ActualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker: reuse "expect-actual" matcher

In scope of: KT-22841
Review: https://jetbrains.team/p/kt/reviews/11867/timeline

Reduce complexity by reusing "expect-actual matcher" (namely
`AbstractExpectActualCompatibilityChecker.getCallablesCompatibility`)

The current solution has worse algorithmic complexity. Previously it was
O(n) in the best case, where `n` is a number of members. Now, it's
O(m^2), where `m` is number of members in one overload group. But we
prefer to have worse complexity but reuse expect-actual matcher, number
of elements in one overload group shall not be big on real world
examples.

The previous logic was non-trivial because it compared types with with
double comparison in `equals`.

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated.java

@@ -1297,9 +1297,15 @@ public class FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated extends Abst
         }
 
         @Test
-        @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias.kt")
+        @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias_finalMember.kt")
-        public void testMorePermissiveVisibilityOnActualViaTypeAlias() throws Exception {
+        public void testMorePermissiveVisibilityOnActualViaTypeAlias_finalMember() throws Exception {
-            runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias.kt");
+            runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_finalMember.kt");
+        }
+
+        @Test
+        @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias_openMember.kt")
+        public void testMorePermissiveVisibilityOnActualViaTypeAlias_openMember() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_openMember.kt");
         }
 
         @Test

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirOldFrontendMPPDiagnosticsWithPsiTestGenerated.java

@@ -1297,9 +1297,15 @@ public class FirOldFrontendMPPDiagnosticsWithPsiTestGenerated extends AbstractFi
         }
 
         @Test
-        @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias.kt")
+        @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias_finalMember.kt")
-        public void testMorePermissiveVisibilityOnActualViaTypeAlias() throws Exception {
+        public void testMorePermissiveVisibilityOnActualViaTypeAlias_finalMember() throws Exception {
-            runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias.kt");
+            runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_finalMember.kt");
+        }
+
+        @Test
+        @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias_openMember.kt")
+        public void testMorePermissiveVisibilityOnActualViaTypeAlias_openMember() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_openMember.kt");
         }
 
         @Test

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ActualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker.kt

@@ -10,16 +10,16 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.incremental.components.NoLookupLocation
 import org.jetbrains.kotlin.name.FqName
-import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.BindingTrace
-import org.jetbrains.kotlin.resolve.descriptorUtil.*
+import org.jetbrains.kotlin.resolve.calls.mpp.AbstractExpectActualCompatibilityChecker
+import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameSafe
+import org.jetbrains.kotlin.resolve.descriptorUtil.getSuperClassNotAny
+import org.jetbrains.kotlin.resolve.descriptorUtil.getSuperInterfaces
+import org.jetbrains.kotlin.resolve.descriptorUtil.module
 import org.jetbrains.kotlin.resolve.multiplatform.*
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.resolve.source.KotlinSourceElement
-import org.jetbrains.kotlin.types.KotlinType
-import org.jetbrains.kotlin.types.model.TypeSubstitutorMarker
-import java.util.*
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.contract
 
@@ -142,198 +142,71 @@ private fun calculateExpectActualScopeDiff(
         parentSubstitutor = null
     )
 
-    val expectClassCallables = expect.unsubstitutedMemberScope
+    val expectClassCallables = expect.unsubstitutedMemberScope.extractNonPrivateCallables()
-        .extractNonPrivateCallables(classTypeSubstitutor, ExpectActual.EXPECT, matchingContext)
+    val actualClassCallables = actual.unsubstitutedMemberScope.extractNonPrivateCallables()
-    val actualClassCallables = actual.unsubstitutedMemberScope
+        .filter { it.kind.isReal } // Filter out fake-overrides from actual because we compare list of supertypes separately anyway
-        .extractNonPrivateCallables(classTypeSubstitutor, ExpectActual.ACTUAL, matchingContext)
-        .filter { it.descriptor.kind.isReal } // Filter out fake-overrides from actual because we compare list of supertypes separately anyway
 
-    val nameAndKindToExpectCallable = expectClassCallables.groupBy { it.name to it.kind }
+    val nameAndKindToExpectCallables = expectClassCallables.groupBy { it.name to it.functionVsPropertyKind }
 
-    return (actualClassCallables - expectClassCallables).asSequence()
+    return actualClassCallables.flatMap { actualMember ->
-        .flatMap { unmatchedActualCallable ->
+        val potentialExpects = nameAndKindToExpectCallables[actualMember.name to actualMember.functionVsPropertyKind]
-            when (val expectCallablesWithTheSameNameAndKind =
+        if (potentialExpects.isNullOrEmpty()) {
-                nameAndKindToExpectCallable[unmatchedActualCallable.name to unmatchedActualCallable.kind]) {
+            listOf(ExpectActualMemberDiff.Kind.NonPrivateCallableAdded)
-                null -> listOf(ExpectActualMemberDiff.Kind.NonPrivateCallableAdded)
+        } else {
-                else -> expectCallablesWithTheSameNameAndKind.map {
+            potentialExpects
-                    calculateExpectActualMemberDiffKind(
+                .map { expectMember ->
-                        expect = it,
+                    val substitutor = matchingContext.createExpectActualTypeParameterSubstitutor(
-                        actual = unmatchedActualCallable,
+                        expectMember.typeParameters,
-                        checkParameterNames = unmatchedActualCallable.descriptor.hasStableParameterNames()
+                        actualMember.typeParameters,
+                        classTypeSubstitutor
+                    )
+                    AbstractExpectActualCompatibilityChecker.getCallablesCompatibility(
+                        expectMember,
+                        actualMember,
+                        substitutor,
+                        expect,
+                        actual,
+                        matchingContext
                     )
                 }
-            }.filterNotNull().map { kind -> ExpectActualMemberDiff(kind, unmatchedActualCallable.descriptor, expect) }
+                .takeIf { kinds -> kinds.all { it != ExpectActualCompatibility.Compatible } }
+                .orEmpty()
+                .map {
+                    when (it) {
+                        is ExpectActualCompatibility.Compatible -> error("Compatible was filtered out by takeIf")
+                        is ExpectActualCompatibility.Incompatible -> it.toMemberDiffKind()
+                        // If toMemberDiffKind returns null then some Kotlin invariants described in toMemberDiffKind no longer hold.
+                        // We can't throw exception here because it would crash the compilation.
+                        // Those broken invariants just needs to be reported by other checkers.
+                        // But it's better to report some error (ExpectActualMemberDiff.Kind.NonPrivateCallableAdded in our case) to
+                        // make sure that we don't have missed compilation errors if the invariants change
+                            ?: ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
+                    }
+                }
         }
-        .toSet()
+            .map { kind -> ExpectActualMemberDiff(kind, actualMember, expect) }
+    }.toSet()
 }
 
-private fun MemberScope.extractNonPrivateCallables(
+private fun MemberScope.extractNonPrivateCallables(): Sequence<CallableMemberDescriptor> {
-    classTypeSubstitutor: TypeSubstitutorMarker,
-    expectActual: ExpectActual,
-    matchingContext: ClassicExpectActualMatchingContext,
-): Set<Callable> {
     val functions =
         getFunctionNames().asSequence().flatMap { getContributedFunctions(it, NoLookupLocation.WHEN_GET_ALL_DESCRIPTORS) }
     val properties =
         getVariableNames().asSequence().flatMap { getContributedVariables(it, NoLookupLocation.WHEN_GET_ALL_DESCRIPTORS) }
     return (functions + properties).filter { !Visibilities.isPrivate(it.visibility.delegate) }
-        .map { descriptor -> Callable(descriptor, expectActual, classTypeSubstitutor, matchingContext) }
-        .toSet()
 }
 
-private data class Parameter(val name: Name, val type: KotlinType)
 private enum class Kind { FUNCTION, PROPERTY }
-private enum class ExpectActual { EXPECT, ACTUAL }
+private val CallableMemberDescriptor.functionVsPropertyKind: Kind
-private data class TypeParameter(val name: Name, val upperBounds: List<KotlinType>)
+    get() = when (this) {
-private class Callable(
-    val descriptor: CallableMemberDescriptor,
-    val expectActual: ExpectActual,
-    val classTypeSubstitutor: TypeSubstitutorMarker,
-    val matchingContext: ClassicExpectActualMatchingContext,
-) {
-    val name: Name = descriptor.name
-    val kind: Kind = when (descriptor) {
         is PropertyDescriptor -> Kind.PROPERTY
         is FunctionDescriptor -> Kind.FUNCTION
-        else -> error("Unknown kind $descriptor")
+        else -> error("Unknown kind $this")
     }
-    val isVarProperty: Boolean = descriptor is PropertyDescriptor && descriptor.isVar
-    val isLateinitProperty: Boolean = descriptor is PropertyDescriptor && descriptor.isLateInit
-    val modality: Modality = descriptor.modality
-    val visibility: Visibility = descriptor.visibility.delegate
-    val setterVisibility: Visibility? = (descriptor as? PropertyDescriptor)?.setter?.visibility?.delegate
-    val parameters: List<Parameter> = descriptor.valueParameters.map { Parameter(it.name, it.type) }
-    val returnType: KotlinType = descriptor.returnType ?: error("Can't get return type")
-    val extensionReceiverType: KotlinType? = descriptor.extensionReceiverParameter?.type
-    val typeParameters: List<TypeParameter> = descriptor.typeParameters.map { TypeParameter(it.name, it.upperBounds) }
-    val contextReceiverTypes: List<KotlinType> = descriptor.contextReceiverParameters.map(ValueDescriptor::getType)
-
-    override fun equals(other: Any?): Boolean {
-        if (other !is Callable) return false
-        check(classTypeSubstitutor === other.classTypeSubstitutor)
-        check(matchingContext === other.matchingContext)
-        return if (expectActual == other.expectActual) {
-            name == other.name &&
-                    kind == other.kind &&
-                    isVarProperty == other.isVarProperty &&
-                    isLateinitProperty == other.isLateinitProperty &&
-                    modality == other.modality &&
-                    visibility == other.visibility &&
-                    setterVisibility == other.setterVisibility &&
-                    parameters == other.parameters &&
-                    returnType == other.returnType &&
-                    extensionReceiverType == other.extensionReceiverType &&
-                    typeParameters == other.typeParameters &&
-                    contextReceiverTypes == other.contextReceiverTypes
-        } else {
-            val (expect, actual) = if (expectActual == ExpectActual.EXPECT) this to other else other to this
-            calculateExpectActualMemberDiffKind(expect, actual) == null
-        }
-    }
-
-    override fun hashCode(): Int = // Don't hash the types because type comparison is complicated
-        Objects.hash(
-            name,
-            kind,
-            isVarProperty,
-            isLateinitProperty,
-            modality,
-            visibility,
-            setterVisibility,
-            parameters.map(Parameter::name),
-            extensionReceiverType != null,
-            typeParameters.map(TypeParameter::name),
-            contextReceiverTypes.size,
-        )
-}
 
 private val CallableMemberDescriptor.psiIfReal: KtCallableDeclaration?
     get() = takeIf { it.kind.isReal }?.source?.let { it as? KotlinSourceElement }?.psi as? KtCallableDeclaration
 
-private fun ClassicExpectActualMatchingContext.areCompatibleWithSubstitution(
-    expect: KotlinType?,
-    actual: KotlinType?,
-    substitutor: TypeSubstitutorMarker,
-): Boolean = areCompatibleExpectActualTypes(expect?.let { substitutor.safeSubstitute(it) }, actual)
-
-private fun ClassicExpectActualMatchingContext.areCompatibleListWithSubstitution(
-    expect: List<KotlinType>,
-    actual: List<KotlinType>,
-    substitutor: TypeSubstitutorMarker,
-): Boolean = expect.size == actual.size && expect.asSequence().zip(actual.asSequence())
-    .all { (a, b) -> areCompatibleWithSubstitution(a, b, substitutor) }
-
-private fun ClassicExpectActualMatchingContext.areCompatibleUpperBoundsWithSubstitution(
-    expect: List<List<KotlinType>>,
-    actual: List<List<KotlinType>>,
-    substitutor: TypeSubstitutorMarker,
-): Boolean = expect.size == actual.size && expect.asSequence().zip(actual.asSequence())
-    .all { (a, b) -> areCompatibleListWithSubstitution(a, b, substitutor) }
-
-private fun calculateExpectActualMemberDiffKind(
-    expect: Callable,
-    actual: Callable,
-    checkParameterNames: Boolean = true,
-): ExpectActualMemberDiff.Kind? {
-    check(expect.expectActual == ExpectActual.EXPECT)
-    check(actual.expectActual == ExpectActual.ACTUAL)
-    check(expect.classTypeSubstitutor === actual.classTypeSubstitutor)
-    check(expect.matchingContext === actual.matchingContext)
-    val substitutor = actual.matchingContext.createExpectActualTypeParameterSubstitutor(
-        expect.descriptor.typeParameters,
-        actual.descriptor.typeParameters,
-        actual.classTypeSubstitutor
-    )
-    with(actual.matchingContext) {
-        return when {
-            expect.name != actual.name ||
-                    expect.kind != actual.kind ||
-                    !areCompatibleListWithSubstitution(
-                        expect.parameters.map(Parameter::type),
-                        actual.parameters.map(Parameter::type),
-                        substitutor
-                    ) ||
-                    !areCompatibleUpperBoundsWithSubstitution(
-                        expect.typeParameters.map(TypeParameter::upperBounds),
-                        actual.typeParameters.map(TypeParameter::upperBounds),
-                        substitutor
-                    ) ||
-                    !areCompatibleWithSubstitution(
-                        expect.extensionReceiverType,
-                        actual.extensionReceiverType,
-                        substitutor
-                    ) ||
-                    !areCompatibleListWithSubstitution(
-                        expect.contextReceiverTypes,
-                        actual.contextReceiverTypes,
-                        substitutor
-                    ) ->
-                ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
-
-            expect.isVarProperty != actual.isVarProperty -> ExpectActualMemberDiff.Kind.PropertyKindChangedInOverride
-
-            expect.isLateinitProperty != actual.isLateinitProperty -> ExpectActualMemberDiff.Kind.LateinitChangedInOverride
-
-            expect.modality != actual.modality -> ExpectActualMemberDiff.Kind.ModalityChangedInOverride
-
-            expect.visibility != actual.visibility -> ExpectActualMemberDiff.Kind.VisibilityChangedInOverride
-
-            expect.setterVisibility != actual.setterVisibility -> ExpectActualMemberDiff.Kind.SetterVisibilityChangedInOverride
-
-            checkParameterNames && expect.parameters.map(Parameter::name) != actual.parameters.map(Parameter::name) ->
-                ExpectActualMemberDiff.Kind.ParameterNameChangedInOverride
-
-            expect.typeParameters.map(TypeParameter::name) != actual.typeParameters.map(TypeParameter::name) ->
-                ExpectActualMemberDiff.Kind.TypeParameterNamesChangedInOverride
-
-            !areCompatibleWithSubstitution(expect.returnType, actual.returnType, substitutor) ->
-                ExpectActualMemberDiff.Kind.ReturnTypeChangedInOverride
-
-            else -> null
-        }
-    }
-}
-
 private fun BindingTrace.reportIfPossible(diff: ExpectActualMemberDiff<CallableMemberDescriptor, ClassDescriptor>) {
     val psi = diff.actualMember.psiIfReal ?: return
     val diagnostic = when (diff.kind) {

compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/finalMethodIsActualizedByOpenMethod.fir.kt

@@ -1,16 +0,0 @@
-// MODULE: m1-common
-// FILE: common.kt
-
-expect open class Foo {
-    fun foo()
-}
-
-// MODULE: m2-jvm()()(m1-common)
-// FILE: jvm.kt
-
-actual open class Foo {
-    // Hypothetically, it's more restricting than necessary. I can't see how actualizing final -> open can breaking anything.
-    // But technically, actual and expect scopes don't match
-    actual open fun foo() {
-    }
-}

compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/finalMethodIsActualizedByOpenMethod.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // MODULE: m1-common
 // FILE: common.kt
 
@@ -8,9 +9,8 @@ expect open class Foo {
 // MODULE: m2-jvm()()(m1-common)
 // FILE: jvm.kt
 
-actual open <!ACTUAL_CLASSIFIER_MUST_HAVE_THE_SAME_MEMBERS_AS_NON_FINAL_EXPECT_CLASSIFIER!>class Foo<!> {
+actual open class Foo {
-    // Hypothetically, it's more restricting than necessary. I can't see how actualizing final -> open can breaking anything.
+    // final -> open is a legal modality change
-    // But technically, actual and expect scopes don't match
+    actual open fun foo() {
-    actual <!MODALITY_CHANGED_IN_NON_FINAL_EXPECT_CLASSIFIER_ACTUALIZATION!>open<!> fun foo() {
     }
 }

compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/injectContextReceiverOverload.fir.kt

@@ -12,6 +12,8 @@ expect open class Foo {
 actual open class Foo {
     actual fun foo() {}
 
+    // Expected: NON_ACTUAL_MEMBER_DECLARED_IN_EXPECT_NON_FINAL_CLASSIFIER_ACTUALIZATION.
+    // But it doesn't work because context receivers are not yet supported in expect actual matcher KT-61447
     context(Int)
-    fun foo() {} // accidential override can happen with this injected fun. That's why it's prohibited
+    fun foo() {}
 }

compiler/testData/diagnostics/tests/multiplatform/actualClassifierMustHasTheSameMembersAsNonFinalExpectClassifierChecker/injectContextReceiverOverload.kt

@@ -9,9 +9,11 @@ expect open class Foo {
 // MODULE: m2-jvm()()(m1-common)
 // FILE: jvm.kt
 
-actual open <!ACTUAL_CLASSIFIER_MUST_HAVE_THE_SAME_MEMBERS_AS_NON_FINAL_EXPECT_CLASSIFIER!>class Foo<!> {
+actual open class Foo {
     actual fun foo() {}
 
+    // Expected: NON_ACTUAL_MEMBER_DECLARED_IN_EXPECT_NON_FINAL_CLASSIFIER_ACTUALIZATION.
+    // But it doesn't work because context receivers are not yet supported in expect actual matcher KT-61447
     context(Int)
-    fun <!ACTUAL_MISSING, NON_ACTUAL_MEMBER_DECLARED_IN_EXPECT_NON_FINAL_CLASSIFIER_ACTUALIZATION!>foo<!>() {} // accidential override can happen with this injected fun. That's why it's prohibited
+    fun <!ACTUAL_MISSING!>foo<!>() {}
 }

compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_finalMember.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER
 // MODULE: m1-common
 // FILE: common.kt

compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_openMember.fir.kt

@@ -0,0 +1,21 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// MODULE: m1-common
+// FILE: common.kt
+
+<!INCOMPATIBLE_MATCHING{JVM}!>expect open class Container {
+    <!INCOMPATIBLE_MATCHING{JVM}!>internal open fun internalFun()<!>
+}<!>
+
+// MODULE: m2-jvm()()(m1-common)
+
+// FILE: foo/Foo.java
+
+package foo;
+
+public class Foo {
+    public void internalFun() {}
+}
+
+// FILE: jvm.kt
+
+actual typealias <!NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS!>Container<!> = foo.Foo

compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_openMember.kt

@@ -3,7 +3,7 @@
 // FILE: common.kt
 
 expect open class Container {
-    internal fun internalFun()
+    internal open fun internalFun()
 }
 
 // MODULE: m2-jvm()()(m1-common)
@@ -13,9 +13,9 @@ expect open class Container {
 package foo;
 
 public class Foo {
-    public final void internalFun() {}
+    public void internalFun() {}
 }
 
 // FILE: jvm.kt
 
-actual typealias <!ACTUAL_CLASSIFIER_MUST_HAVE_THE_SAME_MEMBERS_AS_NON_FINAL_EXPECT_CLASSIFIER!>Container<!> = foo.Foo
+actual typealias <!NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS!>Container<!> = foo.Foo

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -24166,9 +24166,15 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 }
 
                 @Test
-                @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias.kt")
+                @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias_finalMember.kt")
-                public void testMorePermissiveVisibilityOnActualViaTypeAlias() throws Exception {
+                public void testMorePermissiveVisibilityOnActualViaTypeAlias_finalMember() throws Exception {
-                    runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias.kt");
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_finalMember.kt");
+                }
+
+                @Test
+                @TestMetadata("morePermissiveVisibilityOnActualViaTypeAlias_openMember.kt")
+                public void testMorePermissiveVisibilityOnActualViaTypeAlias_openMember() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/headerClass/morePermissiveVisibilityOnActualViaTypeAlias_openMember.kt");
                 }
 
                 @Test

core/compiler.common/src/org/jetbrains/kotlin/resolve/multiplatform/ExpectActualMemberDiff.kt

@@ -10,7 +10,7 @@ data class ExpectActualMemberDiff<out M, out C>(val kind: Kind, val actualMember
     /**
      * Diff kinds that are legal for fake-overrides in final `expect class`, but illegal for non-final `expect class`
      *
-     * Also see: [toDiffKind]
+     * Also see: [toMemberDiffKind]
      */
     enum class Kind(val rawMessage: String) {
         NonPrivateCallableAdded(
@@ -52,37 +52,31 @@ data class ExpectActualMemberDiff<out M, out C>(val kind: Kind, val actualMember
     }
 }
 
-/**
+fun ExpectActualCompatibility.Incompatible<*>.toMemberDiffKind(): ExpectActualMemberDiff.Kind? = when (this) {
- * This function serves a purpose of type-safe documentation. A mapping can be established between [ExpectActualCompatibility.Incompatible]
- * and [ExpectActualMemberDiff.Kind]. This exhaustive when fixates this mapping, ensuring that we won't forget to add new
- * [ExpectActualMemberDiff.Kind] when [ExpectActualCompatibility.Incompatible] is updated.
- */
-@Suppress("unused") // The function is a documentation. That's why it's unused
-private fun ExpectActualCompatibility.Incompatible<*>.toDiffKind(): ExpectActualMemberDiff.Kind? = when (this) {
     ExpectActualCompatibility.Incompatible.CallableKind -> ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
     ExpectActualCompatibility.Incompatible.ParameterCount -> ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
     ExpectActualCompatibility.Incompatible.ParameterShape -> ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
     ExpectActualCompatibility.Incompatible.ParameterTypes -> ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
     ExpectActualCompatibility.Incompatible.ReturnType -> ExpectActualMemberDiff.Kind.ReturnTypeChangedInOverride
     ExpectActualCompatibility.Incompatible.FunctionTypeParameterCount -> ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
-    ExpectActualCompatibility.Incompatible.ClassTypeParameterCount -> null // Not applicable because ExpectActualMemberDiff is about members
+    ExpectActualCompatibility.Incompatible.ClassTypeParameterCount -> error("Not applicable because ExpectActualMemberDiff is about members")
     ExpectActualCompatibility.Incompatible.FunctionTypeParameterUpperBounds -> ExpectActualMemberDiff.Kind.NonPrivateCallableAdded
-    ExpectActualCompatibility.Incompatible.ClassTypeParameterUpperBounds -> null // Not applicable because ExpectActualMemberDiff is about members
+    ExpectActualCompatibility.Incompatible.ClassTypeParameterUpperBounds -> error("Not applicable because ExpectActualMemberDiff is about members")
     ExpectActualCompatibility.Incompatible.ActualFunctionWithDefaultParameters -> null // It's not possible to add default parameters in override
-    ExpectActualCompatibility.Incompatible.ClassKind -> null // Not applicable because ExpectActualMemberDiff is about members
+    ExpectActualCompatibility.Incompatible.ClassKind -> error("Not applicable because ExpectActualMemberDiff is about members")
-    ExpectActualCompatibility.Incompatible.ClassModifiers -> null // Not applicable because ExpectActualMemberDiff is about members
+    ExpectActualCompatibility.Incompatible.ClassModifiers -> error("Not applicable because ExpectActualMemberDiff is about members")
-    is ExpectActualCompatibility.Incompatible.ClassScopes -> null // Not applicable because ExpectActualMemberDiff is about members
+    is ExpectActualCompatibility.Incompatible.ClassScopes -> error("Not applicable because ExpectActualMemberDiff is about members")
-    ExpectActualCompatibility.Incompatible.EnumEntries -> null // Not applicable because ExpectActualMemberDiff is about members
+    ExpectActualCompatibility.Incompatible.EnumEntries -> error("Not applicable because ExpectActualMemberDiff is about members")
-    ExpectActualCompatibility.Incompatible.FunInterfaceModifier -> null // Not applicable because ExpectActualMemberDiff is about members
+    ExpectActualCompatibility.Incompatible.FunInterfaceModifier -> error("Not applicable because ExpectActualMemberDiff is about members")
-    ExpectActualCompatibility.Incompatible.FunctionModifiersDifferent -> null // It's not possible to override with different function modifier
+    ExpectActualCompatibility.Incompatible.FunctionModifiersDifferent -> null // It's not possible to override with different function modifier (suspend)
-    ExpectActualCompatibility.Incompatible.FunctionModifiersNotSubset -> null // It's not possible to override with different function modifier
+    ExpectActualCompatibility.Incompatible.FunctionModifiersNotSubset -> null // It's not possible to override with different function modifier (infix, inline, operator)
     ExpectActualCompatibility.Incompatible.Modality -> ExpectActualMemberDiff.Kind.ModalityChangedInOverride
     ExpectActualCompatibility.Incompatible.ParameterNames -> ExpectActualMemberDiff.Kind.ParameterNameChangedInOverride
     ExpectActualCompatibility.Incompatible.PropertyConstModifier -> null // const fun can't be overridden
     ExpectActualCompatibility.Incompatible.PropertyKind -> ExpectActualMemberDiff.Kind.PropertyKindChangedInOverride
     ExpectActualCompatibility.Incompatible.PropertyLateinitModifier -> ExpectActualMemberDiff.Kind.LateinitChangedInOverride
     ExpectActualCompatibility.Incompatible.PropertySetterVisibility -> ExpectActualMemberDiff.Kind.SetterVisibilityChangedInOverride
-    ExpectActualCompatibility.Incompatible.Supertypes -> null // Not applicable because ExpectActualMemberDiff is about members. But related: ACTUAL_CLASSIFIER_MUST_HAVE_THE_SAME_SUPERTYPES_AS_NON_FINAL_EXPECT_CLASSIFIER
+    ExpectActualCompatibility.Incompatible.Supertypes -> error("Not applicable because ExpectActualMemberDiff is about members")
     ExpectActualCompatibility.Incompatible.TypeParameterNames -> ExpectActualMemberDiff.Kind.TypeParameterNamesChangedInOverride
     ExpectActualCompatibility.Incompatible.TypeParameterReified -> null // inline fun can't be overridden
     ExpectActualCompatibility.Incompatible.TypeParameterVariance -> null // Members are not allowed to have variance