feat(xatu): report empty let expressions

src/xatu/rules.rs

@@ -2,10 +2,12 @@ use crate::FileId;
 use crate::ast;
 use crate::rules::deprecated_to_path::DeprecatedToPath;
 use crate::rules::empty_inherit::EmptyInherit;
+use crate::rules::empty_let_in::EmptyLetIn;
 use crate::rules::unquoted_uri::UnquotedUri;
 
 pub mod deprecated_to_path;
 pub mod empty_inherit;
+pub mod empty_let_in;
 pub mod unquoted_uri;
 
 #[derive(Debug)]
@@ -54,6 +56,7 @@ pub fn run_rules(file: &ast::ParsedFile) -> Vec<Diagnostic> {
         [
             run_node_rule::<DeprecatedToPath>(node),
             run_node_rule::<EmptyInherit>(node),
+            run_node_rule::<EmptyLetIn>(node),
         ]
         .into_iter()
         .flatten()