Add support for collection expression.

[gustavoaca1997]

This PR addresses #401

This is my first time contributing to a Tree Sitter grammar, so please let me know if you have any concerns, suggestions, extra test cases, etc.

Change details

• Add new test cases to expressions.txt.
• Modify the test case Array with trailing comma. Roselyn is actually matching [ y, ] against collection_expression, so I've updated the test to reflect that. I used SharpLab to verify that.
• Add grammar rules for collection_element , expression_element , spread_element , collection_expression

How the changes were verified

I ran the tests locally, to verify they are passing.

[tris203]

I have updated ci
If you rebase and regenerate with 0.26.3 please

[gustavoaca1997]

I have updated ci If you rebase and regenerate with 0.26.3 please

Done @tris203 :) Thanks

[gustavoaca1997]

@tris203 I have force pushed the branch again, after accidentally the PR was showing changes that were already in the master branch

[gustavoaca1997]

@tris203 the files failing in the CI are valid C# 14, but are using expressions that are not yet supported: #392

These are the statements that are failing to be parsed in my branch, which should fail as well in master:

• This line from PowerToys' ListViewModel. It has a Conditional Access Expression as a L-Value, which is still not supported in the current grammar.

 listPage.Filters?.CurrentFilterId = currentFilterId;

• This line from PowerToys' CommandItemViewModel.cs. It also has a Conditional Access Expression as a L-Value,

_defaultCommandContextItemViewModel?.Command = Command;

• This line from PowerToys' KernelServiceBase.cs. I believe this is a bug in the grammar, but that still could be solved by supporting Conditional Access Expressions as L-Values. I think it's a mistake that it is parsing the macros, instead of pre-processing the file, which is causing the Conditional Access Expression to be treated as an L-Value rather than the return expression of the lambda function.

static string Redact(object data) =>
#if DEBUG
            data?.ToString();
#else
            "[Redacted]";

It's possible that #400 fixes it.