[FIR] Support for FIR_EXPOSED_RECEIVER_TYPE

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

@@ -38,11 +38,26 @@ object FirExposedVisibilityChecker : FirDeclarationChecker<FirMemberDeclaration>
         if (restricting != null) {
             reporter.reportExposure(Error.EXPOSED_PROPERTY_TYPE, declaration.source)
         }
+        checkMemberReceiver(declaration.receiverTypeRef?.coneTypeSafe(), declaration, reporter)
+    }
+
+    private fun checkMemberReceiver(
+        typeRef: ConeClassLikeType?,
+        memberDeclaration: FirCallableMemberDeclaration<*>, reporter: DiagnosticReporter
+    ) {
+        if (typeRef == null) return
+        val receiverParameterType = memberDeclaration.receiverTypeRef?.coneTypeSafe<ConeClassLikeType>()
+        val memberVisibility = memberDeclaration.effectiveVisibility
+        val restricting = receiverParameterType?.leastPermissiveDescriptor(memberDeclaration.session, memberVisibility)
+        if (restricting != null) {
+            reporter.reportExposure(Error.EXPOSED_RECEIVER_TYPE, memberDeclaration.source)
+        }
     }
 
     private enum class Error {
         EXPOSED_TYPEALIAS_EXPANDED_TYPE,
         EXPOSED_PROPERTY_TYPE,
+        EXPOSED_RECEIVER_TYPE,
     }
 
     private fun DiagnosticReporter.reportExposure(
@@ -60,6 +75,11 @@ object FirExposedVisibilityChecker : FirDeclarationChecker<FirMemberDeclaration>
                     report(Errors.FIR_EXPOSED_TYPEALIAS_EXPANDED_TYPE.onSource(it))
                 }
             }
+            Error.EXPOSED_RECEIVER_TYPE -> {
+                source?.let {
+                    report(Errors.FIR_EXPOSED_RECEIVER_TYPE.onSource(it))
+                }
+            }
         }
     }
 }

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -138,6 +138,7 @@ public interface Errors {
     // (FIR) Exposed visibility group
     DiagnosticFactory0<PsiElement> FIR_EXPOSED_TYPEALIAS_EXPANDED_TYPE = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory0<PsiElement> FIR_EXPOSED_PROPERTY_TYPE = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<KtTypeParameter> FIR_EXPOSED_RECEIVER_TYPE = DiagnosticFactory0.create(ERROR);
 
     DiagnosticFactory2<KtExpression, KotlinType, Collection<ClassDescriptor>> INACCESSIBLE_TYPE = DiagnosticFactory2.create(WARNING);
 

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -84,6 +84,7 @@ public class DefaultErrorMessages {
 
         MAP.put(FIR_EXPOSED_TYPEALIAS_EXPANDED_TYPE, "FIR_EXPOSED_TYPEALIAS_EXPANDED_TYPE");
         MAP.put(FIR_EXPOSED_PROPERTY_TYPE, "FIR_EXPOSED_PROPERTY_TYPE");
+        MAP.put(FIR_EXPOSED_RECEIVER_TYPE, "FIR_EXPOSED_RECEIVER_TYPE");
 
         MAP.put(EXTENSION_SHADOWED_BY_MEMBER, "Extension is shadowed by a member: {0}", COMPACT_WITH_MODIFIERS);
         MAP.put(EXTENSION_FUNCTION_SHADOWED_BY_INNER_CLASS_CONSTRUCTOR,