fix complaints from PR review

semantic/if_else_type_mismatch.invalid.java

 class IfElseTypeMismatch {
     public static void main(String[] args) {
-        foo(true)
+        foo(true);
     }
 
     public int foo(boolean b) {

semantic/missing_main.invalid.java

 class MissingMain {
-    int x;
+    public int x;
     public void foo() {}
 }

semantic/namespaces.java

 class Foo {
-    Foo Foo;
+    public Foo Foo;
 
-    Foo Foo(Foo Foo) {
+    public Foo Foo(Foo Foo) {
         Foo.Foo = new Foo();
         return Foo;
     }

semantic/void_field.invalid.java

 class VoidField {
-    void foo;
+    public void foo;
     public static void main(String[] args) {
     }
 }