src/tools/clippy/clippy_lints/src/methods/iter_skip_next.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::is_trait_method;
   3 use clippy_utils::path_to_local;
   4 use clippy_utils::source::snippet;
   5 use rustc_errors::Applicability;
   6 use rustc_hir as hir;
   7 use rustc_hir::{BindingAnnotation, Node, PatKind};
   8 use rustc_lint::LateContext;
   9 use rustc_span::sym;
  10
  11 use super::ITER_SKIP_NEXT;
  12
  13 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
  14     // lint if caller of skip is an Iterator
  15     if is_trait_method(cx, expr, sym::Iterator) {
  16         let mut application = Applicability::MachineApplicable;
  17         span_lint_and_then(
  18             cx,
  19             ITER_SKIP_NEXT,
  20             expr.span.trim_start(recv.span).unwrap(),
  21             "called `skip(..).next()` on an iterator",
  22             |diag| {
  23                 if_chain! {
  24                     if let Some(id) = path_to_local(recv);
  25                     if let Node::Pat(pat) = cx.tcx.hir().get(id);
  26                     if let PatKind::Binding(ann, _, _, _)  = pat.kind;
  27                     if ann != BindingAnnotation::MUT;
  28                     then {
  29                         application = Applicability::Unspecified;
  30                         diag.span_help(
  31                             pat.span,
  32                             format!("for this change `{}` has to be mutable", snippet(cx, pat.span, "..")),
  33                         );
  34                     }
  35                 }
  36
  37                 diag.span_suggestion(
  38                     expr.span.trim_start(recv.span).unwrap(),
  39                     "use `nth` instead",
  40                     format!(".nth({})", snippet(cx, arg.span, "..")),
  41                     application,
  42                 );
  43             },
  44         );
  45     }
  46 }