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Avoid over widening in SpaceEngine #18252

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Jul 20, 2023
Merged

Avoid over widening in SpaceEngine #18252

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8 changes: 7 additions & 1 deletion compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -578,7 +578,13 @@ object SpaceEngine {
if (arity > 0)
productSelectorTypes(resTp, unappSym.srcPos)
else {
val getTp = resTp.select(nme.get).finalResultType.widenTermRefExpr
val getTp = resTp.select(nme.get).finalResultType match
case tp: TermRef if !tp.isOverloaded =>
// Like widenTermRefExpr, except not recursively.
// For example, in i17184 widen Option[foo.type]#get
// to Option[foo.type] instead of Option[Int].
tp.underlying.widenExpr
case tp => tp
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Just curious: Why introduce the guard tp.isOverloaded? A comment will be very helpful.

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It's from the original, widenTermRefExpr, which I reference.

if (argLen == 1) getTp :: Nil
else productSelectorTypes(getTp, unappSym.srcPos)
}
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9 changes: 9 additions & 0 deletions tests/patmat/i17184.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
class Foo
trait Bar:
val foo : Int
val f : Option[foo.type] = Some(foo)

def g : Boolean =
f match
case None => false
case Some(_) => true
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