2017-02-05 04:07:54 +00:00
|
|
|
//! lint when there is an enum with no variants
|
|
|
|
|
2018-05-30 08:15:50 +00:00
|
|
|
use crate::utils::span_lint_and_then;
|
2020-01-11 11:37:08 +00:00
|
|
|
use rustc::lint::{LateContext, LateLintPass};
|
2020-01-06 16:39:50 +00:00
|
|
|
use rustc_hir::*;
|
2020-01-11 11:37:08 +00:00
|
|
|
use rustc_session::{declare_lint_pass, declare_tool_lint};
|
2017-02-05 04:07:54 +00:00
|
|
|
|
2018-03-28 13:24:26 +00:00
|
|
|
declare_clippy_lint! {
|
2019-03-05 16:50:33 +00:00
|
|
|
/// **What it does:** Checks for `enum`s with no variants.
|
|
|
|
///
|
|
|
|
/// **Why is this bad?** Enum's with no variants should be replaced with `!`,
|
|
|
|
/// the uninhabited type,
|
|
|
|
/// or a wrapper around it.
|
|
|
|
///
|
|
|
|
/// **Known problems:** None.
|
|
|
|
///
|
|
|
|
/// **Example:**
|
|
|
|
/// ```rust
|
|
|
|
/// enum Test {}
|
|
|
|
/// ```
|
2017-02-05 04:07:54 +00:00
|
|
|
pub EMPTY_ENUM,
|
2018-03-28 13:24:26 +00:00
|
|
|
pedantic,
|
2017-02-05 04:07:54 +00:00
|
|
|
"enum with no variants"
|
|
|
|
}
|
|
|
|
|
2019-04-08 20:43:55 +00:00
|
|
|
declare_lint_pass!(EmptyEnum => [EMPTY_ENUM]);
|
2017-02-05 04:07:54 +00:00
|
|
|
|
|
|
|
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EmptyEnum {
|
2019-12-22 14:42:41 +00:00
|
|
|
fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &Item<'_>) {
|
2019-07-06 03:52:51 +00:00
|
|
|
let did = cx.tcx.hir().local_def_id(item.hir_id);
|
2019-09-27 15:16:06 +00:00
|
|
|
if let ItemKind::Enum(..) = item.kind {
|
2017-04-27 12:00:35 +00:00
|
|
|
let ty = cx.tcx.type_of(did);
|
2018-11-27 20:14:15 +00:00
|
|
|
let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
|
2017-02-05 04:52:44 +00:00
|
|
|
if adt.variants.is_empty() {
|
|
|
|
span_lint_and_then(cx, EMPTY_ENUM, item.span, "enum with no variants", |db| {
|
2018-11-27 20:14:15 +00:00
|
|
|
db.span_help(
|
|
|
|
item.span,
|
|
|
|
"consider using the uninhabited type `!` or a wrapper around it",
|
|
|
|
);
|
2017-02-05 04:07:54 +00:00
|
|
|
});
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
}
|