Java2Swift: Drop the "as(superclass)" function when generating classes

We don't need this function when generating classes, because we'll already
get the subtype conversion for free.

Author: DougGregor

Sources/JavaKitMacros/JavaClassMacro.swift

@@ -125,13 +125,15 @@ extension JavaClassMacro: MemberMacro {
       """
     )
 
-    members.append("""
-      /// Casting to ``\(raw: superclass)`` will never be nil because ``\(raw: swiftName)`` extends it.
-      public func `as`(_: \(raw: superclass).Type) -> \(raw: superclass) {
-          return \(raw: superclass)(javaHolder: javaHolder)
-      }
-      """
-    )
+    if !isSwiftClass {
+      members.append("""
+        /// Casting to ``\(raw: superclass)`` will never be nil because ``\(raw: swiftName)`` extends it.
+        public func `as`(_: \(raw: superclass).Type) -> \(raw: superclass) {
+            return \(raw: superclass)(javaHolder: javaHolder)
+        }
+        """
+      )
+    }
 
     return members
   }

Tests/JavaKitMacroTests/JavaClassMacroTests.swift

@@ -193,11 +193,6 @@ class JavaKitMacroTests: XCTestCase {
             public required init(javaHolder: JavaObjectHolder) {
                 super.init(javaHolder: javaHolder)
             }
-
-            /// Casting to ``OtherJavaType`` will never be nil because ``HelloWorld`` extends it.
-            public func `as`(_: OtherJavaType.Type) -> OtherJavaType {
-                return OtherJavaType(javaHolder: javaHolder)
-            }
         }
       """,
       macros: Self.javaKitMacros
@@ -241,11 +236,6 @@ class JavaKitMacroTests: XCTestCase {
             public required init(javaHolder: JavaObjectHolder) {
                 self.javaHolder = javaHolder
             }
-
-            /// Casting to ``JavaObject`` will never be nil because ``JavaObject`` extends it.
-            public func `as`(_: JavaObject.Type) -> JavaObject {
-                return JavaObject(javaHolder: javaHolder)
-            }
         }
       """,
       macros: Self.javaKitMacros