1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
use crate::utils::is_adjusted;
use crate::utils::span_lint;
use rustc_hir::def::{DefKind, Res};
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 construction of a structure or tuple just to
/// assign a value in it.
///
/// **Why is this bad?** Readability. If the structure is only created to be
/// updated, why not write the structure you want in the first place?
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// (0, 0).0 = 1
/// ```
pub TEMPORARY_ASSIGNMENT,
complexity,
"assignments to temporaries"
}
fn is_temporary(cx: &LateContext<'_, '_>, expr: &Expr<'_>) -> bool {
match &expr.kind {
ExprKind::Struct(..) | ExprKind::Tup(..) => true,
ExprKind::Path(qpath) => {
if let Res::Def(DefKind::Const, ..) = cx.tables.qpath_res(qpath, expr.hir_id) {
true
} else {
false
}
},
_ => false,
}
}
declare_lint_pass!(TemporaryAssignment => [TEMPORARY_ASSIGNMENT]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TemporaryAssignment {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
if let ExprKind::Assign(target, ..) = &expr.kind {
let mut base = target;
while let ExprKind::Field(f, _) | ExprKind::Index(f, _) = &base.kind {
base = f;
}
if is_temporary(cx, base) && !is_adjusted(cx, base) {
span_lint(cx, TEMPORARY_ASSIGNMENT, expr.span, "assignment to temporary");
}
}
}
}
|
