Add scala.Dynamic language feature check.

5 files changed, 45 insertions, 4 deletions

diff --git a/src/dotty/tools/dotc/core/Definitions.scala b/src/dotty/tools/dotc/core/Definitions.scala
index 5cb373cfd..1fa3f70f9 100644
--- a/src/dotty/tools/dotc/core/Definitions.scala
+++ b/src/dotty/tools/dotc/core/Definitions.scala
@@ -424,8 +424,10 @@ class Definitions {
     def Product_productArity(implicit ctx: Context) = Product_productArityR.symbol
     lazy val Product_productPrefixR = ProductClass.requiredMethodRef(nme.productPrefix)
     def Product_productPrefix(implicit ctx: Context) = Product_productPrefixR.symbol
-  lazy val LanguageModuleRef          = ctx.requiredModule("dotty.language")
+  lazy val LanguageModuleRef = ctx.requiredModule("dotty.language")
   def LanguageModuleClass(implicit ctx: Context) = LanguageModuleRef.symbol.moduleClass.asClass
+  lazy val Scala2LanguageModuleRef = ctx.requiredModule("scala.language")
+  def Scala2LanguageModuleClass(implicit ctx: Context) = Scala2LanguageModuleRef.symbol.moduleClass.asClass
   lazy val NonLocalReturnControlType: TypeRef   = ctx.requiredClassRef("scala.runtime.NonLocalReturnControl")
 
   lazy val ClassTagType = ctx.requiredClassRef("scala.reflect.ClassTag")
diff --git a/src/dotty/tools/dotc/core/StdNames.scala b/src/dotty/tools/dotc/core/StdNames.scala
index 81f6da0e2..345322cf5 100644
--- a/src/dotty/tools/dotc/core/StdNames.scala
+++ b/src/dotty/tools/dotc/core/StdNames.scala
@@ -383,6 +383,7 @@ object StdNames {
     val delayedInit: N          = "delayedInit"
     val delayedInitArg: N       = "delayedInit$body"
     val drop: N                 = "drop"
+    val dynamics: N             = "dynamics"
     val dummyApply: N           = "<dummy-apply>"
     val elem: N                 = "elem"
     val emptyValDef: N          = "emptyValDef"
diff --git a/src/dotty/tools/dotc/core/TypeOps.scala b/src/dotty/tools/dotc/core/TypeOps.scala
index 1288c0b23..3da119a9c 100644
--- a/src/dotty/tools/dotc/core/TypeOps.scala
+++ b/src/dotty/tools/dotc/core/TypeOps.scala
@@ -455,7 +455,8 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
    */
   def featureEnabled(owner: ClassSymbol, feature: TermName): Boolean = {
     def toPrefix(sym: Symbol): String =
-      if (sym eq defn.LanguageModuleClass) "" else toPrefix(sym.owner) + sym.name + "."
+      if (!sym.exists || (sym eq defn.LanguageModuleClass) || (sym eq defn.Scala2LanguageModuleRef)) ""
+      else toPrefix(sym.owner) + sym.name + "."
     def featureName = toPrefix(owner) + feature
     def hasImport(implicit ctx: Context): Boolean = (
          ctx.importInfo != null
@@ -477,6 +478,9 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
   def scala2Mode =
     featureEnabled(defn.LanguageModuleClass, nme.Scala2)
 
+  def dynamicsEnabled =
+    featureEnabled(defn.Scala2LanguageModuleClass, nme.dynamics)
+
   def testScala2Mode(msg: String, pos: Position) = {
     if (scala2Mode) migrationWarning(msg, pos)
     scala2Mode
diff --git a/src/dotty/tools/dotc/reporting/Reporter.scala b/src/dotty/tools/dotc/reporting/Reporter.scala
index e4169b1fd..bddfd2f68 100644
--- a/src/dotty/tools/dotc/reporting/Reporter.scala
+++ b/src/dotty/tools/dotc/reporting/Reporter.scala
@@ -12,6 +12,7 @@ import config.Printers
 import java.lang.System.currentTimeMillis
 import core.Mode
 import interfaces.Diagnostic.{ERROR, WARNING, INFO}
+import dotty.tools.dotc.core.Symbols.Symbol
 
 object Reporter {
   class Error(msgFn: => String, pos: SourcePosition) extends Diagnostic(msgFn, pos, ERROR)
@@ -68,6 +69,29 @@ trait Reporting { this: Context =>
   def featureWarning(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =
     reporter.report(new FeatureWarning(msg, pos))
 
+  def featureWarning(feature: String, featureDescription: String, isScala2Feature: Boolean,
+      featureUseSite: Symbol, required: Boolean, pos: SourcePosition): Unit = {
+    val req = if (required) "needs to" else "should"
+    val prefix = if (isScala2Feature) "scala." else "dotty."
+    val fqname = prefix + "language." + feature
+
+    val explain = {
+      if (reporter.isReportedFeatureUseSite(featureUseSite)) ""
+      else {
+        reporter.reportNewFeatureUseSite(featureUseSite)
+        s"""|
+            |This can be achieved by adding the import clause 'import $fqname'
+            |or by setting the compiler option -language:$feature.
+            |See the Scala docs for value $fqname for a discussion
+            |why the feature $req be explicitly enabled.""".stripMargin
+      }
+    }
+
+    val msg = s"$featureDescription $req be enabled\nby making the implicit value $fqname visible.$explain"
+    if (required) error(msg, pos)
+    else reporter.report(new FeatureWarning(msg, pos))
+  }
+
   def warning(msg: => String, pos: SourcePosition = NoSourcePosition): Unit =
     reporter.report(new Warning(msg, pos))
 
@@ -172,7 +196,7 @@ abstract class Reporter extends interfaces.ReporterResult {
   /** Report a diagnostic */
   def doReport(d: Diagnostic)(implicit ctx: Context): Unit
 
- /** Whether very long lines can be truncated.  This exists so important
+  /** Whether very long lines can be truncated.  This exists so important
    *  debugging information (like printing the classpath) is not rendered
    *  invisible due to the max message length.
    */
@@ -206,6 +230,10 @@ abstract class Reporter extends interfaces.ReporterResult {
    */
   def errorsReported = hasErrors
 
+  private[this] var reportedFeaturesUseSites = Set[Symbol]()
+  def isReportedFeatureUseSite(featureTrait: Symbol): Boolean = reportedFeaturesUseSites.contains(featureTrait)
+  def reportNewFeatureUseSite(featureTrait: Symbol): Unit = reportedFeaturesUseSites += featureTrait
+
   val unreportedWarnings = new mutable.HashMap[String, Int] {
     override def default(key: String) = 0
   }
diff --git a/src/dotty/tools/dotc/typer/Typer.scala b/src/dotty/tools/dotc/typer/Typer.scala
index 019c460e8..34400ede7 100644
--- a/src/dotty/tools/dotc/typer/Typer.scala
+++ b/src/dotty/tools/dotc/typer/Typer.scala
@@ -1092,7 +1092,13 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
       .withType(dummy.nonMemberTermRef)
     checkVariance(impl1)
     if (!cls.is(AbstractOrTrait) && !ctx.isAfterTyper) checkRealizableBounds(cls.typeRef, cdef.pos)
-    assignType(cpy.TypeDef(cdef)(name, impl1, Nil), cls)
+    val cdef1 = assignType(cpy.TypeDef(cdef)(name, impl1, Nil), cls)
+    if (ctx.phase.isTyper && cdef1.tpe.derivesFrom(defn.DynamicClass) && !ctx.dynamicsEnabled) {
+      val isRequired = parents1.exists(_.tpe.isRef(defn.DynamicClass))
+      ctx.featureWarning(nme.dynamics.toString, "extension of type scala.Dynamic", isScala2Feature = true,
+          cls, isRequired, cdef.pos)
+    }
+    cdef1
 
     // todo later: check that
     //  1. If class is non-abstract, it is instantiatable: