Merge pull request #4964 from dotty-staging/add-matchtype

Add match type

Author: odersky

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

@@ -306,6 +306,7 @@ trait UntypedTreeInfo extends TreeInfo[Untyped] { self: Trees.Instance[Untyped]
     case mdef: TypeDef =>
       def isBounds(rhs: Tree): Boolean = rhs match {
         case _: TypeBoundsTree => true
+        case _: MatchTypeTree => true // Typedefs with Match rhs classify as abstract
         case LambdaTypeTree(_, body) => isBounds(body)
         case _ => false
       }
@@ -392,20 +393,21 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
     case Ident(_) =>
       refPurity(tree)
     case Select(qual, _) =>
-      refPurity(tree).min(exprPurity(qual))
+      if (tree.symbol.is(Erased)) Pure
+      else refPurity(tree).min(exprPurity(qual))
     case New(_) =>
       SimplyPure
     case TypeApply(fn, _) =>
-      exprPurity(fn)
+      if (fn.symbol.is(Erased)) Pure else exprPurity(fn)
     case Apply(fn, args) =>
       def isKnownPureOp(sym: Symbol) =
         sym.owner.isPrimitiveValueClass || sym.owner == defn.StringClass
       if (tree.tpe.isInstanceOf[ConstantType] && isKnownPureOp(tree.symbol)
              // A constant expression with pure arguments is pure.
           || fn.symbol.isStable)
         minOf(exprPurity(fn), args.map(exprPurity)) `min` Pure
-      else
-        Impure
+      else if (fn.symbol.is(Erased)) Pure
+      else Impure
     case Typed(expr, _) =>
       exprPurity(expr)
     case Block(stats, expr) =>

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

@@ -661,6 +661,12 @@ object Trees {
     type ThisTree[-T >: Untyped] = LambdaTypeTree[T]
   }
 
+  /** [bound] selector match { cases } */
+  case class MatchTypeTree[-T >: Untyped] private[ast] (bound: Tree[T], selector: Tree[T], cases: List[CaseDef[T]])
+    extends TypTree[T] {
+    type ThisTree[-T >: Untyped] = MatchTypeTree[T]
+  }
+
   /** => T */
   case class ByNameTypeTree[-T >: Untyped] private[ast] (result: Tree[T])
   extends TypTree[T] {
@@ -916,6 +922,7 @@ object Trees {
     type RefinedTypeTree = Trees.RefinedTypeTree[T]
     type AppliedTypeTree = Trees.AppliedTypeTree[T]
     type LambdaTypeTree = Trees.LambdaTypeTree[T]
+    type MatchTypeTree = Trees.MatchTypeTree[T]
     type ByNameTypeTree = Trees.ByNameTypeTree[T]
     type TypeBoundsTree = Trees.TypeBoundsTree[T]
     type Bind = Trees.Bind[T]
@@ -1099,6 +1106,10 @@ object Trees {
         case tree: LambdaTypeTree if (tparams eq tree.tparams) && (body eq tree.body) => tree
         case _ => finalize(tree, untpd.LambdaTypeTree(tparams, body))
       }
+      def MatchTypeTree(tree: Tree)(bound: Tree, selector: Tree, cases: List[CaseDef]): MatchTypeTree = tree match {
+        case tree: MatchTypeTree if (bound eq tree.bound) && (selector eq tree.selector) && (cases eq tree.cases) => tree
+        case _ => finalize(tree, untpd.MatchTypeTree(bound, selector, cases))
+      }
       def ByNameTypeTree(tree: Tree)(result: Tree): ByNameTypeTree = tree match {
         case tree: ByNameTypeTree if result eq tree.result => tree
         case _ => finalize(tree, untpd.ByNameTypeTree(result))
@@ -1255,6 +1266,8 @@ object Trees {
           case LambdaTypeTree(tparams, body) =>
             implicit val ctx = localCtx
             cpy.LambdaTypeTree(tree)(transformSub(tparams), transform(body))
+          case MatchTypeTree(bound, selector, cases) =>
+            cpy.MatchTypeTree(tree)(transform(bound), transform(selector), transformSub(cases))
           case ByNameTypeTree(result) =>
             cpy.ByNameTypeTree(tree)(transform(result))
           case TypeBoundsTree(lo, hi) =>
@@ -1389,6 +1402,8 @@ object Trees {
           case LambdaTypeTree(tparams, body) =>
             implicit val ctx = localCtx
             this(this(x, tparams), body)
+          case MatchTypeTree(bound, selector, cases) =>
+            this(this(this(x, bound), selector), cases)
           case ByNameTypeTree(result) =>
             this(x, result)
           case TypeBoundsTree(lo, hi) =>

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

@@ -115,10 +115,10 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   }
 
   def CaseDef(pat: Tree, guard: Tree, body: Tree)(implicit ctx: Context): CaseDef =
-    ta.assignType(untpd.CaseDef(pat, guard, body), body)
+    ta.assignType(untpd.CaseDef(pat, guard, body), pat, body)
 
   def Match(selector: Tree, cases: List[CaseDef])(implicit ctx: Context): Match =
-    ta.assignType(untpd.Match(selector, cases), cases)
+    ta.assignType(untpd.Match(selector, cases), selector, cases)
 
   def Labeled(bind: Bind, expr: Tree)(implicit ctx: Context): Labeled =
     ta.assignType(untpd.Labeled(bind, expr))
@@ -165,6 +165,9 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
   def LambdaTypeTree(tparams: List[TypeDef], body: Tree)(implicit ctx: Context): LambdaTypeTree =
     ta.assignType(untpd.LambdaTypeTree(tparams, body), tparams, body)
 
+  def MatchTypeTree(bound: Tree, selector: Tree, cases: List[CaseDef])(implicit ctx: Context): MatchTypeTree =
+    ta.assignType(untpd.MatchTypeTree(bound, selector, cases), bound, selector, cases)
+
   def TypeBoundsTree(lo: Tree, hi: Tree)(implicit ctx: Context): TypeBoundsTree =
     ta.assignType(untpd.TypeBoundsTree(lo, hi), lo, hi)
 
@@ -575,7 +578,6 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
       }
     }
 
-
     override def Closure(tree: Tree)(env: List[Tree], meth: Tree, tpt: Tree)(implicit ctx: Context): Closure = {
       val tree1 = untpd.cpy.Closure(tree)(env, meth, tpt)
       tree match {
@@ -584,19 +586,20 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
         case _ => ta.assignType(tree1, meth, tpt)
       }
     }
+
     override def Match(tree: Tree)(selector: Tree, cases: List[CaseDef])(implicit ctx: Context): Match = {
       val tree1 = untpd.cpy.Match(tree)(selector, cases)
       tree match {
         case tree: Match if sameTypes(cases, tree.cases) => tree1.withTypeUnchecked(tree.tpe)
-        case _ => ta.assignType(tree1, cases)
+        case _ => ta.assignType(tree1, selector, cases)
       }
     }
 
     override def CaseDef(tree: Tree)(pat: Tree, guard: Tree, body: Tree)(implicit ctx: Context): CaseDef = {
       val tree1 = untpd.cpy.CaseDef(tree)(pat, guard, body)
       tree match {
         case tree: CaseDef if body.tpe eq tree.body.tpe => tree1.withTypeUnchecked(tree.tpe)
-        case _ => ta.assignType(tree1, body)
+        case _ => ta.assignType(tree1, pat, body)
       }
     }
 
@@ -821,7 +824,10 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
 
     /** `tree == that` */
     def equal(that: Tree)(implicit ctx: Context) =
-      applyOverloaded(tree, nme.EQ, that :: Nil, Nil, defn.BooleanType)
+      if (that.tpe.widen.isRef(defn.NothingClass))
+        Literal(Constant(false))
+      else
+        applyOverloaded(tree, nme.EQ, that :: Nil, Nil, defn.BooleanType)
 
     /** `tree.isInstanceOf[tp]`, with special treatment of singleton types */
     def isInstance(tp: Type)(implicit ctx: Context): Tree = tp.dealias match {

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

@@ -293,6 +293,7 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def RefinedTypeTree(tpt: Tree, refinements: List[Tree]): RefinedTypeTree = new RefinedTypeTree(tpt, refinements)
   def AppliedTypeTree(tpt: Tree, args: List[Tree]): AppliedTypeTree = new AppliedTypeTree(tpt, args)
   def LambdaTypeTree(tparams: List[TypeDef], body: Tree): LambdaTypeTree = new LambdaTypeTree(tparams, body)
+  def MatchTypeTree(bound: Tree, selector: Tree, cases: List[CaseDef]): MatchTypeTree = new MatchTypeTree(bound, selector, cases)
   def ByNameTypeTree(result: Tree): ByNameTypeTree = new ByNameTypeTree(result)
   def TypeBoundsTree(lo: Tree, hi: Tree): TypeBoundsTree = new TypeBoundsTree(lo, hi)
   def Bind(name: Name, body: Tree): Bind = new Bind(name, body)

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

@@ -6,6 +6,7 @@ object Config {
   final val cacheAsSeenFrom = true
   final val cacheMemberNames = true
   final val cacheImplicitScopes = true
+  final val cacheMatchReduced = true
 
   final val checkCacheMembersNamed = false
 

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

@@ -35,6 +35,11 @@ trait ConstraintHandling {
   /** If the constraint is frozen we cannot add new bounds to the constraint. */
   protected var frozenConstraint = false
 
+  /** Potentially a type lambda that is still instantiatable, even though the constraint
+   *  is generally frozen.
+   */
+  protected var caseLambda: Type = NoType
+
   /** If set, align arguments `S1`, `S2`when taking the glb
    *  `T1 { X = S1 } & T2 { X = S2 }` of a constraint upper bound for some type parameter.
    *  Aligning means computing `S1 =:= S2` which may change the current constraint.
@@ -47,7 +52,7 @@ trait ConstraintHandling {
    */
   protected var comparedTypeLambdas: Set[TypeLambda] = Set.empty
 
-  private def addOneBound(param: TypeParamRef, bound: Type, isUpper: Boolean): Boolean =
+  protected def addOneBound(param: TypeParamRef, bound: Type, isUpper: Boolean): Boolean =
     !constraint.contains(param) || {
       def occursIn(bound: Type): Boolean = {
         val b = bound.dealias
@@ -167,19 +172,20 @@ trait ConstraintHandling {
       isSubType(tp1, tp2)
   }
 
-  final def isSubTypeWhenFrozen(tp1: Type, tp2: Type): Boolean = {
-    val saved = frozenConstraint
+  @forceInline final def inFrozenConstraint[T](op: => T): T = {
+    val savedFrozen = frozenConstraint
+    val savedLambda = caseLambda
     frozenConstraint = true
-    try isSubType(tp1, tp2)
-    finally frozenConstraint = saved
+    caseLambda = NoType
+    try op
+    finally {
+      frozenConstraint = savedFrozen
+      caseLambda = savedLambda
+    }
   }
 
-  final def isSameTypeWhenFrozen(tp1: Type, tp2: Type): Boolean = {
-    val saved = frozenConstraint
-    frozenConstraint = true
-    try isSameType(tp1, tp2)
-    finally frozenConstraint = saved
-  }
+  final def isSubTypeWhenFrozen(tp1: Type, tp2: Type): Boolean = inFrozenConstraint(isSubType(tp1, tp2))
+  final def isSameTypeWhenFrozen(tp1: Type, tp2: Type): Boolean = inFrozenConstraint(isSameType(tp1, tp2))
 
   /** Test whether the lower bounds of all parameters in this
    *  constraint are a solution to the constraint.
@@ -319,7 +325,7 @@ trait ConstraintHandling {
     }
 
   /** The current bounds of type parameter `param` */
-  final def bounds(param: TypeParamRef): TypeBounds = {
+  def bounds(param: TypeParamRef): TypeBounds = {
     val e = constraint.entry(param)
     if (e.exists) e.bounds
     else {
@@ -355,7 +361,7 @@ trait ConstraintHandling {
 
   /** Can `param` be constrained with new bounds? */
   final def canConstrain(param: TypeParamRef): Boolean =
-    !frozenConstraint && (constraint contains param)
+    (!frozenConstraint || (caseLambda `eq` param.binder)) && constraint.contains(param)
 
   /** Add constraint `param <: bound` if `fromBelow` is false, `param >: bound` otherwise.
    *  `bound` is assumed to be in normalized form, as specified in `firstTry` and
@@ -492,19 +498,18 @@ trait ConstraintHandling {
   /** Check that constraint is fully propagated. See comment in Config.checkConstraintsPropagated */
   def checkPropagated(msg: => String)(result: Boolean): Boolean = {
     if (Config.checkConstraintsPropagated && result && addConstraintInvocations == 0) {
-      val saved = frozenConstraint
-      frozenConstraint = true
-      for (p <- constraint.domainParams) {
-        def check(cond: => Boolean, q: TypeParamRef, ordering: String, explanation: String): Unit =
-          assert(cond, i"propagation failure for $p $ordering $q: $explanation\n$msg")
-        for (u <- constraint.upper(p))
-          check(bounds(p).hi <:< bounds(u).hi, u, "<:", "upper bound not propagated")
-        for (l <- constraint.lower(p)) {
-          check(bounds(l).lo <:< bounds(p).hi, l, ">:", "lower bound not propagated")
-          check(constraint.isLess(l, p), l, ">:", "reverse ordering (<:) missing")
+      inFrozenConstraint {
+        for (p <- constraint.domainParams) {
+          def check(cond: => Boolean, q: TypeParamRef, ordering: String, explanation: String): Unit =
+            assert(cond, i"propagation failure for $p $ordering $q: $explanation\n$msg")
+          for (u <- constraint.upper(p))
+            check(bounds(p).hi <:< bounds(u).hi, u, "<:", "upper bound not propagated")
+          for (l <- constraint.lower(p)) {
+            check(bounds(l).lo <:< bounds(p).hi, l, ">:", "lower bound not propagated")
+            check(constraint.isLess(l, p), l, ">:", "reverse ordering (<:) missing")
+          }
         }
       }
-      frozenConstraint = saved
     }
     result
   }

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

@@ -2,7 +2,7 @@ package dotty.tools.dotc
 package core
 
 import Contexts._
-import config.Printers.typr
+import config.Printers.{default, typr}
 
 trait ConstraintRunInfo { self: Run =>
   private[this] var maxSize = 0
@@ -12,8 +12,9 @@ trait ConstraintRunInfo { self: Run =>
       maxSize = size
       maxConstraint = c
     }
-  def printMaxConstraint()(implicit ctx: Context) =
-    if (maxSize > 0) typr.println(s"max constraint = ${maxConstraint.show}")
-
+  def printMaxConstraint()(implicit ctx: Context) = {
+    val printer = if (ctx.settings.YdetailedStats.value) default else typr
+    if (maxSize > 0) printer.println(s"max constraint = ${maxConstraint.show}")
+  }
   protected def reset() = maxConstraint = null
 }

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

@@ -218,6 +218,15 @@ class Definitions {
     lazy val Sys_errorR = SysPackage.moduleClass.requiredMethodRef(nme.error)
     def Sys_error(implicit ctx: Context) = Sys_errorR.symbol
 
+  lazy val TypelevelPackageObjectRef = ctx.requiredModuleRef("scala.typelevel.package")
+  lazy val TypelevelPackageObject = TypelevelPackageObjectRef.symbol.moduleClass
+    lazy val Typelevel_errorR = TypelevelPackageObjectRef.symbol.requiredMethodRef(nme.error)
+    def Typelevel_error(implicit ctx: Context) = Typelevel_errorR.symbol
+    lazy val Typelevel_constValueR = TypelevelPackageObjectRef.symbol.requiredMethodRef("constValue")
+    def Typelevel_constValue(implicit ctx: Context) = Typelevel_constValueR.symbol
+    lazy val Typelevel_constValueOptR = TypelevelPackageObjectRef.symbol.requiredMethodRef("constValueOpt")
+    def Typelevel_constValueOpt(implicit ctx: Context) = Typelevel_constValueOptR.symbol
+
   /** The `scalaShadowing` package is used to safely modify classes and
    *  objects in scala so that they can be used from dotty. They will
    *  be visible as members of the `scala` package, replacing any objects
@@ -712,6 +721,8 @@ class Definitions {
 
   lazy val TupleTypeRef = ctx.requiredClassRef("scala.Tuple")
   def TupleClass(implicit ctx: Context) = TupleTypeRef.symbol.asClass
+  lazy val NonEmptyTupleTypeRef = ctx.requiredClassRef("scala.NonEmptyTuple")
+  def NonEmptyTupleClass(implicit ctx: Context) = NonEmptyTupleTypeRef.symbol.asClass
 
   lazy val PairType = ctx.requiredClassRef("scala.*:")
   def PairClass(implicit ctx: Context) = PairType.symbol.asClass
@@ -888,6 +899,9 @@ class Definitions {
     }
   }
 
+  final def isTypelevel_S(sym: Symbol)(implicit ctx: Context) =
+    sym.name == tpnme.S && sym.owner == TypelevelPackageObject
+
   // ----- Symbol sets ---------------------------------------------------
 
   lazy val AbstractFunctionType = mkArityArray("scala.runtime.AbstractFunction", MaxImplementedFunctionArity, 0)
@@ -1217,7 +1231,7 @@ class Definitions {
   def isValueSubClass(sym1: Symbol, sym2: Symbol) =
     valueTypeEnc(sym2.asClass.name) % valueTypeEnc(sym1.asClass.name) == 0
 
-  lazy val erasedToObject = Set[Symbol](AnyClass, AnyValClass, TupleClass, SingletonClass)
+  lazy val erasedToObject = Set[Symbol](AnyClass, AnyValClass, TupleClass, NonEmptyTupleClass, SingletonClass)
 
   // ----- Initialization ---------------------------------------------------
 

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

@@ -204,6 +204,7 @@ object StdNames {
     final val Object: N              = "Object"
     final val PartialFunction: N     = "PartialFunction"
     final val PrefixType: N          = "PrefixType"
+    final val S: N                   = "S"
     final val Serializable: N        = "Serializable"
     final val Singleton: N           = "Singleton"
     final val Throwable: N           = "Throwable"

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

@@ -12,6 +12,7 @@ import util.common._
 import Names._
 import NameOps._
 import NameKinds._
+import Constants.Constant
 import Flags._
 import StdNames.tpnme
 import util.Positions.Position
@@ -337,8 +338,8 @@ class TypeApplications(val self: Type) extends AnyVal {
             tl => arg.paramInfos.map(_.subst(arg, tl).bounds),
             tl => arg.resultType.subst(arg, tl)
           )
-        case arg @ TypeAlias(alias) =>
-          arg.derivedTypeAlias(adaptArg(alias))
+        case arg: AliasingBounds =>
+          arg.derivedAlias(adaptArg(arg.alias))
         case arg @ TypeBounds(lo, hi) =>
           arg.derivedTypeBounds(adaptArg(lo), adaptArg(hi))
         case _ =>
@@ -401,8 +402,8 @@ class TypeApplications(val self: Type) extends AnyVal {
         dealiased.derivedAndType(dealiased.tp1.appliedTo(args), dealiased.tp2.appliedTo(args))
       case dealiased: OrType =>
         dealiased.derivedOrType(dealiased.tp1.appliedTo(args), dealiased.tp2.appliedTo(args))
-      case dealiased: TypeAlias =>
-        dealiased.derivedTypeAlias(dealiased.alias.appliedTo(args))
+      case dealiased: AliasingBounds =>
+        dealiased.derivedAlias(dealiased.alias.appliedTo(args))
       case dealiased: TypeBounds =>
         dealiased.derivedTypeBounds(dealiased.lo.appliedTo(args), dealiased.hi.appliedTo(args))
       case dealiased: LazyRef =>
@@ -434,10 +435,13 @@ class TypeApplications(val self: Type) extends AnyVal {
       appliedTo(args)
   }
 
-  /** Turns non-bounds types to type aliases */
+  /** Turns non-bounds types to type bounds.
+   *  A (possible lambda abstracted) match type is turned into an abstract type.
+   *  Every other type is turned into a type alias
+   */
   final def toBounds(implicit ctx: Context): TypeBounds = self match {
     case self: TypeBounds => self // this can happen for wildcard args
-    case _ => TypeAlias(self)
+    case _ => if (self.isMatch) MatchAlias(self) else TypeAlias(self)
   }
 
   /** Translate a type of the form From[T] to To[T], keep other types as they are.