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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_trait_method;
use clippy_utils::ty::has_iter_method;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use rustc_span::source_map::Span;
use rustc_span::symbol::{sym, Symbol};
use super::INTO_ITER_ON_REF;
pub(super) fn check(
cx: &LateContext<'_>,
expr: &hir::Expr<'_>,
method_span: Span,
method_name: Symbol,
args: &[hir::Expr<'_>],
) {
let self_ty = cx.typeck_results().expr_ty_adjusted(&args[0]);
if_chain! {
if let ty::Ref(..) = self_ty.kind();
if method_name == sym::into_iter;
if is_trait_method(cx, expr, sym::IntoIterator);
if let Some((kind, method_name)) = ty_has_iter_method(cx, self_ty);
then {
span_lint_and_sugg(
cx,
INTO_ITER_ON_REF,
method_span,
&format!(
"this `.into_iter()` call is equivalent to `.{}()` and will not consume the `{}`",
method_name, kind,
),
"call directly",
method_name.to_string(),
Applicability::MachineApplicable,
);
}
}
}
fn ty_has_iter_method(cx: &LateContext<'_>, self_ref_ty: Ty<'_>) -> Option<(Symbol, &'static str)> {
has_iter_method(cx, self_ref_ty).map(|ty_name| {
let mutbl = match self_ref_ty.kind() {
ty::Ref(_, _, mutbl) => mutbl,
_ => unreachable!(),
};
let method_name = match mutbl {
hir::Mutability::Not => "iter",
hir::Mutability::Mut => "iter_mut",
};
(ty_name, method_name)
})
}
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