Merge pull request scala#1067 from scalamacros/topic/ultimate-reflection-pull-request

Ultimate reflection pull request #2

Author: Adriaan Moors

src/compiler/scala/tools/reflect/ToolBoxFactory.scala

@@ -256,7 +256,8 @@ abstract class ToolBoxFactory[U <: JavaUniverse](val u: U) { factorySelf =>
         // }
         val (singleton, jmeth) = compileExpr(expr)
         val result = jmeth.invoke(singleton, thunks map (_.asInstanceOf[AnyRef]): _*)
-        result
+        if (jmeth.getReturnType == java.lang.Void.TYPE) ()
+        else result
       }
 
       def parseExpr(code: String): Tree = {

src/reflect/scala/reflect/api/Mirrors.scala

@@ -33,6 +33,14 @@ trait Mirrors { self: Universe =>
     /** Reflects against a field symbol and returns a mirror
      *  that can be used to get and, if appropriate, set the value of the field.
      *
+     *  FieldMirrors are the only way to get at private[this] vals and vars and
+     *  might be useful to inspect the data of underlying Java fields.
+     *  For all other uses, it's better to go through the fields accessor.
+     *
+     *  In particular, there should be no need to ever access a field mirror
+     *  when reflecting on just the public members of a class or trait.
+     *  Note also that only accessor MethodMirrors, but not FieldMirrors will accurately reflect overriding behavior.
+     *
      *  To get a field symbol by the name of the field you would like to reflect,
      *  use `<this mirror>.symbol.typeSignature.member(newTermName(<name of the field>)).asTerm.accessed`.
      *  For further information about member lookup refer to `Symbol.typeSignature`.
@@ -91,7 +99,7 @@ trait Mirrors { self: Universe =>
   trait FieldMirror {
 
     /** The object containing the field */
-    def receiver: AnyRef
+    def receiver: Any
 
     /** The field symbol representing the field.
      *
@@ -107,6 +115,10 @@ trait Mirrors { self: Universe =>
      *  Scala reflection uses reflection capabilities of the underlying platform,
      *  so `FieldMirror.get` might throw platform-specific exceptions associated
      *  with getting a field or invoking a getter method of the field.
+     *
+     *  If `symbol` represents a field of a base class with respect to the class of the receiver,
+     *  and this base field is overriden in the class of the receiver, then this method will retrieve
+     *  the value of the base field. To achieve overriding behavior, use reflectMethod on an accessor.
      */
     def get: Any
 
@@ -117,6 +129,10 @@ trait Mirrors { self: Universe =>
      *  Scala reflection uses reflection capabilities of the underlying platform,
      *  so `FieldMirror.get` might throw platform-specific exceptions associated
      *  with setting a field or invoking a setter method of the field.
+     *
+     *  If `symbol` represents a field of a base class with respect to the class of the receiver,
+     *  and this base field is overriden in the class of the receiver, then this method will set
+     *  the value of the base field. To achieve overriding behavior, use reflectMethod on an accessor.
      */
     def set(value: Any): Unit
   }
@@ -125,7 +141,7 @@ trait Mirrors { self: Universe =>
   trait MethodMirror {
 
     /** The receiver object of the method */
-    def receiver: AnyRef
+    def receiver: Any
 
     /** The method symbol representing the method */
     def symbol: MethodSymbol
@@ -226,7 +242,9 @@ trait Mirrors { self: Universe =>
      *  Such a mirror can be used to further reflect against the members of the object
      *  to get/set fields, invoke methods and inspect inner classes and objects.
      */
-    def reflect(obj: Any): InstanceMirror
+    // we need a ClassTag here to preserve boxity of primitives
+    // the class tag lets us tell apart `mirror.reflect(2)` and `mirror.reflect(new Integer(2))`
+    def reflect[T: ClassTag](obj: T): InstanceMirror
 
     /** Reflects against a static class symbol and returns a mirror
      *  that can be used to create instances of the class, inspect its companion object or perform further reflections.

src/reflect/scala/reflect/internal/StdNames.scala

@@ -937,6 +937,12 @@ trait StdNames {
       case _          => NO_NAME
     }
 
+    def primitiveMethodName(name: Name): TermName =
+      primitiveInfixMethodName(name) match {
+        case NO_NAME => primitivePostfixMethodName(name)
+        case name => name
+      }
+
     /** Translate a String into a list of simple TypeNames and TermNames.
      *  In all segments before the last, type/term is determined by whether
      *  the following separator char is '.' or '#'.  In the last segment,

src/reflect/scala/reflect/runtime/JavaMirrors.scala

@@ -20,6 +20,8 @@ import internal.Flags._
 //import scala.tools.nsc.util.ScalaClassLoader._
 import ReflectionUtils.{singletonInstance}
 import language.existentials
+import scala.runtime.{ScalaRunTime, BoxesRunTime}
+import scala.reflect.internal.util.Collections._
 
 trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: SymbolTable =>
 
@@ -124,15 +126,16 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
     private def ErrorStaticClass(wannabe: Symbol) = throw new ScalaReflectionException(s"$wannabe is a static class, use reflectClass on a RuntimeMirror to obtain its ClassMirror")
     private def ErrorStaticModule(wannabe: Symbol) = throw new ScalaReflectionException(s"$wannabe is a static module, use reflectModule on a RuntimeMirror to obtain its ModuleMirror")
     private def ErrorNotMember(wannabe: Symbol, owner: Symbol) = throw new ScalaReflectionException(s"expected a member of $owner, you provided ${wannabe.kind} ${wannabe.fullName}")
-    private def ErrorNotField(wannabe: Symbol) = throw new ScalaReflectionException(s"expected a field or an accessor method symbol, you provided $wannabe}")
+    private def ErrorNotField(wannabe: Symbol) = throw new ScalaReflectionException(s"expected a field or an accessor method symbol, you provided $wannabe")
     private def ErrorNonExistentField(wannabe: Symbol) = throw new ScalaReflectionException(s"""
       |Scala field ${wannabe.name} isn't represented as a Java field, neither it has a Java accessor method
       |note that private parameters of class constructors don't get mapped onto fields and/or accessors,
       |unless they are used outside of their declaring constructors.
     """.trim.stripMargin)
     private def ErrorSetImmutableField(wannabe: Symbol) = throw new ScalaReflectionException(s"cannot set an immutable field ${wannabe.name}")
+    private def ErrorNotConstructor(wannabe: Symbol, owner: Symbol) = throw new ScalaReflectionException(s"expected a constructor of $owner, you provided $wannabe")
 
-    def reflect(obj: Any): InstanceMirror = new JavaInstanceMirror(obj.asInstanceOf[AnyRef])
+    def reflect[T: ClassTag](obj: T): InstanceMirror = new JavaInstanceMirror(obj)
 
     def reflectClass(cls: ClassSymbol): ClassMirror = {
       if (!cls.isStatic) ErrorInnerClass(cls)
@@ -152,13 +155,25 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
 
     def moduleSymbol(rtcls: RuntimeClass): ModuleSymbol = classToScala(rtcls).companionModule.asModule
 
-    private def checkMemberOf(wannabe: Symbol, owner: Symbol) =
-      if (!owner.info.member(wannabe.name).alternatives.contains(wannabe)) ErrorNotMember(wannabe, owner)
+    private def checkMemberOf(wannabe: Symbol, owner: ClassSymbol) {
+      if (wannabe.owner == AnyClass || wannabe.owner == AnyRefClass || wannabe.owner == ObjectClass) {
+        // do nothing
+      } else if (wannabe.owner == AnyValClass) {
+        if (!owner.isPrimitiveValueClass && !owner.isDerivedValueClass) ErrorNotMember(wannabe, owner)
+      } else {
+        if (!(owner.info.baseClasses contains wannabe.owner)) ErrorNotMember(wannabe, owner)
+      }
+    }
+
+    private def preciseClass[T: ClassTag](instance: T) = {
+      val staticClazz = classTag[T].runtimeClass
+      val dynamicClazz = instance.getClass
+      if (staticClazz.isPrimitive) staticClazz else dynamicClazz
+    }
 
-    private class JavaInstanceMirror(obj: AnyRef)
+    private class JavaInstanceMirror[T: ClassTag](val instance: T)
             extends InstanceMirror {
-      def instance = obj
-      def symbol = wholemirror.classSymbol(obj.getClass)
+      def symbol = wholemirror.classSymbol(preciseClass(instance))
       def reflectField(field: TermSymbol): FieldMirror = {
         checkMemberOf(field, symbol)
         if ((field.isMethod && !field.isAccessor) || field.isModule) ErrorNotField(field)
@@ -171,26 +186,26 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
         catch {
           case _: NoSuchFieldException => ErrorNonExistentField(field1)
         }
-        new JavaFieldMirror(obj, field1)
+        new JavaFieldMirror(instance, field1)
       }
       def reflectMethod(method: MethodSymbol): MethodMirror = {
         checkMemberOf(method, symbol)
-        new JavaMethodMirror(obj, method)
+        mkJavaMethodMirror(instance, method)
       }
       def reflectClass(cls: ClassSymbol): ClassMirror = {
         if (cls.isStatic) ErrorStaticClass(cls)
         checkMemberOf(cls, symbol)
-        new JavaClassMirror(instance, cls)
+        new JavaClassMirror(instance.asInstanceOf[AnyRef], cls)
       }
       def reflectModule(mod: ModuleSymbol): ModuleMirror = {
         if (mod.isStatic) ErrorStaticModule(mod)
         checkMemberOf(mod, symbol)
-        new JavaModuleMirror(instance, mod)
+        new JavaModuleMirror(instance.asInstanceOf[AnyRef], mod)
       }
-      override def toString = s"instance mirror for $obj"
+      override def toString = s"instance mirror for $instance"
     }
 
-    private class JavaFieldMirror(val receiver: AnyRef, val symbol: TermSymbol)
+    private class JavaFieldMirror(val receiver: Any, val symbol: TermSymbol)
             extends FieldMirror {
       lazy val jfield = {
         val jfield = fieldToJava(symbol)
@@ -230,26 +245,115 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
       sig
     }
 
-    private class JavaMethodMirror(val receiver: AnyRef, val symbol: MethodSymbol)
+    // the "symbol == Any_getClass || symbol == Object_getClass" test doesn't cut it
+    // because both AnyVal and its primitive descendants define their own getClass methods
+    private def isGetClass(meth: MethodSymbol) = meth.name.toString == "getClass" && meth.params.flatten.isEmpty
+    private def isMagicPrimitiveMethod(meth: MethodSymbol) = meth.owner.isPrimitiveValueClass
+    private def isStringConcat(meth: MethodSymbol) = meth == String_+ || (isMagicPrimitiveMethod(meth) && meth.returnType =:= StringClass.toType)
+    lazy val magicMethodOwners = Set[Symbol](AnyClass, AnyValClass, AnyRefClass, ObjectClass, ArrayClass) ++ ScalaPrimitiveValueClasses
+    lazy val nonMagicObjectMethods = Set[Symbol](Object_clone, Object_equals, Object_finalize, Object_hashCode, Object_toString,
+                                     Object_notify, Object_notifyAll) ++ ObjectClass.info.member(nme.wait_).asTerm.alternatives.map(_.asMethod)
+    private def isMagicMethod(meth: MethodSymbol): Boolean = {
+      if (isGetClass(meth) || isStringConcat(meth) || isMagicPrimitiveMethod(meth) || meth == Predef_classOf || meth.isTermMacro) return true
+      magicMethodOwners(meth.owner) && !nonMagicObjectMethods(meth)
+    }
+
+    // unlike other mirrors, method mirrors are created by a factory
+    // that's because we want to have decent performance
+    // therefore we move special cases into separate subclasses
+    // rather than have them on a hot path them in a unified implementation of the `apply` method
+    private def mkJavaMethodMirror[T: ClassTag](receiver: T, symbol: MethodSymbol): JavaMethodMirror = {
+      if (isMagicMethod(symbol)) new JavaMagicMethodMirror(receiver, symbol)
+      else if (symbol.params.flatten exists (p => isByNameParamType(p.info))) new JavaByNameMethodMirror(receiver, symbol)
+      else new JavaVanillaMethodMirror(receiver, symbol)
+    }
+
+    private abstract class JavaMethodMirror(val symbol: MethodSymbol)
             extends MethodMirror {
       lazy val jmeth = {
         val jmeth = methodToJava(symbol)
         if (!jmeth.isAccessible) jmeth.setAccessible(true)
         jmeth
       }
-      def apply(args: Any*): Any =
-        if (symbol.owner == ArrayClass)
-          symbol.name match {
-            case nme.length => jArray.getLength(receiver)
-            case nme.apply => jArray.get(receiver, args(0).asInstanceOf[Int])
-            case nme.update => jArray.set(receiver, args(0).asInstanceOf[Int], args(1))
-            case _ => assert(false, s"unexpected array method: $symbol")
-          }
-        else
-          jmeth.invoke(receiver, args.asInstanceOf[Seq[AnyRef]]: _*)
+
+      def jinvoke(jmeth: jMethod, receiver: Any, args: Seq[Any]): Any = {
+        val result = jmeth.invoke(receiver, args.asInstanceOf[Seq[AnyRef]]: _*)
+        if (jmeth.getReturnType == java.lang.Void.TYPE) ()
+        else result
+      }
+
       override def toString = s"method mirror for ${showMethodSig(symbol)} (bound to $receiver)"
     }
 
+    private class JavaVanillaMethodMirror(val receiver: Any, symbol: MethodSymbol)
+            extends JavaMethodMirror(symbol) {
+      def apply(args: Any*): Any = jinvoke(jmeth, receiver, args)
+    }
+
+    private class JavaByNameMethodMirror(val receiver: Any, symbol: MethodSymbol)
+            extends JavaMethodMirror(symbol) {
+      def apply(args: Any*): Any = {
+        val transformed = map2(args.toList, symbol.params.flatten)((arg, param) => if (isByNameParamType(param.info)) () => arg else arg)
+        jinvoke(jmeth, receiver, transformed)
+      }
+    }
+
+    private class JavaMagicMethodMirror[T: ClassTag](val receiver: T, symbol: MethodSymbol)
+            extends JavaMethodMirror(symbol) {
+       def apply(args: Any*): Any = {
+        // checking type conformance is too much of a hassle, so we don't do it here
+        // actually it's not even necessary, because we manually dispatch arguments to magic methods below
+        val params = symbol.paramss.flatten
+        val perfectMatch = args.length == params.length
+        // todo. this doesn't account for multiple vararg parameter lists
+        // however those aren't supported by the mirror API: https://issues.scala-lang.org/browse/SI-6182
+        // hence I leave this code as is, to be fixed when the corresponding bug is fixed
+        val varargMatch = args.length >= params.length - 1 && isVarArgsList(params)
+        if (!perfectMatch && !varargMatch) {
+          val n_arguments = if (isVarArgsList(params)) s"${params.length - 1} or more" else s"${params.length}"
+          var s_arguments = if (params.length == 1 && !isVarArgsList(params)) "argument" else "arguments"
+          throw new ScalaReflectionException(s"${showMethodSig(symbol)} takes $n_arguments $s_arguments")
+        }
+
+        def objReceiver       = receiver.asInstanceOf[AnyRef]
+        def objArg0           = args(0).asInstanceOf[AnyRef]
+        def objArgs           = args.asInstanceOf[Seq[AnyRef]]
+        def fail(msg: String) = throw new ScalaReflectionException(msg + ", it cannot be invoked with mirrors")
+
+        def invokeMagicPrimitiveMethod = {
+          val jmeths = classOf[BoxesRunTime].getDeclaredMethods.filter(_.getName == nme.primitiveMethodName(symbol.name).toString)
+          assert(jmeths.length == 1, jmeths.toList)
+          jinvoke(jmeths.head, null, objReceiver +: objArgs)
+        }
+
+        symbol match {
+          case Any_== | Object_==                 => ScalaRunTime.inlinedEquals(objReceiver, objArg0)
+          case Any_!= | Object_!=                 => !ScalaRunTime.inlinedEquals(objReceiver, objArg0)
+          case Any_## | Object_##                 => ScalaRunTime.hash(objReceiver)
+          case Any_equals                         => receiver.equals(objArg0)
+          case Any_hashCode                       => receiver.hashCode
+          case Any_toString                       => receiver.toString
+          case Object_eq                          => objReceiver eq objArg0
+          case Object_ne                          => objReceiver ne objArg0
+          case Object_synchronized                => objReceiver.synchronized(objArg0)
+          case sym if isGetClass(sym)             => preciseClass(receiver)
+          case Any_asInstanceOf                   => fail("Any.asInstanceOf requires a type argument")
+          case Any_isInstanceOf                   => fail("Any.isInstanceOf requires a type argument")
+          case Object_asInstanceOf                => fail("AnyRef.$asInstanceOf is an internal method")
+          case Object_isInstanceOf                => fail("AnyRef.$isInstanceOf is an internal method")
+          case Array_length                       => ScalaRunTime.array_length(objReceiver)
+          case Array_apply                        => ScalaRunTime.array_apply(objReceiver, args(0).asInstanceOf[Int])
+          case Array_update                       => ScalaRunTime.array_update(objReceiver, args(0).asInstanceOf[Int], args(1))
+          case Array_clone                        => ScalaRunTime.array_clone(objReceiver)
+          case sym if isStringConcat(sym)         => receiver.toString + objArg0
+          case sym if isMagicPrimitiveMethod(sym) => invokeMagicPrimitiveMethod
+          case sym if sym == Predef_classOf       => fail("Predef.classOf is a compile-time function")
+          case sym if sym.isTermMacro             => fail(s"${symbol.fullName} is a macro, i.e. a compile-time function")
+          case _                                  => assert(false, this)
+        }
+      }
+    }
+
     private class JavaConstructorMirror(val outer: AnyRef, val symbol: MethodSymbol)
             extends MethodMirror {
       override val receiver = outer
@@ -259,6 +363,9 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
         jconstr
       }
       def apply(args: Any*): Any = {
+        if (symbol.owner == ArrayClass)
+          throw new ScalaReflectionException("Cannot instantiate arrays with mirrors. Consider using `scala.reflect.ClassTag(<class of element>).newArray(<length>)` instead")
+
         val effectiveArgs =
           if (outer == null) args.asInstanceOf[Seq[AnyRef]]
           else outer +: args.asInstanceOf[Seq[AnyRef]]
@@ -279,7 +386,11 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
             extends JavaTemplateMirror with ClassMirror {
       def erasure = symbol
       def isStatic = false
-      def reflectConstructor(constructor: MethodSymbol) = new JavaConstructorMirror(outer, constructor)
+      def reflectConstructor(constructor: MethodSymbol) = {
+        if (!constructor.isClassConstructor) ErrorNotConstructor(constructor, symbol)
+        if (!symbol.info.decls.toList.contains(constructor)) ErrorNotConstructor(constructor, symbol)
+        new JavaConstructorMirror(outer, constructor)
+      }
       def companion: Option[ModuleMirror] = symbol.companionModule match {
        case module: ModuleSymbol => Some(new JavaModuleMirror(outer, module))
        case _ => None
@@ -1067,7 +1178,7 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
     mirrors(rootToLoader getOrElseUpdate(root, findLoader)).get.get
   }
 
-  private lazy val magicSymbols: Map[(String, Name), Symbol] = {
+  private lazy val magicClasses: Map[(String, Name), Symbol] = {
     def mapEntry(sym: Symbol): ((String, Name), Symbol) = (sym.owner.fullName, sym.name) -> sym
     Map() ++ (definitions.magicSymbols filter (_.isType) map mapEntry)
   }
@@ -1088,7 +1199,7 @@ trait JavaMirrors extends internal.SymbolTable with api.JavaUniverse { self: Sym
       if (name.isTermName && !owner.isEmptyPackageClass)
         return mirror.makeScalaPackage(
           if (owner.isRootSymbol) name.toString else owner.fullName+"."+name)
-      magicSymbols get (owner.fullName, name) match {
+      magicClasses get (owner.fullName, name) match {
         case Some(tsym) =>
           owner.info.decls enter tsym
           return tsym