rust-clippy/clippy_lints/src/methods/manual_ok_or.rs

use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::{indent_of, reindent_multiline, snippet_opt};
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::{is_lang_ctor, path_to_local_id};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::LangItem::{ResultErr, ResultOk};
use rustc_hir::{Closure, Expr, ExprKind, PatKind};
use rustc_lint::LateContext;
use rustc_span::symbol::sym;

use super::MANUAL_OK_OR;

pub(super) fn check<'tcx>(
    cx: &LateContext<'tcx>,
    expr: &'tcx Expr<'tcx>,
    recv: &'tcx Expr<'_>,
    or_expr: &'tcx Expr<'_>,
    map_expr: &'tcx Expr<'_>,
) {
    if_chain! {
        if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
        if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id), sym::Option);
        if let ExprKind::Call(Expr { kind: ExprKind::Path(err_path), .. }, [err_arg]) = or_expr.kind;
        if is_lang_ctor(cx, err_path, ResultErr);
        if is_ok_wrapping(cx, map_expr);
        if let Some(recv_snippet) = snippet_opt(cx, recv.span);
        if let Some(err_arg_snippet) = snippet_opt(cx, err_arg.span);
        if let Some(indent) = indent_of(cx, expr.span);
        then {
            let reindented_err_arg_snippet = reindent_multiline(err_arg_snippet.into(), true, Some(indent + 4));
            span_lint_and_sugg(
                cx,
                MANUAL_OK_OR,
                expr.span,
                "this pattern reimplements `Option::ok_or`",
                "replace with",
                format!(
                    "{recv_snippet}.ok_or({reindented_err_arg_snippet})"
                ),
                Applicability::MachineApplicable,
            );
        }
    }
}

fn is_ok_wrapping(cx: &LateContext<'_>, map_expr: &Expr<'_>) -> bool {
    if let ExprKind::Path(ref qpath) = map_expr.kind {
        if is_lang_ctor(cx, qpath, ResultOk) {
            return true;
        }
    }
    if_chain! {
        if let ExprKind::Closure(&Closure { body, .. }) = map_expr.kind;
        let body = cx.tcx.hir().body(body);
        if let PatKind::Binding(_, param_id, ..) = body.params[0].pat.kind;
        if let ExprKind::Call(Expr { kind: ExprKind::Path(ok_path), .. }, [ok_arg]) = body.value.kind;
        if is_lang_ctor(cx, ok_path, ResultOk);
        then { path_to_local_id(ok_arg, param_id) } else { false }
    }
}