1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution.
4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7 // option. This file may not be copied, modified, or distributed
8 // except according to those terms.
10 use crate::rustc::hir::{Expr, ExprKind};
11 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
12 use crate::rustc::{declare_tool_lint, lint_array};
13 use crate::utils::is_adjusted;
14 use crate::utils::span_lint;
16 /// **What it does:** Checks for construction of a structure or tuple just to
17 /// assign a value in it.
19 /// **Why is this bad?** Readability. If the structure is only created to be
20 /// updated, why not write the structure you want in the first place?
22 /// **Known problems:** None.
28 declare_clippy_lint! {
29 pub TEMPORARY_ASSIGNMENT,
31 "assignments to temporaries"
34 fn is_temporary(expr: &Expr) -> bool {
36 ExprKind::Struct(..) | ExprKind::Tup(..) => true,
41 #[derive(Copy, Clone)]
44 impl LintPass for Pass {
45 fn get_lints(&self) -> LintArray {
46 lint_array!(TEMPORARY_ASSIGNMENT)
50 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
51 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
52 if let ExprKind::Assign(ref target, _) = expr.node {
53 if let ExprKind::Field(ref base, _) = target.node {
54 if is_temporary(base) && !is_adjusted(cx, base) {
55 span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary");