clippy_lints/src/methods/bytes_nth.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::snippet_with_applicability;
   3 use clippy_utils::ty::is_type_diagnostic_item;
   4 use if_chain::if_chain;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{Expr, ExprKind};
   7 use rustc_lint::LateContext;
   8 use rustc_span::sym;
   9
  10 use super::BYTES_NTH;
  11
  12 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, iter_args: &'tcx [Expr<'tcx>]) {
  13     if_chain! {
  14         if let ExprKind::MethodCall(_, _, ref args, _) = expr.kind;
  15         let ty = cx.typeck_results().expr_ty(&iter_args[0]).peel_refs();
  16         let caller_type = if is_type_diagnostic_item(cx, ty, sym::string_type) {
  17             Some("String")
  18         } else if ty.is_str() {
  19             Some("str")
  20         } else {
  21             None
  22         };
  23         if let Some(caller_type) = caller_type;
  24         then {
  25             let mut applicability = Applicability::MachineApplicable;
  26             span_lint_and_sugg(
  27                 cx,
  28                 BYTES_NTH,
  29                 expr.span,
  30                 &format!("called `.byte().nth()` on a `{}`", caller_type),
  31                 "try",
  32                 format!(
  33                     "{}.as_bytes().get({})",
  34                     snippet_with_applicability(cx, iter_args[0].span, "..", &mut applicability),
  35                     snippet_with_applicability(cx, args[1].span, "..", &mut applicability)
  36                 ),
  37                 applicability,
  38             );
  39         }
  40     }
  41 }