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author | Olivier Blanvillain <olivier.blanvillain@gmail.com> | 2017-04-13 09:18:46 +0200 |
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committer | Olivier Blanvillain <olivier.blanvillain@gmail.com> | 2017-04-13 10:39:29 +0200 |
commit | 3e04b6f3aa4e4088220f199bd6aa5c6644c22354 (patch) | |
tree | c2b1a480a11ea6b23b2bc2f1b322203a8425c4da /tests | |
parent | 3a9deec8e7a3a093e9b56461650857c4cb7a9d8c (diff) | |
download | dotty-3e04b6f3aa4e4088220f199bd6aa5c6644c22354.tar.gz dotty-3e04b6f3aa4e4088220f199bd6aa5c6644c22354.tar.bz2 dotty-3e04b6f3aa4e4088220f199bd6aa5c6644c22354.zip |
Revert <: Product requierment in pattern matching
The change in question broke the following pattern, commonly used in name based pattern matching:
```scala
object ProdEmpty {
def _1: Int = ???
def _2: String = ???
def isEmpty = true
def get = this
}
```
This type define both `_1` and `get` + `isEmpty` (but is not <: Product). After #1938, `ProdEmpty` became eligibles for both product and name based pattern. Because "in case of ambiguities, *Product Pattern* is preferred over *Name Based Pattern*", isEmpty wouldn't be used, breaking the scalac semantics.
Diffstat (limited to 'tests')
-rw-r--r-- | tests/run/1938-2.scala | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/tests/run/1938-2.scala b/tests/run/1938-2.scala new file mode 100644 index 000000000..32e4c4518 --- /dev/null +++ b/tests/run/1938-2.scala @@ -0,0 +1,37 @@ +object ProdNonEmpty { + def _1: Int = 0 + def _2: String = "???" // Slight variation with scalac: this test passes + // with ??? here. I think dotty behavior is fine + // according to the spec given that methods involved + // in pattern matching should be pure. + def isEmpty = false + def unapply(s: String): this.type = this + def get = this +} + +object ProdEmpty { + def _1: Int = ??? + def _2: String = ??? + def isEmpty = true + def unapply(s: String): this.type = this + def get = this +} + +object Test { + def main(args: Array[String]): Unit = { + "" match { + case ProdNonEmpty(0, _) => () + case _ => ??? + } + + "" match { + case ProdNonEmpty(1, _) => ??? + case _ => () + } + + "" match { + case ProdEmpty(_, _) => ??? + case _ => () + } + } +} |