forest: clone correctly

Now the forest can detect if a node is packed or cloned, and correctly
clones a node in those circumstances.  But it still needs to be
tested.

1 files changed, 18 insertions, 4 deletions

diff --git a/grammar/src/label.rs b/grammar/src/label.rs
index 58eaddc..05b0b1e 100644
--- a/grammar/src/label.rs
+++ b/grammar/src/label.rs
@@ -93,10 +93,24 @@ impl GrammarLabel {
     /// Return a string description with the help of the associated
     /// grammar.
     pub fn to_string(&self, grammar: &Grammar) -> Result<String, Error> {
-        // REVIEW: It needs at least 34 bytes, so we just double it.
-        // Of course we can also calculate the length exactly, but
-        // this can be postponed till later.
-        let mut s = String::with_capacity(68);
+        // First calculate the length of the resulting string.
+
+        let mut num = 2 + 7 + 14 + 6;
+
+        num += self.label().name(grammar)?.len();
+
+        num += format!("{} ", self.start()).len();
+
+        if let Some(end) = self.end() {
+            num += format!("to {end}").len();
+        } else {
+            num += 7;
+        }
+
+        let num = num;
+
+        let mut s = String::with_capacity(num);
+
         s.push_str("a ");
 
         if self.is_packed() {