List pattern syntax #51299

alrz · 2021-02-18T05:22:40Z

Spec: https://github.com/dotnet/csharplang/blob/main/proposals/list-patterns.md
Test plan: #51289

src/Compilers/CSharp/Portable/Parser/LanguageParser.cs

.editorconfig

src/Compilers/CSharp/Portable/Syntax/Syntax.xml

jcouv · 2021-03-01T22:39:48Z

I couldn't find the csharplang spec/proposal. Was it uploaded? #Closed

alrz · 2021-03-02T04:52:29Z

I couldn't find the csharplang spec/proposal. Was it uploaded?

Not yet. The proposal is updated at dotnet/csharplang#3245 #Closed

…t-patterns-syntax

src/Compilers/CSharp/Portable/Parser/LanguageParser.cs

jcouv · 2021-03-24T04:59:23Z

...tures/CSharp/Portable/Completion/CompletionProviders/PropertySubPatternCompletionProvider.cs

@@ -124,7 +124,7 @@ private static SyntaxToken TryGetOpenBraceOrCommaInPropertyPatternClause(SyntaxT
 return default;
 }

- return token.Parent.IsKind(SyntaxKind.PropertyPatternClause) ? token : default;
+ return token.Parent.IsKind(SyntaxKind.PropertyPatternClause, SyntaxKind.ListPatternClause) ? token : default;


Is there a test for this change?

Lots of failing tests for this completion provider.

{ $$ } always see a list pattern clause.

jcouv · 2021-03-24T04:59:38Z

...s/SharedUtilitiesAndExtensions/Compiler/CSharp/Formatting/Rules/IndentBlockFormattingRule.cs

@@ -219,7 +220,7 @@ private void AddBlockIndentationOperation(List<IndentBlockOperation> list, Synta
 }

 // for lambda, set alignment around braces so that users can put brace wherever they want
- if (node.IsLambdaBodyBlock() || node.IsAnonymousMethodBlock() || node.IsKind(SyntaxKind.PropertyPatternClause) || node.IsKind(SyntaxKind.SwitchExpression))
+ if (node.IsLambdaBodyBlock() || node.IsAnonymousMethodBlock() || node.IsKind(SyntaxKind.PropertyPatternClause, SyntaxKind.ListPatternClause) || node.IsKind(SyntaxKind.SwitchExpression))


Do we have a corresponding test?

Just one, failing in the previous test runs.

For cases with no failing test I added a comment to cover later.

jcouv

Compiler changes LGTM Thanks (iteration 23)

jcouv · 2021-03-24T05:03:36Z

The correctness leg reports a diagnostic that probably needs to be suppressed:
error RS0027: Symbol 'PropertyPatternClause' violates the backcompat requirement: 'Public API with optional parameter(s) should have the most parameters amongst its public overloads'. See 'https://github.com/dotnet/roslyn/blob/master/docs/Adding%20Optional%20Parameters%20in%20Public%20API.md' for details. #Closed

jcouv · 2021-03-31T21:00:52Z

@333fred @dotnet/roslyn-compiler for a second review. Thanks

jasonmalinowski · 2021-03-31T21:21:59Z

src/Compilers/CSharp/Portable/Syntax/Syntax.xml

+ <Field Name="DotDotToken" Type="SyntaxToken">
+ <Kind Name="DotDotToken"/>
+ </Field>
+ <Field Name="Pattern" Type="PatternSyntax" Optional="true"/>


Is there an example for what this field is being used for? The proposal implied that nothing can be listed after the .. in the list or that there was still an open question there.

The proposal implied that nothing can be listed after the .. in the list

That's true only for enumerable and multi-dimensional arrays.

For compatible types this optionally matches the returned slice. See https://github.com/dotnet/csharplang/blob/main/proposals/list-patterns.md#lowering-on-countableindexeablesliceable-type

src/Compilers/CSharp/Test/Syntax/Parsing/PatternParsingTests_ListPatterns.cs

333fred · 2021-04-05T23:34:34Z

src/Compilers/CSharp/Test/Syntax/Parsing/PatternParsingTests_ListPatterns.cs

+ }
+
+ [Fact]
+ public void SlicePattern_10()


It would be good to have variations on these slice tests that have the .. after the other pattern component. Also, some pattern combinations with positional and length patterns would be good.

Added a few tests. Let me know if you have any specific scenario that is not covered.

I'd expect to see some of the previous variations you had here. For example, c is { {}.. } from SlicePattern_05. I'd go through your existing tests and add flipped versions of these.

In reply to: 608770979 [](ancestors = 608770979)

333fred · 2021-04-05T23:35:44Z

Done review pass (commit 24). Code looks good, but I'd like a few more tests before signing off. #Closed

333fred · 2021-04-07T20:00:44Z

Done review pass (commit 25)

…t-patterns-syntax # Conflicts: # src/Compilers/CSharp/Portable/CSharpResources.resx # src/Compilers/CSharp/Portable/xlf/CSharpResources.cs.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.de.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.es.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.fr.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.it.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.ja.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.ko.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.pl.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.pt-BR.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.ru.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.tr.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hans.xlf # src/Compilers/CSharp/Portable/xlf/CSharpResources.zh-Hant.xlf

jcouv · 2021-04-19T16:52:01Z

@333fred Please take another look

333fred

LGTM (commit 28). @jcouv, do you want to take another look?

jcouv

Still LGTM Thanks (iteration 28)

jcouv · 2021-04-20T06:05:22Z

Merged/squashed. Thanks!

alrz · 2021-04-20T12:09:14Z

FYI, this is pending a few open questions especially around binding which I'm going to do next.
(while we're awaiting LDM I'm open to move forward with the other PR if there's enough bandwidth)

jcouv · 2021-05-06T06:16:05Z

@alrz I reached out on discord. I didn't realize there were blocking questions for LDM.
Do you mean the question about multi-dimensional arrays described here? Anything else?

alrz · 2021-05-06T07:40:58Z

@jcouv That's not all. Look for "open question" in the document. A few of those are critical to move forward with the first iteration of list patterns.

jcouv · 2021-05-07T04:12:00Z

@alrz Collected the open issues from the list-pattern spec:

Open question: Should we accept a general pattern following .. in a slice_pattern? Answer: let's say yes for now. Allowing some nested patterns versus allowing all isn't a deep change. We can add that before shipping.
Open question: Should we support all these combinations? Answer: LDM already confirmed, yes.
Open question: We should define the exact binding rules for any of these members and decide if we want to diverge from the range spec. Answer: we should stick to the same behavior as ranges. In short, we bind to indexers if available, otherwise special Slice method.
Open question: Should extension methods play a role in sliceability? Answer: we may change that later (for slicing and slice pattern, thus transforming an error scenario into a working scenario) but should assume "no" for now (keep the existing rules from ranges).
Open question: The pattern {..} tests for expr.Length >= 0. Should we omit such test (assuming Length is always non-negative)? Answer: this doesn't need to be spec'ed, it is an implementation detail. We are free to change/optimize what we emit for this case. I'd start without the optimization. We can add if we have time.
Question on multi-dimensional arrays: I didn't quite understand this one...

Tagging @dotnet/roslyn-compiler as FYI

alrz · 2021-05-07T07:25:51Z

@jcouv Ok, that is not very distant from my draft except for "explicit range indexer support" that needs to be added. I will tidy it up and finish the array match lowering for review. Would you prefer a single PR or should I divide it up?

Question on multi-dimensional arrays: I didn't quite understand this one...

That's only a question on the lowering strategy. Given array is {{1}} which one of the following is expected:

array.GetLength(0) == 1 && array.GetLength(1) == 1 && array[0, 0] is 1

array.GetLength(0) == 1 && array.GetLength(1) == 1 &&
array.GetLowerBound(0) is var b0 && array.GetLowerBound(1) is var b1 &&
array[b0 + 0, b1 + 0] is 1

or something else? I think the latter is actually the correct one, but needed a confirmation.

EDIT: I will do md arrays separately, I think that makes it a lot more manageable.

alrz · 2021-05-20T10:46:44Z

A few questions on md arrays in addition to the lowering issue above:

Should we allow length patterns with md arrays (probably no, unless we want to change the syntax to accept [0,0] etc)
Should we allow length patterns in nested lists? (probably no, there's no point to give a length when all of them must match)
Should we allow slice patterns (without subpatterns) in a nested list? (this is possible unless we decide against it)
Should we treat {} as an empty list in a nested pattern? (in that case new int[,] {{},{}} is {{},{}} returns true)

alrz added 3 commits February 18, 2021 08:41

List pattern syntax

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alrz commented Feb 27, 2021

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Diagnostic suppressions from editorconfig are ignored in source-generated syntax trees #52014

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Implement extended property patterns #52139

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List pattern syntax #51299

List pattern syntax #51299

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List pattern syntax #51299

List pattern syntax #51299

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