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liufengyun opened this issue Apr 17, 2020 · 2 comments · Fixed by #17483
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No warnings for union type test pattern #8742

liufengyun opened this issue Apr 17, 2020 · 2 comments · Fixed by #17483
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@liufengyun
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area:transform itype:bug

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@liufengyun
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Minimized code

class A
class B
class C

object Test {
  def bar(x: A) = x match {
    case x: (B | C) => x // no warning?
    case _ =>
  }
}

Output

No warnings

Expectation

The compiler should produce a warning, as the test is always false.
@liufengyun liufengyun self-assigned this Apr 18, 2020
@liufengyun liufengyun mentioned this issue Apr 19, 2020
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@Decel
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Decel commented May 11, 2023

There is a warning message since 3.2.0, I think?

ckipp01 added a commit to ckipp01/dotty that referenced this issue May 12, 2023
@ckipp01
test: add in a regression test for scala#8742
d23db88 
There was also some other tests that were _very_ similar to this, so it
seemed like the logical place to also just include this one instead of
creating another file for it.

Closes scala#8742
@ckipp01 ckipp01 mentioned this issue May 12, 2023
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ckipp01 commented May 12, 2023

Thanks for pointing this out @Decel! Yes, it does seem to be fixed. I added this to a test case in #17483.

nicolasstucki added a commit that referenced this issue May 12, 2023
@nicolasstucki
test: add in a regression test for #8742 (#17483)
fdbdb70 
There was also some other tests that were _very_ similar to this, so it
seemed like the logical place to also just include this one instead of
creating another file for it.

Closes #8742
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test: add in a regression test for #8742 ckipp01/dotty
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@liufengyun @Decel @ckipp01