fix #10247: skip deprecation warnings in synthetic definitions

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -55,6 +55,7 @@ class CompilationTests {
       compileFile("tests/pos-special/kind-projector.scala", defaultOptions.and("-Ykind-projector")),
       compileFile("tests/run/i5606.scala", defaultOptions.and("-Yretain-trees")),
       compileFile("tests/pos-custom-args/i5498-postfixOps.scala", defaultOptions withoutLanguageFeature "postfixOps"),
+      compileFilesInDir("tests/pos-custom-args/deprecation", defaultOptions.and("-deprecation", "-Xfatal-warnings")),
       compileFile("tests/pos-custom-args/i8875.scala", defaultOptions.and("-Xprint:getters")),
       compileFile("tests/pos-custom-args/i9267.scala", defaultOptions.and("-Ystop-after:erasure")),
       compileFile("tests/pos-special/extend-java-enum.scala", defaultOptions.and("-source", "3.0-migration")),

tests/neg-custom-args/deprecation/i10247.scala

@@ -0,0 +1,5 @@
+def usered = Color.Red // error: value Red is deprecated
+
+enum Color {
+  @deprecated("no Red", "0.1") case Red
+}

tests/pos-custom-args/deprecation/i10247.scala

@@ -0,0 +1,20 @@
+// check that deprecation warnings of Red are not caught in its enclosing scope
+enum Color(rgb: Int) {
+
+  @deprecated("stop using Red", "0.1")
+  case Red extends Color(0xff0000)
+
+  case Green extends Color(0x00ff00)
+
+  case Blue  extends Color(0x0000ff)
+
+  final def colorCode: Option[Int] = this match {
+    case Red => None
+    case _   => Some(rgb)
+  }
+
+}
+
+object Color {
+  val deprecatedMembers = Set(Red)
+}