, E> {
     type Item = &'g N;
 
     fn next(&mut self) -> Option<&'g N> {
@@ -311,12 +365,12 @@ impl<'g, N, E> Iterator for DepthFirstTraversal<'g, N, E> {
             if !self.visited.insert(idx.node_id()) {
                 continue;
             }
-            self.graph.each_outgoing_edge(idx, |_, e| -> bool {
-                if !self.visited.contains(&e.target().node_id()) {
-                    self.stack.push(e.target());
+
+            for (_, edge) in self.graph.outgoing_edges(idx) {
+                if !self.visited.contains(edge.target().node_id()) {
+                    self.stack.push(edge.target());
                 }
-                true
-            });
+            }
 
             return Some(self.graph.node_data(idx));
         }
@@ -329,7 +383,7 @@ pub fn each_edge_index<F>(max_edge_index: EdgeIndex, mut f: F) where
     F: FnMut(EdgeIndex) -> bool,
 {
     let mut i = 0;
-    let n = max_edge_index.get();
+    let n = max_edge_index.0;
     while i < n {
         if !f(EdgeIndex(i)) {
             return;
@@ -347,138 +401,3 @@ impl<E> Edge<E> {
         self.target
     }
 }
-
-#[cfg(test)]
-mod test {
-    use middle::graph::*;
-    use std::fmt::Debug;
-
-    type TestNode = Node<&'static str>;
-    type TestEdge = Edge<&'static str>;
-    type TestGraph = Graph<&'static str, &'static str>;
-
-    fn create_graph() -> TestGraph {
-        let mut graph = Graph::new();
-
-        // Create a simple graph
-        //
-        //    A -+> B --> C
-        //       |  |     ^
-        //       |  v     |
-        //       F  D --> E
-
-        let a = graph.add_node("A");
-        let b = graph.add_node("B");
-        let c = graph.add_node("C");
-        let d = graph.add_node("D");
-        let e = graph.add_node("E");
-        let f = graph.add_node("F");
-
-        graph.add_edge(a, b, "AB");
-        graph.add_edge(b, c, "BC");
-        graph.add_edge(b, d, "BD");
-        graph.add_edge(d, e, "DE");
-        graph.add_edge(e, c, "EC");
-        graph.add_edge(f, b, "FB");
-
-        return graph;
-    }
-
-    #[test]
-    fn each_node() {
-        let graph = create_graph();
-        let expected = ["A", "B", "C", "D", "E", "F"];
-        graph.each_node(|idx, node| {
-            assert_eq!(&expected[idx.get()], graph.node_data(idx));
-            assert_eq!(expected[idx.get()], node.data);
-            true
-        });
-    }
-
-    #[test]
-    fn each_edge() {
-        let graph = create_graph();
-        let expected = ["AB", "BC", "BD", "DE", "EC", "FB"];
-        graph.each_edge(|idx, edge| {
-            assert_eq!(&expected[idx.get()], graph.edge_data(idx));
-            assert_eq!(expected[idx.get()], edge.data);
-            true
-        });
-    }
-
-    fn test_adjacent_edges<N:PartialEq+Debug,E:PartialEq+Debug>(graph: &Graph<N,E>,
-                                      start_index: NodeIndex,
-                                      start_data: N,
-                                      expected_incoming: &[(E,N)],
-                                      expected_outgoing: &[(E,N)]) {
-        assert!(graph.node_data(start_index) == &start_data);
-
-        let mut counter = 0;
-        graph.each_incoming_edge(start_index, |edge_index, edge| {
-            assert!(graph.edge_data(edge_index) == &edge.data);
-            assert!(counter < expected_incoming.len());
-            debug!("counter={:?} expected={:?} edge_index={:?} edge={:?}",
-                   counter, expected_incoming[counter], edge_index, edge);
-            match expected_incoming[counter] {
-                (ref e, ref n) => {
-                    assert!(e == &edge.data);
-                    assert!(n == graph.node_data(edge.source));
-                    assert!(start_index == edge.target);
-                }
-            }
-            counter += 1;
-            true
-        });
-        assert_eq!(counter, expected_incoming.len());
-
-        let mut counter = 0;
-        graph.each_outgoing_edge(start_index, |edge_index, edge| {
-            assert!(graph.edge_data(edge_index) == &edge.data);
-            assert!(counter < expected_outgoing.len());
-            debug!("counter={:?} expected={:?} edge_index={:?} edge={:?}",
-                   counter, expected_outgoing[counter], edge_index, edge);
-            match expected_outgoing[counter] {
-                (ref e, ref n) => {
-                    assert!(e == &edge.data);
-                    assert!(start_index == edge.source);
-                    assert!(n == graph.node_data(edge.target));
-                }
-            }
-            counter += 1;
-            true
-        });
-        assert_eq!(counter, expected_outgoing.len());
-    }
-
-    #[test]
-    fn each_adjacent_from_a() {
-        let graph = create_graph();
-        test_adjacent_edges(&graph, NodeIndex(0), "A",
-                            &[],
-                            &[("AB", "B")]);
-    }
-
-    #[test]
-    fn each_adjacent_from_b() {
-        let graph = create_graph();
-        test_adjacent_edges(&graph, NodeIndex(1), "B",
-                            &[("FB", "F"), ("AB", "A"),],
-                            &[("BD", "D"), ("BC", "C"),]);
-    }
-
-    #[test]
-    fn each_adjacent_from_c() {
-        let graph = create_graph();
-        test_adjacent_edges(&graph, NodeIndex(2), "C",
-                            &[("EC", "E"), ("BC", "B")],
-                            &[]);
-    }
-
-    #[test]
-    fn each_adjacent_from_d() {
-        let graph = create_graph();
-        test_adjacent_edges(&graph, NodeIndex(3), "D",
-                            &[("BD", "B")],
-                            &[("DE", "E")]);
-    }
-}
diff --git a/src/librustc_data_structures/graph/test.rs b/src/librustc_data_structures/graph/test.rs
new file mode 100644
index 00000000000..a26d1d2fbd9
--- /dev/null
+++ b/src/librustc_data_structures/graph/test.rs
@@ -0,0 +1,129 @@
+use graph::*;
+use std::fmt::Debug;
+
+type TestNode = Node<&'static str>;
+type TestEdge = Edge<&'static str>;
+type TestGraph = Graph<&'static str, &'static str>;
+
+fn create_graph() -> TestGraph {
+    let mut graph = Graph::new();
+
+    // Create a simple graph
+    //
+    //    A -+> B --> C
+    //       |  |     ^
+    //       |  v     |
+    //       F  D --> E
+
+    let a = graph.add_node("A");
+    let b = graph.add_node("B");
+    let c = graph.add_node("C");
+    let d = graph.add_node("D");
+    let e = graph.add_node("E");
+    let f = graph.add_node("F");
+
+    graph.add_edge(a, b, "AB");
+    graph.add_edge(b, c, "BC");
+    graph.add_edge(b, d, "BD");
+    graph.add_edge(d, e, "DE");
+    graph.add_edge(e, c, "EC");
+    graph.add_edge(f, b, "FB");
+
+    return graph;
+}
+
+#[test]
+fn each_node() {
+    let graph = create_graph();
+    let expected = ["A", "B", "C", "D", "E", "F"];
+    graph.each_node(|idx, node| {
+        assert_eq!(&expected[idx.0], graph.node_data(idx));
+        assert_eq!(expected[idx.0], node.data);
+        true
+    });
+}
+
+#[test]
+fn each_edge() {
+    let graph = create_graph();
+    let expected = ["AB", "BC", "BD", "DE", "EC", "FB"];
+    graph.each_edge(|idx, edge| {
+        assert_eq!(&expected[idx.0], graph.edge_data(idx));
+        assert_eq!(expected[idx.0], edge.data);
+        true
+    });
+}
+
+fn test_adjacent_edges<N:PartialEq+Debug,E:PartialEq+Debug>(graph: &Graph<N,E>,
+                                                            start_index: NodeIndex,
+                                                            start_data: N,
+                                                            expected_incoming: &[(E,N)],
+                                                            expected_outgoing: &[(E,N)]) {
+    assert!(graph.node_data(start_index) == &start_data);
+
+    let mut counter = 0;
+    for (edge_index, edge) in graph.incoming_edges(start_index) {
+        assert!(graph.edge_data(edge_index) == &edge.data);
+        assert!(counter < expected_incoming.len());
+        debug!("counter={:?} expected={:?} edge_index={:?} edge={:?}",
+               counter, expected_incoming[counter], edge_index, edge);
+        match expected_incoming[counter] {
+            (ref e, ref n) => {
+                assert!(e == &edge.data);
+                assert!(n == graph.node_data(edge.source()));
+                assert!(start_index == edge.target);
+            }
+        }
+        counter += 1;
+    }
+    assert_eq!(counter, expected_incoming.len());
+
+    let mut counter = 0;
+    for (edge_index, edge) in graph.outgoing_edges(start_index) {
+        assert!(graph.edge_data(edge_index) == &edge.data);
+        assert!(counter < expected_outgoing.len());
+        debug!("counter={:?} expected={:?} edge_index={:?} edge={:?}",
+               counter, expected_outgoing[counter], edge_index, edge);
+        match expected_outgoing[counter] {
+            (ref e, ref n) => {
+                assert!(e == &edge.data);
+                assert!(start_index == edge.source);
+                assert!(n == graph.node_data(edge.target));
+            }
+        }
+        counter += 1;
+    }
+    assert_eq!(counter, expected_outgoing.len());
+}
+
+#[test]
+fn each_adjacent_from_a() {
+    let graph = create_graph();
+    test_adjacent_edges(&graph, NodeIndex(0), "A",
+                        &[],
+                        &[("AB", "B")]);
+}
+
+#[test]
+fn each_adjacent_from_b() {
+    let graph = create_graph();
+    test_adjacent_edges(&graph, NodeIndex(1), "B",
+                        &[("FB", "F"), ("AB", "A"),],
+                        &[("BD", "D"), ("BC", "C"),]);
+}
+
+#[test]
+fn each_adjacent_from_c() {
+    let graph = create_graph();
+    test_adjacent_edges(&graph, NodeIndex(2), "C",
+                        &[("EC", "E"), ("BC", "B")],
+                        &[]);
+}
+
+#[test]
+fn each_adjacent_from_d() {
+    let graph = create_graph();
+    test_adjacent_edges(&graph, NodeIndex(3), "D",
+                        &[("BD", "B")],
+                        &[("DE", "E")]);
+}
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index 5f2f430df50..d90a40941cb 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -33,3 +33,5 @@
 extern crate serialize as rustc_serialize; // used by deriving
 
 pub mod snapshot_vec;
+pub mod graph;
+pub mod bitvec;
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index bdc3fdcfc14..33a817cfedb 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -1886,14 +1886,13 @@ impl LintPass for UnconditionalRecursion {
                 continue;
             }
             // add the successors of this node to explore the graph further.
-            cfg.graph.each_outgoing_edge(idx, |_, edge| {
+            for (_, edge) in cfg.graph.outgoing_edges(idx) {
                 let target_idx = edge.target();
                 let target_cfg_id = target_idx.node_id();
                 if !visited.contains(&target_cfg_id) {
                     work_queue.push(target_idx)
                 }
-                true
-            });
+            }
         }
 
         // Check the number of self calls because a function that