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Fix parents of tuple classes #13659

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Merged
merged 3 commits into from
Oct 6, 2021
Merged

Fix parents of tuple classes #13659

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c0db02c
Harden orDominator
odersky Oct 2, 2021
837afec
Better fix: Fix parents of tuple classes
odersky Oct 5, 2021
eb81076
Fix tuple erasure (2nd attempt)
odersky Oct 5, 2021
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6 changes: 5 additions & 1 deletion compiler/src/dotty/tools/dotc/core/TypeOps.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -349,7 +349,11 @@ object TypeOps:
val doms = dominators(commonBaseClasses, Nil)
def baseTp(cls: ClassSymbol): Type =
tp.baseType(cls).mapReduceOr(identity)(mergeRefinedOrApplied)
doms.map(baseTp).reduceLeft(AndType.apply)
def meet(tp1: Type, tp2: Type) =
if !tp1.exists then tp2
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I don't understand why this is needed, we do:

val commonBaseClasses = tp.mapReduceOr(_.baseClasses)(intersect)

(btw, how is this different from tp.baseClasses ?)
So I would expect tp.baseType on any of the common base classes to exist, but in fact the base classes of Tuple1[(Axis, Int)] | ((Axis, Int), (Axis, Int)) contains Product2, even though Tuple1 does not extend Product2, so I think there's a bug in how we compute base classes for unions, either here or in OrType#baseClasses.

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(btw, how is this different from tp.baseClasses ?)

Turns out it's different for Null. Since Null is also outside the inheritance hierarchy.

else if !tp2.exists then tp1
else AndType(tp1, tp2)
doms.map(baseTp).reduceLeft(meet)
}

tp match {
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12 changes: 12 additions & 0 deletions tests/neg/i13435.check
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@@ -0,0 +1,12 @@
-- [E029] Pattern Match Exhaustivity Warning: tests/neg/i13435.scala:7:2 -----------------------------------------------
7 | s match
| ^
| match may not be exhaustive.
|
| It would fail on pattern case: (_), ((_, _), (_, _))

longer explanation available when compiling with `-explain`
-- Error: tests/neg/i13435.scala:8:10 ----------------------------------------------------------------------------------
8 | case (dim: Axis, size: Int) => dim // error
| ^^^^^^^^^
| trait Singleton cannot be used in runtime type tests
8 changes: 8 additions & 0 deletions tests/neg/i13435.scala
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@@ -0,0 +1,8 @@
type Axis = String&Singleton
type ShapeTuple = Tuple1[(Axis, Int)]|Tuple2[(Axis, Int), (Axis, Int)]
type Shape = (Axis, Int) |ShapeTuple


def mkSchema(s: Shape) =
s match
case (dim: Axis, size: Int) => dim // error