org.jetbrains.kotlin.types.EnrichedProjectionKind.kt Maven / Gradle / Ivy
/*
* Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
* Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
*/
package org.jetbrains.kotlin.types
enum class EnrichedProjectionKind {
IN, OUT, INV, STAR;
companion object {
@JvmStatic
fun fromVariance(variance: Variance): EnrichedProjectionKind {
return when (variance) {
Variance.INVARIANT -> INV
Variance.IN_VARIANCE -> IN
Variance.OUT_VARIANCE -> OUT
}
}
// If class C then C and C mean the same
// out * out = out
// out * in = *
// out * inv = out
//
// in * out = *
// in * in = in
// in * inv = in
//
// inv * out = out
// inv * in = out
// inv * inv = inv
fun getEffectiveProjectionKind(
typeParameterVariance: Variance,
typeArgumentVariance: Variance
): EnrichedProjectionKind {
var a = typeParameterVariance
var b = typeArgumentVariance
// If they are not both invariant, let's make b not invariant for sure
if (b === Variance.INVARIANT) {
val t = a
a = b
b = t
}
// Opposites yield STAR
if (a === Variance.IN_VARIANCE && b === Variance.OUT_VARIANCE) {
return STAR
}
return if (a === Variance.OUT_VARIANCE && b === Variance.IN_VARIANCE) {
STAR
} else fromVariance(b)
// If they are not opposite, return b, because b is either equal to a or b is in/out and a is inv
}
}
}