Merge pull request #15330 from dotty-staging/fix-15302

Handle & and | types when computing tuple arity

Author: nicolasstucki

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

@@ -691,7 +691,7 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
   private def erasePair(tp: Type)(using Context): Type = {
     // NOTE: `tupleArity` does not consider TypeRef(EmptyTuple$) equivalent to EmptyTuple.type,
     // we fix this for printers, but type erasure should be preserved.
-    val arity = tp.tupleArity()
+    val arity = tp.tupleArity
     if (arity < 0) defn.ProductClass.typeRef
     else if (arity <= Definitions.MaxTupleArity) defn.TupleType(arity).nn
     else defn.TupleXXLClass.typeRef

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -215,15 +215,17 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
 
     def appliedText(tp: Type): Text = tp match
       case tp @ AppliedType(tycon, args) =>
-        val cls = tycon.typeSymbol
-        if tycon.isRepeatedParam then toTextLocal(args.head) ~ "*"
-        else if defn.isFunctionClass(cls) then toTextFunction(args, cls.name.isContextFunction, cls.name.isErasedFunction)
-        else if tp.tupleArity(relaxEmptyTuple = true) >= 2 && !printDebug then toTextTuple(tp.tupleElementTypes)
-        else if isInfixType(tp) then
-          val l :: r :: Nil = args: @unchecked
-          val opName = tyconName(tycon)
-          toTextInfixType(tyconName(tycon), l, r) { simpleNameString(tycon.typeSymbol) }
-        else Str("")
+        tp.tupleElementTypes match
+          case Some(types) if types.size >= 2 && !printDebug => toTextTuple(types)
+          case _ =>
+            val cls = tycon.typeSymbol
+            if tycon.isRepeatedParam then toTextLocal(args.head) ~ "*"
+            else if defn.isFunctionClass(cls) then toTextFunction(args, cls.name.isContextFunction, cls.name.isErasedFunction)
+            else if isInfixType(tp) then
+              val l :: r :: Nil = args: @unchecked
+              val opName = tyconName(tycon)
+              toTextInfixType(tyconName(tycon), l, r) { simpleNameString(tycon.typeSymbol) }
+            else Str("")
       case _ =>
         Str("")
 

compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala

@@ -248,7 +248,7 @@ object GenericSignatures {
               case _ => jsig(elemtp)
 
         case RefOrAppliedType(sym, pre, args) =>
-          if (sym == defn.PairClass && tp.tupleArity() > Definitions.MaxTupleArity)
+          if (sym == defn.PairClass && tp.tupleArity > Definitions.MaxTupleArity)
             jsig(defn.TupleXXLClass.typeRef)
           else if (isTypeParameterInSig(sym, sym0)) {
             assert(!sym.isAliasType, "Unexpected alias type: " + sym)

compiler/src/dotty/tools/dotc/transform/TypeUtils.scala

@@ -51,41 +51,44 @@ object TypeUtils {
 
     /** The arity of this tuple type, which can be made up of EmptyTuple, TupleX and `*:` pairs,
      *  or -1 if this is not a tuple type.
-     *
-     *  @param relaxEmptyTuple if true then TypeRef(EmptyTuple$) =:= EmptyTuple.type
      */
-    def tupleArity(relaxEmptyTuple: Boolean = false)(using Context): Int = self match {
+    def tupleArity(using Context): Int = self/*.dealias*/ match { // TODO: why does dealias cause a failure in tests/run-deep-subtype/Tuple-toArray.scala
       case AppliedType(tycon, _ :: tl :: Nil) if tycon.isRef(defn.PairClass) =>
-        val arity = tl.tupleArity(relaxEmptyTuple)
+        val arity = tl.tupleArity
         if (arity < 0) arity else arity + 1
       case self: SingletonType =>
         if self.termSymbol == defn.EmptyTupleModule then 0 else -1
-      case self: TypeRef if relaxEmptyTuple && self.classSymbol == defn.EmptyTupleModule.moduleClass =>
-        0
-      case self if defn.isTupleClass(self.classSymbol) =>
-        self.dealias.argInfos.length
+      case self: AndOrType =>
+        val arity1 = self.tp1.tupleArity
+        val arity2 = self.tp2.tupleArity
+        if arity1 == arity2 then arity1 else -1
       case _ =>
-        -1
+        if defn.isTupleClass(self.classSymbol) then self.dealias.argInfos.length
+        else -1
     }
 
     /** The element types of this tuple type, which can be made up of EmptyTuple, TupleX and `*:` pairs */
-    def tupleElementTypes(using Context): List[Type] = self match {
+    def tupleElementTypes(using Context): Option[List[Type]] = self.dealias match {
       case AppliedType(tycon, hd :: tl :: Nil) if tycon.isRef(defn.PairClass) =>
-        hd :: tl.tupleElementTypes
+        tl.tupleElementTypes.map(hd :: _)
       case self: SingletonType =>
-        assert(self.termSymbol == defn.EmptyTupleModule, "not a tuple")
-        Nil
-      case self: TypeRef if self.classSymbol == defn.EmptyTupleModule.moduleClass =>
-         Nil
-      case self if defn.isTupleClass(self.classSymbol) =>
-        self.dealias.argInfos
+        if self.termSymbol == defn.EmptyTupleModule then Some(Nil) else None
+      case AndType(tp1, tp2) =>
+        // We assume that we have the following property:
+        // (T1, T2, ..., Tn) & (U1, U2, ..., Un) = (T1 & U1, T2 & U2, ..., Tn & Un)
+        tp1.tupleElementTypes.zip(tp2.tupleElementTypes).map { case (t1, t2) => t1 & t2 }
+      case OrType(tp1, tp2) =>
+        None // We can't combine the type of two tuples
       case _ =>
-        throw new AssertionError("not a tuple")
+        if defn.isTupleClass(self.classSymbol) then Some(self.dealias.argInfos)
+        else None
     }
 
     /** The `*:` equivalent of an instance of a Tuple class */
     def toNestedPairs(using Context): Type =
-      TypeOps.nestedPairs(tupleElementTypes)
+      tupleElementTypes match
+        case Some(types) => TypeOps.nestedPairs(types)
+        case None => throw new AssertionError("not a tuple")
 
     def refinedWith(name: Name, info: Type)(using Context) = RefinedType(self, name, info)
 

compiler/src/dotty/tools/dotc/typer/Synthesizer.scala

@@ -355,13 +355,15 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
           reduce(tp.underlying)
       case tp: HKTypeLambda if tp.resultType.isInstanceOf[HKTypeLambda] =>
         Left(i"its subpart `$tp` is not a supported kind (either `*` or `* -> *`)")
-      case tp @ AppliedType(tref: TypeRef, _)
-        if tref.symbol == defn.PairClass
-        && tp.tupleArity(relaxEmptyTuple = true) > 0 =>
-        // avoid type aliases for tuples
-        Right(MirrorSource.GenericTuple(tp.tupleElementTypes))
       case tp: TypeProxy =>
-        reduce(tp.underlying)
+        tp match
+          case tp @ AppliedType(tref: TypeRef, _) if tref.symbol == defn.PairClass =>
+            tp.tupleElementTypes match
+              case Some(types) =>
+                // avoid type aliases for tuples
+                Right(MirrorSource.GenericTuple(types))
+              case _ => reduce(tp.underlying)
+          case _ => reduce(tp.underlying)
       case tp @ AndType(l, r) =>
         for
           lsrc <- reduce(l)

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2768,8 +2768,9 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
       typed(desugar.smallTuple(tree).withSpan(tree.span), pt)
     else {
       val pts =
-        if (arity == pt.tupleArity()) pt.tupleElementTypes
-        else List.fill(arity)(defn.AnyType)
+        pt.tupleElementTypes match
+          case Some(types) if types.size == arity => types
+          case _ => List.fill(arity)(defn.AnyType)
       val elems = tree.trees.lazyZip(pts).map(
         if ctx.mode.is(Mode.Type) then typedType(_, _, mapPatternBounds = true)
         else typed(_, _))

tests/run/i15302a.scala

@@ -0,0 +1,6 @@
+inline def flatConcat2[A, B](a: A, b: B) =
+  b match
+    case bs: *:[bh, bt]  => a *: bs
+
+@main def Test =
+  val x: (Int, Int, Int) = flatConcat2(1, (2,3))

tests/run/i15302b.scala

@@ -0,0 +1,12 @@
+@main def Test =
+  val tup2: Any = (1, 2)
+  val x1: (Int, Int) = tup2.asInstanceOf[(Int *: Int *: EmptyTuple) & (Int, Int)]
+  val x2: (Int, Int) = tup2.asInstanceOf[(Int *: Int *: Tuple) & (Int, Int)]
+  val x3: (Int, Int) = tup2.asInstanceOf[(Int *: Int *: EmptyTuple) | (Int, Int)]
+  val x4: Tuple = tup2.asInstanceOf[(Int *: Int *: Tuple) | (Int, Int)]
+
+  val tup3: Any = (1, 2, 3)
+  val x5: (Int, Int, Int) = tup3.asInstanceOf[Int *: ((Int *: Int *: EmptyTuple) & (Int, Int))]
+  val x6: (Int, Int, Int) = tup3.asInstanceOf[Int *: ((Int *: Int *: Tuple) & (Int, Int))]
+  val x7: (Int, Int, Int) = tup3.asInstanceOf[Int *: ((Int *: Int *: EmptyTuple) | (Int, Int))]
+  val x8: Tuple = tup3.asInstanceOf[Int *: ((Int *: Int *: Tuple) | (Int, Int))]