1 files changed, 58 insertions, 0 deletions
diff --git a/compiler/rustc_query_system/src/dep_graph/debug.rs b/compiler/rustc_query_system/src/dep_graph/debug.rs
new file mode 100644
index 00000000000..718a2f1039a
--- /dev/null
+++ b/compiler/rustc_query_system/src/dep_graph/debug.rs
@@ -0,0 +1,58 @@
+//! Code for debugging the dep-graph.
+
+use super::{DepKind, DepNode};
+use std::error::Error;
+
+/// A dep-node filter goes from a user-defined string to a query over
+/// nodes. Right now the format is like this:
+///
+///     x & y & z
+///
+/// where the format-string of the dep-node must contain `x`, `y`, and
+/// `z`.
+#[derive(Debug)]
+pub struct DepNodeFilter {
+    text: String,
+}
+
+impl DepNodeFilter {
+    pub fn new(text: &str) -> Self {
+        DepNodeFilter { text: text.trim().to_string() }
+    }
+
+    /// Returns `true` if all nodes always pass the filter.
+    pub fn accepts_all(&self) -> bool {
+        self.text.is_empty()
+    }
+
+    /// Tests whether `node` meets the filter, returning true if so.
+    pub fn test<K: DepKind>(&self, node: &DepNode<K>) -> bool {
+        let debug_str = format!("{:?}", node);
+        self.text.split('&').map(|s| s.trim()).all(|f| debug_str.contains(f))
+    }
+}
+
+/// A filter like `F -> G` where `F` and `G` are valid dep-node
+/// filters. This can be used to test the source/target independently.
+pub struct EdgeFilter {
+    pub source: DepNodeFilter,
+    pub target: DepNodeFilter,
+}
+
+impl EdgeFilter {
+    pub fn new(test: &str) -> Result<EdgeFilter, Box<dyn Error>> {
+        let parts: Vec<_> = test.split("->").collect();
+        if parts.len() != 2 {
+            Err(format!("expected a filter like `a&b -> c&d`, not `{}`", test).into())
+        } else {
+            Ok(EdgeFilter {
+                source: DepNodeFilter::new(parts[0]),
+                target: DepNodeFilter::new(parts[1]),
+            })
+        }
+    }
+
+    pub fn test<K: DepKind>(&self, source: &DepNode<K>, target: &DepNode<K>) -> bool {
+        self.source.test(source) && self.target.test(target)
+    }
+}