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Parse [ after nullable type as part of the type#55044

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cston merged 2 commits intodotnet:release/dev16.11from
cston:55013
Jul 23, 2021
Merged

Parse [ after nullable type as part of the type#55044
cston merged 2 commits intodotnet:release/dev16.11from
cston:55013

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@cston cston commented Jul 22, 2021 •
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Parse ? [ as a nullable array type always in switch and is expression pattern types: x switch { string ? [] y => y }

As a result, parentheses are required when the [ starts a lambda expression with attributes: x is string ? ([A] y => y) : z

Fixes #55013.

@ghost ghost added the Area-Compilers label Jul 22, 2021
@cston cston marked this pull request as ready for review July 22, 2021 07:51
@cston cston requested a review from a team as a code owner July 22, 2021 07:51
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cston commented Jul 22, 2021 •
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                        return !CanStartExpression();

Before this change, CanStartExpression() returned true for [ in x switch { string?[] y => y } so [] y => y was treated as a lambda expression with attributes rather than a well-formed switch expression arm.

In reply to: 885021921

Refers to: src/Compilers/CSharp/Portable/Parser/LanguageParser.cs:6861 in 4b559f9. [](commit_id = 4b559f9, deletion_comment = False)

@cston cston added this to the 16.11 milestone Jul 22, 2021
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cston commented Jul 22, 2021

@dotnet/roslyn-compiler, please review this fix for parsing nullable array types in switch and is patterns. The actual parsing change is small, but there are a number of parsing tests included. Thanks.

jcouv
jcouv reviewed Jul 22, 2021
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Comment thread src/Compilers/CSharp/Test/Syntax/Parsing/LambdaAttributeParsingTests.cs
[Fact]
public void NullableType_Switch_03()
{
string source = "x switch { string? [A] y => y }";
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Makes me glad that we decided to separate list-pattern from the more general recursive pattern ;-)

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jcouv approved these changes Jul 22, 2021
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LGTM Thanks (iteration 2)

@jcouv jcouv self-assigned this Jul 22, 2021
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jcouv commented Jul 23, 2021

Approved by BU and Division triage in email. Can be merged to 16.11
FYI @allisonchou

@cston cston merged commit ebbae5b into dotnet:release/dev16.11 Jul 23, 2021
@cston cston mentioned this pull request Jul 23, 2021
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@cston cston deleted the 55013 branch March 15, 2024 18:18
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