[FIR] Properly calculate visibilities

`testIntersectionOfPrimitiveBasedFunctions`
is fine, because we deprecate this
already in ^KT-63243.

`CANNOT_INFER_VISIBILITY` is
positioned as `DECLARATION_NAME`,
just in case we decide for
some reason that we do want to
report it along with
`MANY_*_NOT_IMPLEMENTED`. In that
case, we'd get a problem that
their bounds overlap, but not
completely contain one another.

^KT-63741 Fixed
^KT-59400 Fixed

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -2718,6 +2718,13 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.CANNOT_INFER_VISIBILITY) { firDiagnostic ->
+        CannotInferVisibilityImpl(
+            firSymbolBuilder.callableBuilder.buildCallableSymbol(firDiagnostic.a),
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES) { firDiagnostic ->
         MultipleDefaultsInheritedFromSupertypesImpl(
             firDiagnostic.a,

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -1927,6 +1927,11 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         val containingClassName: Name
     }
 
+    interface CannotInferVisibility : KtFirDiagnostic<KtDeclaration> {
+        override val diagnosticClass get() = CannotInferVisibility::class
+        val callable: KtCallableSymbol
+    }
+
     interface MultipleDefaultsInheritedFromSupertypes : KtFirDiagnostic<KtElement> {
         override val diagnosticClass get() = MultipleDefaultsInheritedFromSupertypes::class
         val name: Name

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -2315,6 +2315,12 @@ internal class CannotChangeAccessPrivilegeImpl(
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<KtModifierListOwner>(firDiagnostic, token), KtFirDiagnostic.CannotChangeAccessPrivilege
 
+internal class CannotInferVisibilityImpl(
+    override val callable: KtCallableSymbol,
+    firDiagnostic: KtPsiDiagnostic,
+    token: KtLifetimeToken,
+) : KtAbstractFirDiagnostic<KtDeclaration>(firDiagnostic, token), KtFirDiagnostic.CannotInferVisibility
+
 internal class MultipleDefaultsInheritedFromSupertypesImpl(
     override val name: Name,
     override val valueParameter: KtSymbol,

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithImplicitTypeInsideAnonymousObject.after.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 
 public open override [ResolvedTo(BODY_RESOLVE)] [SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 
@@ -18,11 +18,11 @@ public open [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|F
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|
 
 
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: R|T & Any|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: R|T & Any|
 
 
 

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithImplicitTypeInsideAnonymousObject.before.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverrideFunctionSymbol second/B.foo), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverrideFunctionSymbol second/B.foo), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): <implicit>
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirNamedFunctionSymbol second/B.foo, FirNamedFunctionSymbol second/B.foo]), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirNamedFunctionSymbol second/B.foo, FirNamedFunctionSymbol second/B.foo]), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): <implicit>
 
 public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> T}, baseSymbol=FirNamedFunctionSymbol second/C.foo), SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): <implicit>
 
@@ -14,11 +14,11 @@ public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalcula
 
 public open [ResolvedTo(STATUS)] fun foo([ResolvedTo(STATUS)] x: R|F| = LAZY_EXPRESSION): <implicit> { LAZY_BLOCK }
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverridePropertySymbol second/B.bar), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverridePropertySymbol second/B.bar), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: <implicit>
 
 
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirPropertySymbol second/B.bar, FirPropertySymbol second/B.bar]), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirPropertySymbol second/B.bar, FirPropertySymbol second/B.bar]), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: <implicit>
 
 
 

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithImplicitTypeInsideAnonymousObjectScript.after.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 
 public open override [ResolvedTo(BODY_RESOLVE)] [SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 
@@ -18,11 +18,11 @@ public open [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|F
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|
 
 
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: R|T & Any|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: R|T & Any|
 
 
 

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithImplicitTypeInsideAnonymousObjectScript.before.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverrideFunctionSymbol second/B.foo), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverrideFunctionSymbol second/B.foo), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String|): <implicit>
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirNamedFunctionSymbol second/B.foo, FirNamedFunctionSymbol second/B.foo]), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirNamedFunctionSymbol second/B.foo, FirNamedFunctionSymbol second/B.foo]), IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): <implicit>
 
 public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> T}, baseSymbol=FirNamedFunctionSymbol second/C.foo), SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): <implicit>
 
@@ -14,11 +14,11 @@ public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalcula
 
 public open [ResolvedTo(STATUS)] fun foo([ResolvedTo(STATUS)] x: R|F| = LAZY_EXPRESSION): <implicit> { LAZY_BLOCK }
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverridePropertySymbol second/B.bar), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopySubstitution(substitutor={T -> @R|second/Anno|(str = <strcat>(String(object ), R|second/constant|))  kotlin/String}, baseSymbol=FirIntersectionOverridePropertySymbol second/B.bar), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/B.bar] var bar: <implicit>
 
 
 
-public open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirPropertySymbol second/B.bar, FirPropertySymbol second/B.bar]), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: <implicit>
+public? open override [ResolvedTo(STATUS)] [CallableCopyDeferredReturnTypeCalculationKey=CallableCopyIntersection(mostSpecific=[FirPropertySymbol second/B.bar, FirPropertySymbol second/B.bar]), IntersectionOverrideOriginalKey=second/B.bar, SubstitutedOverrideOriginalKey=second/C.bar] var bar: <implicit>
 
 
 

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithoutImplicitTypeInsideAnonymousObject.after.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 
 public open override [ResolvedTo(BODY_RESOLVE)] [SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithoutImplicitTypeInsideAnonymousObject.before.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
+public? open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
 
-public open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): R|kotlin/Unit|
+public? open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): R|kotlin/Unit|
 
 public open override [ResolvedTo(STATUS)] [SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): R|kotlin/Unit|
 

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithoutImplicitTypeInsideAnonymousObjectScript.after.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
 
-public open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
+public? open override [ResolvedTo(BODY_RESOLVE)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 
 public open override [ResolvedTo(BODY_RESOLVE)] [SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|T|): R|kotlin/Unit|
 

analysis/low-level-api-fir/testData/lazyResolveScopes/intersectionOverrideWithoutImplicitTypeInsideAnonymousObjectScript.before.txt

@@ -1,10 +1,10 @@
-public open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
+public? open override [ResolvedTo(BODY_RESOLVE)] fun foo([ResolvedTo(BODY_RESOLVE)] x: R|kotlin/String|): R|kotlin/Unit| {
     ^foo Q|kotlin/Unit|
 }
 
-public open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
+public? open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/B.foo] fun foo([ResolvedTo(STATUS)] x: R|@R|second/Anno|(str = <strcat>(String(super ), R|second/constant|))  kotlin/String|): R|kotlin/Unit|
 
-public open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): R|kotlin/Unit|
+public? open override [ResolvedTo(STATUS)] [IntersectionOverrideOriginalKey=second/B.foo, SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): R|kotlin/Unit|
 
 public open override [ResolvedTo(STATUS)] [SubstitutedOverrideOriginalKey=second/C.foo] fun foo([ResolvedTo(STATUS)] x: R|T|): R|kotlin/Unit|
 

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosticCompilerTestFE10TestdataTestGenerated.java

@@ -1059,6 +1059,12 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
             runTest("compiler/testData/diagnostics/tests/PackageQualified.kt");
         }
 
+        @Test
+        @TestMetadata("phantomIntersections.kt")
+        public void testPhantomIntersections() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
+        }
+
         @Test
         @TestMetadata("prefixIncReturnType.kt")
         public void testPrefixIncReturnType() throws Exception {
@@ -28954,12 +28960,6 @@ public class DiagnosticCompilerTestFE10TestdataTestGenerated extends AbstractDia
                 runTest("compiler/testData/diagnostics/tests/override/kt2052.kt");
             }
 
-            @Test
-            @TestMetadata("kt2491.kt")
-            public void testKt2491() throws Exception {
-                runTest("compiler/testData/diagnostics/tests/override/kt2491.kt");
-            }
-
             @Test
             @TestMetadata("kt4763.kt")
             public void testKt4763() throws Exception {

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated.java

@@ -1059,6 +1059,12 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
             runTest("compiler/testData/diagnostics/tests/PackageQualified.kt");
         }
 
+        @Test
+        @TestMetadata("phantomIntersections.kt")
+        public void testPhantomIntersections() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
+        }
+
         @Test
         @TestMetadata("prefixIncReturnType.kt")
         public void testPrefixIncReturnType() throws Exception {
@@ -28954,12 +28960,6 @@ public class LLFirPreresolvedReversedDiagnosticCompilerFE10TestDataTestGenerated
                 runTest("compiler/testData/diagnostics/tests/override/kt2052.kt");
             }
 
-            @Test
-            @TestMetadata("kt2491.kt")
-            public void testKt2491() throws Exception {
-                runTest("compiler/testData/diagnostics/tests/override/kt2491.kt");
-            }
-
             @Test
             @TestMetadata("kt4763.kt")
             public void testKt4763() throws Exception {

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

@@ -1059,6 +1059,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
             runTest("compiler/testData/diagnostics/tests/PackageQualified.kt");
         }
 
+        @Test
+        @TestMetadata("phantomIntersections.kt")
+        public void testPhantomIntersections() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
+        }
+
         @Test
         @TestMetadata("prefixIncReturnType.kt")
         public void testPrefixIncReturnType() throws Exception {
@@ -26700,12 +26706,6 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                 runTest("compiler/testData/diagnostics/tests/override/kt2052.kt");
             }
 
-            @Test
-            @TestMetadata("kt2491.kt")
-            public void testKt2491() throws Exception {
-                runTest("compiler/testData/diagnostics/tests/override/kt2491.kt");
-            }
-
             @Test
             @TestMetadata("kt4763.kt")
             public void testKt4763() throws Exception {

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

@@ -1059,6 +1059,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
             runTest("compiler/testData/diagnostics/tests/PackageQualified.kt");
         }
 
+        @Test
+        @TestMetadata("phantomIntersections.kt")
+        public void testPhantomIntersections() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
+        }
+
         @Test
         @TestMetadata("prefixIncReturnType.kt")
         public void testPrefixIncReturnType() throws Exception {
@@ -26706,12 +26712,6 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                 runTest("compiler/testData/diagnostics/tests/override/kt2052.kt");
             }
 
-            @Test
-            @TestMetadata("kt2491.kt")
-            public void testKt2491() throws Exception {
-                runTest("compiler/testData/diagnostics/tests/override/kt2491.kt");
-            }
-
             @Test
             @TestMetadata("kt4763.kt")
             public void testKt4763() throws Exception {

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -926,6 +926,9 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<FirCallableSymbol<*>>("overridden")
             parameter<Name>("containingClassName")
         }
+        val CANNOT_INFER_VISIBILITY by error<KtDeclaration>(PositioningStrategy.DECLARATION_NAME) {
+            parameter<FirCallableSymbol<*>>("callable")
+        }
 
         val MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES by error<KtElement>(PositioningStrategy.DECLARATION_SIGNATURE_OR_DEFAULT) {
             parameter<Name>("name")

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -517,6 +517,7 @@ 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 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)

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirNonSuppressibleErrorNames.kt

@@ -335,6 +335,7 @@ val FIR_NON_SUPPRESSIBLE_ERROR_NAMES: Set<String> = setOf(
     "DATA_CLASS_OVERRIDE_DEFAULT_VALUES",
     "CANNOT_WEAKEN_ACCESS_PRIVILEGE",
     "CANNOT_CHANGE_ACCESS_PRIVILEGE",
+    "CANNOT_INFER_VISIBILITY",
     "MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES",
     "MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_WHEN_NO_EXPLICIT_OVERRIDE",
     "TYPEALIAS_EXPANDS_TO_ARRAY_OF_NOTHINGS",

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt

@@ -25,10 +25,6 @@ import org.jetbrains.kotlin.fir.declarations.CallToPotentiallyHiddenSymbolResult
 import org.jetbrains.kotlin.fir.declarations.utils.*
 import org.jetbrains.kotlin.fir.languageVersionSettings
 import org.jetbrains.kotlin.fir.originalOrSelf
-import org.jetbrains.kotlin.fir.declarations.utils.isFinal
-import org.jetbrains.kotlin.fir.declarations.utils.isOverride
-import org.jetbrains.kotlin.fir.declarations.utils.modality
-import org.jetbrains.kotlin.fir.declarations.utils.visibility
 import org.jetbrains.kotlin.fir.resolve.substitution.substitutorByMap
 import org.jetbrains.kotlin.fir.resolve.toSymbol
 import org.jetbrains.kotlin.fir.scopes.FirTypeScope
@@ -46,7 +42,6 @@ import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.fir.types.typeContext
 import org.jetbrains.kotlin.fir.visibilityChecker
-import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.resolve.deprecation.DeprecationLevelValue
 import org.jetbrains.kotlin.resolve.deprecation.SimpleDeprecationInfo
@@ -183,6 +178,16 @@ 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)
+            }
+            return
+        }
+
         if (overriddenSymbols.isEmpty()) return
         val visibilities = overriddenSymbols.map {
             it to it.visibility

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrorsDefaultMessages.kt

@@ -124,6 +124,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_BE_IMPORTE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_CHANGE_ACCESS_PRIVILEGE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_CHECK_FOR_ERASED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_INFER_PARAMETER_TYPE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_INFER_VISIBILITY
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_OVERRIDE_INVISIBLE_MEMBER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_WEAKEN_ACCESS_PRIVILEGE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CAN_BE_REPLACED_WITH_OPERATOR_ASSIGNMENT
@@ -1652,6 +1653,11 @@ object FirErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             DECLARATION_NAME,
             TO_STRING
         )
+        map.put(
+            CANNOT_INFER_VISIBILITY,
+            "Cannot infer visibility for ''{0}''. Please specify it explicitly",
+            DECLARATION_NAME,
+        )
 
         map.put(
             ABSTRACT_MEMBER_NOT_IMPLEMENTED,

compiler/fir/providers/src/org/jetbrains/kotlin/fir/scopes/impl/FirTypeIntersectionScopeContext.kt

@@ -22,6 +22,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.name.StandardClassIds
 import org.jetbrains.kotlin.utils.addToStdlib.runIf
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.contract
@@ -321,17 +322,52 @@ class FirTypeIntersectionScopeContext(
 
     private fun <D : FirCallableSymbol<*>> chooseIntersectionVisibility(
         extractedOverrides: Collection<MemberWithBaseScope<D>>
-    ): Visibility {
+    ): Visibility = chooseIntersectionVisibilityOrNull(extractedOverrides) ?: Visibilities.Unknown
+
+    private fun <D : FirCallableSymbol<*>> chooseIntersectionVisibilityOrNull(
+        extractedOverrides: Collection<MemberWithBaseScope<D>>
+    ): Visibility? {
+        val overridesWithoutIntersections = extractedOverrides.flatMap { it.flattenIntersectionsRecursively() }
+        val nonSubsumed = overridesWithoutIntersections.nonSubsumed().filterOutDuplicates()
+        val nonAbstract = nonSubsumed.filter {
+            require(it.member.rawStatus is FirResolvedDeclarationStatus) {
+                "We expect that to be true already, but we can't yet call resolvedStatus"
+            }
+            // Kotlin's Cloneable interface contains phantom `protected open fun clone()`.
+            it.member.rawStatus.modality != Modality.ABSTRACT && it.member.callableId != StandardClassIds.Callables.clone
+        }
+        val allAreAbstract = nonAbstract.isEmpty()
+
+        if (allAreAbstract) {
+            return findMaxVisibilityOrNull(nonSubsumed)
+        }
+
+        if (nonAbstract.size >= 2) {
+            return null
+        }
+
+        return nonAbstract.single().member.rawStatus.visibility
+    }
+
+    private fun <D : FirCallableSymbol<*>> List<MemberWithBaseScope<D>>.filterOutDuplicates(): List<MemberWithBaseScope<D>> {
+        val uniqueSymbols = mutableSetOf<FirCallableSymbol<*>>()
+        return filter { uniqueSymbols.add(it.member.fir.unwrapSubstitutionOverrides().symbol) }
+    }
+
+    private fun <D : FirCallableSymbol<*>> findMaxVisibilityOrNull(
+        extractedOverrides: Collection<MemberWithBaseScope<D>>
+    ): Visibility? {
         var maxVisibility: Visibility = Visibilities.Private
+
         for ((override) in extractedOverrides) {
             val visibility = (override.fir as FirMemberDeclaration).visibility
-            // TODO: There is more complex logic at org.jetbrains.kotlin.resolve.OverridingUtil.resolveUnknownVisibilityForMember
+            val compare = Visibilities.compare(visibility, maxVisibility) ?: return null
-            // TODO: and org.jetbrains.kotlin.resolve.OverridingUtil.findMaxVisibility
+
-            val compare = Visibilities.compare(visibility, maxVisibility) ?: return Visibilities.DEFAULT_VISIBILITY
             if (compare > 0) {
                 maxVisibility = visibility
             }
         }
+
         return maxVisibility
     }
 

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/EffectiveVisibilityUtils.kt

@@ -37,6 +37,10 @@ fun Visibility.toEffectiveVisibility(
         }
         Visibilities.Public -> EffectiveVisibility.Public
         Visibilities.Local -> EffectiveVisibility.Local
+        // Unknown visibility should not provoke errors,
+        // because they can naturally appear when intersection
+        // overrides' bases have inconsistent forms.
+        Visibilities.Unknown -> EffectiveVisibility.Unknown
         else -> errorWithAttachment("Unknown visibility: $this") {
             withFirLookupTagEntry("owner", owner)
         }

compiler/testData/diagnostics/tests/j+k/primitiveOverrides/triangleWithFlexibleTypeAndSubstitution4.fir.overrides.txt

@@ -1,5 +1,5 @@
 E:
-  [IntersectionOverride]: public open override fun foo(x: R|kotlin/Int|): R|kotlin/String| from Use site scope of /E [id: 0]
+  [IntersectionOverride]: public? open override fun foo(x: R|kotlin/Int|): R|kotlin/String| from Use site scope of /E [id: 0]
     [SubstitutionOverride(DeclarationSite)]: public open override fun foo(x: R|kotlin/Int!|): R|kotlin/String!| from Use site scope of /C [id: 1]
       [SubstitutionOverride(DeclarationSite)]: public open override fun foo(x: R|kotlin/Int!|): R|kotlin/String!| from Substitution scope for [Java enhancement scope for /A] for type C [id: 1]
         [Enhancement]: public open fun foo(x: R|ft<T & Any, T?>|): R|kotlin/String!| from Java enhancement scope for /A [id: 2]

compiler/testData/diagnostics/tests/override/kt2491.fir.kt

@@ -1,11 +0,0 @@
-interface T {
-    public fun foo()
-}
-
-open class C {
-    protected fun foo() {}
-}
-
-class D : C(), T
-
-val obj: C = object : C(), T {}

compiler/testData/diagnostics/tests/override/kt2491.kt

@@ -1,11 +0,0 @@
-interface T {
-    public fun foo()
-}
-
-open class C {
-    protected fun foo() {}
-}
-
-class <!CANNOT_INFER_VISIBILITY!>D<!> : C(), T
-
-val obj: C = <!CANNOT_INFER_VISIBILITY!>object<!> : C(), T {}

compiler/testData/diagnostics/tests/override/kt2491.txt

@@ -1,26 +0,0 @@
-package
-
-public val obj: C
-
-public open class C {
-    public constructor C()
-    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    protected final fun foo(): kotlin.Unit
-    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}
-
-public final class D : C, T {
-    public constructor D()
-    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public final override /*2*/ /*fake_override*/ fun foo(): kotlin.Unit
-    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
-}
-
-public interface T {
-    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
-    public abstract fun foo(): kotlin.Unit
-    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
-    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
-}

compiler/testData/diagnostics/tests/override/kt4785.fir.kt

@@ -1,3 +1,5 @@
+// ISSUES: KT-2491, KT-4785, KT-63741, KT-59400
+
 interface T {
     fun foo()
 }
@@ -6,6 +8,6 @@ open class C {
     protected fun foo() {}
 }
 
-class E : C(), T
+class <!CANNOT_WEAKEN_ACCESS_PRIVILEGE!>E<!> : C(), T
 
-val z: T = object : C(), T {}
+val z: T = <!CANNOT_WEAKEN_ACCESS_PRIVILEGE!>object<!> : C(), T {}

compiler/testData/diagnostics/tests/override/kt4785.kt

@@ -1,3 +1,5 @@
+// ISSUES: KT-2491, KT-4785, KT-63741, KT-59400
+
 interface T {
     fun foo()
 }

compiler/testData/diagnostics/tests/phantomIntersections.kt

@@ -0,0 +1,14 @@
+// FIR_IDENTICAL
+// ISSUE: KT-63741
+
+interface AreaInstance {
+    fun getExtensionArea(): Int
+}
+
+interface ComponentManager : AreaInstance {
+    override fun getExtensionArea() = 10
+}
+
+interface Project : ComponentManager, AreaInstance
+
+class MockProject : ComponentManager, Project

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

@@ -1059,6 +1059,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
             runTest("compiler/testData/diagnostics/tests/PackageQualified.kt");
         }
 
+        @Test
+        @TestMetadata("phantomIntersections.kt")
+        public void testPhantomIntersections() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/phantomIntersections.kt");
+        }
+
         @Test
         @TestMetadata("prefixIncReturnType.kt")
         public void testPrefixIncReturnType() throws Exception {
@@ -28954,12 +28960,6 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/override/kt2052.kt");
             }
 
-            @Test
-            @TestMetadata("kt2491.kt")
-            public void testKt2491() throws Exception {
-                runTest("compiler/testData/diagnostics/tests/override/kt2491.kt");
-            }
-
             @Test
             @TestMetadata("kt4763.kt")
             public void testKt4763() throws Exception {

core/compiler.common/src/org/jetbrains/kotlin/descriptors/EffectiveVisibility.kt

@@ -14,18 +14,18 @@ import org.jetbrains.kotlin.types.model.TypeConstructorMarker
 sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = false, val privateApi: Boolean = false) {
     override fun toString() = name
 
-    //                    Public
+    //                    Public                                                   Unknown
-    //                /--/   |  \-------------\
+    //                /--/   |  \-------------\                                      /
-    // Protected(Base)       |                 \
+    // Protected(Base)       |                 \                                    /
-    //       |         Protected(Other)        Internal = PackagePrivate
+    //       |         Protected(Other)        Internal = PackagePrivate           /
-    // Protected(Derived) |                   /     \
+    // Protected(Derived) |                   /     \                             /
-    //             |      |                  /    InternalProtected(Base)
+    //             |      |                  /    InternalProtected(Base)        /
-    //       ProtectedBound                 /        \
+    //       ProtectedBound                 /        \                          /
-    //                    \                /       /InternalProtected(Derived)
+    //                    \                /       /InternalProtected(Derived) /
-    //                     \InternalProtectedBound/
+    //                     \InternalProtectedBound/                           /
-    //                              |
+    //                              |                                        /
-    //                        PrivateInFile
+    //                        PrivateInFile                                 /
-    //                              |
+    //                              |--------------------------------------/
     //                        PrivateInClass = Local
 
     // Private class (interface) member
@@ -44,6 +44,17 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
         override fun toVisibility(): Visibility = Visibilities.Local
     }
 
+    // Reflects CANNOT_INFER_VISIBILITY
+    object Unknown : EffectiveVisibility("unknown") {
+        override fun relation(other: EffectiveVisibility, typeCheckerContextProvider: TypeCheckerProviderContext): Permissiveness =
+            if (other == Unknown)
+                Permissiveness.SAME
+            else
+                Permissiveness.UNKNOWN
+
+        override fun toVisibility(): Visibility = Visibilities.Unknown
+    }
+
     // Private with File container
     object PrivateInFile : EffectiveVisibility("private-in-file", privateApi = true) {
         override fun relation(other: EffectiveVisibility, typeCheckerContextProvider: TypeCheckerProviderContext): Permissiveness =
@@ -58,7 +69,11 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
 
     object Public : EffectiveVisibility("public", publicApi = true) {
         override fun relation(other: EffectiveVisibility, typeCheckerContextProvider: TypeCheckerProviderContext): Permissiveness =
-            if (this == other) Permissiveness.SAME else Permissiveness.MORE
+            when (other) {
+                this -> Permissiveness.SAME
+                Unknown -> Permissiveness.UNKNOWN
+                else -> Permissiveness.MORE
+            }
 
         override fun toVisibility(): Visibility = Visibilities.Public
     }
@@ -71,7 +86,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                 Public -> Permissiveness.LESS
                 PrivateInClass, PrivateInFile, Local, InternalProtectedBound, is InternalProtected -> Permissiveness.MORE
                 is InternalOrPackage -> Permissiveness.SAME
-                ProtectedBound, is Protected -> Permissiveness.UNKNOWN
+                ProtectedBound, is Protected, Unknown -> Permissiveness.UNKNOWN
             }
 
         override fun lowerBound(other: EffectiveVisibility, typeCheckerContextProvider: TypeCheckerProviderContext): EffectiveVisibility =
@@ -79,6 +94,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                 Public -> this
                 PrivateInClass, PrivateInFile, Local, InternalProtectedBound, is InternalOrPackage, is InternalProtected -> other
                 is Protected -> InternalProtected(other.containerTypeConstructor)
+                is Unknown -> Local
                 ProtectedBound -> InternalProtectedBound
             }
     }
@@ -113,7 +129,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                     Permissiveness.SAME, Permissiveness.MORE -> Permissiveness.MORE
                     Permissiveness.UNKNOWN, Permissiveness.LESS -> Permissiveness.UNKNOWN
                 }
-                is InternalOrPackage -> Permissiveness.UNKNOWN
+                is InternalOrPackage, is Unknown -> Permissiveness.UNKNOWN
             }
 
         override fun lowerBound(other: EffectiveVisibility, typeCheckerContextProvider: TypeCheckerProviderContext): EffectiveVisibility =
@@ -130,6 +146,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                     else -> InternalProtectedBound
                 }
                 is InternalOrPackage -> InternalProtected(containerTypeConstructor)
+                is Unknown -> Local
             }
 
         override fun toVisibility(): Visibility = Visibilities.Protected
@@ -142,7 +159,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                 Public, is Protected -> Permissiveness.LESS
                 PrivateInClass, PrivateInFile, Local, InternalProtectedBound -> Permissiveness.MORE
                 ProtectedBound -> Permissiveness.SAME
-                is InternalOrPackage, is InternalProtected -> Permissiveness.UNKNOWN
+                is InternalOrPackage, is InternalProtected, is Unknown -> Permissiveness.UNKNOWN
             }
 
         override fun lowerBound(other: EffectiveVisibility, typeCheckerContextProvider: TypeCheckerProviderContext): EffectiveVisibility =
@@ -150,6 +167,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                 Public, is Protected -> this
                 PrivateInClass, PrivateInFile, Local, ProtectedBound, InternalProtectedBound -> other
                 is InternalOrPackage, is InternalProtected -> InternalProtectedBound
+                is Unknown -> Local
             }
 
         override fun toVisibility(): Visibility = Visibilities.Protected
@@ -184,7 +202,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                     Permissiveness.SAME, Permissiveness.LESS -> Permissiveness.LESS
                     Permissiveness.UNKNOWN, Permissiveness.MORE -> Permissiveness.UNKNOWN
                 }
-                ProtectedBound -> Permissiveness.UNKNOWN
+                ProtectedBound, Unknown -> Permissiveness.UNKNOWN
             }
 
         override fun lowerBound(other: EffectiveVisibility, typeCheckerContextProvider: TypeCheckerProviderContext): EffectiveVisibility =
@@ -197,6 +215,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                     Permissiveness.UNKNOWN -> InternalProtectedBound
                 }
                 ProtectedBound -> InternalProtectedBound
+                Unknown -> Local
             }
 
         override fun toVisibility(): Visibility = Visibilities.Private
@@ -209,6 +228,7 @@ sealed class EffectiveVisibility(val name: String, val publicApi: Boolean = fals
                 Public, is Protected, is InternalProtected, ProtectedBound, is InternalOrPackage -> Permissiveness.LESS
                 PrivateInClass, PrivateInFile, Local -> Permissiveness.MORE
                 InternalProtectedBound -> Permissiveness.SAME
+                Unknown -> Permissiveness.UNKNOWN
             }
 
         override fun toVisibility(): Visibility = Visibilities.Private