SI-4700 Add `@infix` annotation for type printing

```
scala> import scala.annotation.infix
import scala.annotation.infix

scala> @infix class &&[T, U]
defined class $amp$amp

scala> def foo: Int && Boolean = ???
foo: Int && Boolean
```

1 files changed, 21 insertions, 0 deletions

diff --git a/src/library/scala/annotation/showAsInfix.scala b/src/library/scala/annotation/showAsInfix.scala
new file mode 100644
index 0000000000..41c93b697f
--- /dev/null
+++ b/src/library/scala/annotation/showAsInfix.scala
@@ -0,0 +1,21 @@
+package scala.annotation
+
+/**
+ * This annotation, used for two-parameter generic types makes Scala print
+ * the type using infix notation:
+ *
+ * ```
+ * scala> class &&[T, U]
+ * defined class $amp$amp
+ *
+ * scala> def foo: Int && Int = ???
+ * foo: &&[Int,Int]
+ *
+ * scala> @showAsInfix class &&[T, U]
+ * defined class $amp$amp
+ *
+ * scala> def foo: Int && Int = ???
+ * foo: Int && Int
+ * ```
+ */
+class showAsInfix extends annotation.StaticAnnotation
\ No newline at end of file