Fix the bug of forgetting to check cloned nodes.

In the process of splitting, cloning, and planting the forest, I
forgot to check whether some cloned node of the node inquestion
satisfy the condition.  This used to cause forests that violate some
fundamental assumptions.  Now this is supposed to be fixed, but more
tests await us.

1 files changed, 42 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 685c66e..5412ed7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -8,6 +8,11 @@ extern crate grammar;
 use chain::{atom::DefaultAtom, default::DefaultChain, Chain};
 use grammar::Grammar;
 
+// For printing forests
+use chain::item::{default::DefaultForest, ForestLabel};
+use grammar::GrammarLabel;
+use graph::LabelGraph;
+
 /// This struct is the representation of a parser.
 ///
 /// When the user constructs a parser, an instance of this struct will
@@ -545,4 +550,41 @@ extern "C" fn parser_parse(
     }
 }
 
+// TODO: Write a function to print the node label of a forest and
+// expose it to C ABI.
+//
+// This can be used in LLDB.
+
+/// This struct is a wrapper around the forest.
+///
+/// This is used so that we can call a C function receiving a pointer
+/// to a forest struct.
+#[derive(Debug, Clone)]
+#[repr(C)]
+pub struct CForest {
+    forest: DefaultForest<ForestLabel<GrammarLabel>>,
+}
+
+/// Print the label of the node with id `node` in the forest `forest`.
+///
+/// The parameter `node` should point to 8 bytes of unsigned
+/// characters, which forms a number in 64 bits, in the *big endian*
+/// format.
+#[no_mangle]
+extern "C" fn print_forest_node(forest: *mut CForest, node: *mut std::os::raw::c_uchar) {
+    let node = usize::from_be_bytes(
+        unsafe { std::slice::from_raw_parts(node, 8) }
+            .try_into()
+            .unwrap(),
+    );
+
+    let forest = unsafe { (*forest).forest.clone() };
+
+    let Ok(Some(label)) = forest.vertex_label(node) else {
+        return;
+    };
+
+    println!("node {node} has label {label}");
+}
+
 pub mod bytes;