Use a macro to create declare_clippy_lint macro (DRY)

This was first suggested by `@camsteffen` in rust-lang#6830. Back then, it was decided to avoid this implementation to keep the macro simple. Now it makes sense to again use this macro, as the implementation of the macro will get a bit more complicated to support nightly lints.

Credit where credit is due:

Co-authored-by: camsteffen <[email protected]>

Author: xFrednet

clippy_lints/src/lib.rs

@@ -97,65 +97,41 @@ use rustc_session::Session;
 /// }
 /// ```
 /// [lint_naming]: https://rust-lang.github.io/rfcs/0344-conventions-galore.html#lints
-#[macro_export]
-macro_rules! declare_clippy_lint {
-    { $(#[$attr:meta])* pub $name:tt, style, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Warn, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, correctness, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Deny, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, suspicious, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Warn, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, complexity, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Warn, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, perf, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Warn, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, pedantic, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Allow, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, restriction, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Allow, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, cargo, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Allow, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, nursery, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Allow, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, internal, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Allow, $description, report_in_external_macro: true
-        }
-    };
-    { $(#[$attr:meta])* pub $name:tt, internal_warn, $description:tt } => {
-        declare_tool_lint! {
-            $(#[$attr])* pub clippy::$name, Warn, $description, report_in_external_macro: true
+macro_rules! declare_clippy_lint_macro {
+    ({ $($category:tt: $level:tt,)* }, $d:tt) => {
+        macro_rules! declare_clippy_lint {
+            $(
+                ($d(#[$d meta:meta])* pub $d name:tt, $category, $d description:tt) => {
+                    declare_tool_lint! {
+                        $d(#[$d meta])*
+                        pub clippy::$d name,
+                        $level,
+                        $d description,
+                        report_in_external_macro: true
+                    }
+                };
+            )*
         }
     };
 }
 
+declare_clippy_lint_macro! {
+    {
+        correctness:   Deny,
+        complexity:    Warn,
+        internal_warn: Warn,
+        perf:          Warn,
+        suspicious:    Warn,
+        style:         Warn,
+        cargo:         Allow,
+        internal:      Allow,
+        nursery:       Allow,
+        pedantic:      Allow,
+        restriction:   Allow,
+    },
+    $
+}
+
 #[cfg(feature = "internal")]
 mod deprecated_lints;
 #[cfg_attr(feature = "internal", allow(clippy::missing_clippy_version_attribute))]