Type.matches is still incomplete

[DarkDimius]

ListBuffer += does not match Growable += before erasure.
Here are their types:

ListBuffer.+= MethodType(List(xs), List(RefinedType(TypeRef(ThisType(TypeRef(NoPrefix,collection)),TraversableOnce), scala$collection$TraversableOnce$$A, TypeAlias(TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,mutable)),ListBuffer)),scala$collection$mutable$ListBuffer$$A)) | -1582256965)), 
/*returnType*/ ThisType(TypeRef(ThisType(TypeRef(NoPrefix,mutable)),ListBuffer)))

Growable  .+= MethodType(List(xs), List(RefinedType(TypeRef(ThisType(TypeRef(NoPrefix,collection)),TraversableOnce), scala$collection$TraversableOnce$$A, TypeAlias(TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,generic)),Growable)),scala$collection$generic$Growable$$A)) | 607071156)), 
/*returnType*/ ThisType(TypeRef(ThisType(TypeRef(NoPrefix,generic)),Growable)))

matchingParams for those types is false, and the only thing that is different is type aliases inside.
Note that ListBuffer[A] extends Builder[A, List[A]], and Builder[A, List[A]] extends Growable[A], so I guess those type aliases should be considered =:=

[DarkDimius]

Maybe has to do with #813, as there we have

class GenericCompanion[+CC[X] <: GenTraversable[X]] {
    protected[this] type Coll = CC[_]
}

class GenTraversableFactory[CC[X] <: GenTraversable[X] with GenericTraversableTemplate[X, CC]]
extends GenericCompanion[CC] {
// Dotty does not consider Coll as a subtype of GenericTraversableTemplate here
// Scalac does
}

[DarkDimius]

My bad. I need to use asSeenFrom before comparing the types.