[fixes #3310] Ignore non-static/non-public extension methods

test/transform/resource/before/ExtensionMethodNonStatic.java

@@ -0,0 +1,15 @@
+import lombok.experimental.ExtensionMethod;
+
+@ExtensionMethod({ExtensionMethodNonStatic.Extensions.class})
+class ExtensionMethodNonStatic {
+	public void test() {
+		String s = "test";
+		s.startsWith("");
+	}
+
+	static class Extensions {
+		public boolean startsWith(String s, String prefix) {
+			return s.startsWith(prefix);
+		}
+	}
+}