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Type match with a match type when a match type is expected #15599

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Merged
merged 1 commit into from
Oct 3, 2022
Merged

Type match with a match type when a match type is expected #15599

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2 changes: 2 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 @@ -1609,6 +1609,8 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
}

val result = pt match {
case mt: MatchType if isMatchTypeShaped(mt) =>
typedDependentMatchFinish(tree, sel1, selType, tree.cases, mt)
case MatchType.InDisguise(mt) if isMatchTypeShaped(mt) =>
typedDependentMatchFinish(tree, sel1, selType, tree.cases, mt)
case _ =>
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22 changes: 22 additions & 0 deletions tests/pos/match-type-inference.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,22 @@
type IsString[T <: Any] = T match {
case String => true
case _ => false
}

def isString(x: Any): IsString[x.type] = x match
case _: String => true
case _ => false

def isString2(x: Any): x.type match {
case String => true
case _ => false
} = x match
case _: String => true
case _ => false

def isString3[T](x: T): T match {
case String => true
case _ => false
} = x match
case _: String => true
case _ => false