diff options
Diffstat (limited to 'src/compiler/scala/tools/nsc/transform/UnCurry.scala')
| -rw-r--r-- | src/compiler/scala/tools/nsc/transform/UnCurry.scala | 41 |
1 files changed, 39 insertions, 2 deletions
diff --git a/src/compiler/scala/tools/nsc/transform/UnCurry.scala b/src/compiler/scala/tools/nsc/transform/UnCurry.scala index 79a77d7a0c..57639a94c7 100644 --- a/src/compiler/scala/tools/nsc/transform/UnCurry.scala +++ b/src/compiler/scala/tools/nsc/transform/UnCurry.scala @@ -703,9 +703,46 @@ abstract class UnCurry extends InfoTransform // declared type and assign this to a synthetic val. Later, we'll patch // the method body to refer to this, rather than the parameter. val tempVal: ValDef = { + // SI-9442: using the "uncurry-erased" type (the one after the uncurry phase) can lead to incorrect + // tree transformations. For example, compiling: + // ``` + // def foo(c: Ctx)(l: c.Tree): Unit = { + // val l2: c.Tree = l + // } + // ``` + // Results in the following AST: + // ``` + // def foo(c: Ctx, l: Ctx#Tree): Unit = { + // val l$1: Ctx#Tree = l.asInstanceOf[Ctx#Tree] + // val l2: c.Tree = l$1 // no, not really, it's not. + // } + // ``` + // Of course, this is incorrect, since `l$1` has type `Ctx#Tree`, which is not a subtype of `c.Tree`. + // + // So what we need to do is to use the pre-uncurry type when creating `l$1`, which is `c.Tree` and is + // correct. Now, there are two additional problems: + // 1. when varargs and byname params are involved, the uncurry transformation desugares these special + // cases to actual typerefs, eg: + // ``` + // T* ~> Seq[T] (Scala-defined varargs) + // T* ~> Array[T] (Java-defined varargs) + // =>T ~> Function0[T] (by name params) + // ``` + // we use the DesugaredParameterType object (defined in scala.reflect.internal.transform.UnCurry) + // to redo this desugaring manually here + // 2. the type needs to be normalized, since `gen.mkCast` checks this (no HK here, just aliases have + // to be expanded before handing the type to `gen.mkAttributedCast`, which calls `gen.mkCast`) + val info0 = + enteringUncurry(p.symbol.info) match { + case DesugaredParameterType(desugaredTpe) => + desugaredTpe + case tpe => + tpe + } + val info = info0.normalize val tempValName = unit freshTermName (p.name + "$") - val newSym = dd.symbol.newTermSymbol(tempValName, p.pos, SYNTHETIC).setInfo(p.symbol.info) - atPos(p.pos)(ValDef(newSym, gen.mkAttributedCast(Ident(p.symbol), p.symbol.info))) + val newSym = dd.symbol.newTermSymbol(tempValName, p.pos, SYNTHETIC).setInfo(info) + atPos(p.pos)(ValDef(newSym, gen.mkAttributedCast(Ident(p.symbol), info))) } Packed(newParam, tempVal) } |