New anonymous class definition will be duplicated at each inline site #22951
Description
Compiler version
3.3.5
Minimized code
trait JsonWriter[T] { def writeValues(value: T, out: TokenWriter): Unit } object JsonWriter: inline def derived[T]: JsonWriter[T] = new JsonWriter[T]: def writeValues(value: T, out: TokenWriter): Unit = () // here should be some macro code } Output
Warning
New anonymous class definition will be duplicated at each inline siteExpectation
No warning. Disabling warning in all project may cause that I miss correct warnings
Why I expect no warning?
- Because for different types generated body may vary for performance reasons. (Not full example, just to explain)
case class Foo(foo: String) new JsonWriter[Foo]: def writeValues(value: Foo, out: TokenWriter): Unit = tokenWriter.writeFieldName("foo") tokenWriter.writeString(value.foo) case class Bar(bar: Int) new JsonWriter[Bar]: def writeValues(value: Bar, out: TokenWriter): Unit = tokenWriter.writeFieldName("bar") tokenWriter.writeint(value.bar)- Creating class now allows to pass some compile time configuration to derivation
sealed trait WriterBuilder[A]: def rename[B](field: A => B)(rename: String): WriterBuilder[A] def fieldStyle(style: FieldStyle): WriterBuilder[A] object WriterBuilder: @scala.annotation.compileTimeOnly( "Should be declared as inline given or provided directly to derives" ) def apply[A](using mirror: scala.deriving.Mirror.ProductOf[A] ): WriterBuilder[A] = throw IllegalStateException( "Config must be an inlined given or provided directly to 'derived'" )Usage is:
given JsonWriter[Foo] = JsonWriter.derived { WriterBuilder[Foo].rename(_.foo)("baz") } // and now it should generate new JsonWriter[Foo]: def writeValues(value: Foo, out: TokenWriter): Unit = tokenWriter.writeFieldName("baz") tokenWriter.writeString(value.foo)