//! lint when there is an enum with no variants
-use crate::utils::span_lint_and_then;
+use clippy_utils::diagnostics::span_lint_and_help;
use rustc_hir::{Item, ItemKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
- /// **What it does:** Checks for `enum`s with no variants.
+ /// ### What it does
+ /// Checks for `enum`s with no variants.
///
- /// **Why is this bad?** If you want to introduce a type which
- /// can't be instantiated, you should use `!` (the never type),
+ /// As of this writing, the `never_type` is still a
+ /// nightly-only experimental API. Therefore, this lint is only triggered
+ /// if the `never_type` is enabled.
+ ///
+ /// ### Why is this bad?
+ /// If you want to introduce a type which
+ /// can't be instantiated, you should use `!` (the primitive type "never"),
/// or a wrapper around it, because `!` has more extensive
/// compiler support (type inference, etc...) and wrappers
/// around it are the conventional way to define an uninhabited type.
/// For further information visit [never type documentation](https://doc.rust-lang.org/std/primitive.never.html)
///
///
- /// **Known problems:** None.
- ///
- /// **Example:**
- ///
+ /// ### Example
/// Bad:
/// ```rust
/// enum Test {}
///
/// struct Test(!);
/// ```
+ #[clippy::version = "pre 1.29.0"]
pub EMPTY_ENUM,
pedantic,
"enum with no variants"
declare_lint_pass!(EmptyEnum => [EMPTY_ENUM]);
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EmptyEnum {
- fn check_item(&mut self, cx: &LateContext<'_, '_>, item: &Item<'_>) {
- let did = cx.tcx.hir().local_def_id(item.hir_id);
+impl<'tcx> LateLintPass<'tcx> for EmptyEnum {
+ fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
+ // Only suggest the `never_type` if the feature is enabled
+ if !cx.tcx.features().never_type {
+ return;
+ }
+
if let ItemKind::Enum(..) = item.kind {
- let ty = cx.tcx.type_of(did);
+ let ty = cx.tcx.type_of(item.def_id);
let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
if adt.variants.is_empty() {
- span_lint_and_then(cx, EMPTY_ENUM, item.span, "enum with no variants", |diag| {
- diag.span_help(
- item.span,
- "consider using the uninhabited type `!` (never type) or a wrapper \
- around it to introduce a type which can't be instantiated",
- );
- });
+ span_lint_and_help(
+ cx,
+ EMPTY_ENUM,
+ item.span,
+ "enum with no variants",
+ None,
+ "consider using the uninhabited type `!` (never type) or a wrapper \
+ around it to introduce a type which can't be instantiated",
+ );
}
}
}