Add test for i18806

tests/run-macros/i18806.check

@@ -0,0 +1 @@
+hi

tests/run-macros/i18806/Macro_1.scala

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+import scala.annotation.{experimental, MacroAnnotation}
+import scala.quoted._
+
+@experimental
+class gen extends MacroAnnotation:
+  def transform(using Quotes)(tree: quotes.reflect.Definition): List[quotes.reflect.Definition] =
+    import quotes.reflect._
+    tree match
+      case ClassDef(name, ctr, parents, self, body) =>
+        val cls = tree.symbol
+        // val meth = cls.methodMember("foo").head
+        // val fooTpe = cls.typeRef.memberType(meth)
+
+        val overrideTpe =  MethodType(Nil)(_ => Nil, _ => defn.StringClass.typeRef)
+
+        val fooOverrideSym = Symbol.newMethod(cls, "foo", overrideTpe, Flags.Override, Symbol.noSymbol)
+
+        val fooDef = DefDef(fooOverrideSym, _ => Some(Literal(StringConstant("hi"))))
+
+        val newClassDef = ClassDef.copy(tree)(name, ctr, parents, self, fooDef :: body)
+        List(newClassDef)
+      case _ =>
+        report.error("Annotation only supports `class`")
+        List(tree)

tests/run-macros/i18806/Test_2.scala

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+import scala.annotation.experimental
+
+class Base:
+  def foo(): Object = ???
+
+@experimental
+@gen
+class Sub extends Base
+// > override def foo(): String = "hi"
+
+@experimental
+@main def Test(): Unit =
+  val sub = new Sub
+  println(sub.foo())

tests/run/i18806.check

@@ -0,0 +1 @@
+hi