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Fix SubMatch wrapped in Typed node by ensureNoLocalRefs #25778

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Fix SubMatch wrapped in Typed node by ensureNoLocalRefs #25778

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a9b2a7e
handle SubMatch in ensureNoLocalRefs
zielinsky Apr 13, 2026
c2096b3
add i25746 to excludelist for coverage test
zielinsky Apr 14, 2026
5527de6
use .tpes instead of map
zielinsky Apr 14, 2026
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5 changes: 5 additions & 0 deletions compiler/src/dotty/tools/dotc/typer/Typer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1589,6 +1589,11 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
case block @ Block(stats, expr) if !expr.isInstanceOf[Closure] =>
val expr1 = ascribeType(expr, pt)
cpy.Block(block)(stats, expr1).withType(expr1.tpe) // no assignType here because avoid is redundant
case m @ Match(selector, cases) if m.isSubMatch =>
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@noti0na1 noti0na1 Apr 22, 2026

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I'm not sure why we only need to handle SubMatch here?

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@zielinsky zielinsky Apr 23, 2026

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It's because of how transformMatch handles a simple Match vs SubMatch. For the first one, wrapping it in Typed is not a problem

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@EugeneFlesselle EugeneFlesselle Apr 22, 2026

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IIUC this case is added to avoid the Typed wrapper?

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@zielinsky zielinsky Apr 23, 2026

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Exactly

val newCases = cases.map: cdef =>
val newBody = ascribeType(cdef.body, pt)
cpy.CaseDef(cdef)(body = newBody).withType(newBody.tpe)
cpy.Match(m)(selector, newCases).withType(TypeComparer.lub(newCases.tpes))
case _ =>
val target = pt.simplified
val targetTpt = TypeTree(target, inferred = true)
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1 change: 1 addition & 0 deletions compiler/test/dotc/scoverage-ignore.excludelist
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Expand Up @@ -84,3 +84,4 @@ tailrec.scala
traitParams.scala
i25460.scala
matrix.scala
i25746.scala
9 changes: 9 additions & 0 deletions tests/pos/i25746.scala
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@@ -0,0 +1,9 @@
import scala.language.experimental.subCases

@main def test =
val r1 = "^foo".r.unanchored
val r2 = "bar$".r.unanchored

val result1 = "foo bar" match
case s @ r1() if s match { case r2() => s }
case _ => "no"
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