Don't report incompatibility expect/actual errors on usual overloads

Divide incompatibility on two groups: strong and weak. Strong incompatibility means that if declaration with such incompatibility has no `actual` modifier then it's considered as usual overload and we'll not report any error on it.

 #KT-20540 Fixed
 #KT-20680 Fixed

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

@@ -84,7 +84,7 @@ object ExpectedActualDeclarationChecker : DeclarationChecker {
         val compatibility = findActualForExpected(descriptor, platformModule) ?: return
 
         val shouldReportError =
-                compatibility.isEmpty() ||
+                compatibility.allStrongIncompatibilities() ||
                 Compatible !in compatibility && compatibility.values.flatMapTo(hashSetOf()) { it }.all { actual ->
                     val expectedOnes = findExpectedForActual(actual, descriptor.module)
                     expectedOnes != null && Compatible in expectedOnes.keys
@@ -98,6 +98,9 @@ object ExpectedActualDeclarationChecker : DeclarationChecker {
         }
     }
 
+    fun Map<out Compatibility, Collection<MemberDescriptor>>.allStrongIncompatibilities(): Boolean =
+            this.keys.all { it is Incompatible && it.kind == Compatibility.IncompatibilityKind.STRONG }
+
     private fun findActualForExpected(expected: MemberDescriptor, platformModule: ModuleDescriptor): Map<Compatibility, List<MemberDescriptor>>? {
         return when (expected) {
             is CallableMemberDescriptor -> {
@@ -131,7 +134,7 @@ object ExpectedActualDeclarationChecker : DeclarationChecker {
 
         val hasActualModifier = descriptor.isActual && reportOn.hasActualModifier()
         if (!hasActualModifier) {
-            if (compatibility.isEmpty()) return
+            if (compatibility.allStrongIncompatibilities()) return
 
             if (Compatible in compatibility) {
                 // we suppress error, because annotation classes can only have one constructor and it's a 100% boilerplate
@@ -163,6 +166,7 @@ object ExpectedActualDeclarationChecker : DeclarationChecker {
                 val actualMember = incompatibility.values.singleOrNull()?.singleOrNull()
                 return actualMember != null &&
                        actualMember.isExplicitActualDeclaration() &&
+                       !incompatibility.allStrongIncompatibilities() &&
                        findExpectedForActual(actualMember, expectedMember.module)?.values?.singleOrNull()?.singleOrNull() == expectedMember
             }
 
@@ -293,16 +297,21 @@ object ExpectedActualDeclarationChecker : DeclarationChecker {
     }
 
     sealed class Compatibility {
+        // For IncompatibilityKind.STRONG `actual` declaration is considered as overload and error reports on expected declaration
+        enum class IncompatibilityKind {
+            WEAK, STRONG
+        }
+
         // Note that the reason is used in the diagnostic output, see PlatformIncompatibilityDiagnosticRenderer
-        sealed class Incompatible(val reason: String?) : Compatibility() {
+        sealed class Incompatible(val reason: String?, val kind: IncompatibilityKind = IncompatibilityKind.WEAK) : Compatibility() {
             // Callables
 
             object ParameterShape : Incompatible("parameter shapes are different (extension vs non-extension)")
 
-            object ParameterCount : Incompatible("number of value parameters is different")
+            object ParameterCount : Incompatible("number of value parameters is different", IncompatibilityKind.STRONG)
             object TypeParameterCount : Incompatible("number of type parameters is different")
 
-            object ParameterTypes : Incompatible("parameter types are different")
+            object ParameterTypes : Incompatible("parameter types are different", IncompatibilityKind.STRONG)
             object ReturnType : Incompatible("return type is different")
 
             object ParameterNames : Incompatible("parameter names are different")

compiler/testData/diagnostics/tests/multiplatform/headerClass/actualClassWithDefaultValuesInAnnotationViaTypealias.txt

@@ -42,6 +42,13 @@ public final expect annotation class Foo6 : kotlin.Annotation {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
+public final expect annotation class Foo7 : kotlin.Annotation {
+    public constructor Foo7()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
 
 // -- Module: <m2-jvm> --
 package
@@ -89,5 +96,14 @@ public final actual annotation class Foo5 : kotlin.Annotation {
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
+
+public final actual annotation class Foo6 : kotlin.Annotation {
+    public constructor Foo6(/*0*/ s: kotlin.String = ...)
+    public final val s: kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
 public typealias Foo1 = Bar1
 public typealias Foo4 = Bar2
+public typealias Foo7 = Bar2

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

@@ -9,6 +9,8 @@ expect class Foo3
 expect class Bar1()
 expect class Bar2()
 expect class Bar3()
+expect class Bar4()
+expect class Bar5()
 
 // MODULE: m2-jvm(m1-common)
 
@@ -30,6 +32,14 @@ actual class Foo1(val s: String)
 actual class Foo2(val p: String = "value", <!UNUSED_PARAMETER!>i<!>: Int)
 actual typealias Foo3 = JavaFoo
 
-actual class Bar1<!ACTUAL_WITHOUT_EXPECT!>(val s: String)<!>
-actual class Bar2<!ACTUAL_WITHOUT_EXPECT!>(val p: String = "value", <!UNUSED_PARAMETER!>i<!>: Int)<!>
-<!NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS!>actual typealias Bar3 = JavaBar<!>
+actual class <!NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS!>Bar1<!>(val s: String)
+actual class <!NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS!>Bar2<!>(val p: String = "value", <!UNUSED_PARAMETER!>i<!>: Int)
+actual typealias <!NO_ACTUAL_CLASS_MEMBER_FOR_EXPECTED_CLASS!>Bar3<!> = JavaBar
+actual class Bar4(val s: String) {
+    <!ACTUAL_MISSING!>constructor() : this("")<!>
+}
+
+actual class Bar5 {
+    actual constructor()
+    constructor(s: String)
+}

compiler/testData/diagnostics/tests/multiplatform/headerClass/actualClassWithDifferentConstructors.txt

@@ -22,6 +22,20 @@ public final expect class Bar3 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
+public final expect class Bar4 {
+    public constructor Bar4()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final expect class Bar5 {
+    public constructor Bar5()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
 public final expect class Foo1 {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
@@ -60,6 +74,23 @@ public final actual class Bar2 {
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 }
 
+public final actual class Bar4 {
+    public constructor Bar4()
+    public constructor Bar4(/*0*/ s: kotlin.String)
+    public final val s: kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final actual class Bar5 {
+    public constructor Bar5()
+    public constructor Bar5(/*0*/ s: kotlin.String)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
 public final actual class Foo1 {
     public constructor Foo1(/*0*/ s: kotlin.String)
     public final val s: kotlin.String

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

@@ -0,0 +1,27 @@
+// !LANGUAGE: +MultiPlatformProjects
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// MODULE: m1-common
+// FILE: common.kt
+
+expect fun foo1(x: Int)
+expect fun foo2<!JVM:NO_ACTUAL_FOR_EXPECT!>(x: Int)<!>
+
+expect class NoArgConstructor()
+
+// MODULE: m2-jvm(m1-common)
+
+// FILE: jvm.kt
+
+actual fun foo1(x: Int) {}
+
+fun foo1(x: Int, y: Int) {}
+fun foo1(x: String) {}
+
+fun foo2(x: Int, y: Int) {}
+fun foo2(x: String) {}
+
+actual class NoArgConstructor {
+    actual constructor()
+    actual constructor<!ACTUAL_WITHOUT_EXPECT!>(x: Int)<!>
+    constructor(x: String)
+}

compiler/testData/diagnostics/tests/multiplatform/headerClass/expectDeclarationWithStrongIncompatibilities.txt

@@ -0,0 +1,31 @@
+// -- Module: <m1-common> --
+package
+
+public expect fun foo1(/*0*/ x: kotlin.Int): kotlin.Unit
+public expect fun foo2(/*0*/ x: kotlin.Int): kotlin.Unit
+
+public final expect class NoArgConstructor {
+    public constructor NoArgConstructor()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+
+// -- Module: <m2-jvm> --
+package
+
+public actual fun foo1(/*0*/ x: kotlin.Int): kotlin.Unit
+public fun foo1(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int): kotlin.Unit
+public fun foo1(/*0*/ x: kotlin.String): kotlin.Unit
+public fun foo2(/*0*/ x: kotlin.Int, /*1*/ y: kotlin.Int): kotlin.Unit
+public fun foo2(/*0*/ x: kotlin.String): kotlin.Unit
+
+public final actual class NoArgConstructor {
+    public constructor NoArgConstructor()
+    public constructor NoArgConstructor(/*0*/ x: kotlin.Int)
+    public constructor NoArgConstructor(/*0*/ x: kotlin.String)
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -0,0 +1,23 @@
+// !LANGUAGE: +MultiPlatformProjects
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// MODULE: m1-common
+// FILE: common.kt
+
+expect class Foo1
+expect class Foo2
+
+expect fun foo1(): Int
+expect fun foo2(): Int
+expect fun foo3<!JVM:NO_ACTUAL_FOR_EXPECT!>()<!>: Int
+
+// MODULE: m2-jvm(m1-common)
+
+// FILE: jvm.kt
+
+<!ACTUAL_WITHOUT_EXPECT!>interface<!> Foo1
+actual <!ACTUAL_WITHOUT_EXPECT!>interface<!> Foo2
+
+actual fun foo1(): <!ACTUAL_WITHOUT_EXPECT!>String<!> = ""
+
+fun <!ACTUAL_MISSING!>foo2<!>(): Int = 0
+fun foo3(x: Int): String = ""

compiler/testData/diagnostics/tests/multiplatform/headerClass/expectDeclarationWithWeakIncompatibilities.txt

@@ -0,0 +1,38 @@
+// -- Module: <m1-common> --
+package
+
+public expect fun foo1(): kotlin.Int
+public expect fun foo2(): kotlin.Int
+public expect fun foo3(): kotlin.Int
+
+public final expect class Foo1 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final expect class Foo2 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+
+// -- Module: <m2-jvm> --
+package
+
+public actual fun foo1(): kotlin.String
+public fun foo2(): kotlin.Int
+public fun foo3(/*0*/ x: kotlin.Int): kotlin.String
+
+public interface Foo1 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public actual interface Foo2 {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/multiplatform/topLevelFun/valueParameterModifiers.kt

@@ -11,8 +11,8 @@ expect fun f4(s: () -> String)
 expect inline fun f5(s: () -> String)
 expect inline fun f6(crossinline s: () -> String)
 
-expect fun f7(x: Any)
-expect fun f8(vararg x: Any)
+expect fun f7<!JVM:NO_ACTUAL_FOR_EXPECT!>(x: Any)<!>
+expect fun f8<!JVM:NO_ACTUAL_FOR_EXPECT!>(vararg x: Any)<!>
 
 // MODULE: m2-jvm(m1-common)
 // FILE: jvm.kt

compiler/testData/multiplatform/classScopes/constructorIncorrectSignature/output.txt

@@ -5,6 +5,15 @@ Output:
 -- JVM --
 Exit code: COMPILATION_ERROR
 Output:
+compiler/testData/multiplatform/classScopes/constructorIncorrectSignature/jvm.kt:1:14: error: actual class 'Foo' has no corresponding members for expected class members:
+
+    public constructor Foo(s: String)
+
+    The following declaration is incompatible because parameter types are different:
+        public constructor Foo(s: Array<String>)
+
+actual class Foo {
+             ^
 compiler/testData/multiplatform/classScopes/constructorIncorrectSignature/jvm.kt:2:23: error: actual constructor of 'Foo' has no corresponding expected declaration
 The following declaration is incompatible because parameter types are different:
     public constructor Foo(s: String)

compiler/testData/multiplatform/incompatibleCallables/output.txt

@@ -8,6 +8,36 @@ expect fun f21(c: suspend Unit.() -> Unit)
 -- JVM --
 Exit code: COMPILATION_ERROR
 Output:
+compiler/testData/multiplatform/incompatibleCallables/common.kt:5:14: error: expected function 'f3' has no actual declaration in module
+The following declaration is incompatible because parameter types are different:
+    public actual fun f3(name: Double): Unit
+
+expect fun f3(name: String)
+             ^
+compiler/testData/multiplatform/incompatibleCallables/common.kt:6:24: error: expected function 'f3ext' has no actual declaration in module
+The following declaration is incompatible because parameter types are different:
+    public actual fun Double.f3ext(): Unit
+
+expect fun String.f3ext()
+                       ^
+compiler/testData/multiplatform/incompatibleCallables/common.kt:12:14: error: expected function 'f6' has no actual declaration in module
+The following declaration is incompatible because number of value parameters is different:
+    public actual fun f6(p2: Int): Unit
+
+expect fun f6(p1: String, p2: Int)
+             ^
+compiler/testData/multiplatform/incompatibleCallables/common.kt:32:15: error: expected function 'f21' has no actual declaration in module
+The following declaration is incompatible because parameter types are different:
+    public actual fun f21(c: Unit.() -> Unit): Unit
+
+expect fun f21(c: suspend Unit.() -> Unit)
+              ^
+compiler/testData/multiplatform/incompatibleCallables/common.kt:33:15: error: expected function 'f22' has no actual declaration in module
+The following declaration is incompatible because parameter types are different:
+    public actual fun f22(c: suspend Unit.() -> Unit): Unit
+
+expect fun f22(c: Unit.() -> Unit)
+              ^
 compiler/testData/multiplatform/incompatibleCallables/jvm.kt:1:18: error: actual function 'f1' has no corresponding expected declaration
 The following declaration is incompatible because return type is different:
     public expect fun f1(): Unit

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -14127,6 +14127,18 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("expectDeclarationWithStrongIncompatibilities.kt")
+                public void testExpectDeclarationWithStrongIncompatibilities() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/expectDeclarationWithStrongIncompatibilities.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("expectDeclarationWithWeakIncompatibilities.kt")
+                public void testExpectDeclarationWithWeakIncompatibilities() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/expectDeclarationWithWeakIncompatibilities.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("explicitConstructorDelegation.kt")
                 public void testExplicitConstructorDelegation() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/explicitConstructorDelegation.kt");

compiler/tests/org/jetbrains/kotlin/checkers/javac/DiagnosticsUsingJavacTestGenerated.java

@@ -14127,6 +14127,18 @@ public class DiagnosticsUsingJavacTestGenerated extends AbstractDiagnosticsUsing
                     doTest(fileName);
                 }
 
+                @TestMetadata("expectDeclarationWithStrongIncompatibilities.kt")
+                public void testExpectDeclarationWithStrongIncompatibilities() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/expectDeclarationWithStrongIncompatibilities.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("expectDeclarationWithWeakIncompatibilities.kt")
+                public void testExpectDeclarationWithWeakIncompatibilities() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/expectDeclarationWithWeakIncompatibilities.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("explicitConstructorDelegation.kt")
                 public void testExplicitConstructorDelegation() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/multiplatform/headerClass/explicitConstructorDelegation.kt");