Prohibit protected method calls from inline function

#KT-21178 Fixed

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

@@ -1086,6 +1086,7 @@ public interface Errors {
     DiagnosticFactory0<KtDeclaration> INLINE_PROPERTY_WITH_BACKING_FIELD = DiagnosticFactory0.create(ERROR, DECLARATION_SIGNATURE);
     DiagnosticFactory0<KtAnnotationEntry> NON_INTERNAL_PUBLISHED_API = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory1<PsiElement, CallableDescriptor> PROTECTED_CALL_FROM_PUBLIC_INLINE = DiagnosticFactory1.create(WARNING);
+    DiagnosticFactory1<PsiElement, CallableDescriptor> PROTECTED_CALL_FROM_PUBLIC_INLINE_ERROR = DiagnosticFactory1.create(ERROR);
     DiagnosticFactory2<KtElement, KtExpression, DeclarationDescriptor> INVALID_DEFAULT_FUNCTIONAL_PARAMETER_FOR_INLINE = DiagnosticFactory2.create(ERROR);
     DiagnosticFactory2<KtElement, KtExpression, DeclarationDescriptor> NOT_SUPPORTED_INLINE_PARAMETER_IN_INLINE_PARAMETER_DEFAULT_VALUE = DiagnosticFactory2.create(ERROR);
 

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

@@ -975,6 +975,7 @@ public class DefaultErrorMessages {
         MAP.put(INLINE_PROPERTY_WITH_BACKING_FIELD, "Inline property cannot have backing field");
         MAP.put(NON_INTERNAL_PUBLISHED_API, "@PublishedApi annotation is only applicable for internal declaration");
         MAP.put(PROTECTED_CALL_FROM_PUBLIC_INLINE, "Protected function call from public-API inline function is deprecated", NAME);
+        MAP.put(PROTECTED_CALL_FROM_PUBLIC_INLINE_ERROR, "Protected function call from public-API inline function is prohibited", NAME);
         MAP.put(INVALID_DEFAULT_FUNCTIONAL_PARAMETER_FOR_INLINE, "Invalid default value for inline parameter: ''{0}''. Only lambdas, anonymous functions, and callable references are supported", ELEMENT_TEXT, SHORT_NAMES_IN_TYPES);
         MAP.put(NOT_SUPPORTED_INLINE_PARAMETER_IN_INLINE_PARAMETER_DEFAULT_VALUE, "Usage of inline parameter ''{0}'' in default value for another inline parameter is not supported", ELEMENT_TEXT, SHORT_NAMES_IN_TYPES);
         //Inline non locals

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/checkers/InlineChecker.kt

@@ -21,7 +21,6 @@ import org.jetbrains.kotlin.builtins.isBuiltinFunctionalType
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.contracts.parsing.isFromContractDsl
 import org.jetbrains.kotlin.descriptors.*
-import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.diagnostics.Errors.*
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
@@ -58,10 +57,13 @@ internal class InlineChecker(private val descriptor: FunctionDescriptor) : CallC
 
     private var supportDefaultValueInline by Delegates.notNull<Boolean>()
 
+    private var prohibitProtectedCallFromInline by Delegates.notNull<Boolean>()
+
     override fun check(resolvedCall: ResolvedCall<*>, reportOn: PsiElement, context: CallCheckerContext) {
         val expression = resolvedCall.call.calleeExpression ?: return
 
         supportDefaultValueInline = context.languageVersionSettings.supportsFeature(LanguageFeature.InlineDefaultFunctionalParameters)
+        prohibitProtectedCallFromInline = context.languageVersionSettings.supportsFeature(LanguageFeature.ProhibitProtectedCallFromInline)
 
         //checking that only invoke or inlinable extension called on function parameter
         val targetDescriptor = resolvedCall.resultingDescriptor
@@ -227,7 +229,7 @@ internal class InlineChecker(private val descriptor: FunctionDescriptor) : CallC
         expression: KtElement
     ) {
         if (targetDescriptor.original === descriptor) {
-            context.trace.report(Errors.RECURSION_IN_INLINE.on(expression, expression, descriptor))
+            context.trace.report(RECURSION_IN_INLINE.on(expression, expression, descriptor))
         }
     }
 
@@ -258,7 +260,7 @@ internal class InlineChecker(private val descriptor: FunctionDescriptor) : CallC
         if (isInlineFunPublicOrPublishedApi &&
             !isCalledFunPublicOrPublishedApi &&
             calledDescriptor.visibility !== Visibilities.LOCAL) {
-            context.trace.report(Errors.NON_PUBLIC_CALL_FROM_PUBLIC_INLINE.on(expression, calledDescriptor, descriptor))
+            context.trace.report(NON_PUBLIC_CALL_FROM_PUBLIC_INLINE.on(expression, calledDescriptor, descriptor))
         } else {
             checkPrivateClassMemberAccess(calledDescriptor, expression, context)
         }
@@ -267,7 +269,11 @@ internal class InlineChecker(private val descriptor: FunctionDescriptor) : CallC
             isInlineFunPublicOrPublishedApi &&
             inlineFunEffectiveVisibility.toVisibility() !== Visibilities.PROTECTED &&
             calledFunEffectiveVisibility.toVisibility() === Visibilities.PROTECTED) {
-            context.trace.report(Errors.PROTECTED_CALL_FROM_PUBLIC_INLINE.on(expression, calledDescriptor))
+            if (prohibitProtectedCallFromInline) {
+                context.trace.report(PROTECTED_CALL_FROM_PUBLIC_INLINE_ERROR.on(expression, calledDescriptor))
+            } else {
+                context.trace.report(PROTECTED_CALL_FROM_PUBLIC_INLINE.on(expression, calledDescriptor))
+            }
         }
     }
 
@@ -278,7 +284,7 @@ internal class InlineChecker(private val descriptor: FunctionDescriptor) : CallC
     ) {
         if (!isEffectivelyPrivateApiFunction) {
             if (declarationDescriptor.isInsidePrivateClass) {
-                context.trace.report(Errors.PRIVATE_CLASS_MEMBER_FROM_INLINE.on(expression, declarationDescriptor, descriptor))
+                context.trace.report(PRIVATE_CLASS_MEMBER_FROM_INLINE.on(expression, declarationDescriptor, descriptor))
             }
         }
     }