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Add special handling for comparisons with Singleton types #20474

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merged 1 commit into from
May 28, 2024
Merged

Add special handling for comparisons with Singleton types #20474

merged 1 commit into from
May 28, 2024

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odersky
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@odersky odersky commented May 26, 2024

Fixes #15030

@odersky odersky marked this pull request as ready for review May 27, 2024 11:43
@odersky odersky requested a review from smarter May 27, 2024 11:43
@odersky odersky assigned odersky and smarter and unassigned odersky May 27, 2024
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smarter approved these changes May 28, 2024
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LGTM but this might need equivalent handling in tasty-query /cc @sjrd

@smarter smarter merged commit 9b5ab2e into scala:main May 28, 2024
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@smarter smarter deleted the fix-15030 branch May 28, 2024 13:40
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noti0na1 commented May 28, 2024 •
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I don't think the rule in this PR is correct:

class A
class B extends A

def f(a: A, c: A) =
  val b1: a.type = a
  val b2: a.type & B = a.asInstanceOf[a.type & B]
  val b3: c.type & A = c
  val b4: a.type | c.type = c

  val d1: b1.type = a
  val d2: b2.type = a // ok
  val d3: b3.type = a // error
  val d4: b4.type = a // error

In 3.4.2:

> scala-cli compile -S 3.4 Stest.scala
Compiling project (Scala 3.4.2, JVM (21))
[error] ./Stest.scala:324:21
[error] Found:    (a : A)
[error] Required: (b3 : (c : A) & A)
[error]   val d3: b3.type = a // error
[error]                     ^
[error] ./Stest.scala:325:21
[error] Found:    (a : A)
[error] Required: (b4 : (a : A) | (c : A))
[error]   val d4: b4.type = a // error
[error]                     ^
Error compiling project (Scala 3.4.2, JVM (21))
Compilation failed

cc @sjrd

odersky added a commit to dotty-staging/dotty that referenced this pull request May 28, 2024
@odersky
Fix isEffectivelySingleton
d04005c 
As usual, OrTypes need to be excluded. a.type | b.type is not effectively a
singleton. It seems to be an easy trap to fall into.

Follow-up to scala#20474
@odersky odersky mentioned this pull request May 28, 2024
Merged
noti0na1 added a commit that referenced this pull request May 28, 2024
@noti0na1
Fix isEffectivelySingleton (#20486)
a21d2af 
As usual, OrTypes need to be excluded. a.type | b.type is not
effectively a singleton. It seems to be an easy trap to fall into.

Follow-up to #20474
@Kordyjan Kordyjan added this to the 3.5.1 milestone Jul 3, 2024
@WojciechMazur WojciechMazur mentioned this pull request Jul 8, 2024
Merged
WojciechMazur pushed a commit that referenced this pull request Jul 8, 2024
@odersky @WojciechMazur
Fix isEffectivelySingleton
a88da44 
As usual, OrTypes need to be excluded. a.type | b.type is not effectively a
singleton. It seems to be an easy trap to fall into.

Follow-up to #20474

[Cherry-picked d04005c]
WojciechMazur added a commit that referenced this pull request Jul 9, 2024
@WojciechMazur
Backport "Add special handling for comparisons with Singleton types" …
737c2bc 
…to LTS (#21126)

Backports #20474 to the LTS branch.

PR submitted by the release tooling.
[skip ci]
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