1 files changed, 37 insertions, 0 deletions

diff --git a/lib/src/lints/empty_pattern.rs b/lib/src/lints/empty_pattern.rs
new file mode 100644
index 0000000..6fb7558
--- /dev/null
+++ b/lib/src/lints/empty_pattern.rs
@@ -0,0 +1,37 @@
+use crate::{make, Lint, Metadata, Report, Rule, Suggestion};
+
+use if_chain::if_chain;
+use macros::lint;
+use rnix::{
+    types::{Pattern, TypedNode},
+    NodeOrToken, SyntaxElement, SyntaxKind,
+};
+
+#[lint(
+    name = "empty pattern",
+    note = "Found empty pattern in function argument",
+    code = 10,
+    match_with = SyntaxKind::NODE_PATTERN
+)]
+struct EmptyPattern;
+
+impl Rule for EmptyPattern {
+    fn validate(&self, node: &SyntaxElement) -> Option<Report> {
+        if_chain! {
+            if let NodeOrToken::Node(node) = node;
+            if let Some(pattern) = Pattern::cast(node.clone());
+            // no patterns within `{ }`
+            if pattern.entries().count() == 0;
+            // pattern is not bound
+            if pattern.at().is_none();
+            then {
+                let at = node.text_range();
+                let message = "This pattern is empty, use `_` instead";
+                let replacement = make::ident("_").node().clone();
+                Some(Self::report().suggest(at, message, Suggestion::new(at, replacement)))
+            } else {
+                None
+            }
+        }
+    }
+}