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Add readonly modifier support for property getters#357

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JoeRobich merged 3 commits intomainfrom
copilot/fix-readonly-getter-setter
Jan 6, 2026
Merged

Add readonly modifier support for property getters#357
JoeRobich merged 3 commits intomainfrom
copilot/fix-readonly-getter-setter

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Copilot AI commented Dec 20, 2025 •
edited
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The readonly keyword was not being highlighted when used as an accessor modifier for getters in properties and indexers (C# 8.0+).

struct M
{
    public int Counter
    {
        get => counter;
        readonly set { }  // readonly is not valid on setters
    }
    
    public int this[int i]
    {
        readonly get => counter;  // readonly was not highlighted
        set { }
    }
}

Changes

  • Grammar: Added readonly as an optional modifier specifically for get accessors only (not set or init, as per C# language specification)
  • Tests: Added coverage for readonly getters with both expression bodies and block bodies

The readonly modifier is now correctly restricted to getter accessors, matching C# 8.0+ language semantics for readonly instance members in structs.

Original prompt

This section details on the original issue you should resolve

<issue_title>[Textmate] readonly getter and setter in struct</issue_title>
<issue_description>## Details

What editor are you seeing the problem in? (e.g. Atom, Visual Studio Code, etc.)
vscode
What version of the editor are you using?
1.85.1
What color theme are you using?
dark plus

Repro

struct M
{
    private int counter;
    public int Counter
    {
        get => counter;
        readonly set { }
    }
    public int this[int i]
    {
        readonly get => counter;
        set { }
    }
    public readonly void Method()
    {
        counter++;
    }
}

image

Please provide a code example and (optionally) a screenshot demonstrating the problem.</issue_description>

<agent_instructions>From the example, it appears that readonly is not being classified in readonly getters</agent_instructions>

Comments on the Issue (you are @copilot in this section)

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@JoeRobich
Add support for readonly accessor modifiers
6035027 
- Added readonly to accessor modifier pattern in property-accessors
- Added three comprehensive tests for readonly getters and setters
- All 896 tests passing

Co-authored-by: JoeRobich <611219+JoeRobich@users.noreply.github.com>
Copilot AI changed the title [WIP] Fix readonly getter and setter classification in struct Add readonly modifier support for property accessors Dec 20, 2025
Copilot AI requested a review from JoeRobich December 20, 2025 02:39
JoeRobich
JoeRobich reviewed Dec 20, 2025
View reviewed changes
@JoeRobich
Restrict readonly modifier to getter accessors only
86c7e3c 
Per reviewer feedback, readonly is only applicable to getters, not setters.
- Moved readonly pattern from general accessor modifiers to getter-specific pattern
- Updated tests to only validate readonly on getters (removed invalid readonly setter tests)
- All 895 tests passing

Co-authored-by: JoeRobich <611219+JoeRobich@users.noreply.github.com>
Copilot AI changed the title Add readonly modifier support for property accessors Add readonly modifier support for property getters Dec 20, 2025
Copilot AI requested a review from JoeRobich December 20, 2025 03:06
@JoeRobich JoeRobich marked this pull request as ready for review December 20, 2025 03:22
@JoeRobich JoeRobich merged commit 049c5d4 into main Jan 6, 2026
2 checks passed
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@dibarbet dibarbet dibarbet approved these changes

@JoeRobich JoeRobich Awaiting requested review from JoeRobich

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[Textmate] readonly getter and setter in struct

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@JoeRobich @dibarbet