Merge pull request #14124 from dotty-staging/add-reflect-ClassDef-apply

Add reflect `ClassDef.apply` and `Symbol.newClass`

Author: nicolasstucki

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

@@ -575,7 +575,7 @@ object Symbols {
       def complete(denot: SymDenotation)(using Context): Unit = {
         val cls = denot.asClass.classSymbol
         val decls = newScope
-        denot.info = ClassInfo(owner.thisType, cls, parentTypes.map(_.dealias), decls)
+        denot.info = ClassInfo(owner.thisType, cls, parentTypes.map(_.dealias), decls, selfInfo)
       }
     }
     newClassSymbol(owner, name, flags, completer, privateWithin, coord, assocFile)

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -230,6 +230,11 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
     end ClassDefTypeTest
 
     object ClassDef extends ClassDefModule:
+      def apply(cls: Symbol, parents: List[Tree], body: List[Statement]): ClassDef =
+        val untpdCtr = untpd.DefDef(nme.CONSTRUCTOR, Nil, tpd.TypeTree(dotc.core.Symbols.defn.UnitClass.typeRef), tpd.EmptyTree)
+        val ctr = ctx.typeAssigner.assignType(untpdCtr, cls.primaryConstructor)
+        tpd.ClassDefWithParents(cls.asClass, ctr, parents, body)
+
       def copy(original: Tree)(name: String, constr: DefDef, parents: List[Tree], selfOpt: Option[ValDef], body: List[Statement]): ClassDef = {
         val dotc.ast.Trees.TypeDef(_, originalImpl: tpd.Template) = original
         tpd.cpy.TypeDef(original)(name.toTypeName, tpd.cpy.Template(originalImpl)(constr, parents, derived = Nil, selfOpt.getOrElse(tpd.EmptyValDef), body))
@@ -262,6 +267,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
 
     object DefDef extends DefDefModule:
       def apply(symbol: Symbol, rhsFn: List[List[Tree]] => Option[Term]): DefDef =
+        assert(symbol.isTerm, s"expected a term symbol but received $symbol")
         withDefaultPos(tpd.DefDef(symbol.asTerm, prefss =>
           xCheckMacroedOwners(xCheckMacroValidExpr(rhsFn(prefss)), symbol).getOrElse(tpd.EmptyTree)
         ))
@@ -1049,6 +1055,9 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
     object TypeTree extends TypeTreeModule:
       def of[T <: AnyKind](using tp: scala.quoted.Type[T]): TypeTree =
         tp.asInstanceOf[TypeImpl].typeTree
+      def ref(sym: Symbol): TypeTree =
+        assert(sym.isType, "Expected a type symbol, but got " + sym)
+        tpd.ref(sym)
     end TypeTree
 
     given TypeTreeMethods: TypeTreeMethods with
@@ -1806,7 +1815,7 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         (x.prefix, x.name.toString)
     end TermRef
 
-    type TypeRef = dotc.core.Types.NamedType
+    type TypeRef = dotc.core.Types.TypeRef
 
     object TypeRefTypeTest extends TypeTest[TypeRepr, TypeRef]:
       def unapply(x: TypeRepr): Option[TypeRef & x.type] = x match
@@ -2456,6 +2465,20 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
       def requiredModule(path: String): Symbol = dotc.core.Symbols.requiredModule(path)
       def requiredMethod(path: String): Symbol = dotc.core.Symbols.requiredMethod(path)
       def classSymbol(fullName: String): Symbol = dotc.core.Symbols.requiredClass(fullName)
+
+      def newClass(owner: Symbol, name: String, parents: List[TypeRepr], decls: Symbol => List[Symbol], selfType: Option[TypeRepr]): Symbol =
+        assert(parents.nonEmpty && !parents.head.typeSymbol.is(dotc.core.Flags.Trait), "First parent must be a class")
+        val cls = dotc.core.Symbols.newNormalizedClassSymbol(
+          owner,
+          name.toTypeName,
+          dotc.core.Flags.EmptyFlags,
+          parents,
+          selfType.getOrElse(Types.NoType),
+          dotc.core.Symbols.NoSymbol)
+        cls.enter(dotc.core.Symbols.newConstructor(cls, dotc.core.Flags.Synthetic, Nil, Nil))
+        for sym <- decls(cls) do cls.enter(sym)
+        cls
+
       def newMethod(owner: Symbol, name: String, tpe: TypeRepr): Symbol =
         newMethod(owner, name, tpe, Flags.EmptyFlags, noSymbol)
       def newMethod(owner: Symbol, name: String, tpe: TypeRepr, flags: Flags, privateWithin: Symbol): Symbol =
@@ -2624,6 +2647,8 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
         def companionClass: Symbol = self.denot.companionClass
         def companionModule: Symbol = self.denot.companionModule
         def children: List[Symbol] = self.denot.children
+        def typeRef: TypeRef = self.denot.typeRef
+        def termRef: TermRef = self.denot.termRef
 
         def show(using printer: Printer[Symbol]): String = printer.show(self)
 

library/src/scala/quoted/Quotes.scala

@@ -460,6 +460,15 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
 
     /** Methods of the module object `val ClassDef` */
     trait ClassDefModule { this: ClassDef.type =>
+      /** Create a class definition tree
+       *
+       *  @param cls The class symbol. A new class symbol can be created using `Symbol.newClass`.
+       *  @param parents The parents trees class. The trees must align with the parent types of `cls`.
+       *                 Parents can be `TypeTree`s if they don't have term parameter,
+       *                 otherwise the can be `Term` containing the `New` applied to the parameters of the extended class.
+       *  @param body List of members of the class. The members must align with the members of `cls`.
+       */
+      @experimental def apply(cls: Symbol, parents: List[Tree /* Term | TypeTree */], body: List[Statement]): ClassDef
       def copy(original: Tree)(name: String, constr: DefDef, parents: List[Tree /* Term | TypeTree */], selfOpt: Option[ValDef], body: List[Statement]): ClassDef
       def unapply(cdef: ClassDef): (String, DefDef, List[Tree /* Term | TypeTree */], Option[ValDef], List[Statement])
     }
@@ -1719,6 +1728,13 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
     trait TypeTreeModule { this: TypeTree.type =>
       /** Returns the tree of type or kind (TypeTree) of T */
       def of[T <: AnyKind](using Type[T]): TypeTree
+
+      /** Returns a type tree reference to the symbol
+       *
+       *  @param sym  The type symbol for which we are creating a type tree reference.
+       */
+      @experimental
+      def ref(typeSymbol: Symbol): TypeTree
     }
 
     /** Makes extension methods on `TypeTree` available without any imports */
@@ -2571,6 +2587,11 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
         def typeSymbol: Symbol
         def termSymbol: Symbol
         def isSingleton: Boolean
+
+       /** The type of `member` as seen from prefix `self`.
+        *
+        *  Also see `typeRef` and `termRef`
+        */
         def memberType(member: Symbol): TypeRepr
 
         /** The base classes of this type with the class itself as first element. */
@@ -3578,19 +3599,73 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
       /** The class Symbol of a global class definition */
       def classSymbol(fullName: String): Symbol
 
+      /** Generates a new class symbol for a class with a parameterless constructor.
+       *
+       *  Example usage:
+       *  ```
+       *  val name: String = "myClass"
+       *  val parents = List(TypeTree.of[Object], TypeTree.of[Foo])
+       *  def decls(cls: Symbol): List[Symbol] =
+       *    List(Symbol.newMethod(cls, "foo", MethodType(Nil)(_ => Nil, _ => TypeRepr.of[Unit])))
+       *
+       *  val cls = Symbol.newClass(Symbol.spliceOwner, name, parents = parents.map(_.tpe), decls, selfInfo = None)
+       *  val fooSym = cls.declaredMethod("foo").head
+       *
+       *  val fooDef = DefDef(fooSym, argss => Some('{println(s"Calling foo")}.asTerm))
+       *  val clsDef = ClassDef(cls, parents, body = List(fooDef))
+       *  val newCls = Typed(Apply(Select(New(TypeIdent(cls)), cls.primaryConstructor), Nil), TypeTree.of[Foo])
+       *
+       *  Block(List(clsDef), newCls).asExprOf[Foo]
+       *  ```
+       *  constructs the equivalent to
+       *   ```
+       *  '{
+       *    class myClass() extends Object with Foo {
+       *      def foo(): Unit = println("Calling foo")
+       *    }
+       *    new myClass(): Foo
+       *  }
+       *  ```
+       *
+       *  @param parent The owner of the class
+       *  @param name The name of the class
+       *  @param parents The parent classes of the class. The first parent must not be a trait.
+       *  @param decls The member declarations of the class provided the symbol of this class
+       *  @param selfType The self type of the class if it has one
+       *
+       *  This symbol starts without an accompanying definition.
+       *  It is the meta-programmer's responsibility to provide exactly one corresponding definition by passing
+       *  this symbol to the ClassDef constructor.
+       *
+       *  @note As a macro can only splice code into the point at which it is expanded, all generated symbols must be
+       *        direct or indirect children of the reflection context's owner.
+       */
+      @experimental def newClass(parent: Symbol, name: String, parents: List[TypeRepr], decls: Symbol => List[Symbol], selfType: Option[TypeRepr]): Symbol
+
       /** Generates a new method symbol with the given parent, name and type.
-      *
-      *  This symbol starts without an accompanying definition.
-      *  It is the meta-programmer's responsibility to provide exactly one corresponding definition by passing
-      *  this symbol to the DefDef constructor.
-      *
-      *  @note As a macro can only splice code into the point at which it is expanded, all generated symbols must be
-      *        direct or indirect children of the reflection context's owner.
-      */
+       *
+       *  To define a member method of a class, use the `newMethod` within the `decls` function of `newClass`.
+       *
+       *  @param parent The owner of the method
+       *  @param name The name of the method
+       *  @param tpe The type of the method (MethodType, PolyType, ByNameType)
+       *
+       *  This symbol starts without an accompanying definition.
+       *  It is the meta-programmer's responsibility to provide exactly one corresponding definition by passing
+       *  this symbol to the DefDef constructor.
+       *
+       *  @note As a macro can only splice code into the point at which it is expanded, all generated symbols must be
+       *        direct or indirect children of the reflection context's owner.
+       */
       def newMethod(parent: Symbol, name: String, tpe: TypeRepr): Symbol
 
       /** Works as the other newMethod, but with additional parameters.
       *
+      *  To define a member method of a class, use the `newMethod` within the `decls` function of `newClass`.
+      *
+      *  @param parent The owner of the method
+      *  @param name The name of the method
+      *  @param tpe The type of the method (MethodType, PolyType, ByNameType)
       *  @param flags extra flags to with which the symbol should be constructed
       *  @param privateWithin the symbol within which this new method symbol should be private. May be noSymbol.
       */
@@ -3604,6 +3679,9 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
       *
       *  Note: Also see reflect.let
       *
+      *  @param parent The owner of the val/var/lazy val
+      *  @param name The name of the val/var/lazy val
+      *  @param tpe The type of the val/var/lazy val
       *  @param flags extra flags to with which the symbol should be constructed
       *  @param privateWithin the symbol within which this new method symbol should be private. May be noSymbol.
       *  @note As a macro can only splice code into the point at which it is expanded, all generated symbols must be
@@ -3617,7 +3695,10 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
       *  It is the meta-programmer's responsibility to provide exactly one corresponding definition by passing
       *  this symbol to the BindDef constructor.
       *
+      *  @param parent The owner of the binding
+      *  @param name The name of the binding
       *  @param flags extra flags to with which the symbol should be constructed
+      *  @param tpe The type of the binding
       *  @note As a macro can only splice code into the point at which it is expanded, all generated symbols must be
       *        direct or indirect children of the reflection context's owner.
       */
@@ -3679,9 +3760,11 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
          *
          *      symbol.tree.tpe
          *
-         *  It should be replaced by the following code:
+         *  It should be replaced by one of the following:
          *
          *      tp.memberType(symbol)
+         *      symbol.typeRef
+         *      symbol.termRef
          *
          */
         def tree: Tree
@@ -3880,6 +3963,19 @@ trait Quotes { self: runtime.QuoteUnpickler & runtime.QuoteMatching =>
         @experimental
         def asQuotes: Nested
 
+        /** Type reference to the symbol usable in the scope of its owner.
+         *
+         *  To get a reference to a symbol from a specific prefix `tp`, use `tp.select(symbol)` instead.
+         *  @see TypeReprMethods.select
+         *
+         *  @pre symbol.isType returns true
+         */
+        @experimental
+        def typeRef: TypeRef
+
+        /** Term reference to the symbol usable in the scope of its owner. */
+        @experimental
+        def termRef: TermRef
       end extension
     }
 

project/MiMaFilters.scala

@@ -21,6 +21,16 @@ object MiMaFilters {
     ProblemFilters.exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#CompilationInfoModule.XmacroSettings"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("scala.deriving.Mirror.fromProductTyped"),
     ProblemFilters.exclude[DirectMissingMethodProblem]("scala.deriving.Mirror.fromTuple"),
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#ClassDefModule.apply"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#ClassDefModule.apply"),
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolModule.newClass"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolModule.newClass"),
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolMethods.typeRef"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolMethods.typeRef"),
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolMethods.termRef"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#SymbolMethods.termRef"),
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("scala.quoted.Quotes#reflectModule#TypeTreeModule.ref"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.quoted.Quotes#reflectModule#TypeTreeModule.ref"),
 
     // Private to the compiler - needed for forward binary compatibility
     ProblemFilters.exclude[MissingClassProblem]("scala.annotation.since"),

tests/neg-macros/newClassExtendsNoParents/Macro_1.scala

@@ -0,0 +1,23 @@
+import scala.quoted.*
+
+inline def makeClass(inline name: String): Any = ${ makeClassExpr('name) }
+private def makeClassExpr(nameExpr: Expr[String])(using Quotes): Expr[Any] = {
+  import quotes.reflect.*
+
+  val name = nameExpr.valueOrAbort
+  val parents = List.empty[Tree] // BUG: first parent is not a class
+  def decls(cls: Symbol): List[Symbol] = Nil
+
+  val cls = Symbol.newClass(Symbol.spliceOwner, name, parents = Nil, decls, selfType = None)
+  val clsDef = ClassDef(cls, parents, body = List())
+  val newCls = Typed(Apply(Select(New(TypeIdent(cls)), cls.primaryConstructor), Nil), TypeTree.of[Object])
+
+  Block(List(clsDef), newCls).asExpr
+
+  // '{
+  //   class `name`() {
+  //     def foo(): Unit = println("Calling `name`.foo")
+  //   }
+  //   new `name`()
+  // }
+}

tests/neg-macros/newClassExtendsNoParents/Test_2.scala

@@ -0,0 +1 @@
+def test: Any = makeClass("foo") // error

tests/neg-macros/newClassExtendsOnlyTrait/Macro_1.scala

@@ -0,0 +1,31 @@
+import scala.quoted.*
+
+inline def makeClass(inline name: String): Foo = ${ makeClassExpr('name) }
+private def makeClassExpr(nameExpr: Expr[String])(using Quotes): Expr[Foo] = {
+  import quotes.reflect.*
+
+  val name = nameExpr.valueOrAbort
+  val parents = List(TypeTree.of[Foo]) // BUG: first parent is not a class
+  def decls(cls: Symbol): List[Symbol] =
+    List(Symbol.newMethod(cls, "foo", MethodType(Nil)(_ => Nil, _ => TypeRepr.of[Unit])))
+
+  val cls = Symbol.newClass(Symbol.spliceOwner, name, parents = parents.map(_.tpe), decls, selfType = None)
+  val fooSym = cls.declaredMethod("foo").head
+
+  val fooDef = DefDef(fooSym, argss => Some('{println(s"Calling ${$nameExpr}.foo")}.asTerm))
+  val clsDef = ClassDef(cls, parents, body = List(fooDef))
+  val newCls = Typed(Apply(Select(New(TypeIdent(cls)), cls.primaryConstructor), Nil), TypeTree.of[Foo])
+
+  Block(List(clsDef), newCls).asExprOf[Foo]
+
+  // '{
+  //   class `name`() extends Foo {
+  //     def foo(): Unit = println("Calling `name`.foo")
+  //   }
+  //   new `name`()
+  // }
+}
+
+trait Foo {
+  def foo(): Unit
+}

tests/neg-macros/newClassExtendsOnlyTrait/Test_2.scala

@@ -0,0 +1 @@
+def test: Foo = makeClass("foo") // error

tests/run-macros/newClass.check

@@ -0,0 +1,4 @@
+Constructing foo
+class Test_2$package$foo$1
+Constructing bar
+class Test_2$package$bar$1

tests/run-macros/newClass/Macro_1.scala

@@ -0,0 +1,21 @@
+import scala.quoted.*
+
+inline def makeClass(inline name: String): Any = ${ makeClassExpr('name) }
+private def makeClassExpr(nameExpr: Expr[String])(using Quotes): Expr[Any] = {
+  import quotes.reflect.*
+
+  val name = nameExpr.valueOrAbort
+  val parents = List(TypeTree.of[Object])
+  def decls(cls: Symbol): List[Symbol] = Nil
+
+  val cls = Symbol.newClass(Symbol.spliceOwner, name, parents = parents.map(_.tpe), decls, selfType = None)
+
+  val clsDef = ClassDef(cls, parents, body = List('{println(s"Constructing ${$nameExpr}")}.asTerm))
+  val newCls = Typed(Apply(Select(New(TypeIdent(cls)), cls.primaryConstructor), Nil), TypeTree.of[Object])
+
+  Block(List(clsDef), newCls).asExpr
+  // '{
+  //   class `name`() { println("Constructing `name`") }
+  //   new `name`()
+  // }
+}