Merge commit '4911ab124c481430672a3833b37075e6435ec34d' into clippyup

[rust.git] / clippy_lints / src / empty_enum.rs

diff --git a/clippy_lints/src/empty_enum.rs b/clippy_lints/src/empty_enum.rs
index f95ae32d5611d87dfc9b24f8b0fe08f9a2a7b771..a249117d182fa360c4156b3e3abeb1d471e008c5 100644 (file)
--- a/clippy_lints/src/empty_enum.rs
+++ b/clippy_lints/src/empty_enum.rs
@@ -1,48 +1,59 @@
 //! lint when there is an enum with no variants
 
-use rustc::lint::*;
-use rustc::{declare_lint, lint_array};
-use rustc::hir::*;
-use crate::utils::span_lint_and_then;
+use crate::utils::span_lint_and_help;
+use rustc_hir::{Item, ItemKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
 
-/// **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 {}
-/// ```
 declare_clippy_lint! {
+    /// **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),
+    /// 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:**
+    ///
+    /// Bad:
+    /// ```rust
+    /// enum Test {}
+    /// ```
+    ///
+    /// Good:
+    /// ```rust
+    /// #![feature(never_type)]
+    ///
+    /// struct Test(!);
+    /// ```
     pub EMPTY_ENUM,
     pedantic,
     "enum with no variants"
 }
 
-#[derive(Copy, Clone)]
-pub struct EmptyEnum;
+declare_lint_pass!(EmptyEnum => [EMPTY_ENUM]);
 
-impl LintPass for EmptyEnum {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(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.id);
-        if let ItemKind::Enum(..) = item.node {
+impl<'tcx> LateLintPass<'tcx> for EmptyEnum {
+    fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
+        let did = cx.tcx.hir().local_def_id(item.hir_id);
+        if let ItemKind::Enum(..) = item.kind {
             let ty = cx.tcx.type_of(did);
-            let adt = ty.ty_adt_def()
-                .expect("already checked whether this is an enum");
+            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", |db| {
-                    db.span_help(item.span, "consider using the uninhabited type `!` or a wrapper around it");
-                });
+                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",
+                );
             }
         }
     }