plugins/kotlin/analysis/src/org/jetbrains/kotlin/idea/inspections/AbstractResultUnusedChecker.kt


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// Copyright 2000-2021 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.

package org.jetbrains.kotlin.idea.inspections

import com.intellij.psi.PsiElement
import org.jetbrains.kotlin.idea.util.safeAnalyzeNonSourceRootCode
import org.jetbrains.kotlin.psi.*
import org.jetbrains.kotlin.resolve.BindingContext
import org.jetbrains.kotlin.resolve.bindingContextUtil.isUsedAsExpression
import org.jetbrains.kotlin.resolve.calls.util.getResolvedCall
import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode

abstract class AbstractResultUnusedChecker(
    private val expressionChecker: (KtExpression, AbstractResultUnusedChecker) -> Boolean,
    private val callChecker: (ResolvedCall<*>, AbstractResultUnusedChecker) -> Boolean
) : AbstractKotlinInspection() {
    protected fun check(expression: KtExpression): Boolean {
        // Check whatever possible by PSI
        if (!expressionChecker(expression, this)) return false
        var current: PsiElement? = expression
        var parent: PsiElement? = expression.parent
        while (parent != null) {
            if (parent is KtBlockExpression || parent is KtFunction || parent is KtFile) break
            if (parent is KtValueArgument || parent is KtBinaryExpression || parent is KtUnaryExpression) return false
            if (parent is KtQualifiedExpression && parent.receiverExpression == current) return false
            // TODO: add when condition, if condition (later when it's applicable not only to Deferred)
            current = parent
            parent = parent.parent
        }
        // Then check by call
        val context = expression.safeAnalyzeNonSourceRootCode(BodyResolveMode.PARTIAL_WITH_CFA)
        if (context == BindingContext.EMPTY || expression.isUsedAsExpression(context)) return false
        val resolvedCall = expression.getResolvedCall(context) ?: return false
        return callChecker(resolvedCall, this)
    }
}