chore(bin/lean-gdb): pretty-print lean::optional

bin/lean-gdb.py

@@ -9,6 +9,27 @@
 import gdb
 import gdb.printing
 
+class LeanOptionalPrinter:
+    """Print a lean::optional object."""
+
+    def __init__(self, val):
+        self.val = val
+
+    def get_val(self):
+        if hasattr(self.val, 'm_some'):
+            if not self.val['m_some']:
+                return None
+        elif not self.val['m_value'].cast(gdb.lookup_type('char').pointer()):
+            return None
+        return self.val['m_value']
+
+    def children(self):
+        val = self.get_val()
+        return [('', val)] if val else []
+
+    def to_string(self):
+        return str(self.val.type)
+
 class LeanNamePrinter:
     """Print a lean::name object."""
 
@@ -143,6 +164,7 @@ class LeanRBMapPrinter:
 
 def build_pretty_printer():
     pp = gdb.printing.RegexpCollectionPrettyPrinter("lean")
+    pp.add_printer('optional', '^lean::optional', LeanOptionalPrinter)
     pp.add_printer('name', '^lean::name$', LeanNamePrinter)
     pp.add_printer('expr', '^lean::expr$', LeanExprPrinter)
     pp.add_printer('list', '^lean::list', LeanListPrinter)