EqualsAlwaysReturnsTrueOrFalse fails hard on override fun equals(other:Any) = ...

[mikesamuel]

A minimal repro code sample below.
It looks like the Detekt pass fails when there are zero return statements, e.g. when using fun equals(...) = expression syntax.

Stack Trace

The original exception message was: List is empty.
Running detekt '1.2.0' on Java '11.0.5-ea+10-post-Ubuntu-0ubuntu1' on OS 'Linux'.
If the exception message does not help, please feel free to create an issue on our GitHub page.
kotlin.collections.CollectionsKt___CollectionsKt.first(_Collections.kt:196)
io.gitlab.arturbosch.detekt.rules.bugs.EqualsAlwaysReturnsTrueOrFalse.isSingleReturnWithBooleanConstant(EqualsAlwaysReturnsTrueOrFalse.kt:71)
io.gitlab.arturbosch.detekt.rules.bugs.EqualsAlwaysReturnsTrueOrFalse.returnsBooleanConstant(EqualsAlwaysReturnsTrueOrFalse.kt:63)
io.gitlab.arturbosch.detekt.rules.bugs.EqualsAlwaysReturnsTrueOrFalse.visitNamedFunction(EqualsAlwaysReturnsTrueOrFalse.kt:52)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitNamedFunction(KtVisitorVoid.java:483)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitNamedFunction(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtNamedFunction.accept(KtNamedFunction.java:50)
org.jetbrains.kotlin.psi.KtElementImplStub.accept(KtElementImplStub.java:59)
org.jetbrains.kotlin.com.intellij.psi.impl.PsiElementBase.acceptChildren(PsiElementBase.java:69)
org.jetbrains.kotlin.psi.KtTreeVisitorVoid.visitElement(KtTreeVisitorVoid.java:25)
org.jetbrains.kotlin.psi.KtVisitor.visitKtElement(KtVisitor.java:24)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtElement(KtVisitorVoid.java:25)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtElement(KtVisitorVoid.java:447)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtElement(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtVisitor.visitClassBody(KtVisitor.java:98)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClassBody(KtVisitorVoid.java:89)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClassBody(KtVisitorVoid.java:537)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClassBody(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtClassBody.accept(KtClassBody.kt:38)
org.jetbrains.kotlin.psi.KtElementImplStub.accept(KtElementImplStub.java:59)
org.jetbrains.kotlin.com.intellij.psi.impl.PsiElementBase.acceptChildren(PsiElementBase.java:69)
org.jetbrains.kotlin.psi.KtTreeVisitorVoid.visitElement(KtTreeVisitorVoid.java:25)
org.jetbrains.kotlin.psi.KtVisitor.visitKtElement(KtVisitor.java:24)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtElement(KtVisitorVoid.java:25)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtElement(KtVisitorVoid.java:447)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtElement(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtVisitor.visitExpression(KtVisitor.java:182)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitExpression(KtVisitorVoid.java:169)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitExpression(KtVisitorVoid.java:659)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitExpression(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtVisitor.visitDeclaration(KtVisitor.java:29)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitDeclaration(KtVisitorVoid.java:29)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitDeclaration(KtVisitorVoid.java:453)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitDeclaration(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtVisitor.visitNamedDeclaration(KtVisitor.java:398)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitNamedDeclaration(KtVisitorVoid.java:381)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitNamedDeclaration(KtVisitorVoid.java:959)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitNamedDeclaration(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtVisitor.visitClassOrObject(KtVisitor.java:41)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClassOrObject(KtVisitorVoid.java:37)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClassOrObject(KtVisitorVoid.java:465)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClassOrObject(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtVisitor.visitClass(KtVisitor.java:33)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClass(KtVisitorVoid.java:33)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClass(KtVisitorVoid.java:459)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitClass(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtClass.accept(KtClass.kt:20)
org.jetbrains.kotlin.psi.KtElementImplStub.accept(KtElementImplStub.java:59)
org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.SharedImplUtil.acceptChildren(SharedImplUtil.java:200)
org.jetbrains.kotlin.com.intellij.psi.impl.source.PsiFileImpl.acceptChildren(PsiFileImpl.java:735)
org.jetbrains.kotlin.psi.KtTreeVisitorVoid.visitElement(KtTreeVisitorVoid.java:25)
org.jetbrains.kotlin.com.intellij.psi.PsiElementVisitor.visitFile(PsiElementVisitor.java:34)
org.jetbrains.kotlin.psi.KtVisitor.visitKtFile(KtVisitor.java:73)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtFile(KtVisitorVoid.java:69)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtFile(KtVisitorVoid.java:513)
org.jetbrains.kotlin.psi.KtVisitorVoid.visitKtFile(KtVisitorVoid.java:21)
org.jetbrains.kotlin.psi.KtFile.accept(KtFile.kt:242)
org.jetbrains.kotlin.psi.KtFile.accept(KtFile.kt:229)
io.gitlab.arturbosch.detekt.api.BaseRule.visit(BaseRule.kt:53)
io.gitlab.arturbosch.detekt.api.BaseRule.visitFile(BaseRule.kt:43)
io.gitlab.arturbosch.detekt.api.RuleSet.accept(RuleSet.kt:35)
io.gitlab.arturbosch.detekt.core.Detektor.analyze(Detektor.kt:76)
io.gitlab.arturbosch.detekt.core.Detektor.runSync(Detektor.kt:44)
io.gitlab.arturbosch.detekt.core.Detektor.run(Detektor.kt:28)
io.gitlab.arturbosch.detekt.core.DetektFacade.run(DetektFacade.kt:41)
io.gitlab.arturbosch.detekt.cli.runners.Runner.execute(Runner.kt:29)
io.gitlab.arturbosch.detekt.cli.Main.main(Main.kt:16)

MinimalRepro.kt

package com.example

abstract class MinimalRepro {
    var childList = mutableListOf<Any>()

    open fun value(): Any? = null

    override fun equals(other: Any?): Boolean =
        if (other == null || this::class != other::class) {
            false
        } else {
            val otherSameType = other as MinimalRepro
            childList == otherSameType.childList && value() == otherSameType.value()
        }

    override fun hashCode() = childList.hashCode() + 31 * (value()?.hashCode() ?: 0)

}

Detekt Config

potential-bugs:
  active: true
  Deprecation:
    active: true
  DuplicateCaseInWhenExpression:
    active: true
  EqualsAlwaysReturnsTrueOrFalse:
    active: true

Version

From my build.gradle

plugins {
    id 'org.jetbrains.kotlin.multiplatform' version '1.3.60'
    id 'org.jlleitschuh.gradle.ktlint' version '9.1.1'
    id 'io.gitlab.arturbosch.detekt' version '1.2.0'
    id 'org.jetbrains.dokka' version '0.10.0'
}

Expected Behavior

No exception thrown.

Observed Behavior

Exception thrown. See above.

Steps to Reproduce

• Put the above code snippet in src/commonMain/kotlin/com/example/MinimalRepro.kt
• Add a build.gradle that loads detekt plugin 1.2.0 (see config snippet above) and that scans src/
• gradle detekt

Observe stack trace.

Context

Workaround was to change fun equals(...) = ... to fun equals(...) { return ... }

Impact is low.

Your Environment

• Version of detekt used: 1.2.0
• Version of Gradle used (if applicable):6.0.1
• Operating System and version: Linux pop-os 5.3.0-22-generic#24+system76~1573659475~19.10~26b2022-Ubuntu SMP Wed Nov 13 20:0 x86_64 x86_64 x86_64 GNU/Linux
• Link to your project (if it's a public repository): https://gitlab.com/temper-lang/pattern

[schalkms]

Thanks for the detailed bug report! It was really easy to understand and investigate the issue.
Whilst investigating I couldn't reproduce the crash. This has been fixed by #2124 and is part of v1.2.2.

[mikesamuel]

Sorry, should have upgraded to latest before posting. Thanks for making/maintaining detekt.

[schalkms]

No worries..
Thanks for the kind words! That's really motivating to read. 😊