Regression test for rust-lang#56327.

Author: pnkfelix

src/test/ui/dyn-keyword/issue-56327-dyn-trait-in-macro-is-okay.rs

@@ -0,0 +1,25 @@
+// compile-pass
+
+// rust-lang/rust#56327: Some occurrences of `dyn` within a macro are
+// not instances of identifiers, and thus should *not* be caught by the
+// keyword_ident lint.
+//
+// Otherwise, rustfix replaces the type `Box<dyn Drop>` with
+// `Box<r#dyn Drop>`, which is injecting a bug rather than fixing
+// anything.
+
+#![deny(rust_2018_compatibility)]
+
+macro_rules! foo {
+    () => {
+        fn generated_foo() {
+            let _x: Box<dyn Drop>;
+        }
+    }
+}
+
+foo!();
+
+fn main() {
+    generated_foo();
+}