use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_trait_method;
use clippy_utils::ty::{get_iterator_item_ty, is_copy};
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_span::{sym, Span};

use super::CLONED_INSTEAD_OF_COPIED;

pub fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, span: Span) {
    let recv_ty = cx.typeck_results().expr_ty_adjusted(recv);
    let inner_ty = match recv_ty.kind() {
        // `Option<T>` -> `T`
        ty::Adt(adt, subst) if cx.tcx.is_diagnostic_item(sym::option_type, adt.did) => subst.type_at(0),
        _ if is_trait_method(cx, expr, sym::Iterator) => match get_iterator_item_ty(cx, recv_ty) {
            // <T as Iterator>::Item
            Some(ty) => ty,
            _ => return,
        },
        _ => return,
    };
    match inner_ty.kind() {
        // &T where T: Copy
        ty::Ref(_, ty, _) if is_copy(cx, ty) => {},
        _ => return,
    };
    span_lint_and_sugg(
        cx,
        CLONED_INSTEAD_OF_COPIED,
        span,
        "used `cloned` where `copied` could be used instead",
        "try",
        "copied".into(),
        Applicability::MachineApplicable,
    )
}