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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::higher::Range;
use clippy_utils::is_integer_const;
use rustc_ast::ast::RangeLimits;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, QPath};
use rustc_lint::LateContext;
use rustc_span::symbol::sym;
use rustc_span::Span;
use super::ITER_WITH_DRAIN;
pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span: Span, arg: &Expr<'_>) {
if !matches!(recv.kind, ExprKind::Field(..))
&& let Some(adt) = cx.typeck_results().expr_ty(recv).ty_adt_def()
&& let Some(ty_name) = cx.tcx.get_diagnostic_name(adt.did())
&& matches!(ty_name, sym::Vec | sym::VecDeque)
&& let Some(range) = Range::hir(arg)
&& is_full_range(cx, recv, range)
{
span_lint_and_sugg(
cx,
ITER_WITH_DRAIN,
span.with_hi(expr.span.hi()),
&format!("`drain(..)` used on a `{}`", ty_name),
"try this",
"into_iter()".to_string(),
Applicability::MaybeIncorrect,
);
};
}
fn is_full_range(cx: &LateContext<'_>, container: &Expr<'_>, range: Range<'_>) -> bool {
range.start.map_or(true, |e| is_integer_const(cx, e, 0))
&& range.end.map_or(true, |e| {
if range.limits == RangeLimits::HalfOpen
&& let ExprKind::Path(QPath::Resolved(None, container_path)) = container.kind
&& let ExprKind::MethodCall(name, self_arg, [], _) = e.kind
&& name.ident.name == sym::len
&& let ExprKind::Path(QPath::Resolved(None, path)) = self_arg.kind
{
container_path.res == path.res
} else {
false
}
})
}
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