Add an immutable array type #5885
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odersky force-pushed the add-immutable-array branch from a96c5a3 to 1783f42 Compare 
| Btw, the first lines of |
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| val xs = IArray(1, 2, 3) | ||
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| def f[T](ys: IArray[T]) = { |
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What type does this method erase to? f(ys: Array[AnyRef])? Or f(ys: AnyRef)?
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No, it's Object. Just what Array[T] erases to.
| I tried to make opaque type IArray[+T] = Array[_ <: T]Unfortunately, that runs into problems when it comes to class tags. I get: Indeed, there's no way to create an |
| That shouldn't matter outside of the companion of |
odersky force-pushed the add-immutable-array branch from 1783f42 to f0eb2bb Compare | @sjrd Right. After adding some casts in iArray's implementation, I could make them covariant, after all. 👍 |
odersky force-pushed the add-immutable-array branch from 1e8f916 to 4f98732 Compare | @@ -0,0 +1,3 @@ | |||
| import annotation.unchecked.uncheckedVariance | |||
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Typo in the file name: “covariant-opaque.scala”
| val bs: IArray[Double] = IArray(1.0, 2.0) | ||
| val cs: Array[Double] = bs.asInstanceOf[Array[Double]] | ||
| cs(1) = 3.0 | ||
| assert(bs(1) == 3.0) |
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Can we also check that apply and update don’t box elements?
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That's harder. I believe there are ways to test it, but I don't know them. The fact that apply is an inline method means it is literally replaced by its right-hand side, so by the rules of inlining there can't be any boxing. I verified the code after erasure by looking at it to make sure that's the case.
odersky force-pushed the add-immutable-array branch 2 times, most recently from bbca7f0 to c7b0651 Compare | Community build fails with: |
| Are the changes to the community build submodules in c7b0651 intentional? |
Unary extension methods are inlined before the end of `extMethodApply`. Have to take this into account when checking that the call is to an extension method.
IArray[T] is an opaque alias for Array[T]
This gives us the right error message if we try to instantiate an hk opaque type with `new`.
Also, add `empty` method.
odersky force-pushed the add-immutable-array branch from c7b0651 to c532d3e Compare | @OlivierBlanvillain No, I discovered my error: pushed wrong submodule hashes. |
Need to drop the explicit result type since apparently Array's unapplySeq type is different between 2.12 and 2.13.
odersky force-pushed the add-immutable-array branch from a8b794c to b9decdc Compare | Going to merge this now, to avoid further breakage by fast-moving infrastructure changes. |
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So far, it's called
scala.IArray[T]. I am not super happy with the name but could not come up with anything better yet.It's an opaque alias of
Array[T]that only exposes theapplyandlengthmethods.Still missing: Wrappers that add all sequence ops to IArrays. We should upgrade to the new collections before we do this.