Parser refactoring to use new (Maybe)ParseResult types, WIP.

dm/src/repl.rs

@@ -105,12 +105,14 @@ fn compile_statement(
     register_count: usize,
     constants_table: &mut ConstantsTable,
 ) -> Result<Function, Diagnostics> {
-    let (maybe_statement, parse_diagnostics) = parse_statement(input);
-    if !parse_diagnostics.is_empty() {
-        Err(parse_diagnostics)
-    } else if let Some(statement) = maybe_statement {
-        session.compile_statement(&statement, register_count, constants_table)
+    let maybe_statement = parse_statement(input);
+    if !maybe_statement.is_ok() {
+        Err(maybe_statement.into_diagnostics())
     } else {
-        panic!("Unable to unwrap statement from previous input.")
+        session.compile_statement(
+            &maybe_statement.into_inner(),
+            register_count,
+            constants_table,
+        )
     }
 }