Implement HugrView::get_{parent,{node,op}type,metadata} once only, wi…

…th valid_node checks

==> SiblingGraph::new's "get_optype" will implicitly check the root is in the base view.

This does mean some unnecessary index checking for &Hugr's. We could continue to
reimplement those methods for AsRef<Hugr> if we want to avoid this inefficiency.
Alternatively we could make UnmanagedDenseMap return Options rather than unwrapping.

Some other ugly alternative/hacks for returning default values - DEFAULT_{NODE,OP}TYPE

src/hugr.rs

@@ -29,7 +29,7 @@ pub use self::views::HugrView;
 use crate::extension::{
     infer_extensions, ExtensionRegistry, ExtensionSet, ExtensionSolution, InferExtensionError,
 };
-use crate::ops::{OpTag, OpTrait, OpType};
+use crate::ops::{OpTag, OpTrait, OpType, DEFAULT_OPTYPE};
 use crate::types::{FunctionType, Signature};
 
 use delegate::delegate;
@@ -64,6 +64,12 @@ pub struct NodeType {
     input_extensions: Option<ExtensionSet>,
 }
 
+/// The default NodeType, with open extensions
+pub const DEFAULT_NODETYPE: NodeType = NodeType {
+    op: DEFAULT_OPTYPE,
+    input_extensions: None, // Default for any Option
+};
+
 impl NodeType {
     /// Create a new optype with some ExtensionSet
     pub fn new(op: impl Into<OpType>, input_extensions: impl Into<Option<ExtensionSet>>) -> Self {

src/hugr/views.rs

@@ -18,7 +18,7 @@ use itertools::{Itertools, MapInto};
 use portgraph::dot::{DotFormat, EdgeStyle, NodeStyle, PortStyle};
 use portgraph::{multiportgraph, LinkView, MultiPortGraph, PortView};
 
-use super::{Hugr, HugrError, NodeMetadata, NodeType};
+use super::{Hugr, HugrError, NodeMetadata, NodeType, DEFAULT_NODETYPE};
 use crate::ops::handle::NodeHandle;
 use crate::ops::{FuncDecl, FuncDefn, OpName, OpTag, OpType, DFG};
 use crate::types::{EdgeKind, FunctionType};
@@ -105,16 +105,42 @@ pub trait HugrView: sealed::HugrInternals {
     }
 
     /// Returns the parent of a node.
-    fn get_parent(&self, node: Node) -> Option<Node>;
+    #[inline]
+    fn get_parent(&self, node: Node) -> Option<Node> {
+        self.valid_non_root(node).ok()?;
+        self.base_hugr()
+            .hierarchy
+            .parent(node.index)
+            .map(Into::into)
+    }
 
     /// Returns the operation type of a node.
-    fn get_optype(&self, node: Node) -> &OpType;
+    #[inline]
+    fn get_optype(&self, node: Node) -> &OpType {
+        &self.get_nodetype(node).op
+    }
 
     /// Returns the type of a node.
-    fn get_nodetype(&self, node: Node) -> &NodeType;
+    #[inline]
+    fn get_nodetype(&self, node: Node) -> &NodeType {
+        match self.contains_node(node) {
+            true => self.base_hugr().op_types.get(node.index),
+            false => &DEFAULT_NODETYPE,
+        }
+    }
 
     /// Returns the metadata associated with a node.
-    fn get_metadata(&self, node: Node) -> &NodeMetadata;
+    #[inline]
+    fn get_metadata(&self, node: Node) -> &NodeMetadata {
+        // The other way to do it - exploit the UnmanagedDenseMap's get() returning &default
+        let md = &self.base_hugr().metadata;
+
+        let idx = match self.contains_node(node) {
+            true => node.index,
+            false => portgraph::NodeIndex::new(md.capacity() + 1),
+        };
+        md.get(idx)
+    }
 
     /// Returns the number of nodes in the hugr.
     fn node_count(&self) -> usize;
@@ -311,21 +337,6 @@ where
         self.as_ref().graph.contains_node(node.index)
     }
 
-    #[inline]
-    fn get_parent(&self, node: Node) -> Option<Node> {
-        self.as_ref().hierarchy.parent(node.index).map(Into::into)
-    }
-
-    #[inline]
-    fn get_optype(&self, node: Node) -> &OpType {
-        &self.as_ref().op_types.get(node.index).op
-    }
-
-    #[inline]
-    fn get_nodetype(&self, node: Node) -> &NodeType {
-        self.as_ref().op_types.get(node.index)
-    }
-
     #[inline]
     fn node_count(&self) -> usize {
         self.as_ref().graph.node_count()
@@ -410,11 +421,6 @@ where
             None
         }
     }
-
-    #[inline]
-    fn get_metadata(&self, node: Node) -> &NodeMetadata {
-        self.as_ref().metadata.get(node.index)
-    }
 }
 
 pub(crate) mod sealed {

src/hugr/views/descendants.rs

@@ -7,9 +7,9 @@ use portgraph::{LinkView, MultiPortGraph, PortIndex, PortView};
 
 use crate::ops::handle::NodeHandle;
 use crate::ops::OpTrait;
-use crate::{hugr::NodeType, hugr::OpType, Direction, Hugr, Node, Port};
+use crate::{Direction, Hugr, Node, Port};
 
-use super::{sealed::HugrInternals, HierarchyView, HugrView, NodeMetadata};
+use super::{sealed::HugrInternals, HierarchyView, HugrView};
 
 type RegionGraph<'g> = portgraph::view::Region<'g, &'g MultiPortGraph>;
 
@@ -94,29 +94,6 @@ where
         self.graph.contains_node(node.index)
     }
 
-    #[inline]
-    fn get_parent(&self, node: Node) -> Option<Node> {
-        self.hugr
-            .get_parent(node)
-            .filter(|&parent| self.graph.contains_node(parent.index))
-            .map(Into::into)
-    }
-
-    #[inline]
-    fn get_optype(&self, node: Node) -> &OpType {
-        self.hugr.get_optype(node)
-    }
-
-    #[inline]
-    fn get_nodetype(&self, node: Node) -> &NodeType {
-        self.hugr.get_nodetype(node)
-    }
-
-    #[inline]
-    fn get_metadata(&self, node: Node) -> &NodeMetadata {
-        self.hugr.get_metadata(node)
-    }
-
     #[inline]
     fn node_count(&self) -> usize {
         self.graph.node_count()

src/hugr/views/sibling.rs

@@ -8,9 +8,9 @@ use portgraph::{LinkView, MultiPortGraph, PortIndex, PortView};
 
 use crate::ops::handle::NodeHandle;
 use crate::ops::OpTrait;
-use crate::{hugr::NodeType, hugr::OpType, Direction, Hugr, Node, Port};
+use crate::{Direction, Hugr, Node, Port};
 
-use super::{sealed::HugrInternals, HierarchyView, HugrView, NodeMetadata};
+use super::{sealed::HugrInternals, HierarchyView, HugrView};
 
 type FlatRegionGraph<'g> = portgraph::view::FlatRegion<'g, &'g MultiPortGraph>;
 
@@ -94,26 +94,6 @@ where
         self.graph.contains_node(node.index)
     }
 
-    #[inline]
-    fn get_parent(&self, node: Node) -> Option<Node> {
-        self.hugr.get_parent(node).filter(|&n| n == self.root)
-    }
-
-    #[inline]
-    fn get_optype(&self, node: Node) -> &OpType {
-        self.hugr.get_optype(node)
-    }
-
-    #[inline]
-    fn get_nodetype(&self, node: Node) -> &NodeType {
-        self.hugr.get_nodetype(node)
-    }
-
-    #[inline]
-    fn get_metadata(&self, node: Node) -> &NodeMetadata {
-        self.hugr.get_metadata(node)
-    }
-
     #[inline]
     fn node_count(&self) -> usize {
         self.base_hugr().hierarchy.child_count(self.root.index) + 1

src/ops.rs

@@ -52,9 +52,12 @@ pub enum OpType {
     Case,
 }
 
+/// The default OpType (as returned by [Default::default])
+pub const DEFAULT_OPTYPE: OpType = OpType::Module(Module);
+
 impl Default for OpType {
     fn default() -> Self {
-        Module.into()
+        DEFAULT_OPTYPE
     }
 }