Drop old deriving infrastructure

Drop old deriving infrastructure that was based on reflect.Generic

Author: odersky

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -706,17 +706,6 @@ class Definitions {
   lazy val Mirror_SingletonProxyType: TypeRef = ctx.requiredClassRef("scala.deriving.Mirror.SingletonProxy")
   def Mirror_SingletonProxyClass(implicit ctx: Context): ClassSymbol = Mirror_SingletonProxyType.symbol.asClass
 
-  lazy val GenericType: TypeRef                = ctx.requiredClassRef("scala.reflect.Generic")
-  def GenericClass(implicit ctx: Context): ClassSymbol    = GenericType.symbol.asClass
-  lazy val ShapeType: TypeRef                  = ctx.requiredClassRef("scala.compiletime.Shape")
-  def ShapeClass(implicit ctx: Context): ClassSymbol      = ShapeType.symbol.asClass
-  lazy val ShapeCaseType: TypeRef              = ctx.requiredClassRef("scala.compiletime.Shape.Case")
-  def ShapeCaseClass(implicit ctx: Context): ClassSymbol  = ShapeCaseType.symbol.asClass
-  lazy val ShapeCasesType: TypeRef             = ctx.requiredClassRef("scala.compiletime.Shape.Cases")
-  def ShapeCasesClass(implicit ctx: Context): ClassSymbol = ShapeCasesType.symbol.asClass
-  lazy val ReflectMirrorType: TypeRef          = ctx.requiredClassRef("scala.reflect.Mirror")
-  lazy val GenericClassType: TypeRef           = ctx.requiredClassRef("scala.reflect.GenericClass")
-
   lazy val LanguageModuleRef: TermSymbol = ctx.requiredModule("scala.language")
   def LanguageModuleClass(implicit ctx: Context): ClassSymbol = LanguageModuleRef.moduleClass.asClass
   lazy val NonLocalReturnControlType: TypeRef   = ctx.requiredClassRef("scala.runtime.NonLocalReturnControl")

compiler/src/dotty/tools/dotc/typer/Deriving.scala

@@ -800,21 +800,6 @@ trait Implicits { self: Typer =>
       }
     }
 
-  /** If `formal` is of the form `scala.reflect.Generic[T]` for some class type `T`,
-   *  synthesize an instance for it.
-   */
-  lazy val synthesizedGeneric: SpecialHandler =
-    (formal: Type, span: Span) => implicit (ctx: Context) =>
-      formal.argTypes match {
-        case arg :: Nil =>
-          val pos = ctx.source.atSpan(span)
-          val arg1 = fullyDefinedType(arg, "Generic argument", span)
-          val clsType = checkClassType(arg1, pos, traitReq = false, stablePrefixReq = true)
-          new Deriver(clsType.classSymbol.asClass, pos).genericInstance(clsType)
-        case _ =>
-          EmptyTree
-      }
-
   /** Create an anonymous class `new Object { type MirroredMonoType = ... }`
    *  and mark it with given attachment so that it is made into a mirror at PostTyper.
    */
@@ -955,7 +940,6 @@ trait Implicits { self: Typer =>
       mySpecialHandlers = List(
         defn.ClassTagClass        -> synthesizedClassTag,
         defn.QuotedTypeClass      -> synthesizedTypeTag,
-        defn.GenericClass         -> synthesizedGeneric,
         defn.TastyReflectionClass -> synthesizedTastyContext,
         defn.EqlClass             -> synthesizedEq,
         defn.ValueOfClass         -> synthesizedValueOf,