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use super::ERR_EXPECT;
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::msrvs::{self, Msrv};
use clippy_utils::ty::has_debug_impl;
use clippy_utils::ty::is_type_diagnostic_item;
use rustc_errors::Applicability;
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_middle::ty::Ty;
use rustc_span::{sym, Span};
pub(super) fn check(
cx: &LateContext<'_>,
_expr: &rustc_hir::Expr<'_>,
recv: &rustc_hir::Expr<'_>,
expect_span: Span,
err_span: Span,
msrv: &Msrv,
) {
if_chain! {
if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result);
// Test the version to make sure the lint can be showed (expect_err has been
// introduced in rust 1.17.0 : https://github.com/rust-lang/rust/pull/38982)
if msrv.meets(msrvs::EXPECT_ERR);
// Grabs the `Result<T, E>` type
let result_type = cx.typeck_results().expr_ty(recv);
// Tests if the T type in a `Result<T, E>` is not None
if let Some(data_type) = get_data_type(cx, result_type);
// Tests if the T type in a `Result<T, E>` implements debug
if has_debug_impl(cx, data_type);
then {
span_lint_and_sugg(
cx,
ERR_EXPECT,
err_span.to(expect_span),
"called `.err().expect()` on a `Result` value",
"try",
"expect_err".to_string(),
Applicability::MachineApplicable
);
}
};
}
/// Given a `Result<T, E>` type, return its data (`T`).
fn get_data_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
match ty.kind() {
ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym::Result) => substs.types().next(),
_ => None,
}
}
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