Fix #10108: Distinguish between soft and hard union types #10112
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odersky
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isSoft flag in OrTypes
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It turned out that it's generally clear whether an OrType should be soft or hard, so this is a good first step to solve the problem.
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@liufengyun We get quite a few different check files in pattern matching. One problem is that an extra empty line got added in several of them. There are also two completely different outputs for tests involving hard union types. In one case, the check file is now 8MB long! I updated the check files in 248f9eb. Can you take a look at the failures, and possibly also revert 248f9eb? |
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OK, I'll have a look and fix the exhaustivity check problems. |
It seems it's not needed since erasure already takes care of inserting the necessary casts
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- show at most 6 unmatched cases
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| @@ -18,7 +18,7 @@ import org.junit.Test | |||
| class PatmatExhaustivityTest { | |||
| val testsDir = "tests/patmat" | |||
| // stop-after: patmatexhaust-huge.scala crash compiler | |||
| val options = List("-color:never", "-Ystop-after:crossCast", "-Ycheck-all-patmat", "-classpath", TestConfiguration.basicClasspath) | |||
| val options = List("-color:never", "-Ystop-after:explicitSelf", "-Ycheck-all-patmat", "-classpath", TestConfiguration.basicClasspath) | |||
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That explains the mystery of the added lines, I suppose? Good catch!
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Yes, most failures come from this change. The test case i8922c.scala and i4030.scala are due to type inference change.
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| ss.foldLeft(LazyList(Nil : List[Space])) { (acc, flat) => | ||
| for { sps <- acc; s <- flat } | ||
| yield sps :+ s |
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Thanks for the fixes Fengyun! Your changes LGTM. Can you do the review for the rest? |
| @@ -18,7 +18,7 @@ import org.junit.Test | |||
| class PatmatExhaustivityTest { | |||
| val testsDir = "tests/patmat" | |||
| // stop-after: patmatexhaust-huge.scala crash compiler | |||
| val options = List("-color:never", "-Ystop-after:crossCast", "-Ycheck-all-patmat", "-classpath", TestConfiguration.basicClasspath) | |||
| val options = List("-color:never", "-Ystop-after:explicitSelf", "-Ycheck-all-patmat", "-classpath", TestConfiguration.basicClasspath) | |||
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Yes, most failures come from this change. The test case i8922c.scala and i4030.scala are due to type inference change.
| @@ -9,5 +9,6 @@ object TestGADT { | |||
| def f[A <: Seq[_], B, Foo >: A => B](v: Root[Foo], u: Root[Foo]) = (v, u) match { | |||
| case (C3(), C3()) => | |||
| } | |||
| f(C3[Seq[_], Long](), C4[Seq[_], Long]()) | |||
| // The following line no longer type checks | |||
| // f(C3[Seq[_], Long](), C4[Seq[_], Long]()) | |||
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This test case shows that this PR improves over the previous handling of union types 👍
The new system widens only soft union types using a join. If a hard union type appears in a soft one, it is dissolved together with the soft union type. Unions with Null continue to be treated specially.