use crate::utils::{eq_expr_value, snippet, span_lint}; use rustc_hir::{Expr, ExprKind}; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::{declare_lint_pass, declare_tool_lint}; declare_clippy_lint! { /// **What it does:** Checks for explicit self-assignments. /// /// **Why is this bad?** Self-assignments are redundant and unlikely to be /// intentional. /// /// **Known problems:** If expression contains any deref coercions or /// indexing operations they are assumed not to have any side effects. /// /// **Example:** /// /// ```rust /// struct Event { /// id: usize, /// x: i32, /// y: i32, /// } /// /// fn copy_position(a: &mut Event, b: &Event) { /// a.x = b.x; /// a.y = a.y; /// } /// ``` pub SELF_ASSIGNMENT, correctness, "explicit self-assignment" } declare_lint_pass!(SelfAssignment => [SELF_ASSIGNMENT]); impl<'tcx> LateLintPass<'tcx> for SelfAssignment { fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { if let ExprKind::Assign(lhs, rhs, _) = &expr.kind { if eq_expr_value(cx, lhs, rhs) { let lhs = snippet(cx, lhs.span, ""); let rhs = snippet(cx, rhs.span, ""); span_lint( cx, SELF_ASSIGNMENT, expr.span, &format!("self-assignment of `{}` to `{}`", rhs, lhs), ); } } } }