2 files changed, 73 insertions, 0 deletions

diff --git a/lib/src/lints.rs b/lib/src/lints.rs
index 0add458..d31a754 100644
--- a/lib/src/lints.rs
+++ b/lib/src/lints.rs
@@ -16,4 +16,5 @@ lints! {
     deprecated_is_null,
     empty_inherit,
     faster_groupby,
+    faster_zipattrswith,
 }
diff --git a/lib/src/lints/faster_zipattrswith.rs b/lib/src/lints/faster_zipattrswith.rs
new file mode 100644
index 0000000..139d499
--- /dev/null
+++ b/lib/src/lints/faster_zipattrswith.rs
@@ -0,0 +1,72 @@
+use crate::{
+    make,
+    session::{SessionInfo, Version},
+    Metadata, Report, Rule, Suggestion,
+};
+
+use if_chain::if_chain;
+use macros::lint;
+use rnix::{
+    types::{Select, TypedNode},
+    NodeOrToken, SyntaxElement, SyntaxKind,
+};
+
+/// ## What it does
+/// Checks for `lib.zipAttrsWith`.
+///
+/// ## Why is this bad?
+/// Nix 2.6 introduces `builtins.zipAttrsWith` which is faster and does
+/// not require a lib import.
+///
+/// ## Example
+///
+/// ```nix
+/// lib.zipAttrsWith (name: values: values) [ {a = "x";} {a = "y"; b = "z";} ]
+/// # { a = ["x" "y"]; b = ["z"] }
+/// ```
+///
+/// Replace `lib.zipAttrsWith` with `builtins.zipAttrsWith`:
+///
+/// ```nix
+/// builtins.zipAttrsWith (name: values: values) [ {a = "x";} {a = "y"; b = "z";} ]
+/// ```
+#[lint(
+    name = "faster_zipattrswith",
+    note = "Found lib.zipAttrsWith",
+    code = 16,
+    match_with = SyntaxKind::NODE_SELECT
+)]
+struct FasterZipAttrsWith;
+
+impl Rule for FasterZipAttrsWith {
+    fn validate(&self, node: &SyntaxElement, sess: &SessionInfo) -> Option<Report> {
+        let lint_version = "2.6".parse::<Version>().unwrap();
+        if_chain! {
+            if sess.version() >= &lint_version;
+            if let NodeOrToken::Node(node) = node;
+            if let Some(select_expr) = Select::cast(node.clone());
+            if let Some(select_from) = select_expr.set();
+            if let Some(zip_attrs_with) = select_expr.index();
+
+            // a heuristic to lint on nixpkgs.lib.zipAttrsWith
+            // and lib.zipAttrsWith and its variants
+            if select_from.text().to_string() != "builtins";
+            if zip_attrs_with.text().to_string() == "zipAttrsWith";
+
+            then {
+                let at = node.text_range();
+                let replacement = {
+                    let builtins = make::ident("builtins");
+                    make::select(builtins.node(), &zip_attrs_with).node().clone()
+                };
+                let message = format!("Prefer `builtins.zipAttrsWith` over `{}.zipAttrsWith`", select_from);
+                Some(
+                    self.report()
+                        .suggest(at, message, Suggestion::new(at, replacement)),
+                )
+            } else {
+                None
+            }
+        }
+    }
+}