feat(xatu): report empty let expressions

src/xatu/parser.rs

@@ -1,3 +1,4 @@
+use rnix::ast::HasEntry;
 use rowan::ast::AstNode;
 
 use crate::{FileId, ast};
@@ -37,6 +38,7 @@ fn convert_syntax(syntax: rnix::SyntaxNode) -> (Vec<ast::Node>, Vec<ast::Token>)
 fn convert_node(node: rnix::SyntaxNode) -> Option<ast::Node> {
     match node.kind() {
         rnix::SyntaxKind::NODE_APPLY => convert_apply(node),
+        rnix::SyntaxKind::NODE_LET_IN => convert_let_in(node),
         rnix::SyntaxKind::NODE_INHERIT => convert_inherit(node),
         _ => None,
     }
@@ -102,6 +104,27 @@ impl TryFrom<rnix::ast::Select> for ast::Select {
     }
 }
 
+fn convert_let_in(node: rnix::SyntaxNode) -> Option<ast::Node> {
+    let let_in = rnix::ast::LetIn::cast(node)?;
+
+    Some(ast::Node {
+        range: let_in.syntax().text_range().into(),
+        data: ast::NodeData::LetIn(let_in.into()),
+    })
+}
+
+impl From<rnix::ast::LetIn> for ast::LetIn {
+    fn from(let_in: rnix::ast::LetIn) -> Self {
+        Self {
+            binding_count: let_in.attrpath_values().count()
+                + let_in
+                    .inherits()
+                    .map(|inherit| inherit.attrs().count())
+                    .sum::<usize>(),
+        }
+    }
+}
+
 fn convert_inherit(node: rnix::SyntaxNode) -> Option<ast::Node> {
     let inherit = rnix::ast::Inherit::cast(node)?;