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Fix #1753: Better comparison of path types #1760

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Merged
merged 1 commit into from
Nov 30, 2016
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Fix #1753: Better comparison of path types #1760

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6 changes: 4 additions & 2 deletions compiler/src/dotty/tools/dotc/core/TypeComparer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -541,9 +541,11 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling {
/** if `tp2 == p.type` and `p: q.type` then try `tp1 <:< q.type` as a last effort.*/
def comparePaths = tp2 match {
case tp2: TermRef =>
tp2.info.widenExpr match {
tp2.info.widenExpr.dealias match {
case tp2i: SingletonType =>
isSubType(tp1, tp2i) // see z1720.scala for a case where this can arise even in typer.
isSubType(tp1, tp2i)
// see z1720.scala for a case where this can arise even in typer.
// Also, i1753.scala, to show why the dealias above is necessary.
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strange indentation here?

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I use this style on occasion. Basically, if an end of line comment is too long I put several
indented lines after the commented statement. I find it sometimes clearer than having the comments before (depends on the wording of the comment).

case _ => false
}
case _ =>
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22 changes: 22 additions & 0 deletions tests/pos/i1753.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
abstract class BackendInterface {
type Symbol >: Null
type ClassDef >: Null
}

class BTypesFromSymbols[I <: BackendInterface](val int: I) {
def isRemote(s: int.Symbol) = println("might've been remote")
}

trait BCodeIdiomatic {
val int: BackendInterface
final lazy val bTypes = new BTypesFromSymbols[int.type](int)
}

trait BCodeSkelBuilder extends BCodeIdiomatic {
import int._
import bTypes._
val b: BTypesFromSymbols[int.type] = bTypes
val x: int.type = bTypes.int
val y: bTypes.int.type = int
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What are these two lines with x and y?

Used it for debugging?

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Break the problem apart into two subtype tests. I thought it was good to add this.

def getPlainClass(cd: ClassDef) = bTypes.isRemote(null: Symbol)
}