don't lint macro_rules! in items_after_statements

Author: oli-obk

clippy_lints/src/items_after_statements.rs

@@ -58,6 +58,10 @@ impl EarlyLintPass for ItemsAfterStatements {
                 if in_macro(cx, it.span) {
                     return;
                 }
+                if let ItemKind::MacroDef(..) = it.node {
+                    // do not lint `macro_rules`, but continue processing further statements
+                    continue;
+                }
                 span_lint(cx,
                           ITEMS_AFTER_STATEMENTS,
                           it.span,

tests/ui/item_after_statement.rs

@@ -17,3 +17,14 @@ fn main() {
     fn foo() { println!("foo"); }
     foo();
 }
+
+fn mac() {
+    let mut a = 5;
+    println!("{}", a);
+    // do not lint this, because it needs to be after `a`
+    macro_rules! b {
+        () => {{ a = 6 }}
+    }
+    b!();
+    println!("{}", a);
+}