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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::higher::Range;
   3 use clippy_utils::is_integer_const;
   4 use rustc_ast::ast::RangeLimits;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{Expr, ExprKind, QPath};
   7 use rustc_lint::LateContext;
   8 use rustc_span::symbol::sym;
   9 use rustc_span::Span;
  10
  11 use super::ITER_WITH_DRAIN;
  12
  13 pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span: Span, arg: &Expr<'_>) {
  14     if !matches!(recv.kind, ExprKind::Field(..))
  15         && let Some(adt) = cx.typeck_results().expr_ty(recv).ty_adt_def()
  16         && let Some(ty_name) = cx.tcx.get_diagnostic_name(adt.did())
  17         && matches!(ty_name, sym::Vec | sym::VecDeque)
  18         && let Some(range) = Range::hir(arg)
  19         && is_full_range(cx, recv, range)
  20     {
  21         span_lint_and_sugg(
  22             cx,
  23             ITER_WITH_DRAIN,
  24             span.with_hi(expr.span.hi()),
  25             &format!("`drain(..)` used on a `{ty_name}`"),
  26             "try this",
  27             "into_iter()".to_string(),
  28             Applicability::MaybeIncorrect,
  29         );
  30     };
  31 }
  32
  33 fn is_full_range(cx: &LateContext<'_>, container: &Expr<'_>, range: Range<'_>) -> bool {
  34     range.start.map_or(true, |e| is_integer_const(cx, e, 0))
  35         && range.end.map_or(true, |e| {
  36             if range.limits == RangeLimits::HalfOpen
  37                 && let ExprKind::Path(QPath::Resolved(None, container_path)) = container.kind
  38                 && let ExprKind::MethodCall(name, self_arg, [], _) = e.kind
  39                 && name.ident.name == sym::len
  40                 && let ExprKind::Path(QPath::Resolved(None, path)) = self_arg.kind
  41             {
  42                 container_path.res == path.res
  43             } else {
  44                 false
  45             }
  46         })
  47 }