[IR] Add diagnostics to forbid annotations for MFVC-typed elements

Signed-off-by: Evgeniy.Zhelenskiy <Evgeniy.Zhelenskiy@jetbrains.com>

#KT-1179

core/compiler.common.jvm/src/org/jetbrains/kotlin/JvmFieldApplicabilityProblem.kt

@@ -18,5 +18,5 @@ enum class JvmFieldApplicabilityProblem(val errorMessage: String) {
     NOT_PUBLIC_VAL_WITH_JVMFIELD("JvmField could be applied only if all interface companion properties are 'public final val' with '@JvmField' annotation"),
     TOP_LEVEL_PROPERTY_OF_MULTIFILE_FACADE("JvmField cannot be applied to top level property of a file annotated with ${JVM_MULTIFILE_CLASS_SHORT}"),
     DELEGATE("JvmField cannot be applied to delegated property"),
-    RETURN_TYPE_IS_INLINE_CLASS("JvmField cannot be applied to a property of an inline class type")
+    RETURN_TYPE_IS_VALUE_CLASS("JvmField cannot be applied to a property of a value class type"),
 }

core/descriptors/src/org/jetbrains/kotlin/resolve/inlineClassesUtils.kt

@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.TypeSubstitutor
 import org.jetbrains.kotlin.types.TypeUtils
 import org.jetbrains.kotlin.types.Variance
+import org.jetbrains.kotlin.types.checker.SimpleClassicTypeSystemContext.isNullableType
 
 val JVM_INLINE_ANNOTATION_FQ_NAME = FqName("kotlin.jvm.JvmInline")
 val JVM_INLINE_ANNOTATION_CLASS_ID = ClassId.topLevel(JVM_INLINE_ANNOTATION_FQ_NAME)
@@ -42,6 +43,9 @@ fun KotlinType.unsubstitutedUnderlyingTypes(): List<KotlinType> {
 
 fun KotlinType.isInlineClassType(): Boolean = constructor.declarationDescriptor?.isInlineClass() ?: false
 
+fun KotlinType.needsMfvcFlattening(): Boolean =
+    constructor.declarationDescriptor?.run { isMultiFieldValueClass() && !isNullableType() } == true
+
 fun KotlinType.substitutedUnderlyingType(): KotlinType? =
     unsubstitutedUnderlyingType()?.let { TypeSubstitutor.create(this).substitute(it, Variance.INVARIANT) }