fix #10247: do not warn deprecated enum cases at declaration

Author: bishabosha

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

@@ -888,8 +888,32 @@ object RefChecks {
    * in either a deprecated member or a scala bridge method, issue a warning.
    */
   private def checkDeprecated(sym: Symbol, pos: SrcPos)(using Context): Unit =
+
+    /** is the owner an enum or its companion and also the owner of sym */
+    def isEnumOwner(owner: Symbol)(using Context) =
+      // pre: sym is an enumcase
+      if owner.isEnumClass then owner.companionClass eq sym.owner
+      else if owner.is(ModuleClass) && owner.companionClass.isEnumClass then owner eq sym.owner
+      else false
+
+    def isDeprecatedOrEnum(owner: Symbol)(using Context) =
+      // pre: sym is an enumcase
+      owner.isDeprecated
+      || isEnumOwner(owner)
+
+    /**Scan the chain of outer declaring scopes from the current context
+     * a deprecation warning will be skipped if one the following holds
+     * for a given declaring scope:
+     * - the symbol associated with the scope is also deprecated.
+     * - if and only if `sym` is an enum case, the scope is either
+     *   a module that declares `sym`, or the companion class of the
+     *   module that declares `sym`.
+     */
+    def skipWarning(using Context) =
+      ctx.owner.ownersIterator.exists(if sym.isEnumCase then isDeprecatedOrEnum else _.isDeprecated)
+
     for annot <- sym.getAnnotation(defn.DeprecatedAnnot) do
-      if !ctx.owner.ownersIterator.exists(_.isDeprecated) then
+      if !skipWarning then
         val msg = annot.argumentConstant(0).map(": " + _.stringValue).getOrElse("")
         val since = annot.argumentConstant(1).map(" since " + _.stringValue).getOrElse("")
         report.deprecationWarning(s"${sym.showLocated} is deprecated${since}${msg}", pos)

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

@@ -32,7 +32,8 @@ class CompilationTests {
       compileFile("tests/pos-special/utf16encoded.scala", explicitUTF16),
       compileFilesInDir("tests/pos-special/sourcepath/outer", defaultOptions.and("-sourcepath", "tests/pos-special/sourcepath")),
       compileFile("tests/pos-special/sourcepath/outer/nested/Test4.scala", defaultOptions.and("-sourcepath", "tests/pos-special/sourcepath")),
-      compileFilesInDir("tests/pos-special/fatal-warnings", defaultOptions.and("-Xfatal-warnings", "-feature")),
+      compileFilesInDir("tests/pos-special/fatal-warnings", defaultOptions.and("-Xfatal-warnings", "-deprecation", "-feature")),
+      compileFile("tests/pos-special/avoid-warn-deprecation.scala", defaultOptions.and("-Xfatal-warnings", "-feature")),
       compileFilesInDir("tests/pos-special/spec-t5545", defaultOptions),
       compileFilesInDir("tests/pos-special/strawman-collections", allowDeepSubtypes),
       compileFilesInDir("tests/pos-special/isInstanceOf", allowDeepSubtypes.and("-Xfatal-warnings")),
@@ -55,7 +56,6 @@ 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

@@ -1,5 +1,26 @@
 def usered = Color.Red // error: value Red is deprecated
 
+object DeprecatedContainer {
+  @deprecated("no foo", "0.1") val foo = 23
+}
+
+enum Day {
+
+  @deprecated("no more Mondays!", "0.1") case Monday
+
+}
+
 enum Color {
+
   @deprecated("no Red", "0.1") case Red
+
+  @deprecated("no Generic", "0.1") case Generic(rgb: Int)
+
+  def useFoo1 = DeprecatedContainer.foo // error // check that only enum cases are avoided
+  def useMonday = Day.Monday // error // check that enum cases are declared in this enum
+
+}
+
+object Color {
+  def useFoo2 = DeprecatedContainer.foo // error // check that only enum cases are avoided
 }