Restrict syntax of typed patterns #16150

dwijnand · 2022-10-07T09:50:37Z

Fix nested named irrefutable typetest pattern causes exhaustivity warning #10994: align typed pattern syntax to Scala 2
Fixes Erratic compiler behavior for inlined function definitions #15893

In Scala 2, a typed pattern `p: T` restricts that `p` can only be a pattern variable. In Dotty, scala#6919 allows `p` to be any pattern, in order to support pattern matching on generic number literals. This PR aligns the syntax with Scala 2 by stipulating that in a typed pattern `p: T`, either - `p` is a pattern variable, or - `p` is a number literal

The test case `tests/explicit-nulls/neg/strip.scala` specify that null unions inside intersection types should work. After changing the scrutinee type of the extractor `OrNull` it is no longer the case. Changing the scrutinee type is still justified because it agrees with the name as well as the usage in `Types.scala`. In contrast, in `Typer.scala`, the logic is more clear without using `OrNull`.

Co-authored-by: Jamie Thompson <bishbashboshjt@gmail.com>

odersky · 2022-10-15T14:42:10Z

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

     */
    def pattern1(location: Location = Location.InPattern): Tree =
      val p = pattern2()
-      if in.isColon then
+      if (isVarPattern(p) || p.isInstanceOf[Number]) && in.isColon then


The code does not match the syntax: simple literals can also be strings, characters, or booleans. Also there should be tests that all simple literals can be given a type ascription.

The numeric literal tests are in your genericNumLits, BigFloat, GenericNumLits tests.

docs/_docs/internals/syntax.md

bishabosha

approve for change to syntax documents

dwijnand · 2022-11-14T10:06:45Z

@odersky happy to go with this, allowing only numeric literals (in addition to pattern variables)? Wouldn't want this to slip to 3.4.0.

odersky

LGTM. But I am not sure what happens with quotes and splices. Don't we need something like

$x : T

? Is that still allowed?

Reassigning to @nicolasstucki to get his input.

dwijnand · 2022-11-17T12:22:35Z

It is, like

x match
  case '{ $x: T } => // match using outer `T`

in tests/pos-macros/i10050.scala.

Done

odersky · 2022-11-17T12:51:35Z

OK, then it's good to go.

PR scala#16257 introduced a test for bindings in type annotations. Simultanously, scala#16150 disallowed the syntax that allowed the test to parse and compile. The test should be no longer needed.

smarter · 2022-11-17T19:01:25Z

This broke the CI, but @dwijnand is currently looking into it: #16361

Should fix CI. PR #16257 introduced a test for handling bindings in type annotations inside match cases. Simultaneously, #16150 disallowed the same syntax. Because of that the test should no longer be necessary, as it only pertains to the removed feature.

This kind of patterns were disabled in scala#16150. Fixes scala#16367

This kind of patterns were disabled in #16150. Fixes #16367

WojciechMazur · 2022-12-08T15:37:57Z

The following snippet fails in nightly. Bisect points to this PR. Was that behaviour expected?:

@main def Test = 
    val x: Any = 1
    x match
      case x @ (works: Long) => x
      case x @ fails: Int => x

errror

[error] bisect/test.scala:5:21: '=>' expected, but ':' found
[error]       case x @ fails: Int => x 
[error]

The snippet is based on a code found in tasty-query by Open CB

odersky · 2022-12-08T15:44:49Z

I think the error is expected.

dwijnand · 2022-12-12T09:45:56Z

Yes, that's expected. And it's just a test case (https://github.com/scalacenter/tasty-query/blob/main/test-sources/src/main/scala/simple_trees/Bind.scala)

PR scala#16257 introduced a test for bindings in type annotations. Simultanously, scala#16150 disallowed the syntax that allowed the test to parse and compile. The test should be no longer needed.

This kind of patterns were disabled in scala#16150. Fixes scala#16367

…attern other than a variable or a number literal. This partially reverts the changes from scala#16150. This change is motivated by not breaking source compatibility for a number of projects in the Open Community Build.

…n other than a variable or a number literal. This partially reverts the changes from scala#16150. This change is motivated by not breaking source compatibility for a number of projects in the Open Community Build.

Raise a warning instead of an error for a type ascription on a pattern other than a variable or a number literal. This partially reverts the changes from #16150. This change is motivated by not breaking source compatibility for a number of projects in the Open Community Build.

…n other than a variable or a number literal. This partially reverts the changes from #16150. This change is motivated by not breaking source compatibility for a number of projects in the Open Community Build.

liufengyun and others added 7 commits October 7, 2022 09:47

Fix bootstrapping

50e3a77

Fix tests

8275f32

Update docs/docs/internals/syntax.md

ddcecd1

Co-authored-by: Jamie Thompson <bishbashboshjt@gmail.com>

Fix tests

0bce5e5

Add latest test case

4baaa50

dwijnand marked this pull request as ready for review October 7, 2022 14:43

dwijnand requested a review from odersky October 7, 2022 14:43

dwijnand assigned odersky Oct 7, 2022

odersky previously requested changes Oct 15, 2022

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odersky assigned dwijnand and unassigned odersky Oct 15, 2022

Only allow _numeric_ literals in typed patterns

2c459cd

bishabosha reviewed Oct 17, 2022

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docs/_docs/internals/syntax.md Show resolved Hide resolved

Copy changes from internal/syntax to reference/syntax

27ba2e1

dwijnand assigned bishabosha and unassigned dwijnand Nov 5, 2022

dwijnand requested a review from bishabosha November 5, 2022 10:04

bishabosha approved these changes Nov 7, 2022

View reviewed changes

dwijnand assigned odersky and unassigned bishabosha Nov 7, 2022

dwijnand requested a review from odersky November 7, 2022 09:29

dwijnand added this to the 3.3.0-RC1 milestone Nov 14, 2022

bishabosha added the needs-minor-release This PR cannot be merged until the next minor release label Nov 14, 2022

odersky reviewed Nov 17, 2022

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odersky assigned nicolasstucki and unassigned odersky Nov 17, 2022

dwijnand merged commit c5181b9 into scala:main Nov 17, 2022

dwijnand deleted the disable-typed-unapply branch November 17, 2022 12:23

jchyb mentioned this pull request Nov 17, 2022

Remove an outdated test #16361

Merged

nicolasstucki mentioned this pull request Nov 18, 2022

Nightly Dotty workflow of 2022-11-18 failed #16367

Closed

nicolasstucki added a commit to dotty-staging/dotty that referenced this pull request Nov 18, 2022

Workaround case x @ U() : T =>

aa51517

This kind of patterns were disabled in scala#16150. Fixes scala#16367

nicolasstucki mentioned this pull request Nov 18, 2022

Workaround case x @ U() : T => (fix main branch) #16369

Merged

nicolasstucki added a commit to dotty-staging/dotty that referenced this pull request Nov 18, 2022

Workaround case x @ U() : T =>

a01248f

This kind of patterns were disabled in scala#16150. Fixes scala#16367

nicolasstucki added a commit that referenced this pull request Nov 18, 2022

Workaround case x @ U() : T => (fix main branch) (#16369)

298ff3f

This kind of patterns were disabled in #16150. Fixes #16367

little-inferno pushed a commit to little-inferno/dotty that referenced this pull request Jan 25, 2023

Workaround case x @ U() : T =>

697dccb

This kind of patterns were disabled in scala#16150. Fixes scala#16367

prolativ mentioned this pull request May 10, 2023

Just warn on type ascription on a pattern #17454

Merged

Kordyjan modified the milestones: 3.3.0-RC1, 3.3.0 Aug 1, 2023

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Restrict syntax of typed patterns #16150

Restrict syntax of typed patterns #16150

dwijnand commented Oct 7, 2022 •

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Restrict syntax of typed patterns #16150

Restrict syntax of typed patterns #16150

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