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Commit | Line | Data |
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f20569fa XL |
1 | use rustc_ast::LitKind; |
2 | use rustc_errors::Applicability; | |
3 | use rustc_hir::{Expr, ExprKind}; | |
4 | use rustc_lint::LateContext; | |
5 | use rustc_middle::ty::{self, UintTy}; | |
6 | ||
7 | use if_chain::if_chain; | |
8 | ||
9 | use crate::utils::{snippet_with_applicability, span_lint_and_then}; | |
10 | ||
11 | use super::CHAR_LIT_AS_U8; | |
12 | ||
13 | pub(super) fn check(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { | |
14 | if_chain! { | |
15 | if let ExprKind::Cast(e, _) = &expr.kind; | |
16 | if let ExprKind::Lit(l) = &e.kind; | |
17 | if let LitKind::Char(c) = l.node; | |
18 | if ty::Uint(UintTy::U8) == *cx.typeck_results().expr_ty(expr).kind(); | |
19 | then { | |
20 | let mut applicability = Applicability::MachineApplicable; | |
21 | let snippet = snippet_with_applicability(cx, e.span, "'x'", &mut applicability); | |
22 | ||
23 | span_lint_and_then( | |
24 | cx, | |
25 | CHAR_LIT_AS_U8, | |
26 | expr.span, | |
27 | "casting a character literal to `u8` truncates", | |
28 | |diag| { | |
29 | diag.note("`char` is four bytes wide, but `u8` is a single byte"); | |
30 | ||
31 | if c.is_ascii() { | |
32 | diag.span_suggestion( | |
33 | expr.span, | |
34 | "use a byte literal instead", | |
35 | format!("b{}", snippet), | |
36 | applicability, | |
37 | ); | |
38 | } | |
39 | }); | |
40 | } | |
41 | } | |
42 | } |