Add special case for Optional type emission

trans/transpiler/phases/emit_cpp/__init__.py

@@ -9,7 +9,7 @@ from transpiler.phases.emit_cpp.consts import MAPPINGS
 from transpiler.phases.typing import TypeVariable
 from transpiler.phases.typing.exceptions import UnresolvedTypeVariableError
 from transpiler.phases.typing.types import BaseType, TY_INT, TY_BOOL, TY_NONE, Promise, PromiseKind, TY_STR, UserType, \
-    TypeType, TypeOperator, TY_FLOAT, FunctionType
+    TypeType, TypeOperator, TY_FLOAT, FunctionType, UnionType
 from transpiler.utils import UnsupportedNodeError, highlight
 
 
@@ -100,6 +100,10 @@ class NodeVisitor(UniversalVisitor):
         elif isinstance(node, TypeVariable):
             # yield f"TYPEVAR_{node.name}";return
             raise UnresolvedTypeVariableError(node)
+        elif isinstance(node, UnionType) and (ty := node.is_optional()):
+            yield "std::optional<"
+            yield from self.visit(ty)
+            yield ">"
         elif isinstance(node, TypeOperator):
             yield "typon::Py" + node.name.title()
             if node.args: