Implement Sizable for both OwnedLiterals and serde_json.

src/renderer/parameters_context.rs

@@ -21,6 +21,7 @@ use crate::renderer::Walkable;
 use std::borrow::Borrow;
 use std::cmp::Ordering;
 use std::collections::HashMap;
+use std::convert::TryInto;
 
 #[derive(Debug)]
 pub struct ParametersContext<'a> {
@@ -192,7 +193,14 @@ impl Walkable for OwnedLiteral {
 
 impl Sizable for OwnedLiteral {
     fn get_size<'a>(&'a self) -> Option<IceResult<'a>> {
-        todo!()
+        match self {
+            OwnedLiteral::LFloat(_) => Some(IceResult::from_borrowed(self)),
+            OwnedLiteral::LPositiveInteger(_) => Some(IceResult::from_borrowed(self)),
+            OwnedLiteral::LNegativeInteger(_) => Some(IceResult::from_borrowed(self)),
+            OwnedLiteral::LString(text) => Some(IceResult::from_owned(
+                OwnedLiteral::LPositiveInteger(text.len().try_into().unwrap()),
+            )),
+        }
     }
 }