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Deriving path-dependent type equality from value identity (in turn proved by singleton type inhabitation). For context see: https://gist.github.com/copumpkin/cb26bb921bbb81183299
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| scala> trait Foo { type T; val t: T } | |
| defined trait Foo | |
| scala> val x = new Foo { type T = Int ; val t = 23 } | |
| x: Foo{type T = Int} = $anon$1@5aeea69b | |
| scala> val y = new Foo { type T = String ; val t = "foo" } | |
| y: Foo{type T = String} = $anon$1@7d7902b8 | |
| scala> def compare(a: Foo, b: Foo): Option[b.T] = a match { case a2: b.type => Some(a2.t) ; case _ => None } | |
| compare: (a: Foo, b: Foo)Option[b.T] | |
| scala> compare(x, y) | |
| res0: Option[y.T] = None | |
| scala> compare(y, x) | |
| res1: Option[x.T] = None | |
| scala> compare(y, y) | |
| res2: Option[y.T] = Some(foo) | |
| scala> compare(x, x) | |
| res3: Option[x.T] = Some(23) |
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