clippy_lints/src/methods/get_first.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::is_slice_of_primitives;
   3 use clippy_utils::source::snippet_with_applicability;
   4 use if_chain::if_chain;
   5 use rustc_ast::LitKind;
   6 use rustc_errors::Applicability;
   7 use rustc_hir as hir;
   8 use rustc_lint::LateContext;
   9 use rustc_span::source_map::Spanned;
  10
  11 use super::GET_FIRST;
  12
  13 pub(super) fn check<'tcx>(
  14     cx: &LateContext<'tcx>,
  15     expr: &'tcx hir::Expr<'_>,
  16     recv: &'tcx hir::Expr<'_>,
  17     arg: &'tcx hir::Expr<'_>,
  18 ) {
  19     if_chain! {
  20         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
  21         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
  22         if cx.tcx.type_of(impl_id).is_slice();
  23         if let Some(_) = is_slice_of_primitives(cx, recv);
  24         if let hir::ExprKind::Lit(Spanned { node: LitKind::Int(0, _), .. }) = arg.kind;
  25         then {
  26             let mut app = Applicability::MachineApplicable;
  27             let slice_name = snippet_with_applicability(cx, recv.span, "..", &mut app);
  28             span_lint_and_sugg(
  29                 cx,
  30                 GET_FIRST,
  31                 expr.span,
  32                 &format!("accessing first element with `{slice_name}.get(0)`"),
  33                 "try",
  34                 format!("{slice_name}.first()"),
  35                 app,
  36             );
  37         }
  38     }
  39 }