Different type sizes for TupleN vs nested pairs encoding

[mbovel]

package dotty.tools.dotc.core

import dotty.tools.DottyTest
import dotty.tools.dotc.core.Symbols.defn
import dotty.tools.dotc.core.TypeOps

import org.junit.Test
import org.junit.Assert.assertEquals

class TypesTest extends DottyTest:

 @Test def tuple3TypeSize =
 val tpe = defn.TupleType(3).nn.appliedTo(List(defn.IntType, defn.BooleanType, defn.DoubleType))
 assertEquals(3, tpe.typeSize) // false, tpe.typeSize == 1 🤔

 @Test def tuple3ConsTypeSize =
 val tpe = TypeOps.nestedPairs(List(defn.IntType, defn.BooleanType, defn.DoubleType))
 assertEquals(3, tpe.typeSize)

Shouldn't the size of a 3-tuple always be 3, whereas it is encoded with a Tuple3 type application or with nested pairs?

[mbovel]

cc @Lluc24

[hamzaremmal]

@mbovel Did we establish if typeSize actually means typeDepth or not?

[mbovel]

It actually computes the number of type constructors and refinements:

scala3/compiler/src/dotty/tools/dotc/core/Types.scala

Lines 2097 to 2099 in 837607b

	/** The number of applications and refinements in this type, after all aliases are expanded */
	def typeSize(using Context): Int =
	(new TypeSizeAccumulator).apply(0, this)

I think it make sense to return the same result for tuples encoded as TupleN or nested :* pairs.

[hamzaremmal]

It actually computes the number of type constructors and refinements:

So it is a depth.

I think it make sense to return the same result for tuples encoded as TupleN or nested :* pairs.

Euuh, but Tuple3[Int, Int, Int] is one application and Int *: Int *: Int *: EmptyTuple -> *:[Int, *:[Int, *:[Int, EmptyTuple]]] is 3 applications.