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Changes to wildApprox #1054

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7f27b80
Changes to wildApprox
odersky Feb 4, 2016
2e3e67f
Fix doc comment
odersky Feb 4, 2016
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4 changes: 2 additions & 2 deletions src/dotty/tools/dotc/typer/Implicits.scala
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Expand Up @@ -56,9 +56,9 @@ object Implicits {
case mt: MethodType =>
mt.isImplicit ||
mt.paramTypes.length != 1 ||
!(argType relaxed_<:< wildApprox(mt.paramTypes.head)(ctx.fresh.setExploreTyperState))
!(argType relaxed_<:< wildApprox(mt.paramTypes.head, poly)(ctx.fresh.setExploreTyperState))
case rtp =>
discardForView(wildApprox(rtp), argType)
discardForView(wildApprox(rtp, poly), argType)
}
case tpw: TermRef =>
false // can't discard overloaded refs
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20 changes: 18 additions & 2 deletions src/dotty/tools/dotc/typer/ProtoTypes.scala
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Expand Up @@ -379,6 +379,19 @@ object ProtoTypes {
}
}

/** Like wildApprox, but assume that all parameters of `disregarded` are not
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It's a bit weird to say "Like wildApprox" when this method is called wildApprox too, maybe use another name, or say, "Like the other overload of wildApprox"?

* bound in current constraint. This is necessary because an instance of
* the type of a polymorphic function might already be part of the current
* constraint when we try to check another occurrence of the same polymorphic
* function for eligibility. An example is in i1044.scala where one expression
* requires two implicit calls of the same refArrayOps method. When approximating
* the parameter types of such a method we should always ignore type parameters of
* the method itself, even though some of these parameters might still be
* bound in the constraint.
*/
final def wildApprox(tp: Type, disregarded: PolyType)(implicit ctx: Context): Type =
wildApprox(tp, new WildApproxMap(disregarded))

/** Approximate occurrences of parameter types and uninstantiated typevars
* by wildcard types.
*/
Expand All @@ -391,7 +404,10 @@ object ProtoTypes {
case tp: TypeAlias => // default case, inlined for speed
tp.derivedTypeAlias(wildApprox(tp.alias, theMap))
case tp @ PolyParam(poly, pnum) =>
ctx.typerState.constraint.entry(tp) match {
val constrOrInst =
if (theMap != null && (poly eq theMap.disregarded)) NoType
else ctx.typerState.constraint.entry(tp)
constrOrInst match {
case bounds: TypeBounds => wildApprox(WildcardType(bounds))
case NoType => WildcardType(wildApprox(poly.paramBounds(pnum)).bounds)
case inst => wildApprox(inst)
Expand Down Expand Up @@ -426,7 +442,7 @@ object ProtoTypes {
(if (theMap != null) theMap else new WildApproxMap).mapOver(tp)
}

private[ProtoTypes] class WildApproxMap(implicit ctx: Context) extends TypeMap {
private[ProtoTypes] class WildApproxMap(val disregarded: Type = NoType)(implicit ctx: Context) extends TypeMap {
def apply(tp: Type) = wildApprox(tp, this)
}

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3 changes: 3 additions & 0 deletions tests/pos/i1044.scala
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@@ -0,0 +1,3 @@
object Test {
val x = ???.getClass.getMethods.head.getParameterTypes.mkString(",")
}