diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
index 97795825f1b..e8b3a7d6988 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.analysis.api.fir.diagnostics
 
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.psi.impl.source.tree.LeafPsiElement
 import org.jetbrains.kotlin.KtPsiSourceElement
 import org.jetbrains.kotlin.diagnostics.KtPsiDiagnostic
diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
index 628557966c2..dc6fe8160f6 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.analysis.api.fir.diagnostics
 
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.psi.impl.source.tree.LeafPsiElement
 import org.jetbrains.kotlin.analysis.api.diagnostics.KtDiagnosticWithPsi
 import org.jetbrains.kotlin.analysis.api.symbols.KtCallableSymbol
@@ -1927,7 +1928,7 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         val containingClassName: Name
     }
 
-    interface CannotInferVisibility : KtFirDiagnostic<KtDeclaration> {
+    interface CannotInferVisibility : KtFirDiagnostic<PsiNameIdentifierOwner> {
         override val diagnosticClass get() = CannotInferVisibility::class
         val callable: KtCallableSymbol
     }
diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
index 1ee83ff95fe..e720780bd97 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.analysis.api.fir.diagnostics
 
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.psi.impl.source.tree.LeafPsiElement
 import org.jetbrains.kotlin.analysis.api.lifetime.KtLifetimeToken
 import org.jetbrains.kotlin.analysis.api.symbols.KtCallableSymbol
@@ -2319,7 +2320,7 @@ internal class CannotInferVisibilityImpl(
     override val callable: KtCallableSymbol,
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,
-) : KtAbstractFirDiagnostic<KtDeclaration>(firDiagnostic, token), KtFirDiagnostic.CannotInferVisibility
+) : KtAbstractFirDiagnostic<PsiNameIdentifierOwner>(firDiagnostic, token), KtFirDiagnostic.CannotInferVisibility
 
 internal class MultipleDefaultsInheritedFromSupertypesImpl(
     override val name: Name,
diff --git a/compiler/fir/analysis-tests/testData/resolve/incorrectSuperCall.kt b/compiler/fir/analysis-tests/testData/resolve/incorrectSuperCall.kt
index 0e9c05726da..6dcae6c07c0 100644
--- a/compiler/fir/analysis-tests/testData/resolve/incorrectSuperCall.kt
+++ b/compiler/fir/analysis-tests/testData/resolve/incorrectSuperCall.kt
@@ -11,7 +11,7 @@ open class B {
     open fun baz() {}
 }
 
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C<!> : A, B() {
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C<!> : A, B() {
     override fun foo() {
         super.foo()
 
diff --git a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
index 57992456ae0..74f2e7bed40 100644
--- a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
+++ b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.checkers.generator.diagnostics
 
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.psi.impl.source.tree.LeafPsiElement
 import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.builtins.functions.FunctionTypeKind
@@ -926,7 +927,7 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<FirCallableSymbol<*>>("overridden")
             parameter<Name>("containingClassName")
         }
-        val CANNOT_INFER_VISIBILITY by error<KtDeclaration>(PositioningStrategy.DECLARATION_NAME) {
+        val CANNOT_INFER_VISIBILITY by error<PsiNameIdentifierOwner>(PositioningStrategy.DECLARATION_NAME) {
             parameter<FirCallableSymbol<*>>("callable")
         }
 
diff --git a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
index 6bf2cb3e1b7..a116e852069 100644
--- a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
+++ b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.analysis.diagnostics
 
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiNameIdentifierOwner
 import com.intellij.psi.impl.source.tree.LeafPsiElement
 import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.builtins.functions.FunctionTypeKind
@@ -518,7 +519,7 @@ object FirErrors {
     val DATA_CLASS_OVERRIDE_DEFAULT_VALUES: KtDiagnosticFactory2<FirCallableSymbol<*>, FirClassSymbol<*>> by error2<KtElement, FirCallableSymbol<*>, FirClassSymbol<*>>(SourceElementPositioningStrategies.DATA_MODIFIER)
     val CANNOT_WEAKEN_ACCESS_PRIVILEGE: KtDiagnosticFactory3<Visibility, FirCallableSymbol<*>, Name> by error3<KtModifierListOwner, Visibility, FirCallableSymbol<*>, Name>(SourceElementPositioningStrategies.VISIBILITY_MODIFIER)
     val CANNOT_CHANGE_ACCESS_PRIVILEGE: KtDiagnosticFactory3<Visibility, FirCallableSymbol<*>, Name> by error3<KtModifierListOwner, Visibility, FirCallableSymbol<*>, Name>(SourceElementPositioningStrategies.VISIBILITY_MODIFIER)
-    val CANNOT_INFER_VISIBILITY: KtDiagnosticFactory1<FirCallableSymbol<*>> by error1<KtDeclaration, FirCallableSymbol<*>>(SourceElementPositioningStrategies.DECLARATION_NAME)
+    val CANNOT_INFER_VISIBILITY: KtDiagnosticFactory1<FirCallableSymbol<*>> by error1<PsiNameIdentifierOwner, FirCallableSymbol<*>>(SourceElementPositioningStrategies.DECLARATION_NAME)
     val MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES: KtDiagnosticFactory3<Name, FirValueParameterSymbol, List<FirCallableSymbol<*>>> by error3<KtElement, Name, FirValueParameterSymbol, List<FirCallableSymbol<*>>>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
     val MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_WHEN_NO_EXPLICIT_OVERRIDE: KtDiagnosticFactory3<Name, FirValueParameterSymbol, List<FirCallableSymbol<*>>> by error3<KtElement, Name, FirValueParameterSymbol, List<FirCallableSymbol<*>>>(SourceElementPositioningStrategies.DECLARATION_NAME)
     val MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_DEPRECATION: KtDiagnosticFactoryForDeprecation3<Name, FirValueParameterSymbol, List<FirCallableSymbol<*>>> by deprecationError3<KtElement, Name, FirValueParameterSymbol, List<FirCallableSymbol<*>>>(ProhibitAllMultipleDefaultsInheritedFromSupertypes, SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt
index 668d1c9f3ca..162a339730a 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt
@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
 import org.jetbrains.kotlin.KtFakeSourceElementKind
 import org.jetbrains.kotlin.KtRealSourceElementKind
+import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.builtins.StandardNames
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
@@ -141,17 +142,31 @@ sealed class FirOverrideChecker(mppKind: MppCheckerKind) : FirAbstractOverrideCh
         // Other kinds of fake overrides may also be incorrect, but not to that extent, so we can
         // check them more granularly. See the relevant comments.
 
-        firTypeScope.processAllProperties {
-            if (it.containingClassLookupTag() == declaration.symbol.toLookupTag() && !it.isSubstitutionOverride) {
+        fun checkMember(it: FirCallableSymbol<*>) {
+            val isFromThis = it.containingClassLookupTag() == declaration.symbol.toLookupTag()
+
+            if (isFromThis && !it.isSubstitutionOverride) {
                 checkMember(it, declaration, reporter, typeCheckerState, firTypeScope, context)
+            } else {
+                val source = it.source?.takeIf { isFromThis } ?: declaration.source
+                it.ensureKnownVisibility(context, reporter, source)
             }
         }
 
-        firTypeScope.processAllFunctions {
-            if (it.containingClassLookupTag() == declaration.symbol.toLookupTag() && !it.isSubstitutionOverride) {
-                checkMember(it, declaration, reporter, typeCheckerState, firTypeScope, context)
-            }
-        }
+        firTypeScope.processAllProperties(::checkMember)
+        firTypeScope.processAllFunctions(::checkMember)
+    }
+
+    /**
+     * Returns `false` if [Visibilities.Unknown].
+     */
+    private fun FirCallableSymbol<*>.ensureKnownVisibility(
+        context: CheckerContext,
+        reporter: DiagnosticReporter,
+        source: KtSourceElement? = this.source,
+    ) = when {
+        visibility != Visibilities.Unknown -> true
+        else -> false.also { reporter.reportOn(source, FirErrors.CANNOT_INFER_VISIBILITY, this, context) }
     }
 
     private fun checkModality(
@@ -178,13 +193,7 @@ sealed class FirOverrideChecker(mppKind: MppCheckerKind) : FirAbstractOverrideCh
         overriddenSymbols: List<FirCallableSymbol<*>>,
         context: CheckerContext
     ) {
-        if (visibility == Visibilities.Unknown) {
-            // MANY_*_NOT_IMPLEMENTED implies CANNOT_INFER_VISIBILITY as per KT-63741
-            val isManyNotImplementedDiagnosticReported = overriddenSymbols.count { !it.isAbstract } != 1
-            val isSimpleToReasonAboutSituation = overriddenSymbols.none { it.isIntersectionOverride }
-            if (!(isManyNotImplementedDiagnosticReported && isSimpleToReasonAboutSituation)) {
-                reporter.reportOn(source, FirErrors.CANNOT_INFER_VISIBILITY, this, context)
-            }
+        if (!ensureKnownVisibility(context, reporter)) {
             return
         }
 
diff --git a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
index 610e50fbc35..72e50a851e1 100644
--- a/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
+++ b/compiler/frontend.common-psi/src/org/jetbrains/kotlin/diagnostics/PositioningStrategies.kt
@@ -22,7 +22,7 @@ import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 import org.jetbrains.kotlin.utils.sure
 
 object PositioningStrategies {
-    open class DeclarationHeader<T : KtDeclaration> : PositioningStrategy<T>() {
+    open class DeclarationHeader<T : PsiElement> : PositioningStrategy<T>() {
         override fun isValid(element: T): Boolean {
             if (element is KtNamedDeclaration &&
                 element !is KtObjectDeclaration &&
@@ -142,8 +142,8 @@ object PositioningStrategies {
     }
 
     @JvmField
-    val DECLARATION_NAME: PositioningStrategy<KtNamedDeclaration> = object : DeclarationHeader<KtNamedDeclaration>() {
-        override fun mark(element: KtNamedDeclaration): List<TextRange> {
+    val DECLARATION_NAME: PositioningStrategy<PsiNameIdentifierOwner> = object : DeclarationHeader<PsiNameIdentifierOwner>() {
+        override fun mark(element: PsiNameIdentifierOwner): List<TextRange> {
             val nameIdentifier = element.nameIdentifier
             if (nameIdentifier != null) {
                 if (element is KtClassOrObject) {
diff --git a/compiler/testData/diagnostics/tests/annotations/rendering/notImplementedMembers.fir.kt b/compiler/testData/diagnostics/tests/annotations/rendering/notImplementedMembers.fir.kt
index 11f6723d79c..9c6bb9582c6 100644
--- a/compiler/testData/diagnostics/tests/annotations/rendering/notImplementedMembers.fir.kt
+++ b/compiler/testData/diagnostics/tests/annotations/rendering/notImplementedMembers.fir.kt
@@ -45,4 +45,4 @@ interface GI : G {
 }
 
 <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED("Class 'AG1'; a")!>class AG1<!>(val a: A, val g: G) : A by a, G by g
-<!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED("Class 'AG2'; a")!>class AG2<!>() : AI, GI
+<!CANNOT_INFER_VISIBILITY("a"), MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED("Class 'AG2'; a")!>class AG2<!>() : AI, GI
diff --git a/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.fir.kt b/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.fir.kt
new file mode 100644
index 00000000000..34887b05dd4
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.fir.kt
@@ -0,0 +1,19 @@
+// !DIAGNOSTICS: -CONFLICTING_JVM_DECLARATIONS
+interface One {
+  public <!REDUNDANT_OPEN_IN_INTERFACE!>open<!> fun foo() : Int
+  private fun boo() = 10
+}
+interface Two {
+  public <!REDUNDANT_OPEN_IN_INTERFACE!>open<!> fun foo() : Int
+}
+
+interface OneImpl : One {
+  public override fun foo() = 1
+}
+interface TwoImpl : Two {
+  public override fun foo() = 2
+}
+
+<!CANNOT_INFER_VISIBILITY, MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class Test1<!>() : TwoImpl, OneImpl {}
+class Test2(a : One) : One by a, Two {}
+<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Test3<!>(a : One, b : Two) : Two by b, One by a {}
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.kt b/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.kt
index 93288159c5b..49639167e4e 100644
--- a/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.kt
+++ b/compiler/testData/diagnostics/tests/delegation/Delegation_MultipleDelegates.kt
@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // !DIAGNOSTICS: -CONFLICTING_JVM_DECLARATIONS
 interface One {
   public <!REDUNDANT_OPEN_IN_INTERFACE!>open<!> fun foo() : Int
diff --git a/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_after.fir.kt b/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_after.fir.kt
index 765581922b7..5083fa9ae87 100644
--- a/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_after.fir.kt
+++ b/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_after.fir.kt
@@ -78,7 +78,7 @@ open class NWEH: NotDeprecated, WarningDeprecated, ErrorDeprecated, HiddenDeprec
 
 class WE2: WE()
 
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class NWE2<!>: WE(), NotDeprecated
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class NWE2<!>: WE(), NotDeprecated
 
 class NWE3: WE(), NotDeprecated {
     override fun f() {
diff --git a/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_before.fir.kt b/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_before.fir.kt
index 44193d7f394..14d9be6623f 100644
--- a/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_before.fir.kt
+++ b/compiler/testData/diagnostics/tests/deprecated/deprecatedInheritance_before.fir.kt
@@ -78,7 +78,7 @@ open class NWEH: NotDeprecated, WarningDeprecated, ErrorDeprecated, HiddenDeprec
 
 class WE2: WE()
 
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class NWE2<!>: WE(), NotDeprecated
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class NWE2<!>: WE(), NotDeprecated
 
 class NWE3: WE(), NotDeprecated {
     override fun f() {
diff --git a/compiler/testData/diagnostics/tests/intersectionWithMultipleDefaultsInJava.fir.kt b/compiler/testData/diagnostics/tests/intersectionWithMultipleDefaultsInJava.fir.kt
new file mode 100644
index 00000000000..6ac12129809
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/intersectionWithMultipleDefaultsInJava.fir.kt
@@ -0,0 +1,34 @@
+// TARGET_BACKEND: JVM
+
+// FILE: IntCollection.java
+interface IntCollection<E> {
+    public boolean add(int key);
+}
+
+// FILE: IntSet.java
+interface IntSet extends IntCollection {
+    public default boolean add(Integer it) { return true; }
+
+    // from the supertype
+    // public boolean add(int key);
+}
+
+// FILE: AbstractCollection.java
+abstract class AbstractCollection<E> {
+    public boolean add(E it) { return true; }
+}
+
+// FILE: AbstractIntCollection.java
+abstract class AbstractIntCollection extends AbstractCollection<Integer> {
+    public boolean add(int it) { return true; }
+
+    // from the supertype
+    // public default boolen add(Integer it) { return true; }
+}
+
+// FILE: AbstractIntSet.java
+public abstract class AbstractIntSet extends AbstractIntCollection implements IntSet {}
+
+// FILE: Main.kt
+
+<!CANNOT_INFER_VISIBILITY!>class KotlinClass<!> : AbstractIntSet()
diff --git a/compiler/testData/diagnostics/tests/intersectionWithMultipleDefaultsInJava.kt b/compiler/testData/diagnostics/tests/intersectionWithMultipleDefaultsInJava.kt
index 17048d1fce7..7c0bd32b2b1 100644
--- a/compiler/testData/diagnostics/tests/intersectionWithMultipleDefaultsInJava.kt
+++ b/compiler/testData/diagnostics/tests/intersectionWithMultipleDefaultsInJava.kt
@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // TARGET_BACKEND: JVM
 
 // FILE: IntCollection.java
diff --git a/compiler/testData/diagnostics/tests/j+k/primitiveOverrides/triangleWithFlexibleTypeAndSubstitution4.fir.kt b/compiler/testData/diagnostics/tests/j+k/primitiveOverrides/triangleWithFlexibleTypeAndSubstitution4.fir.kt
index fffdc059ad7..4e38fb6c5b6 100644
--- a/compiler/testData/diagnostics/tests/j+k/primitiveOverrides/triangleWithFlexibleTypeAndSubstitution4.fir.kt
+++ b/compiler/testData/diagnostics/tests/j+k/primitiveOverrides/triangleWithFlexibleTypeAndSubstitution4.fir.kt
@@ -21,7 +21,7 @@ open class C : A<Int>()
 
 interface D : B<Int>
 
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class E<!> : C(), D
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class E<!> : C(), D
 
 fun main() {
     E().foo(42)
diff --git a/compiler/testData/diagnostics/tests/multiplatform/scopes/manyImplMemberNotImplemented.fir.kt b/compiler/testData/diagnostics/tests/multiplatform/scopes/manyImplMemberNotImplemented.fir.kt
index 03c701e8a50..c8365afb9ee 100644
--- a/compiler/testData/diagnostics/tests/multiplatform/scopes/manyImplMemberNotImplemented.fir.kt
+++ b/compiler/testData/diagnostics/tests/multiplatform/scopes/manyImplMemberNotImplemented.fir.kt
@@ -10,8 +10,8 @@
 expect open class C1()
 expect interface I1
 
-open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_1<!> : C1(), I1
-open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_2<!> : I1, C1()
+open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_1<!> : C1(), I1
+open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Common1_2<!> : I1, C1()
 
 expect open class Expect1_1 : C1, I1
 expect open class Expect1_2 : I1, C1
@@ -37,8 +37,8 @@ actual interface I1 {
     fun f() {}
 }
 
-actual open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_1<!> : C1(), I1
-actual open <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_2<!> : I1, C1()
+actual open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_1<!> : C1(), I1
+actual open <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class Expect1_2<!> : I1, C1()
 
 
 actual abstract class C2 actual constructor() {
diff --git a/compiler/testData/diagnostics/tests/multiplatform/scopes/manyInterfacesMemberNotImplemented.fir.kt b/compiler/testData/diagnostics/tests/multiplatform/scopes/manyInterfacesMemberNotImplemented.fir.kt
index 9a8609119df..78df967ff40 100644
--- a/compiler/testData/diagnostics/tests/multiplatform/scopes/manyInterfacesMemberNotImplemented.fir.kt
+++ b/compiler/testData/diagnostics/tests/multiplatform/scopes/manyInterfacesMemberNotImplemented.fir.kt
@@ -11,9 +11,9 @@
 expect interface S1
 expect interface S2
 
-open <!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class A<!> : S1, S2
+open <!CANNOT_INFER_VISIBILITY, MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class A<!> : S1, S2
 
-class B : A()
+<!CANNOT_INFER_VISIBILITY!>class B<!> : A()
 
 // MODULE: jvm()()(common)
 // TARGET_PLATFORM: JVM
diff --git a/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.fir.kt b/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.fir.kt
new file mode 100644
index 00000000000..ea3be88048a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.fir.kt
@@ -0,0 +1,11 @@
+interface A {
+    fun f(): String = "string"
+}
+
+open class B {
+    open fun f(): CharSequence = "charSequence"
+}
+
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C<!> : B(), A
+
+val obj: A = <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>object<!> : B(), A {}
diff --git a/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.kt b/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.kt
index ebf944e3744..aba4ace8df5 100644
--- a/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.kt
+++ b/compiler/testData/diagnostics/tests/override/FakeOverrideDifferentDeclarationSignatures.kt
@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 interface A {
     fun f(): String = "string"
 }
diff --git a/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.fir.kt b/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.fir.kt
new file mode 100644
index 00000000000..49807f48b4b
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.fir.kt
@@ -0,0 +1,17 @@
+package d
+
+interface A {
+    fun foo() = 1
+}
+
+interface B {
+    fun foo() = 2
+}
+
+open <!CANNOT_INFER_VISIBILITY, MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class C<!> : A, B {}
+
+interface E {
+    fun foo(): Int
+}
+
+<!CANNOT_INFER_VISIBILITY!>class D<!> : C() {}
diff --git a/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.kt b/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.kt
index 6e6bfa47ddc..75d9920c5c9 100644
--- a/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.kt
+++ b/compiler/testData/diagnostics/tests/override/ParentInheritsManyImplementations.kt
@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 package d
 
 interface A {
diff --git a/compiler/testData/diagnostics/tests/override/varImplementedByInheritedVal.fir.kt b/compiler/testData/diagnostics/tests/override/varImplementedByInheritedVal.fir.kt
index 66ae9d7edb4..e8af83216aa 100644
--- a/compiler/testData/diagnostics/tests/override/varImplementedByInheritedVal.fir.kt
+++ b/compiler/testData/diagnostics/tests/override/varImplementedByInheritedVal.fir.kt
@@ -20,9 +20,9 @@ open class CVar {
 
 <!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class C1<!> : IVar, IVarDefault
 <!VAR_IMPLEMENTED_BY_INHERITED_VAL_WARNING!>class C2<!> : CVal(), IVar
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C3<!> : CVal(), IVarDefault
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C4<!> : CVal(), IVar, IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C3<!> : CVal(), IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C4<!> : CVal(), IVar, IVarDefault
 class C5 : CVar(), IVar
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C6<!> : CVar(), IVarDefault
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C7<!> : CVar(), IVar, IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C6<!> : CVar(), IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C7<!> : CVar(), IVar, IVarDefault
 <!VAR_OVERRIDDEN_BY_VAL_BY_DELEGATION!>class C8<!>(ival: IVal) : IVar, IVal by ival
diff --git a/compiler/testData/diagnostics/tests/override/varImplementedByInheritedValError.fir.kt b/compiler/testData/diagnostics/tests/override/varImplementedByInheritedValError.fir.kt
index e92b4c97aee..64092078006 100644
--- a/compiler/testData/diagnostics/tests/override/varImplementedByInheritedValError.fir.kt
+++ b/compiler/testData/diagnostics/tests/override/varImplementedByInheritedValError.fir.kt
@@ -20,9 +20,9 @@ open class CVar {
 
 <!MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class C1<!> : IVar, IVarDefault
 <!VAR_IMPLEMENTED_BY_INHERITED_VAL_ERROR!>class C2<!> : CVal(), IVar
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C3<!> : CVal(), IVarDefault
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C4<!> : CVal(), IVar, IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C3<!> : CVal(), IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C4<!> : CVal(), IVar, IVarDefault
 class C5 : CVar(), IVar
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C6<!> : CVar(), IVarDefault
-<!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C7<!> : CVar(), IVar, IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C6<!> : CVar(), IVarDefault
+<!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class C7<!> : CVar(), IVar, IVarDefault
 <!VAR_OVERRIDDEN_BY_VAL_BY_DELEGATION!>class C8<!>(ival: IVal) : IVar, IVal by ival
diff --git a/compiler/testData/diagnostics/tests/regressions/kt302.fir.kt b/compiler/testData/diagnostics/tests/regressions/kt302.fir.kt
new file mode 100644
index 00000000000..0f32c90ddab
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/regressions/kt302.fir.kt
@@ -0,0 +1,13 @@
+// KT-302 Report an error when inheriting many implementations of the same member
+
+package kt302
+
+interface A {
+    open fun foo() {}
+}
+
+interface B {
+    open fun foo() {}
+}
+
+<!CANNOT_INFER_VISIBILITY, MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED!>class C<!> : A, B {} //should be error here
diff --git a/compiler/testData/diagnostics/tests/regressions/kt302.kt b/compiler/testData/diagnostics/tests/regressions/kt302.kt
index 9d1e0328baa..299fd7fafae 100644
--- a/compiler/testData/diagnostics/tests/regressions/kt302.kt
+++ b/compiler/testData/diagnostics/tests/regressions/kt302.kt
@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // KT-302 Report an error when inheriting many implementations of the same member
 
 package kt302
diff --git a/compiler/testData/diagnostics/testsWithStdLib/purelyImplementedCollection/intersectionOfPrimitiveBasedFunctions.fir.kt b/compiler/testData/diagnostics/testsWithStdLib/purelyImplementedCollection/intersectionOfPrimitiveBasedFunctions.fir.kt
index a883f19e03f..906dbfb0b07 100644
--- a/compiler/testData/diagnostics/testsWithStdLib/purelyImplementedCollection/intersectionOfPrimitiveBasedFunctions.fir.kt
+++ b/compiler/testData/diagnostics/testsWithStdLib/purelyImplementedCollection/intersectionOfPrimitiveBasedFunctions.fir.kt
@@ -14,4 +14,4 @@ interface IS {
     fun replace(key: String, value: String): String? = null
 }
 
-abstract <!MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class ZS<!> : MyMap<String, String>(), IS
+abstract <!CANNOT_INFER_VISIBILITY, MANY_IMPL_MEMBER_NOT_IMPLEMENTED!>class ZS<!> : MyMap<String, String>(), IS