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use crate::{make, Metadata, Report, Rule, Suggestion};
use if_chain::if_chain;
use macros::lint;
use rnix::{
types::{Ident, KeyValue, Select, TokenWrapper, TypedNode},
NodeOrToken, SyntaxElement, SyntaxKind,
};
/// ## What it does
/// Checks for bindings of the form `a = someAttr.a`.
///
/// ## Why is this bad?
/// If the aim is to extract or bring attributes of an attrset into
/// scope, prefer an inherit statement.
///
/// ## Example
///
/// ```nix
/// let
/// mtl = pkgs.haskellPackages.mtl;
/// in
/// null
/// ```
///
/// Try `inherit` instead:
///
/// ```nix
/// let
/// inherit (pkgs.haskellPackages) mtl;
/// in
/// null
/// ```
#[lint(
name = "manual inherit from",
note = "Assignment instead of inherit from",
code = 4,
match_with = SyntaxKind::NODE_KEY_VALUE
)]
struct ManualInherit;
impl Rule for ManualInherit {
fn validate(&self, node: &SyntaxElement) -> Option<Report> {
if_chain! {
if let NodeOrToken::Node(node) = node;
if let Some(key_value_stmt) = KeyValue::cast(node.clone());
if let mut key_path = key_value_stmt.key()?.path();
if let Some(key_node) = key_path.next();
// ensure that path has exactly one component
if key_path.next().is_none();
if let Some(key) = Ident::cast(key_node);
if let Some(value_node) = key_value_stmt.value();
if let Some(value) = Select::cast(value_node);
if let Some(index_node) = value.index();
if let Some(index) = Ident::cast(index_node);
if key.as_str() == index.as_str();
then {
let at = node.text_range();
let replacement = {
let set = value.set()?;
make::inherit_from_stmt(set, &[key]).node().clone()
};
let message = "This assignment is better written with `inherit`";
Some(self.report().suggest(at, message, Suggestion::new(at, replacement)))
} else {
None
}
}
}
}
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