FirBasedSignatureComposer: build signature even for private classes

FIR2IR assumes that we can build signature for any non-local class.
Later we can drop this assumption.

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/signaturer/FirBasedSignatureComposer.kt

@@ -63,28 +63,28 @@ class FirBasedSignatureComposer(private val mangler: FirMangler) : Fir2IrSignatu
 
     override fun composeSignature(declaration: FirDeclaration): IdSignature? {
         if (declaration is FirAnonymousObject || declaration is FirAnonymousFunction) return null
-        if (declaration is FirMemberDeclaration) {
-            val effectiveVisibility = declaration.effectiveVisibility
-            if (effectiveVisibility == FirEffectiveVisibilityImpl.Local ||
-                effectiveVisibility == FirEffectiveVisibilityImpl.Private
-            ) return null
+        if (declaration is FirMemberDeclaration && declaration.effectiveVisibility == FirEffectiveVisibilityImpl.Local) {
+            return null
         }
         val builder = SignatureBuilder()
         declaration.accept(builder)
         return when {
             declaration is FirRegularClass && declaration.visibility != Visibilities.LOCAL -> {
+                // TODO: private classes are probably not acceptable here too
                 val classId = declaration.classId
                 IdSignature.PublicSignature(
                     classId.packageFqName.asString(), classId.relativeClassName.asString(), builder.hashId, builder.mask
                 )
             }
             declaration is FirTypeAlias -> {
+                if (declaration.visibility == Visibilities.PRIVATE) return null
                 val classId = declaration.symbol.classId
                 IdSignature.PublicSignature(
                     classId.packageFqName.asString(), classId.relativeClassName.asString(), builder.hashId, builder.mask
                 )
             }
             declaration is FirCallableMemberDeclaration<*> -> {
+                if (declaration.visibility == Visibilities.PRIVATE) return null
                 val callableId = declaration.symbol.callableId
                 if (callableId.classId?.isLocal == true) return null
                 IdSignature.PublicSignature(