Rename transparent methods -> rewrite methods

Also implements rewrite matches and rewrite ifs. Keeps transparent as a separate
modifier with meaning: "inline if called from a rewrite context".

Author: odersky

bench/tests/power-macro/PowerMacro.scala

@@ -2,7 +2,7 @@ import scala.quoted.Expr
 
 object PowerMacro {
 
-  transparent def power(transparent n: Long, x: Double) = ~powerCode(n, '(x))
+  rewrite def power(transparent n: Long, x: Double) = ~powerCode(n, '(x))
 
   def powerCode(n: Long, x: Expr[Double]): Expr[Double] =
     if (n == 0) '(1.0)

compiler/src/dotty/tools/dotc/CompilationUnit.scala

@@ -5,7 +5,7 @@ import core.Types.Type // Do not remove me #3383
 import util.SourceFile
 import ast.{tpd, untpd}
 import tpd.{ Tree, TreeTraverser }
-import typer.PrepareTransparent.InlineAccessors
+import typer.PrepareInlineable.InlineAccessors
 import dotty.tools.dotc.core.Contexts.Context
 import dotty.tools.dotc.core.SymDenotations.ClassDenotation
 import dotty.tools.dotc.core.Symbols._

compiler/src/dotty/tools/dotc/Run.scala

@@ -16,7 +16,7 @@ import scala.io.Codec
 import util.{Set => _, _}
 import reporting.Reporter
 import transform.TreeChecker
-import rewrite.Rewrites
+import rewrites.Rewrites
 import java.io.{BufferedWriter, OutputStreamWriter}
 
 import profile.Profiler

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

@@ -437,7 +437,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
   def refPurity(tree: Tree)(implicit ctx: Context): PurityLevel = {
     val sym = tree.symbol
     if (!tree.hasType) Impure
-    else if (!tree.tpe.widen.isParameterless || sym.is(Erased)) SimplyPure
+    else if (!tree.tpe.widen.isParameterless || sym.isEffectivelyErased) SimplyPure
     else if (!sym.isStable) Impure
     else if (sym.is(Module))
       if (sym.moduleClass.isNoInitsClass) Pure else Idempotent

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

@@ -497,6 +497,10 @@ object Trees {
     extends TermTree[T] {
     type ThisTree[-T >: Untyped] = If[T]
   }
+  class RewriteIf[T >: Untyped] private[ast] (cond: Tree[T], thenp: Tree[T], elsep: Tree[T])
+    extends If(cond, thenp, elsep) {
+    override def toString = s"RewriteIf($cond, $thenp, $elsep)"
+  }
 
   /** A closure with an environment and a reference to a method.
    *  @param env    The captured parameters of the closure
@@ -517,6 +521,10 @@ object Trees {
     extends TermTree[T] {
     type ThisTree[-T >: Untyped] = Match[T]
   }
+  class RewriteMatch[T >: Untyped] private[ast] (selector: Tree[T], cases: List[CaseDef[T]])
+    extends Match(selector, cases) {
+    override def toString = s"RewriteMatch($selector, $cases)"
+  }
 
   /** case pat if guard => body; only appears as child of a Match */
   case class CaseDef[-T >: Untyped] private[ast] (pat: Tree[T], guard: Tree[T], body: Tree[T])
@@ -883,8 +891,10 @@ object Trees {
     type Assign = Trees.Assign[T]
     type Block = Trees.Block[T]
     type If = Trees.If[T]
+    type RewriteIf = Trees.RewriteIf[T]
     type Closure = Trees.Closure[T]
     type Match = Trees.Match[T]
+    type RewriteMatch = Trees.RewriteMatch[T]
     type CaseDef = Trees.CaseDef[T]
     type Return = Trees.Return[T]
     type Try = Trees.Try[T]
@@ -1013,6 +1023,9 @@ object Trees {
         case _ => finalize(tree, untpd.Block(stats, expr))
       }
       def If(tree: Tree)(cond: Tree, thenp: Tree, elsep: Tree)(implicit ctx: Context): If = tree match {
+        case tree: RewriteIf =>
+          if ((cond eq tree.cond) && (thenp eq tree.thenp) && (elsep eq tree.elsep)) tree
+          else finalize(tree, untpd.RewriteIf(cond, thenp, elsep))
         case tree: If if (cond eq tree.cond) && (thenp eq tree.thenp) && (elsep eq tree.elsep) => tree
         case _ => finalize(tree, untpd.If(cond, thenp, elsep))
       }
@@ -1021,6 +1034,9 @@ object Trees {
         case _ => finalize(tree, untpd.Closure(env, meth, tpt))
       }
       def Match(tree: Tree)(selector: Tree, cases: List[CaseDef])(implicit ctx: Context): Match = tree match {
+        case tree: RewriteMatch =>
+          if ((selector eq tree.selector) && (cases eq tree.cases)) tree
+          else finalize(tree, untpd.RewriteMatch(selector, cases))
         case tree: Match if (selector eq tree.selector) && (cases eq tree.cases) => tree
         case _ => finalize(tree, untpd.Match(selector, cases))
       }

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

@@ -132,6 +132,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
 
     case class Lazy() extends Mod(Flags.Lazy)
 
+    case class Rewrite() extends Mod(Flags.Rewrite)
+
     case class Transparent() extends Mod(Flags.Transparent)
 
     case class Enum() extends Mod(Flags.Enum)
@@ -273,8 +275,10 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def Assign(lhs: Tree, rhs: Tree): Assign = new Assign(lhs, rhs)
   def Block(stats: List[Tree], expr: Tree): Block = new Block(stats, expr)
   def If(cond: Tree, thenp: Tree, elsep: Tree): If = new If(cond, thenp, elsep)
+  def RewriteIf(cond: Tree, thenp: Tree, elsep: Tree): If = new RewriteIf(cond, thenp, elsep)
   def Closure(env: List[Tree], meth: Tree, tpt: Tree): Closure = new Closure(env, meth, tpt)
   def Match(selector: Tree, cases: List[CaseDef]): Match = new Match(selector, cases)
+  def RewriteMatch(selector: Tree, cases: List[CaseDef]): Match = new RewriteMatch(selector, cases)
   def CaseDef(pat: Tree, guard: Tree, body: Tree): CaseDef = new CaseDef(pat, guard, body)
   def Return(expr: Tree, from: Tree): Return = new Return(expr, from)
   def Try(expr: Tree, cases: List[CaseDef], finalizer: Tree): Try = new Try(expr, cases, finalizer)
@@ -310,7 +314,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
    *  where `Ts` are the class type arguments of `T` or its class type alias.
    *  Note: we also keep any type arguments as parts of `T`. This is necessary to allow
    *  navigation into these arguments from the IDE, and to do the right thing in
-   *  PrepareTransparent.
+   *  PrepareInlineable.
    */
   def New(tpt: Tree, argss: List[List[Tree]])(implicit ctx: Context): Tree = {
     val (tycon, targs) = tpt match {

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

@@ -5,7 +5,7 @@ import java.io.File
 import dotty.tools.io.{ Directory, PlainDirectory }
 
 import PathResolver.Defaults
-import rewrite.Rewrites
+import rewrites.Rewrites
 
 class ScalaSettings extends Settings.SettingGroup {
 
@@ -43,7 +43,7 @@ class ScalaSettings extends Settings.SettingGroup {
   val pageWidth = IntSetting("-pagewidth", "Set page width", 80)
   val strict = BooleanSetting("-strict", "Use strict type rules, which means some formerly legal code does not typecheck anymore.")
   val language = MultiStringSetting("-language", "feature", "Enable one or more language features.")
-  val rewrite = OptionSetting[Rewrites]("-rewrite", "When used in conjunction with -language:Scala2 rewrites sources to migrate to new syntax")
+  val `rewrite` = OptionSetting[Rewrites]("-rewrite", "When used in conjunction with -language:Scala2 rewrites sources to migrate to new syntax")
   val silentWarnings = BooleanSetting("-nowarn", "Silence all warnings.")
   val fromTasty = BooleanSetting("-from-tasty", "Compile classes from tasty in classpath. The arguments are used as class names.")
 

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

@@ -57,7 +57,7 @@ object Annotations {
   }
 
   /** An annotation indicating the body of a right-hand side,
-   *  typically of a transparent method. Treated specially in
+   *  typically of a rewrite or transparent method. Treated specially in
    *  pickling/unpickling and TypeTreeMaps
    */
   abstract class BodyAnnotation extends Annotation {

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

@@ -307,6 +307,10 @@ object Contexts {
     def isNonEmptyScopeContext: Boolean =
       (this.scope ne outer.scope) && !this.scope.isEmpty
 
+    /** Is this a context for typechecking an inlined body? */
+    def isInlineContext: Boolean =
+      typer.isInstanceOf[Inliner#InlineTyper]
+
     /** The next outer context whose tree is a template or package definition
      *  Note: Currently unused
     def enclTemplate: Context = {

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

@@ -283,6 +283,9 @@ object Flags {
    */
   final val Synthetic = commonFlag(18, "<synthetic>")
 
+  /** Labelled with `rewrite` modifier */
+  final val Rewrite = commonFlag(19, "rewrite")
+
   /** A covariant type variable / an outer accessor */
   final val CovariantOrOuter = commonFlag(20, "")
   final val Covariant = typeFlag(20, "<covariant>")
@@ -433,7 +436,7 @@ object Flags {
 
   /** Flags representing source modifiers */
   final val SourceModifierFlags =
-    commonFlags(Private, Protected, Abstract, Final, Transparent,
+    commonFlags(Private, Protected, Abstract, Final, Rewrite | Transparent,
      Sealed, Case, Implicit, Override, AbsOverride, Lazy, JavaStatic, Erased)
 
   /** Flags representing modifiers that can appear in trees */
@@ -454,7 +457,7 @@ object Flags {
     Scala2ExistentialCommon | Mutable.toCommonFlags | Touched | JavaStatic |
     CovariantOrOuter | ContravariantOrLabel | CaseAccessor.toCommonFlags |
     NonMember | ImplicitCommon | Permanent | Synthetic |
-    SuperAccessorOrScala2x | Transparent
+    SuperAccessorOrScala2x | Rewrite | Transparent
 
   /** Flags that are not (re)set when completing the denotation, or, if symbol is
    *  a top-level class or object, when completing the denotation once the class
@@ -548,8 +551,8 @@ object Flags {
   /** Assumed to be pure */
   final val StableOrErased = Stable | Erased
 
-  /** Labeled `private`, `final`, or `transparent` */
-  final val EffectivelyFinal = Private | Final | Transparent
+  /** Labeled `private`, `final`, `rewrite` or `transparent` */
+  final val EffectivelyFinal = Private | Final | Rewrite | Transparent
 
   /** A private method */
   final val PrivateMethod = allOf(Private, Method)
@@ -560,8 +563,11 @@ object Flags {
   /** A transparent method */
   final val TransparentMethod = allOf(Transparent, Method)
 
-  /** A transparent implicit method */
-  final val TransparentImplicitMethod = allOf(Transparent, Implicit, Method)
+  /** A rewrite method */
+  final val RewriteMethod = allOf(Rewrite, Method)
+
+  /** An implicit rewrite method */
+  final val ImplicitRewriteMethod = allOf(Rewrite, Implicit, Method)
 
   /** A transparent parameter */
   final val TransparentParam = allOf(Transparent, Param)

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

@@ -95,8 +95,8 @@ object Mode {
   /** We are in the IDE */
   val Interactive = newMode(20, "Interactive")
 
-  /** We are typing the body of a transparent method */
-  val TransparentBody = newMode(21, "TransparentBody")
+  /** We are typing the body of a transparent or rewrite method */
+  val InlineableBody = newMode(21, "InlineableBody")
 
   /** Read comments from definitions when unpickling from TASTY */
   val ReadComments = newMode(22, "ReadComments")

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

@@ -45,7 +45,7 @@ object NameKinds {
     }
 
     /** Does this kind define logically a new name (respectively qualified name)?
-     *  Tested by the `rewrite` and `collect` combinators of class `Name`.
+     *  Tested by the `replace` and `collect` combinators of class `Name`.
      */
     def definesNewName = false
     def definesQualifiedName = false
@@ -135,7 +135,7 @@ object NameKinds {
      *  Needed because the suffix of an expanded name may itself be expanded.
      *  For example, look at javap of scala.App.initCode
      */
-    def apply(qual: TermName, name: TermName): TermName = name rewrite {
+    def apply(qual: TermName, name: TermName): TermName = name replace {
       case name: SimpleName => apply(qual, name)
       case AnyQualifiedName(_, _) => apply(qual, name.toSimpleName)
     }
@@ -294,8 +294,8 @@ object NameKinds {
   val SuperArgName             = new UniqueNameKind("$superArg$")
   val DocArtifactName          = new UniqueNameKind("$doc")
   val UniqueInlineName         = new UniqueNameKind("$i")
-  val TransparentScrutineeName = new UniqueNameKind("$scrutinee")
-  val TransparentBinderName    = new UniqueNameKind("$elem")
+  val RewriteScrutineeName     = new UniqueNameKind("$scrutinee")
+  val RewriteBinderName        = new UniqueNameKind("$elem")
 
   /** A kind of unique extension methods; Unlike other unique names, these can be
    *  unmangled.

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

@@ -123,12 +123,12 @@ object NameOps {
 
     /** Revert the expanded name. */
     def unexpandedName: N = likeSpacedN {
-      name.rewrite { case ExpandedName(_, unexp) => unexp }
+      name.replace { case ExpandedName(_, unexp) => unexp }
     }
 
     /** Remove the variance from the name. */
     def invariantName: N = likeSpacedN {
-      name.rewrite { case VariantName(invariant, _) => invariant }
+      name.replace { case VariantName(invariant, _) => invariant }
     }
 
     def implClassName: N = likeSpacedN(name ++ tpnme.IMPL_CLASS_SUFFIX)
@@ -254,11 +254,11 @@ object NameOps {
     }
 
     def unmangle(kind: NameKind): N = likeSpacedN {
-      name rewrite {
+      name replace {
         case unmangled: SimpleName =>
           kind.unmangle(unmangled)
         case ExpandedName(prefix, last) =>
-          kind.unmangle(last) rewrite {
+          kind.unmangle(last) replace {
             case kernel: SimpleName =>
               ExpandedName(prefix, kernel)
           }

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

@@ -83,7 +83,7 @@ object Names {
      *  Stops at derived names whose kind has `definesNewName = true`.
      *  If `f` does not apply to any part, return name unchanged.
      */
-    def rewrite(f: PartialFunction[Name, Name]): ThisName
+    def replace(f: PartialFunction[Name, Name]): ThisName
 
     /** If partial function `f` is defined for some part of this name, apply it
      *  in a Some, otherwise None.
@@ -348,7 +348,7 @@ object Names {
     override def toSimpleName = this
     override final def mangle = encode
 
-    override def rewrite(f: PartialFunction[Name, Name]): ThisName =
+    override def replace(f: PartialFunction[Name, Name]): ThisName =
       if (f.isDefinedAt(this)) likeSpaced(f(this)) else this
     override def collect[T](f: PartialFunction[Name, T]): Option[T] = f.lift(this)
     override def mapLast(f: SimpleName => SimpleName) = f(this)
@@ -447,7 +447,7 @@ object Names {
     override def mangled = toTermName.mangled.toTypeName
     override def mangledString = toTermName.mangledString
 
-    override def rewrite(f: PartialFunction[Name, Name]): ThisName = toTermName.rewrite(f).toTypeName
+    override def replace(f: PartialFunction[Name, Name]): ThisName = toTermName.replace(f).toTypeName
     override def collect[T](f: PartialFunction[Name, T]): Option[T] = toTermName.collect(f)
     override def mapLast(f: SimpleName => SimpleName) = toTermName.mapLast(f).toTypeName
     override def mapParts(f: SimpleName => SimpleName) = toTermName.mapParts(f).toTypeName
@@ -480,11 +480,11 @@ object Names {
     override def toSimpleName = termName(toString)
     override final def mangle = encode.toSimpleName
 
-    override def rewrite(f: PartialFunction[Name, Name]): ThisName =
+    override def replace(f: PartialFunction[Name, Name]): ThisName =
       if (f.isDefinedAt(this)) likeSpaced(f(this))
       else info match {
         case qual: QualifiedInfo => this
-        case _ => underlying.rewrite(f).derived(info)
+        case _ => underlying.replace(f).derived(info)
       }
 
     override def collect[T](f: PartialFunction[Name, T]): Option[T] =

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

@@ -409,7 +409,7 @@ object SymDenotations {
           prefix = prefix.exclude(ModuleClassName)
         def qualify(n: SimpleName) =
           kind(prefix.toTermName, if (filler.isEmpty) n else termName(filler + n))
-        val fn = name rewrite {
+        val fn = name replace {
           case name: SimpleName => qualify(name)
           case name @ AnyQualifiedName(_, _) => qualify(name.mangled.toSimpleName)
         }
@@ -781,11 +781,24 @@ object SymDenotations {
     def isTransparentMethod(implicit ctx: Context): Boolean =
       is(TransparentMethod, butNot = AccessorOrSynthetic)
 
-    /** A transparent method that is not nested inside another transparent method.
-     *  Nested transparents are not inlineable yet, only their inlined copies are.
+    def isRewriteMethod(implicit ctx: Context): Boolean =
+      is(RewriteMethod, butNot = AccessorOrSynthetic)
+
+    /** A transparent or rewrite method */
+    def isInlineable(implicit ctx: Context): Boolean =
+      is(TransparentMethod) || is(RewriteMethod)
+
+    /** An erased value or a rewrite method, excluding @forceInline annotated methods.
+     *  The latter have to be kept around to get to parity with Scala.
+     *  This is necessary at least until we have full bootstrap. Right now
+     *  dotty-bootstrapped involves running the Dotty compiler compiled with Scala 2 with
+     *  a Dotty runtime library compiled with Dotty. If we erase @forceInline annotated
+     *  methods, this means that the support methods in dotty.runtime.LazyVals vanish.
+     *  But they are needed for running the lazy val implementations in the Scala-2 compiled compiler.
      */
-    def isTransparentInlineable(implicit ctx: Context): Boolean =
-      isTransparentMethod && !owner.ownersIterator.exists(_.is(TransparentMethod))
+    def isEffectivelyErased(implicit ctx: Context): Boolean =
+      is(Erased) ||
+      isRewriteMethod && unforcedAnnotation(defn.ForceInlineAnnot).isEmpty
 
     /** ()T and => T types should be treated as equivalent for this symbol.
      *  Note: For the moment, we treat Scala-2 compiled symbols as loose matching,

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

@@ -273,8 +273,8 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
     violations.toList
   }
 
-  /** Are we in a transparent method body? */
-  def inTransparentMethod = owner.ownersIterator.exists(_.isTransparentMethod)
+  /** Are we in a rewrite method body? */
+  def inRewriteMethod = owner.ownersIterator.exists(_.isRewriteMethod)
 
   /** Is `feature` enabled in class `owner`?
    *  This is the case if one of the following two alternatives holds:
@@ -320,10 +320,10 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
   def dynamicsEnabled =
     featureEnabled(defn.LanguageModuleClass, nme.dynamics)
 
-  def testScala2Mode(msg: => Message, pos: Position, rewrite: => Unit = ()) = {
+  def testScala2Mode(msg: => Message, pos: Position, replace: => Unit = ()) = {
     if (scala2Mode) {
       migrationWarning(msg, pos)
-      rewrite
+      replace
     }
     scala2Mode
   }