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
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132

use std::str::Utf8Error;

use rustc_ast::LitKind;
use rustc_hir::{Expr, ExprKind};
use rustc_session::{declare_lint, declare_lint_pass};
use rustc_span::source_map::Spanned;
use rustc_span::sym;

use crate::lints::InvalidFromUtf8Diag;
use crate::{LateContext, LateLintPass, LintContext};

declare_lint! {
    /// The `invalid_from_utf8_unchecked` lint checks for calls to
    /// `std::str::from_utf8_unchecked` and `std::str::from_utf8_unchecked_mut`
    /// with a known invalid UTF-8 value.
    ///
    /// ### Example
    ///
    /// ```rust,compile_fail
    /// # #[allow(unused)]
    /// unsafe {
    ///     std::str::from_utf8_unchecked(b"Ru\x82st");
    /// }
    /// ```
    ///
    /// {{produces}}
    ///
    /// ### Explanation
    ///
    /// Creating such a `str` would result in undefined behavior as per documentation
    /// for `std::str::from_utf8_unchecked` and `std::str::from_utf8_unchecked_mut`.
    pub INVALID_FROM_UTF8_UNCHECKED,
    Deny,
    "using a non UTF-8 literal in `std::str::from_utf8_unchecked`"
}

declare_lint! {
    /// The `invalid_from_utf8` lint checks for calls to
    /// `std::str::from_utf8` and `std::str::from_utf8_mut`
    /// with a known invalid UTF-8 value.
    ///
    /// ### Example
    ///
    /// ```rust
    /// # #[allow(unused)]
    /// std::str::from_utf8(b"Ru\x82st");
    /// ```
    ///
    /// {{produces}}
    ///
    /// ### Explanation
    ///
    /// Trying to create such a `str` would always return an error as per documentation
    /// for `std::str::from_utf8` and `std::str::from_utf8_mut`.
    pub INVALID_FROM_UTF8,
    Warn,
    "using a non UTF-8 literal in `std::str::from_utf8`"
}

declare_lint_pass!(InvalidFromUtf8 => [INVALID_FROM_UTF8_UNCHECKED, INVALID_FROM_UTF8]);

impl<'tcx> LateLintPass<'tcx> for InvalidFromUtf8 {
    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
        if let ExprKind::Call(path, [arg]) = expr.kind
            && let ExprKind::Path(ref qpath) = path.kind
            && let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
            && let Some(diag_item) = cx.tcx.get_diagnostic_name(def_id)
            && [
                sym::str_from_utf8,
                sym::str_from_utf8_mut,
                sym::str_from_utf8_unchecked,
                sym::str_from_utf8_unchecked_mut,
            ]
            .contains(&diag_item)
        {
            let lint = |label, utf8_error: Utf8Error| {
                let method = diag_item.as_str().strip_prefix("str_").unwrap();
                let method = format!("std::str::{method}");
                let valid_up_to = utf8_error.valid_up_to();
                let is_unchecked_variant = diag_item.as_str().contains("unchecked");

                cx.emit_span_lint(
                    if is_unchecked_variant {
                        INVALID_FROM_UTF8_UNCHECKED
                    } else {
                        INVALID_FROM_UTF8
                    },
                    expr.span,
                    if is_unchecked_variant {
                        InvalidFromUtf8Diag::Unchecked { method, valid_up_to, label }
                    } else {
                        InvalidFromUtf8Diag::Checked { method, valid_up_to, label }
                    },
                )
            };

            let mut init = cx.expr_or_init_with_outside_body(arg);
            while let ExprKind::AddrOf(.., inner) = init.kind {
                init = cx.expr_or_init_with_outside_body(inner);
            }
            match init.kind {
                ExprKind::Lit(Spanned { node: lit, .. }) => {
                    if let LitKind::ByteStr(bytes, _) = &lit
                        && let Err(utf8_error) = std::str::from_utf8(bytes)
                    {
                        lint(init.span, utf8_error);
                    }
                }
                ExprKind::Array(args) => {
                    let elements = args
                        .iter()
                        .map(|e| match &e.kind {
                            ExprKind::Lit(Spanned { node: lit, .. }) => match lit {
                                LitKind::Byte(b) => Some(*b),
                                LitKind::Int(b, _) => Some(b.get() as u8),
                                _ => None,
                            },
                            _ => None,
                        })
                        .collect::<Option<Vec<_>>>();

                    if let Some(elements) = elements
                        && let Err(utf8_error) = std::str::from_utf8(&elements)
                    {
                        lint(init.span, utf8_error);
                    }
                }
                _ => {}
            }
        }
    }
}