KT-22274 report error/warning on incorrect return target label

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProvider.kt

@@ -70,7 +70,7 @@ class ControlFlowInformationProvider private constructor(
     ) : this(
         declaration,
         trace,
-        ControlFlowProcessor(trace).generatePseudocode(declaration),
+        ControlFlowProcessor(trace, languageVersionSettings).generatePseudocode(declaration),
         languageVersionSettings,
         diagnosticSuppressor
     )

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowProcessor.kt

@@ -30,11 +30,14 @@ import org.jetbrains.kotlin.cfg.pseudocode.PseudocodeImpl
 import org.jetbrains.kotlin.cfg.pseudocode.instructions.eval.AccessTarget
 import org.jetbrains.kotlin.cfg.pseudocode.instructions.eval.InstructionWithValue
 import org.jetbrains.kotlin.cfg.pseudocode.instructions.eval.MagicKind
+import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.contracts.description.InvocationKind
 import org.jetbrains.kotlin.contracts.description.canBeRevisited
 import org.jetbrains.kotlin.contracts.description.isDefinitelyVisited
 import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.descriptors.impl.AnonymousFunctionDescriptor
+import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.diagnostics.Errors.*
 import org.jetbrains.kotlin.lexer.KtToken
 import org.jetbrains.kotlin.lexer.KtTokens
@@ -63,7 +66,10 @@ import java.util.*
 
 typealias DeferredGenerator = (ControlFlowBuilder) -> Unit
 
-class ControlFlowProcessor(private val trace: BindingTrace) {
+class ControlFlowProcessor(
+    private val trace: BindingTrace,
+    private val languageVersionSettings: LanguageVersionSettings?
+) {
 
     private val builder: ControlFlowBuilder = ControlFlowInstructionsGenerator()
 
@@ -927,12 +933,10 @@ class ControlFlowProcessor(private val trace: BindingTrace) {
             val subroutine: KtElement?
             val labelName = expression.getLabelName()
             subroutine = if (labelElement != null && labelName != null) {
-                val labeledElement = trace.get(BindingContext.LABEL_TARGET, labelElement)
-                if (labeledElement != null) {
-                    assert(labeledElement is KtElement)
-                    labeledElement as KtElement?
-                } else {
-                    null
+                trace.get(BindingContext.LABEL_TARGET, labelElement)?.let { labeledElement ->
+                    val labeledKtElement = labeledElement as KtElement
+                    checkReturnLabelTarget(expression, labeledKtElement)
+                    labeledKtElement
                 }
             } else {
                 builder.returnSubroutine
@@ -951,6 +955,17 @@ class ControlFlowProcessor(private val trace: BindingTrace) {
             }
         }
 
+        private fun checkReturnLabelTarget(returnExpression: KtReturnExpression, labeledElement: KtElement) {
+            if (languageVersionSettings == null) return
+            if (labeledElement !is KtFunctionLiteral && labeledElement !is KtNamedFunction) {
+                if (languageVersionSettings.supportsFeature(LanguageFeature.RestrictReturnStatementTarget)) {
+                    trace.report(Errors.NOT_A_FUNCTION_LABEL.on(returnExpression))
+                } else {
+                    trace.report(Errors.NOT_A_FUNCTION_LABEL_WARNING.on(returnExpression))
+                }
+            }
+        }
+
         override fun visitParameter(parameter: KtParameter) {
             builder.declareParameter(parameter)
             val defaultValue = parameter.defaultValue

compiler/frontend/src/org/jetbrains/kotlin/cfg/pseudocode/PseudocodeUtil.java

@@ -89,7 +89,7 @@ public class PseudocodeUtil {
                 return false;
             }
         };
-        return new ControlFlowProcessor(mockTrace).generatePseudocode(declaration);
+        return new ControlFlowProcessor(mockTrace, null).generatePseudocode(declaration);
     }
 
     @Nullable

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

@@ -819,6 +819,9 @@ public interface Errors {
     DiagnosticFactory0<KtExpressionWithLabel> BREAK_OR_CONTINUE_JUMPS_ACROSS_FUNCTION_BOUNDARY = DiagnosticFactory0.create(ERROR);
     DiagnosticFactory1<KtExpressionWithLabel, String> NOT_A_LOOP_LABEL = DiagnosticFactory1.create(ERROR);
 
+    DiagnosticFactory0<KtExpressionWithLabel> NOT_A_FUNCTION_LABEL = DiagnosticFactory0.create(ERROR);
+    DiagnosticFactory0<KtExpressionWithLabel> NOT_A_FUNCTION_LABEL_WARNING = DiagnosticFactory0.create(WARNING);
+
     // Control flow / Data flow
 
     DiagnosticFactory1<KtElement, List<TextRange>> UNREACHABLE_CODE = DiagnosticFactory1.create(

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

@@ -599,6 +599,9 @@ public class DefaultErrorMessages {
         MAP.put(BREAK_OR_CONTINUE_JUMPS_ACROSS_FUNCTION_BOUNDARY, "'break' or 'continue' jumps across a function or a class boundary");
         MAP.put(NOT_A_LOOP_LABEL, "The label ''{0}'' does not denote a loop", STRING);
 
+        MAP.put(NOT_A_FUNCTION_LABEL, "Target label does not denote a function");
+        MAP.put(NOT_A_FUNCTION_LABEL_WARNING, "Target label does not denote a function");
+
         MAP.put(ANONYMOUS_INITIALIZER_IN_INTERFACE, "Anonymous initializers are not allowed in interfaces");
         MAP.put(NULLABLE_SUPERTYPE, "A supertype cannot be nullable");
         MAP.put(DYNAMIC_SUPERTYPE, "A supertype cannot be dynamic");