--- a/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Source.java	Wed Dec 19 11:45:54 2018 +0000
+++ b/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Source.java	Wed Dec 19 14:02:19 2018 -0500
@@ -189,8 +189,7 @@
         SWITCH_MULTIPLE_CASE_LABELS(JDK13, Fragments.FeatureMultipleCaseLabels, DiagKind.PLURAL),
         SWITCH_RULE(JDK13, Fragments.FeatureSwitchRules, DiagKind.PLURAL),
         SWITCH_EXPRESSION(JDK13, Fragments.FeatureSwitchExpressions, DiagKind.PLURAL),
-        RAW_STRING_LITERALS(JDK13, Fragments.FeatureRawStringLiterals, DiagKind.PLURAL),
-        RETURN_TYPE_SUBSTITUTABLE_SAME_TYPE(JDK13);
+        RAW_STRING_LITERALS(JDK13, Fragments.FeatureRawStringLiterals, DiagKind.PLURAL);
 
         enum DiagKind {
             NORMAL,