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Fix #10174: avoid creating deep nesting union space #11058

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Merged
merged 1 commit into from
Jan 13, 2021
Merged

Fix #10174: avoid creating deep nesting union space #11058

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9 changes: 5 additions & 4 deletions 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 @@ -870,18 +870,19 @@ class SpaceEngine(using Context) extends SpaceLogic {
project(OrType(selTyp, constantNullType, soft = false))

// in redundancy check, take guard as false in order to soundly approximate
def projectPrevCases(cases: List[CaseDef]): Space =
def projectPrevCases(cases: List[CaseDef]): List[Space] =
cases.map { x =>
if (x.guard.isEmpty) project(x.pat)
else Empty
}.reduce((a, b) => Or(List(a, b)))
}

(1 until cases.length).foreach { i =>
val prevs = projectPrevCases(cases.take(i))
val spaces = projectPrevCases(cases)

(1 until cases.length).foreach { i =>
val pat = cases(i).pat

if (pat != EmptyTree) { // rethrow case of catch uses EmptyTree
val prevs = Or(spaces.take(i))
val curr = project(pat)

debug.println(s"---------------reachable? ${show(curr)}")
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