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kotlinlang

How can I find most common super type for two types (IrType) in IR compiler backend?  May be there is already utility function for it?
```fun findMostCommonSuperTypeFor(type1: IrType, type2: IrType) : IrType {
  TODO("?")
}```

You can call <https://github.com/JetBrains/kotlin/blob/dbf37d9030da34504efd67f364153c022eb40a4f/compiler/resolution.common/src/org/jetbrains/kotlin/resolve/calls/NewCommonSuperTypeCalculator.kt#L16|this> method passing proper `IrTypeContext`

<@UKPEELJCW> could you point how to find right IrTypeContext implementation?
I'm trying to use IrTypeSystemContextImpl(IrBuiltIns) but got exception upon calling commonSuperType(List&lt;KotlinTypeMarker&gt;)
```java.lang.IllegalStateException: Should not be called
	at org.jetbrains.kotlin.ir.types.IrTypeSystemContext$DefaultImpls.isError(IrTypeSystemContext.kt:388)
	at org.jetbrains.kotlin.ir.types.IrTypeSystemContextImpl.isError(IrTypeSystemContext.kt:627)
	at org.jetbrains.kotlin.resolve.calls.NewCommonSuperTypeCalculator.findErrorTypeInSupertypes(NewCommonSuperTypeCalculator.kt:262)
	at org.jetbrains.kotlin.resolve.calls.NewCommonSuperTypeCalculator.commonSuperTypeForNotNullTypes(NewCommonSuperTypeCalculator.kt:234)
	at org.jetbrains.kotlin.resolve.calls.NewCommonSuperTypeCalculator.commonSuperTypeForSimpleTypes(NewCommonSuperTypeCalculator.kt:103)
	at org.jetbrains.kotlin.resolve.calls.NewCommonSuperTypeCalculator.commonSuperType(NewCommonSuperTypeCalculator.kt:62)
	at org.jetbrains.kotlin.resolve.calls.NewCommonSuperTypeCalculator.commonSuperType(NewCommonSuperTypeCalculator.kt:27)```

That's interesting
It seems that no one tried to calculate CST in IR before

You can create your own implementation of `IrTypeSystemContext` (with delegation to `IrTypeSystemContextImpl`) and override `isError` (so it will always return `false`)

Yes. For temporary workaround I made like this:
```private val typeSystem = object : IrTypeSystemContext { // TODO temporary workaround
        override val irBuiltIns: IrBuiltIns
            get() = pluginContext.irBuiltIns

        // if not overriden then throws 'Should not be called'
        override fun TypeConstructorMarker.isError(): Boolean {
            return false
        }

        // if not overriden with returning null then call to commonSuperType(List&lt;KotlinTypeMarker&gt;) return Int type for any input
        override fun findCommonIntegerLiteralTypesSuperType(explicitSupertypes: List&lt;SimpleTypeMarker&gt;): SimpleTypeMarker? {
            return null
        }
    }```

You need smth like this:
```val baseContext = IrTypeSystemContextImpl(irBuiltIns)
val context = object : IrTypeSystemContext by baseContext {
    override fun TypeConstructorMarker.isError(): Boolean {
        return false
    }
}```

Ah, I missed that all implementations are actually in the interface
So your option is fine too

There is one more function I need to override (see previous message)
If not override then for any list of types I got Int as common type