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Fix #5402: Avoid duplicate labels in switches #5663

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Merged
merged 1 commit into from
Jan 4, 2019
Merged

Fix #5402: Avoid duplicate labels in switches #5663

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15 changes: 10 additions & 5 deletions compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -711,9 +711,14 @@ object PatternMatcher {
(tpe isRef defn.ShortClass) ||
(tpe isRef defn.CharClass)

def isIntConst(tree: Tree) = tree match {
case Literal(const) => const.isIntRange
case _ => false
val seen = mutable.Set[Int]()

def isNewIntConst(tree: Tree) = tree match {
case Literal(const) if const.isIntRange && !seen.contains(const.intValue) =>
seen += const.intValue
true
case _ =>
false
}

// An extractor to recover the shape of plans that can become alternatives
Expand All @@ -725,7 +730,7 @@ object PatternMatcher {
val alts = List.newBuilder[Tree]
def rec(innerPlan: Plan): Boolean = innerPlan match {
case SeqPlan(TestPlan(EqualTest(tree), scrut, _, ReturnPlan(`innerLabel`)), tail)
if scrut === scrutinee && isIntConst(tree) =>
if scrut === scrutinee && isNewIntConst(tree) =>
alts += tree
rec(tail)
case ReturnPlan(`outerLabel`) =>
Expand All @@ -746,7 +751,7 @@ object PatternMatcher {

def recur(plan: Plan): List[(List[Tree], Plan)] = plan match {
case SeqPlan(testPlan @ TestPlan(EqualTest(tree), scrut, _, ons), tail)
if scrut === scrutinee && isIntConst(tree) && !canFallThrough(ons) =>
if scrut === scrutinee && !canFallThrough(ons) && isNewIntConst(tree) =>
(tree :: Nil, ons) :: recur(tail)
case SeqPlan(AlternativesPlan(alts, ons), tail) =>
(alts, ons) :: recur(tail)
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27 changes: 27 additions & 0 deletions tests/pos/i5402.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
object Main {
val a: Int = 4
a match {
case 1 => println("1")
case 1 | 2 => println("1 or 2")
}

a match {
case 1 => 1
case 0 | 0 => 0
case 2 | 2 | 2 | 3 | 2 | 3 => 0
case 4 | (_ @ 4) => 0
case _ => -1
}

a match {
case 1 => 1
case 0 | 0 => 0
case 2 | 2 | 2 | 3 | 2 | 3 => 0
case _ => -1
}

a match {
case 0 | 1 => 0
case 1 => 1
}
}