test mirror is resynthesized when default arguments are added or changed

Author: EugeneFlesselle

compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala

@@ -431,7 +431,7 @@ class TastyLoader(val tastyFile: AbstractFile) extends SymbolLoader {
       moduleRoot.classSymbol.rootTreeOrProvider = unpickler
     checkTastyUUID(tastyFile, tastyBytes)
 
-    // TODO with checkTastyUUID
+    // TODO merge with checkTastyUUID
     val TastyHeader(_, maj, min, exp, _) = new TastyHeaderUnpickler(tastyBytes).readFullHeader()
     classRoot.classSymbol.tastyVersion = TastyVersion(maj, min, exp)
     moduleRoot.classSymbol.tastyVersion = TastyVersion(maj, min, exp)

compiler/src/dotty/tools/dotc/core/Symbols.scala

@@ -405,7 +405,7 @@ object Symbols {
     private var myTree: TreeOrProvider = tpd.EmptyTree
 
     // TODO private and getter/setter
-    var tastyVersion: TastyVersion = TastyVersion.current // overwritten when loading from Tasty
+    var tastyVersion: TastyVersion = TastyVersion.current // overwritten in TastyLoader
 
     /** If this is a top-level class and `-Yretain-trees` (or `-from-tasty`) is set.
       * Returns the TypeDef tree (possibly wrapped inside PackageDefs) for this class, otherwise EmptyTree.

compiler/src/dotty/tools/dotc/transform/SymUtils.scala

@@ -108,7 +108,9 @@ object SymUtils:
 
     def isGenericProduct(using Context): Boolean = whyNotGenericProduct.isEmpty
 
-    def mirrorCanSupportDefaults: Boolean = self.isClass && self.asClass.tastyVersion.gteq(TastyVersion(28, 4, 1)) // TODO? cst
+    /** Is a case class for which mirrors support access to default arguments.
+     */
+    def mirrorSupportsDefaults: Boolean = self.isClass && self.asClass.tastyVersion.gteq(TastyVersion(28, 4, 1)) // TODO? cst somewhere
 
     /** Is this an old style implicit conversion?
      *  @param directOnly            only consider explicitly written methods

compiler/src/dotty/tools/dotc/transform/SyntheticMembers.scala

@@ -671,7 +671,7 @@ class SyntheticMembers(thisPhase: DenotTransformer) {
       addParent(defn.Mirror_ProductClass.typeRef)
       addMethod(nme.fromProduct, MethodType(defn.ProductClass.typeRef :: Nil, monoType.typeRef), cls,
         fromProductBody(_, _, optInfo).ensureConforms(monoType.typeRef))  // t4758.scala or i3381.scala are examples where a cast is needed
-      if cls.mirrorCanSupportDefaults && cls.primaryConstructor.hasDefaultParams then overrideMethod(
+      if cls.mirrorSupportsDefaults && cls.primaryConstructor.hasDefaultParams then overrideMethod(
         nme.defaultArgument, MethodType(defn.IntType :: Nil, defn.AnyType), cls, defaultArgumentBody(_, _, optInfo))
     }
     def makeSumMirror(cls: Symbol, optInfo: Option[MirrorImpl.OfSum]) = {

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

@@ -417,7 +417,7 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
       val elemsLabels = TypeOps.nestedPairs(elemLabels)
 
       val elemHasDefaults = accessors.map(acc =>
-        ConstantType(Constant(cls.mirrorCanSupportDefaults && acc.is(HasDefault))))
+        ConstantType(Constant(cls.mirrorSupportsDefaults && acc.is(HasDefault))))
       val elemsHasDefaults = TypeOps.nestedPairs(elemHasDefaults)
 
       val typeElems = tps.getOrElse(accessors.map(mirroredType.resultType.memberInfo(_).widenExpr))
@@ -476,7 +476,7 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
               // case class `cls` changes. See `sbt-test/source-dependencies/mirror-product`.
               val rec = ctx.compilationUnit.depRecorder
               rec.addClassDependency(cls, DependencyByMemberRef)
-              rec.addUsedName(cls.primaryConstructor) // TODO test when only adding default
+              rec.addUsedName(cls.primaryConstructor)
             makeProductMirror(pre, cls, None)
           else withErrors(i"$cls is not a generic product because ${cls.whyNotGenericProduct}")
       case Left(msg) =>

sbt-test/scala3-compat/defaultArgument-mirrors-3.3/app/Main.scala

@@ -40,7 +40,7 @@ package app {
       summon[OldMirrors.mOldFoo.MirroredElemHasDefaults <:< Tuple] // old mirrors do not have refinment
 
       // OldBar: anon mirror => could implement defaultArgument
-      // AR but should stay consistent with other mirrors of other old case classes
+      // AR but should stay consistent with other mirrors for other old case classes
 
       assert(NewMirrors.mOldBar ne lib.OldBar)
       assert(!foundDefaultArgument(NewMirrors.mOldBar))

sbt-test/source-dependencies/mirror-product/MyProduct.scala

@@ -1 +1,3 @@
 case class MyProduct(x: Int)
+case class WillGetDefault(x: Int)
+case class WillChangeDefault(x: Int = 1)

sbt-test/source-dependencies/mirror-product/Test.scala

@@ -6,5 +6,9 @@ transparent inline def foo[T](using m: Mirror.Of[T]): Int =
     case _: (Int *: EmptyTuple) => 1
     case _: (Int *: String *: EmptyTuple) => 2
 
+def getDefault[T](using m: Mirror.ProductOf[T]): Any = m.defaultArgument(0)
+
 @main def Test =
   assert(foo[MyProduct] == 2)
+  assert(getDefault[WillGetDefault] == 1)
+  assert(getDefault[WillChangeDefault] == 2)

sbt-test/source-dependencies/mirror-product/changes/MyProduct.scala

@@ -1 +1,3 @@
 case class MyProduct(x: Int, y: String)
+case class WillGetDefault(x: Int = 1)
+case class WillChangeDefault(x: Int = 2)