1 use clippy_utils::diagnostics::span_lint;
2 use clippy_utils::is_adjusted;
3 use rustc_hir::{Expr, ExprKind};
4 use rustc_lint::{LateContext, LateLintPass};
5 use rustc_session::{declare_lint_pass, declare_tool_lint};
9 /// Checks for construction of a structure or tuple just to
10 /// assign a value in it.
12 /// ### Why is this bad?
13 /// Readability. If the structure is only created to be
14 /// updated, why not write the structure you want in the first place?
20 pub TEMPORARY_ASSIGNMENT,
22 "assignments to temporaries"
25 fn is_temporary(expr: &Expr<'_>) -> bool {
26 matches!(&expr.kind, ExprKind::Struct(..) | ExprKind::Tup(..))
29 declare_lint_pass!(TemporaryAssignment => [TEMPORARY_ASSIGNMENT]);
31 impl<'tcx> LateLintPass<'tcx> for TemporaryAssignment {
32 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
33 if let ExprKind::Assign(target, ..) = &expr.kind {
34 let mut base = target;
35 while let ExprKind::Field(f, _) | ExprKind::Index(f, _) = &base.kind {
38 if is_temporary(base) && !is_adjusted(cx, base) {
39 span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary");