1 files changed, 73 insertions, 0 deletions
diff --git a/compiler/rustc_data_structures/src/graph/tests.rs b/compiler/rustc_data_structures/src/graph/tests.rs
new file mode 100644
index 000000000..7f4ef906b
--- /dev/null
+++ b/compiler/rustc_data_structures/src/graph/tests.rs
@@ -0,0 +1,73 @@
+use crate::fx::FxHashMap;
+use std::cmp::max;
+use std::iter;
+use std::slice;
+
+use super::*;
+
+pub struct TestGraph {
+    num_nodes: usize,
+    start_node: usize,
+    successors: FxHashMap<usize, Vec<usize>>,
+    predecessors: FxHashMap<usize, Vec<usize>>,
+}
+
+impl TestGraph {
+    pub fn new(start_node: usize, edges: &[(usize, usize)]) -> Self {
+        let mut graph = TestGraph {
+            num_nodes: start_node + 1,
+            start_node,
+            successors: FxHashMap::default(),
+            predecessors: FxHashMap::default(),
+        };
+        for &(source, target) in edges {
+            graph.num_nodes = max(graph.num_nodes, source + 1);
+            graph.num_nodes = max(graph.num_nodes, target + 1);
+            graph.successors.entry(source).or_default().push(target);
+            graph.predecessors.entry(target).or_default().push(source);
+        }
+        for node in 0..graph.num_nodes {
+            graph.successors.entry(node).or_default();
+            graph.predecessors.entry(node).or_default();
+        }
+        graph
+    }
+}
+
+impl DirectedGraph for TestGraph {
+    type Node = usize;
+}
+
+impl WithStartNode for TestGraph {
+    fn start_node(&self) -> usize {
+        self.start_node
+    }
+}
+
+impl WithNumNodes for TestGraph {
+    fn num_nodes(&self) -> usize {
+        self.num_nodes
+    }
+}
+
+impl WithPredecessors for TestGraph {
+    fn predecessors(&self, node: usize) -> <Self as GraphPredecessors<'_>>::Iter {
+        self.predecessors[&node].iter().cloned()
+    }
+}
+
+impl WithSuccessors for TestGraph {
+    fn successors(&self, node: usize) -> <Self as GraphSuccessors<'_>>::Iter {
+        self.successors[&node].iter().cloned()
+    }
+}
+
+impl<'graph> GraphPredecessors<'graph> for TestGraph {
+    type Item = usize;
+    type Iter = iter::Cloned<slice::Iter<'graph, usize>>;
+}
+
+impl<'graph> GraphSuccessors<'graph> for TestGraph {
+    type Item = usize;
+    type Iter = iter::Cloned<slice::Iter<'graph, usize>>;
+}