Refactor empty_enums: Check the HIR tree before the feature check.

Author: Jarcho

clippy_lints/src/empty_enum.rs

@@ -64,25 +64,21 @@ declare_lint_pass!(EmptyEnum => [EMPTY_ENUM]);
 
 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(item.owner_id).instantiate_identity();
-            let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
-            if adt.variants().is_empty() {
-                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",
-                );
-            }
+        if let ItemKind::Enum(..) = item.kind
+            // Only suggest the `never_type` if the feature is enabled
+            && cx.tcx.features().never_type
+            && let Some(adt) = cx.tcx.type_of(item.owner_id).instantiate_identity().ty_adt_def()
+            && adt.variants().is_empty()
+        {
+            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",
+            );
         }
     }
 }