org.jetbrains.kotlin.backend.common.IrWhenUtils.kt Maven / Gradle / Ivy

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/*
 * Copyright 2010-2022 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.backend.common

import org.jetbrains.kotlin.ir.expressions.*
import org.jetbrains.kotlin.ir.symbols.IrFunctionSymbol
import org.jetbrains.kotlin.ir.types.isBoolean
import org.jetbrains.kotlin.ir.util.dump
import org.jetbrains.kotlin.ir.util.isElseBranch
import org.jetbrains.kotlin.ir.util.isTrueConst

object IrWhenUtils {
// psi2ir lowers multiple cases to nested conditions. For example,
//
// when (subject) {
//   a, b, c -> action
// }
//
// is lowered to
//
// if (if (subject == a)
//       true
//     else
//       if (subject == b)
//         true
//       else
//         subject == c) {
//     action
// }
//
// fir2ir lowers the same to an or sequence:
//
// if (((subject == a) || (subject == b)) || (subject = c)) action
//
// @return true if the conditions are equality checks of constants.
    fun matchConditions(ororSymbol: IrFunctionSymbol, condition: IrExpression): ArrayList? {
        if (condition is IrWhen && condition.origin == IrStatementOrigin.WHEN_COMMA) {
            assert(condition.type.isBoolean()) { "WHEN_COMMA should always be a Boolean: ${condition.dump()}" }

            val candidates = ArrayList()

            // Match the following structure:
            //
            // when() {
            //   cond_1 -> true
            //   cond_2 -> true
            //   ...
            //   else -> cond_N
            // }
            //
            // Namely, the structure which returns true if any one of the condition is true.
            for (branch in condition.branches) {
                candidates += if (isElseBranch(branch)) {
                    assert(branch.condition.isTrueConst()) { "IrElseBranch.condition should be const true: ${branch.condition.dump()}" }
                    matchConditions(ororSymbol, branch.result) ?: return null
                } else {
                    if (!branch.result.isTrueConst()) return null
                    matchConditions(ororSymbol, branch.condition) ?: return null
                }
            }
            return candidates.ifEmpty { null }
        } else if (condition is IrCall && condition.symbol == ororSymbol) {
            val candidates = ArrayList()
            for (i in 0 until condition.valueArgumentsCount) {
                val argument = condition.getValueArgument(i)!!
                candidates += matchConditions(ororSymbol, argument) ?: return null
            }
            return candidates.ifEmpty { null }
        } else if (condition is IrCall) {
            return arrayListOf(condition)
        }

        return null
    }
}