Add lint for default lint description

- Lint for any new lints that have the default lint description
  from the automation

clippy_lints/src/lib.rs

@@ -1086,6 +1086,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         LintId::of(&utils::internal_lints::LINT_WITHOUT_LINT_PASS),
         LintId::of(&utils::internal_lints::OUTER_EXPN_EXPN_DATA),
         LintId::of(&utils::internal_lints::PRODUCE_ICE),
+        LintId::of(&utils::internal_lints::DEFAULT_LINT),
     ]);
 
     store.register_group(true, "clippy::all", Some("clippy"), vec![

clippy_lints/src/utils/internal_lints.rs

@@ -121,6 +121,29 @@ declare_clippy_lint! {
     "this message should not appear anywhere as we ICE before and don't emit the lint"
 }
 
+declare_clippy_lint! {
+    /// **What it does:** Checks for cases of an auto-generated lint without an updated description,
+    /// ie `default lint description`.
+    ///
+    /// **Why is this bad?** Indicates that the lint is not finished.
+    ///
+    /// **Known problems:** None
+    ///
+    /// **Example:**
+    /// Bad:
+    /// ```rust,ignore
+    /// declare_lint! { pub COOL_LINT, nursery, "default lint description" }
+    /// ```
+    ///
+    /// Good:
+    /// ```rust,ignore
+    /// declare_lint! { pub COOL_LINT, nursery, "a great new lint" }
+    /// ```
+    pub DEFAULT_LINT,
+    internal,
+    "found 'default lint description' in a lint declaration"
+}
+
 declare_lint_pass!(ClippyLintsInternal => [CLIPPY_LINTS_INTERNAL]);
 
 impl EarlyLintPass for ClippyLintsInternal {
@@ -345,3 +368,13 @@ fn is_trigger_fn(fn_kind: FnKind<'_>) -> bool {
         FnKind::Closure(..) => false,
     }
 }
+
+declare_lint_pass!(DefaultLint => [DEFAULT_LINT]);
+
+impl EarlyLintPass for DefaultLint {
+    fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::Mac) {
+        if mac.path == sym!(declare_lint) {
+            println!("{:?}", mac);
+        }
+    }
+}