Enums valuesOf exception type conforms to that of Java enums

Author: anatoliykmetyuk

compiler/src/dotty/tools/dotc/ast/DesugarEnums.scala

@@ -86,7 +86,12 @@ object DesugarEnums {
   /**  The following lists of definitions for an enum type E:
    *
    *   private val $values = new EnumValues[E]
-   *   def valueOf = $values.fromName
+   *   def valueOf(name: String) =
+   *     try $values.fromName(name) catch
+   *       {
+   *         case ex$:NoSuchElementException =>
+   *           throw new IllegalArgumentException("key not found: ".concat(name))
+   *       }
    *   def values = $values.values.toArray
    */
   private def enumScaffolding(implicit ctx: Context): List[Tree] = {
@@ -95,9 +100,22 @@ object DesugarEnums {
     val privateValuesDef =
       ValDef(nme.DOLLAR_VALUES, TypeTree(),
         New(TypeTree(defn.EnumValuesType.appliedTo(enumClass.typeRef :: Nil)), ListOfNil))
-        .withFlags(Private)    
+        .withFlags(Private)
+
+    val valuesOfExnMessage = Apply(
+      Select(Literal(Constant("key not found: ")), "concat".toTermName)
+    , Ident(nme.name) :: Nil)
+    val valuesOfBody = Try(
+      expr = Apply(valuesDot("fromName"), Ident(nme.name) :: Nil)
+    , cases = CaseDef(
+        pat = Typed(Ident(nme.DEFAULT_EXCEPTION_NAME), TypeTree(defn.NoSuchElementExceptionType))
+      , guard = EmptyTree
+      , body = Throw(New(TypeTree(defn.IllegalArgumentExceptionType), List(valuesOfExnMessage :: Nil)))
+      ) :: Nil
+    , finalizer = EmptyTree
+    )
     val valueOfDef = DefDef(nme.valueOf, Nil, List(param(nme.name, defn.StringType) :: Nil),
-      TypeTree(), Apply(valuesDot("fromName"), Ident(nme.name) :: Nil))
+      TypeTree(), valuesOfBody)
 
     valuesDef ::
     privateValuesDef ::

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

@@ -605,6 +605,11 @@ class Definitions {
   lazy val SystemClass: ClassSymbol               = ctx.requiredClass("java.lang.System")
   lazy val SystemModule: Symbol              = SystemClass.linkedClass
 
+  lazy val NoSuchElementExceptionClass = ctx.requiredClass("java.util.NoSuchElementException")
+  def NoSuchElementExceptionType = NoSuchElementExceptionClass.typeRef
+  lazy val IllegalArgumentExceptionClass = ctx.requiredClass("java.lang.IllegalArgumentException")
+  def IllegalArgumentExceptionType = IllegalArgumentExceptionClass.typeRef
+
   // in scalac modified to have Any as parent
 
   lazy val ThrowableType: TypeRef          = ctx.requiredClassRef("java.lang.Throwable")