Remove error diagnostic from return in multideclaration

#KT-5100 Fixed

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ControlStructureTypingVisitor.java

@@ -531,7 +531,12 @@ public class ControlStructureTypingVisitor extends ExpressionTypingVisitor {
         }
 
         if (expression.getTargetLabel() == null) {
-            assert parentDeclaration != null;
+            while (parentDeclaration instanceof JetMultiDeclaration) {
+                //TODO: It's hacking fix for KT-5100: Strange "Return is not allowed here" for multi-declaration initializer with elvis expression
+                parentDeclaration = PsiTreeUtil.getParentOfType(parentDeclaration, JetDeclaration.class);
+            }
+
+            assert parentDeclaration != null : "Can't find parent declaration for " + expression.getText();
             DeclarationDescriptor declarationDescriptor = context.trace.get(DECLARATION_TO_DESCRIPTOR, parentDeclaration);
             Pair<FunctionDescriptor, PsiElement> containingFunInfo =
                     BindingContextUtils.getContainingFunctionSkipFunctionLiterals(declarationDescriptor, false);

compiler/testData/codegen/box/multiDecl/returnInElvis.kt

@@ -0,0 +1,22 @@
+data class Z(val p: String, val k: String)
+
+
+fun create(p: Boolean): Z? {
+    return if (p) {
+        Z("O", "K")
+    }
+    else {
+        null;
+    }
+}
+
+fun test(p: Boolean): String {
+    val (a, b) = create(p) ?: return "null"
+    return a + b
+}
+
+fun box(): String {
+    if (test(false) != "null") return "fail 1: ${test(false)}"
+
+    return test(true)
+}

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxCodegenTestGenerated.java

@@ -4633,6 +4633,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("returnInElvis.kt")
+        public void testReturnInElvis() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/multiDecl/returnInElvis.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("SimpleVals.kt")
         public void testSimpleVals() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/box/multiDecl/SimpleVals.kt");