clippy_lints/src/methods/bytes_nth.rs

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