Merge pull request #6189 from dotty-staging/split-unseal-and-cast

Split quoted.Expr casting from sealing

Author: Aggelos Biboudis

compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala

@@ -1681,19 +1681,16 @@ class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.
   // QUOTED SEAL/UNSEAL
   //
 
-  /** View this expression `Expr[_]` as a `Term` */
+  /** View this expression `quoted.Expr[_]` as a `Term` */
   def QuotedExpr_unseal(self: scala.quoted.Expr[_])(implicit ctx: Context): Term =
     PickledQuotes.quotedExprToTree(self)
 
-  /** View this expression `Type[T]` as a `TypeTree` */
+  /** View this expression `quoted.Type[_]` as a `TypeTree` */
   def QuotedType_unseal(self: scala.quoted.Type[_])(implicit ctx: Context): TypeTree =
     PickledQuotes.quotedTypeToTree(self)
 
-  /** Convert `Term` to an `Expr[T]` and check that it conforms to `T` */
-  def QuotedExpr_seal[T](self: Term)(tpe: scala.quoted.Type[T])(implicit ctx: Context): scala.quoted.Expr[T] = {
-
-    val expectedType = QuotedType_unseal(tpe).tpe
-
+  /** Convert `Term` to an `quoted.Expr[Any]`  */
+  def QuotedExpr_seal(self: Term)(implicit ctx: Context): scala.quoted.Expr[Any] = {
     def etaExpand(term: Term): Term = term.tpe.widen match {
       case mtpe: Types.MethodType if !mtpe.isParamDependent =>
         val closureResType = mtpe.resType match {
@@ -1705,20 +1702,25 @@ class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.
         tpd.Closure(closureMethod, tss => etaExpand(new tpd.TreeOps(term).appliedToArgs(tss.head)))
       case _ => term
     }
+    new scala.quoted.Exprs.TastyTreeExpr(etaExpand(self))
+  }
 
-    val expanded = etaExpand(self)
-    if (expanded.tpe <:< expectedType) {
-      new scala.quoted.Exprs.TastyTreeExpr(expanded).asInstanceOf[scala.quoted.Expr[T]]
+  /** Checked cast to a `quoted.Expr[U]` */
+  def QuotedExpr_cast[U](self: scala.quoted.Expr[_])(implicit tp: scala.quoted.Type[U], ctx: Context): scala.quoted.Expr[U] = {
+    val tree = QuotedExpr_unseal(self)
+    val expectedType = QuotedType_unseal(tp).tpe
+    if (tree.tpe <:< expectedType) {
+      self.asInstanceOf[scala.quoted.Expr[U]]
     } else {
-      throw new scala.tasty.TastyTypecheckError(
-        s"""Term: ${self.show}
+      throw new scala.tasty.reflect.ExprCastError(
+        s"""Expr: ${tree.show}
            |did not conform to type: ${expectedType.show}
            |""".stripMargin
       )
     }
   }
 
-  /** Convert `Type` to an `quoted.Type[T]` */
+  /** Convert `Type` to an `quoted.Type[_]` */
   def QuotedType_seal(self: Type)(implicit ctx: Context): scala.quoted.Type[_] = {
     val dummySpan = ctx.owner.span // FIXME
     new scala.quoted.Types.TreeType(tpd.TypeTree(self).withSpan(dummySpan))

library/src-bootstrapped/scala/tasty/reflect/QuotedOps.scala

@@ -4,25 +4,29 @@ package scala.tasty.reflect
 trait QuotedOps extends Core {
 
   implicit class QuotedExprAPI[T](expr: scala.quoted.Expr[T]) {
-    /** View this expression `Expr[T]` as a `Term` */
+    /** View this expression `quoted.Expr[T]` as a `Term` */
     def unseal(implicit ctx: Context): Term =
       kernel.QuotedExpr_unseal(expr)
+
+    /** Checked cast to a `quoted.Expr[U]` */
+    def cast[U: scala.quoted.Type](implicit ctx: Context): scala.quoted.Expr[U] =
+      kernel.QuotedExpr_cast[U](expr)
   }
 
   implicit class QuotedTypeAPI[T <: AnyKind](tpe: scala.quoted.Type[T]) {
-    /** View this expression `Type[T]` as a `TypeTree` */
+    /** View this expression `quoted.Type[T]` as a `TypeTree` */
     def unseal(implicit ctx: Context): TypeTree =
       kernel.QuotedType_unseal(tpe)
   }
 
   implicit class TermToQuotedAPI(term: Term) {
-    /** Convert `Term` to an `Expr[T]` and check that it conforms to `T` */
-    def seal[T](implicit tpe: scala.quoted.Type[T], ctx: Context): scala.quoted.Expr[T] =
-      kernel.QuotedExpr_seal(term)(tpe)
+    /** Convert `Term` to an `quoted.Expr[Any]` */
+    def seal(implicit ctx: Context): scala.quoted.Expr[Any] =
+      kernel.QuotedExpr_seal(term)
   }
 
   implicit class TypeToQuotedAPI(tpe: Type) {
-    /** Convert `Type` to an `quoted.Type[T]` */
+    /** Convert `Type` to an `quoted.Type[_]` */
     def seal(implicit ctx: Context): scala.quoted.Type[_] =
       kernel.QuotedType_seal(tpe)
   }

library/src-bootstrapped/scala/tasty/reflect/utils/TreeUtils.scala

@@ -12,12 +12,12 @@ trait TreeUtils {
   def let(rhs: Term)(body: Ident => Term): Term = {
     type T // TODO probably it is better to use the Sealed contruct rather than let the user create their own existential type
     implicit val rhsTpe: quoted.Type[T] = rhs.tpe.seal.asInstanceOf[quoted.Type[T]]
-    val rhsExpr = rhs.seal[T]
+    val rhsExpr = rhs.seal.cast[T]
     val expr = '{
       val x = $rhsExpr
       ${
         val id = ('x).unseal.asInstanceOf[Ident]
-        body(id).seal[Any]
+        body(id).seal
       }
     }
     expr.unseal

library/src-non-bootstrapped/scala/tasty/reflect/QuotedOps.scala

@@ -4,25 +4,29 @@ package scala.tasty.reflect
 trait QuotedOps extends Core {
 
   implicit class QuotedExprAPI[T](expr: scala.quoted.Expr[T]) {
-    /** View this expression `Expr[T]` as a `Term` */
+    /** View this expression `quoted.Expr[T]` as a `Term` */
     def unseal(implicit ctx: Context): Term =
       kernel.QuotedExpr_unseal(expr)
+
+    /** Checked cast to a `quoted.Expr[U]` */
+    def cast[U: scala.quoted.Type](implicit ctx: Context): scala.quoted.Expr[U] =
+      kernel.QuotedExpr_cast[U](expr)
   }
 
   implicit class QuotedTypeAPI[T](tpe: scala.quoted.Type[T]) {
-    /** View this expression `Type[T]` as a `TypeTree` */
+    /** View this expression `quoted.Type[T]` as a `TypeTree` */
     def unseal(implicit ctx: Context): TypeTree =
       kernel.QuotedType_unseal(tpe)
   }
 
   implicit class TermToQuotedAPI(term: Term) {
-    /** Convert `Term` to an `Expr[T]` and check that it conforms to `T` */
-    def seal[T](implicit tpe: scala.quoted.Type[T], ctx: Context): scala.quoted.Expr[T] =
-      kernel.QuotedExpr_seal(term)(tpe)
+    /** Convert `Term` to an `quoted.Expr[Any]` */
+    def seal(implicit ctx: Context): scala.quoted.Expr[Any] =
+      kernel.QuotedExpr_seal(term)
   }
 
   implicit class TypeToQuotedAPI(tpe: Type) {
-    /** Convert `Type` to an `quoted.Type[T]` */
+    /** Convert `Type` to an `quoted.Type[_]` */
     def seal(implicit ctx: Context): scala.quoted.Type[_] =
       kernel.QuotedType_seal(tpe)
   }

library/src/scala/tasty/TastyTypecheckError.scala

@@ -0,0 +1,3 @@
+package scala.tasty.reflect
+
+class ExprCastError(msg: String) extends Throwable(msg)

library/src/scala/tasty/reflect/ExprCastError.scala

@@ -1375,16 +1375,20 @@ trait Kernel {
   // QUOTED SEAL/UNSEAL
   //
 
-  /** View this expression `Expr[_]` as a `Term` */
+  /** View this expression `quoted.Expr[_]` as a `Term` */
   def QuotedExpr_unseal(self: scala.quoted.Expr[_])(implicit ctx: Context): Term
 
-  /** View this expression `Type[T]` as a `TypeTree` */
+  /** Checked cast to a `quoted.Expr[U]` */
+  def QuotedExpr_cast[U](self: scala.quoted.Expr[_])(implicit tp: scala.quoted.Type[U], ctx: Context): scala.quoted.Expr[U]
+
+  /** View this expression `quoted.Type[T]` as a `TypeTree` */
   def QuotedType_unseal(self: scala.quoted.Type[_])(implicit ctx: Context): TypeTree
 
-  /** Convert `Term` to an `Expr[T]` and check that it conforms to `T` */
-  def QuotedExpr_seal[T](self: Term)(tpe: scala.quoted.Type[T])(implicit ctx: Context): scala.quoted.Expr[T]
+  /** Convert `Term` to an `quoted.Expr[Any]` */
+  def QuotedExpr_seal(self: Term)(implicit ctx: Context): scala.quoted.Expr[Any]
+
 
-  /** Convert `Type` to an `quoted.Type[T]` */
+  /** Convert `Type` to an `quoted.Type[_]` */
   def QuotedType_seal(self: Type)(implicit ctx: Context): scala.quoted.Type[_]
 
   //

library/src/scala/tasty/reflect/Kernel.scala

@@ -19,7 +19,7 @@ object Lens {
 
     // obj.copy(field = value)
     def setterBody(obj: Expr[S], value: Expr[T], field: String): Expr[S] =
-      Select.overloaded(obj.unseal, "copy", Nil, NamedArg(field, value.unseal) :: Nil).seal[S]
+      Select.overloaded(obj.unseal, "copy", Nil, NamedArg(field, value.unseal) :: Nil).seal.cast[S]
 
     // exception: getter.unseal.underlyingArgument
     getter.unseal match {

tests/neg-with-compiler/i5941/macro_1.scala

@@ -34,7 +34,7 @@ object Asserts {
 
     tree match {
       case Inlined(_, Nil, Apply(Select(OpsTree(left), op), right :: Nil)) =>
-        '{assertTrue(${left.seal[Boolean]})} // Buggy code. To generate the errors
+        '{assertTrue(${left.seal.cast[Boolean]})} // Buggy code. To generate the errors
       case _ =>
         '{assertTrue($cond)}
     }

tests/neg/tasty-macro-assert-1/quoted_1.scala

@@ -34,7 +34,7 @@ object Asserts {
 
     tree match {
       case Inlined(_, Nil, Apply(Select(OpsTree(left), op), right :: Nil)) =>
-        '{assertTrue(${left.seal[Boolean]})} // Buggy code. To generate the errors
+        '{assertTrue(${left.seal.cast[Boolean]})} // Buggy code. To generate the errors
       case _ =>
         '{assertTrue($cond)}
     }