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use clippy_utils::diagnostics::span_lint_and_help;
use clippy_utils::ty::{has_debug_impl, is_type_diagnostic_item};
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use rustc_span::sym;
use super::OK_EXPECT;
/// lint use of `ok().expect()` for `Result`s
pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>) {
if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result)
// lint if the caller of `ok()` is a `Result`
&& let result_type = cx.typeck_results().expr_ty(recv)
&& let Some(error_type) = get_error_type(cx, result_type)
&& has_debug_impl(cx, error_type)
{
span_lint_and_help(
cx,
OK_EXPECT,
expr.span,
"called `ok().expect()` on a `Result` value",
None,
"you can call `expect()` directly on the `Result`",
);
}
}
/// Given a `Result<T, E>` type, return its error type (`E`).
fn get_error_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
match ty.kind() {
ty::Adt(_, args) if is_type_diagnostic_item(cx, ty, sym::Result) => args.types().nth(1),
_ => None,
}
}
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