Add tupleOf utility method

Author: odersky

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

@@ -567,4 +567,9 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
 
 object TypeOps {
   @sharable var track: Boolean = false // !!!DEBUG
+
+  // TODO: Move other typeops here. It's a bit weird that they are a part of `ctx`
+
+  def tupleOf(ts: List[Type])(implicit ctx: Context): Type =
+    (ts :\ (defn.UnitType: Type))(defn.PairType.appliedTo(_, _))
 }

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

@@ -48,8 +48,8 @@ object TypeUtils {
         else throw new AssertionError("not a tuple")
     }
 
-    /** The `*:` equivalent of an instantce of a Tuple class */
+    /** The `*:` equivalent of an instance of a Tuple class */
     def toNestedPairs(implicit ctx: Context): Type =
-      (tupleElementTypes :\ (defn.UnitType: Type))(defn.PairType.appliedTo(_, _))
+      TypeOps.tupleOf(tupleElementTypes)
   }
 }

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

@@ -78,14 +78,14 @@ trait Deriving { this: Typer =>
           case _ =>
             (sym.termRef, Nil)
         }
-      val elemShape = (elems :\ (defn.UnitType: Type))(defn.PairType.appliedTo(_, _))
+      val elemShape = TypeOps.tupleOf(elems)
       defn.ShapeCaseType.appliedTo(constr, elemShape)
     }
 
     /** The shape of `cls` if `cls` is sealed */
     private def sealedShape: Type = {
       val cases = children.map(caseShape).filter(_.exists)
-      val casesShape = (cases :\ (defn.UnitType: Type))(defn.PairType.appliedTo(_, _))
+      val casesShape = TypeOps.tupleOf(cases)
       defn.ShapeCasesType.appliedTo(casesShape)
     }
 

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

@@ -1919,7 +1919,7 @@ class Typer extends Namer
         else {
           val elemTpes = (elems, pts).zipped.map((elem, pt) =>
             ctx.typeComparer.widenInferred(elem.tpe, pt))
-          val resTpe = (elemTpes :\ (defn.UnitType: Type))(defn.PairType.appliedTo(_, _))
+          val resTpe = TypeOps.tupleOf(elemTpes)
           app1.cast(resTpe)
         }
       }