1 files changed, 118 insertions, 0 deletions
diff --git a/compiler/rustc_lint/src/invalid_from_utf8.rs b/compiler/rustc_lint/src/invalid_from_utf8.rs
new file mode 100644
index 000000000..3291286ad
--- /dev/null
+++ b/compiler/rustc_lint/src/invalid_from_utf8.rs
@@ -0,0 +1,118 @@
+use std::str::Utf8Error;
+
+use rustc_ast::{BorrowKind, LitKind};
+use rustc_hir::{Expr, ExprKind};
+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 an invalid UTF-8 literal.
+    ///
+    /// ### 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 an invalid UTF-8 literal.
+    ///
+    /// ### 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 = |utf8_error: Utf8Error| {
+                let label = arg.span;
+                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_spanned_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 }
+                    }
+                )
+            };
+
+            match &arg.kind {
+                ExprKind::Lit(Spanned { node: lit, .. }) => {
+                    if let LitKind::ByteStr(bytes, _) = &lit
+                        && let Err(utf8_error) = std::str::from_utf8(bytes)
+                    {
+                        lint(utf8_error);
+                    }
+                },
+                ExprKind::AddrOf(BorrowKind::Ref, _, Expr { kind: 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 as u8),
+                                _ => None
+                            }
+                            _ => None
+                        }
+                    }).collect::<Option<Vec<_>>>();
+
+                    if let Some(elements) = elements
+                        && let Err(utf8_error) = std::str::from_utf8(&elements)
+                    {
+                        lint(utf8_error);
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+}