Address flip1995's review comments
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@ -8,12 +8,12 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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declare_clippy_lint! {
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/// **What it does:** Checks for `enum`s with no variants.
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/// **What it does:** Checks for `enum`s with no variants.
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///
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///
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/// As of this writing, the never type is still a
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/// As of this writing, the `never_type` is still a
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/// nightly-only experimental API. Therefore, this lint is only triggered
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/// nightly-only experimental API. Therefore, this lint is only triggered
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/// if the never type is enabled
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/// if the `never_type` is enabled.
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///
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///
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/// **Why is this bad?** If you want to introduce a type which
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/// **Why is this bad?** If you want to introduce a type which
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/// can't be instantiated, you should use `!` (the never type),
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/// can't be instantiated, you should use `!` (the primitive type never),
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/// or a wrapper around it, because `!` has more extensive
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/// or a wrapper around it, because `!` has more extensive
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/// compiler support (type inference, etc...) and wrappers
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/// compiler support (type inference, etc...) and wrappers
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/// around it are the conventional way to define an uninhabited type.
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/// around it are the conventional way to define an uninhabited type.
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@ -44,13 +44,16 @@ declare_lint_pass!(EmptyEnum => [EMPTY_ENUM]);
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impl<'tcx> LateLintPass<'tcx> for EmptyEnum {
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impl<'tcx> LateLintPass<'tcx> for EmptyEnum {
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fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
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fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
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// Only suggest the `never_type` if the feature is enabled
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if !cx.tcx.features().never_type {
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return;
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}
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let did = cx.tcx.hir().local_def_id(item.hir_id);
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let did = cx.tcx.hir().local_def_id(item.hir_id);
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if let ItemKind::Enum(..) = item.kind {
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if let ItemKind::Enum(..) = item.kind {
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let ty = cx.tcx.type_of(did);
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let ty = cx.tcx.type_of(did);
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let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
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let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
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if adt.variants.is_empty() {
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// Only suggest the never type if the feature is enabled
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if adt.variants.is_empty() && cx.tcx.features().never_type {
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span_lint_and_help(
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span_lint_and_help(
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cx,
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cx,
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EMPTY_ENUM,
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EMPTY_ENUM,
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7
tests/ui/empty_enum_without_never_type.rs
Normal file
7
tests/ui/empty_enum_without_never_type.rs
Normal file
@ -0,0 +1,7 @@
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#![allow(dead_code)]
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#![warn(clippy::empty_enum)]
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// `never_type` is not enabled; this test has no stderr file
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enum Empty {}
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fn main() {}
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