Add internal nightly lint to test nightly features

clippy_lints/src/lib.rs

@@ -498,6 +498,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     {
         store.register_early_pass(|| Box::new(utils::internal_lints::ClippyLintsInternal));
         store.register_early_pass(|| Box::new(utils::internal_lints::ProduceIce));
+        store.register_early_pass(|| Box::new(utils::internal_lints::ForeverNightlyLint));
         store.register_late_pass(|| Box::new(utils::inspector::DeepCodeInspector));
         store.register_late_pass(|| Box::new(utils::internal_lints::CollapsibleCalls));
         store.register_late_pass(|| Box::new(utils::internal_lints::CompilerLintFunctions::new()));

clippy_lints/src/utils/internal_lints.rs

@@ -338,6 +338,21 @@ declare_clippy_lint! {
     "found clippy lint without `clippy::version` attribute"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Not an actual lint. This lint is only meant for testing lints with the
+    /// version set to `nightly`
+    ///
+    /// ### Why is this bad?
+    /// This lint will never be seen by the end user. This text is therefore just
+    /// waisted storage space ^^
+    ///
+    #[clippy::version = "nightly"]
+    pub FOREVER_NIGHTLY_LINT,
+    internal_warn,
+    "achivement: you found a nightly lint (+1xp)"
+}
+
 declare_lint_pass!(ClippyLintsInternal => [CLIPPY_LINTS_INTERNAL]);
 
 impl EarlyLintPass for ClippyLintsInternal {
@@ -652,6 +667,24 @@ fn is_trigger_fn(fn_kind: FnKind<'_>) -> bool {
     }
 }
 
+declare_lint_pass!(ForeverNightlyLint => [FOREVER_NIGHTLY_LINT]);
+
+impl EarlyLintPass for ForeverNightlyLint {
+    fn check_fn(&mut self, cx: &EarlyContext<'_>, fn_kind: FnKind<'_>, _: Span, _: NodeId) {
+        match fn_kind {
+            FnKind::Fn(_, ident, ..) if ident.name.as_str() == "trigger_forever_nightly_lint" => {
+                span_lint(
+                    cx,
+                    FOREVER_NIGHTLY_LINT,
+                    ident.span,
+                    "this triggered a lint that should only be available on nightly",
+                );
+            },
+            _ => {},
+        }
+    }
+}
+
 declare_lint_pass!(CollapsibleCalls => [COLLAPSIBLE_SPAN_LINT_CALLS]);
 
 impl<'tcx> LateLintPass<'tcx> for CollapsibleCalls {

tests/ui-internal/clippy_nightly_lints_disabled.rs

@@ -0,0 +1,8 @@
+// rustc-env:CLIPPY_NIGHTLY=0
+
+// This should trigger `clippy::forever_nightly_lint`
+// The lint is warn by default
+
+fn trigger_forever_nightly_lint() {}
+
+fn main() {}

tests/ui-internal/clippy_nightly_lints_enabled.rs

@@ -0,0 +1,8 @@
+// rustc-env:CLIPPY_NIGHTLY=1
+
+// This should trigger `clippy::forever_nightly_lint`
+// The lint is warn by default
+
+fn trigger_forever_nightly_lint() {}
+
+fn main() {}

tests/ui-internal/clippy_nightly_lints_enabled.stderr

@@ -0,0 +1,10 @@
+error: this triggered a lint that should only be available on nightly
+  --> $DIR/clippy_nightly_lints_enabled.rs:6:4
+   |
+LL | fn trigger_forever_nightly_lint() {}
+   |    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::forever-nightly-lint` implied by `-D warnings`
+
+error: aborting due to previous error
+