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Commit | Line | Data |
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f20569fa XL |
1 | use rustc_hir::{Expr, ExprKind}; |
2 | use rustc_lint::LateContext; | |
3 | use rustc_middle::ty::{self, Ty}; | |
4 | ||
5 | use if_chain::if_chain; | |
6 | ||
7 | use crate::consts::{constant, Constant}; | |
8 | use crate::utils::{method_chain_args, sext, span_lint}; | |
9 | ||
10 | use super::CAST_SIGN_LOSS; | |
11 | ||
12 | pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) { | |
13 | if should_lint(cx, cast_op, cast_from, cast_to) { | |
14 | span_lint( | |
15 | cx, | |
16 | CAST_SIGN_LOSS, | |
17 | expr.span, | |
18 | &format!( | |
19 | "casting `{}` to `{}` may lose the sign of the value", | |
20 | cast_from, cast_to | |
21 | ), | |
22 | ); | |
23 | } | |
24 | } | |
25 | ||
26 | fn should_lint(cx: &LateContext<'_>, cast_op: &Expr<'_>, cast_from: Ty<'_>, cast_to: Ty<'_>) -> bool { | |
27 | match (cast_from.is_integral(), cast_to.is_integral()) { | |
28 | (true, true) => { | |
29 | if !cast_from.is_signed() || cast_to.is_signed() { | |
30 | return false; | |
31 | } | |
32 | ||
33 | // Don't lint for positive constants. | |
34 | let const_val = constant(cx, &cx.typeck_results(), cast_op); | |
35 | if_chain! { | |
36 | if let Some((Constant::Int(n), _)) = const_val; | |
37 | if let ty::Int(ity) = *cast_from.kind(); | |
38 | if sext(cx.tcx, n, ity) >= 0; | |
39 | then { | |
40 | return false; | |
41 | } | |
42 | } | |
43 | ||
44 | // Don't lint for the result of methods that always return non-negative values. | |
45 | if let ExprKind::MethodCall(ref path, _, _, _) = cast_op.kind { | |
46 | let mut method_name = path.ident.name.as_str(); | |
47 | let allowed_methods = ["abs", "checked_abs", "rem_euclid", "checked_rem_euclid"]; | |
48 | ||
49 | if_chain! { | |
50 | if method_name == "unwrap"; | |
51 | if let Some(arglist) = method_chain_args(cast_op, &["unwrap"]); | |
52 | if let ExprKind::MethodCall(ref inner_path, _, _, _) = &arglist[0][0].kind; | |
53 | then { | |
54 | method_name = inner_path.ident.name.as_str(); | |
55 | } | |
56 | } | |
57 | ||
58 | if allowed_methods.iter().any(|&name| method_name == name) { | |
59 | return false; | |
60 | } | |
61 | } | |
62 | ||
63 | true | |
64 | }, | |
65 | ||
66 | (false, true) => !cast_to.is_signed(), | |
67 | ||
68 | (_, _) => false, | |
69 | } | |
70 | } |