Fix J21 nested inner class synthetic params

Author: jaskarth

src/org/jetbrains/java/decompiler/main/rels/NestedClassProcessor.java

@@ -807,7 +807,7 @@ private static String getEnclosingVarField(StructClass cl, MethodWrapper method,
         StructMethodParametersAttribute attr = method.methodStruct.getAttribute(StructGeneralAttribute.ATTRIBUTE_METHOD_PARAMETERS);
 
         List<StructMethodParametersAttribute.Entry> entries = attr.getEntries();
-        if (outerIdx < entries.size() && (entries.get(outerIdx).myAccessFlags & CodeConstants.ACC_MANDATED) == CodeConstants.ACC_MANDATED) {
+        if (outerIdx < entries.size() && (entries.get(outerIdx).myAccessFlags & (CodeConstants.ACC_MANDATED | CodeConstants.ACC_SYNTHETIC)) != 0) {
 
           String name = method.varproc.getVarName(var);
           VarType type = method.varproc.getVarType(var);

test/org/jetbrains/java/decompiler/SingleClassesTest.java

@@ -697,6 +697,7 @@ private void registerDefault() {
     register(JAVA_8, "TestDanglingBoxingCall");
     register(JAVA_21, "TestSwitchOnEnumJ21", "ext/TestEnum2");
     register(JAVA_21, "TestInnerClassesJ21");
+    register(JAVA_21, "TestInnerClasses2J21");
     register(JAVA_8, "TestInnerClassesJ8");
     register(JAVA_8, "TestSwitchInTry");
   }

testData/results/pkg/TestInnerClasses2J21.dec

@@ -0,0 +1,43 @@
+package pkg;
+
+public class TestInnerClasses2J21 {
+   private void test() {
+      new TestInnerClasses2J21.Inner().new Inner2(true, true);// 5
+   }// 6
+
+   private class Inner {
+      private class Inner2 {
+         private Inner2(boolean nonFinal, final boolean finalB) {
+            TestInnerClasses2J21.this.test();// 11
+         }// 12
+      }
+   }
+}
+
+class 'pkg/TestInnerClasses2J21' {
+   method 'test ()V' {
+      c      4
+      d      4
+      12      5
+   }
+}
+
+class 'pkg/TestInnerClasses2J21$Inner$Inner2' {
+   method '<init> (Lpkg/TestInnerClasses2J21$Inner;ZZ)V' {
+      5      10
+      6      10
+      7      10
+      8      10
+      9      10
+      a      10
+      b      11
+   }
+}
+
+Lines mapping:
+5 <-> 5
+6 <-> 6
+11 <-> 11
+12 <-> 12
+Not mapped:
+10

testData/src/java21/pkg/TestInnerClasses2J21.java

@@ -0,0 +1,15 @@
+package pkg;
+
+public class TestInnerClasses2J21 {
+  private void test() {
+    new Inner().new Inner2(true, true);
+  }
+
+  private class Inner {
+    private class Inner2 {
+      private Inner2(boolean nonFinal, final boolean finalB) {
+        TestInnerClasses2J21.this.test();
+      }
+    }
+  }
+}