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smarter opened this issue May 10, 2019 · 1 comment · Fixed by #6850
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Document irrefutable unapply in pattern matching #6490

smarter opened this issue May 10, 2019 · 1 comment · Fixed by #6850
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area:documentation area:pattern-matching

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smarter commented May 10, 2019

Unapply that return Some[X] or true are statically known to always match, and the exhaustiveness checker uses this knowledge (see https://github.com/lampepfl/dotty/blob/494f9e6c2a397ab47a08d16d09d64c88c4a0ee82/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala#L285-L294). This should be documented in http://dotty.epfl.ch/docs/reference/changed-features/pattern-matching.html
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smarter commented May 10, 2019

See also the (incomplete) notion of an irrefutable pattern in the spec: https://www.scala-lang.org/files/archive/spec/2.12/08-pattern-matching.html#irrefutable-patterns

@liufengyun liufengyun self-assigned this May 14, 2019
liufengyun added a commit to dotty-staging/dotty that referenced this issue Jul 12, 2019
@liufengyun
Fix scala#6490: Add spec for irrefutable extractors
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@liufengyun liufengyun mentioned this issue Jul 15, 2019
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liufengyun added a commit to dotty-staging/dotty that referenced this issue Jul 15, 2019
@liufengyun
Fix scala#6490: Add spec for irrefutable extractors
1809a14
liufengyun added a commit to dotty-staging/dotty that referenced this issue Jul 15, 2019
@liufengyun
Fix scala#6490: Add spec for irrefutable extractors
08cf458
@liufengyun liufengyun mentioned this issue Jul 15, 2019
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liufengyun added a commit to dotty-staging/dotty that referenced this issue Dec 13, 2019
@liufengyun
Fix scala#6490: Add spec for irrefutable extractors
fa22f1b
liufengyun added a commit to dotty-staging/dotty that referenced this issue Dec 13, 2019
@liufengyun
Fix scala#6490: Add spec for irrefutable extractors
40337f6
liufengyun added a commit to dotty-staging/dotty that referenced this issue Jan 14, 2020
@liufengyun
Fix scala#6490: Add spec for irrefutable extractors
f824f25
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Fix #6849: support irrefutable sequence match dotty-staging/dotty
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