Introduce language import for experimental.dependent

Author: odersky

compiler/src/dotty/tools/dotc/config/Feature.scala

@@ -3,7 +3,7 @@ package dotc
 package config
 
 import core._
-import Contexts._, Symbols._, Names._
+import Contexts._, Symbols._, Names._, NameOps._
 import StdNames.nme
 import Decorators.{given _}
 import util.SourcePosition
@@ -22,7 +22,7 @@ object Feature:
   def enabledBySetting(feature: TermName, owner: Symbol = NoSymbol)(using Context): Boolean =
     def toPrefix(sym: Symbol): String =
       if !sym.exists || sym == defn.LanguageModule.moduleClass then ""
-      else toPrefix(sym.owner) + sym.name + "."
+      else toPrefix(sym.owner) + sym.name.stripModuleClassSuffix + "."
     val prefix = if owner.exists then toPrefix(owner) else ""
     ctx.base.settings.language.value.contains(prefix + feature)
 
@@ -38,7 +38,7 @@ object Feature:
   def enabledByImport(feature: TermName, owner: Symbol = NoSymbol)(using Context): Boolean =
     ctx.atPhase(ctx.typerPhase) {
       ctx.importInfo != null
-      && ctx.importInfo.featureImported(feature.toTermName,
+      && ctx.importInfo.featureImported(feature,
           if owner.exists then owner else defn.LanguageModule.moduleClass)
     }
 
@@ -57,6 +57,9 @@ object Feature:
   def dynamicsEnabled(using Context): Boolean =
     enabled(nme.dynamics)
 
+  def dependentEnabled(using Context) =
+    enabled(nme.dependent, defn.LanguageExperimentalModule.moduleClass)
+
   def sourceVersionSetting(using Context): SourceVersion =
     SourceVersion.valueOf(ctx.settings.source.value)
 

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

@@ -664,6 +664,7 @@ class Definitions {
   @tu lazy val Mirror_SingletonProxyClass: ClassSymbol = ctx.requiredClass("scala.deriving.Mirror.SingletonProxy")
 
   @tu lazy val LanguageModule: Symbol = ctx.requiredModule("scala.language")
+  @tu lazy val LanguageExperimentalModule: Symbol = ctx.requiredModule("scala.language.experimental")
   @tu lazy val NonLocalReturnControlClass: ClassSymbol = ctx.requiredClass("scala.runtime.NonLocalReturnControl")
   @tu lazy val SelectableClass: ClassSymbol = ctx.requiredClass("scala.Selectable")
 

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

@@ -441,6 +441,7 @@ object StdNames {
     val definitions: N          = "definitions"
     val delayedInit: N          = "delayedInit"
     val delayedInitArg: N       = "delayedInit$body"
+    val dependent: N            = "dependent"
     val derived: N              = "derived"
     val derives: N              = "derives"
     val drop: N                 = "drop"

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1580,7 +1580,8 @@ object Parsers {
 
     /**  SimpleType      ::=  SimpleLiteral
      *                     |  ‘?’ SubtypeBounds
-     *                     |  SimpleType1 { ‘(’ Singletons ‘)’ }
+     *                     |  SimpleType1
+     *                     |  SimpeType ‘(’ Singletons ‘)’  -- under language.experimental.dependent, checked in Typer
      *   Singletons      ::=  Singleton {‘,’ Singleton}
      */
     def simpleType(): Tree =

library/src/scalaShadowing/language.scala

@@ -210,6 +210,9 @@ object language {
      *  to debug and understand.
      */
     implicit lazy val macros: macros = languageFeature.experimental.macros
+
+    /** Experimental support for richer dependent types */
+    object dependent
   }
 
   /** Where imported, a backwards compatibility mode for Scala2 is enabled */
@@ -239,6 +242,9 @@ object language {
    */
   object adhocExtensions
 
+  /** Experimental support for richer dependent types */
+  object dependent
+
   /** Source version */
   object `3.0-migration`
   object `3.0`