[FIR] Report warnings for inconsistent visibilities of accessors

K1 didn't report diagnostics for accessors
of intersection overrides, so this change
prevents a BC.

^KT-66046 Fixed

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

@@ -657,6 +657,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
       runTest("compiler/testData/diagnostics/tests/intersectedVisibilitiesForNonAbstractPropertyAccessors.kt");
     }
 
+    @Test
+    @TestMetadata("intersectedVisibilitiesPropertyAccessorsAdditionalWarnigns.kt")
+    public void testIntersectedVisibilitiesPropertyAccessorsAdditionalWarnigns() {
+      runTest("compiler/testData/diagnostics/tests/intersectedVisibilitiesPropertyAccessorsAdditionalWarnigns.kt");
+    }
+
     @Test
     @TestMetadata("intersectionWithMultipleDefaultsInJava.kt")
     public void testIntersectionWithMultipleDefaultsInJava() {

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

@@ -657,6 +657,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
       runTest("compiler/testData/diagnostics/tests/intersectedVisibilitiesForNonAbstractPropertyAccessors.kt");
     }
 
+    @Test
+    @TestMetadata("intersectedVisibilitiesPropertyAccessorsAdditionalWarnigns.kt")
+    public void testIntersectedVisibilitiesPropertyAccessorsAdditionalWarnigns() {
+      runTest("compiler/testData/diagnostics/tests/intersectedVisibilitiesPropertyAccessorsAdditionalWarnigns.kt");
+    }
+
     @Test
     @TestMetadata("intersectionWithMultipleDefaultsInJava.kt")
     public void testIntersectionWithMultipleDefaultsInJava() {

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

@@ -924,14 +924,27 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<FirCallableSymbol<*>>("overridden")
             parameter<Name>("containingClassName")
         }
+        val CANNOT_WEAKEN_ACCESS_PRIVILEGE_WARNING by warning<KtModifierListOwner>(PositioningStrategy.VISIBILITY_MODIFIER) {
+            parameter<Visibility>("overridingVisibility")
+            parameter<FirCallableSymbol<*>>("overridden")
+            parameter<Name>("containingClassName")
+        }
         val CANNOT_CHANGE_ACCESS_PRIVILEGE by error<KtModifierListOwner>(PositioningStrategy.VISIBILITY_MODIFIER) {
             parameter<Visibility>("overridingVisibility")
             parameter<FirCallableSymbol<*>>("overridden")
             parameter<Name>("containingClassName")
         }
+        val CANNOT_CHANGE_ACCESS_PRIVILEGE_WARNING by warning<KtModifierListOwner>(PositioningStrategy.VISIBILITY_MODIFIER) {
+            parameter<Visibility>("overridingVisibility")
+            parameter<FirCallableSymbol<*>>("overridden")
+            parameter<Name>("containingClassName")
+        }
         val CANNOT_INFER_VISIBILITY by error<KtDeclaration>(PositioningStrategy.DECLARATION_NAME) {
             parameter<FirCallableSymbol<*>>("callable")
         }
+        val CANNOT_INFER_VISIBILITY_WARNING by warning<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

@@ -518,8 +518,11 @@ object FirErrors {
     val DATA_CLASS_OVERRIDE_CONFLICT: KtDiagnosticFactory2<FirCallableSymbol<*>, FirCallableSymbol<*>> by error2<KtClassOrObject, FirCallableSymbol<*>, FirCallableSymbol<*>>(SourceElementPositioningStrategies.DATA_MODIFIER)
     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_WEAKEN_ACCESS_PRIVILEGE_WARNING: KtDiagnosticFactory3<Visibility, FirCallableSymbol<*>, Name> by warning3<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_CHANGE_ACCESS_PRIVILEGE_WARNING: KtDiagnosticFactory3<Visibility, FirCallableSymbol<*>, Name> by warning3<KtModifierListOwner, Visibility, FirCallableSymbol<*>, Name>(SourceElementPositioningStrategies.VISIBILITY_MODIFIER)
     val CANNOT_INFER_VISIBILITY: KtDiagnosticFactory1<FirCallableSymbol<*>> by error1<KtDeclaration, FirCallableSymbol<*>>(SourceElementPositioningStrategies.DECLARATION_NAME)
+    val CANNOT_INFER_VISIBILITY_WARNING: KtDiagnosticFactory1<FirCallableSymbol<*>> by warning1<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/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirOverrideChecker.kt

@@ -166,9 +166,27 @@ sealed class FirOverrideChecker(mppKind: MppCheckerKind) : FirAbstractOverrideCh
         source: KtSourceElement? = this.source,
     ) = when {
         visibility != Visibilities.Unknown -> true
-        else -> false.also { reporter.reportOn(source, FirErrors.CANNOT_INFER_VISIBILITY, this, context) }
+        else -> false.also { reporter.reportOn(source, chooseCannotInferVisibilityFor(this), this, context) }
     }
 
+    private fun chooseCannotInferVisibilityFor(symbol: FirCallableSymbol<*>) = when {
+        !symbol.wouldMissDiagnosticInK1 -> FirErrors.CANNOT_INFER_VISIBILITY
+        else -> FirErrors.CANNOT_INFER_VISIBILITY_WARNING
+    }
+
+    private fun chooseCannotChangeAccessPrivilegeFor(symbol: FirCallableSymbol<*>) = when {
+        !symbol.wouldMissDiagnosticInK1 -> FirErrors.CANNOT_CHANGE_ACCESS_PRIVILEGE
+        else -> FirErrors.CANNOT_CHANGE_ACCESS_PRIVILEGE_WARNING
+    }
+
+    private fun chooseCannotWeakenAccessPrivilegeFor(symbol: FirCallableSymbol<*>) = when {
+        !symbol.wouldMissDiagnosticInK1 -> FirErrors.CANNOT_WEAKEN_ACCESS_PRIVILEGE
+        else -> FirErrors.CANNOT_WEAKEN_ACCESS_PRIVILEGE_WARNING
+    }
+
+    private val FirCallableSymbol<*>.wouldMissDiagnosticInK1 get() =
+        this is FirPropertyAccessorSymbol && propertySymbol.isIntersectionOverride
+
     private fun checkModality(
         overriddenSymbols: List<FirCallableSymbol<*>>,
     ): FirCallableSymbol<*>? {
@@ -494,7 +512,7 @@ sealed class FirOverrideChecker(mppKind: MppCheckerKind) : FirAbstractOverrideCh
         val containingClass = overridden.containingClassLookupTag() ?: return
         reportOn(
             overriding.source,
-            FirErrors.CANNOT_WEAKEN_ACCESS_PRIVILEGE,
+            chooseCannotWeakenAccessPrivilegeFor(overriding),
             overriding.visibility,
             overridden,
             containingClass.name,
@@ -510,7 +528,7 @@ sealed class FirOverrideChecker(mppKind: MppCheckerKind) : FirAbstractOverrideCh
         val containingClass = overridden.containingClassLookupTag() ?: return
         reportOn(
             overriding.source,
-            FirErrors.CANNOT_CHANGE_ACCESS_PRIVILEGE,
+            chooseCannotChangeAccessPrivilegeFor(overriding),
             overriding.visibility,
             overridden,
             containingClass.name,

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

@@ -122,11 +122,14 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CALLABLE_REFERENC
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_ALL_UNDER_IMPORT_FROM_SINGLETON
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_BE_IMPORTED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_CHANGE_ACCESS_PRIVILEGE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CANNOT_CHANGE_ACCESS_PRIVILEGE_WARNING
 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_INFER_VISIBILITY_WARNING
 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.CANNOT_WEAKEN_ACCESS_PRIVILEGE_WARNING
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CAN_BE_REPLACED_WITH_OPERATOR_ASSIGNMENT
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CAN_BE_VAL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.CAPTURED_MEMBER_VAL_INITIALIZATION
@@ -1655,6 +1658,13 @@ object FirErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             DECLARATION_NAME,
             TO_STRING
         )
+        map.put(
+            CANNOT_WEAKEN_ACCESS_PRIVILEGE_WARNING,
+            "Cannot weaken access privilege {0} for ''{1}'' in ''{2}''. This will be prohibited in the future.",
+            VISIBILITY,
+            DECLARATION_NAME,
+            TO_STRING
+        )
         map.put(
             CANNOT_CHANGE_ACCESS_PRIVILEGE,
             "Cannot change access privilege {0} for ''{1}'' in ''{2}''.",
@@ -1662,9 +1672,21 @@ object FirErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             DECLARATION_NAME,
             TO_STRING
         )
+        map.put(
+            CANNOT_CHANGE_ACCESS_PRIVILEGE_WARNING,
+            "Cannot change access privilege {0} for ''{1}'' in ''{2}''. This will be prohibited in the future.",
+            VISIBILITY,
+            DECLARATION_NAME,
+            TO_STRING
+        )
         map.put(
             CANNOT_INFER_VISIBILITY,
-            "Cannot infer visibility for ''{0}''. Please specify it explicitly",
+            "Cannot infer visibility for ''{0}''. Please specify it explicitly.",
+            DECLARATION_NAME,
+        )
+        map.put(
+            CANNOT_INFER_VISIBILITY_WARNING,
+            "Cannot infer visibility for ''{0}''. Please specify it explicitly. This will be prohibited in the future.",
             DECLARATION_NAME,
         )