[Proposal]: readonly parameters

[333fred]

readonly parameters

• Specification: https://github.com/dotnet/csharplang/blob/main/proposals/readonly-parameters.md
• Discussion: [Proposal]: `readonly` parameters #8715

Summary

We allow parameters to be marked with readonly. This disallows them from being assigned to or being passed by ref or out.

Design meetings

• https://github.com/dotnet/csharplang/blob/main/meetings/2021/LDM-2021-10-27.md#readonly-modifiers-for-primary-constructors
• https://github.com/dotnet/csharplang/blob/main/meetings/2023/LDM-2023-07-17.md#readonly-parameters
• https://github.com/dotnet/csharplang/blob/main/meetings/2023/LDM-2023-07-26.md
• https://github.com/dotnet/csharplang/blob/main/meetings/2023/LDM-2023-07-31.md
• https://github.com/dotnet/csharplang/blob/main/meetings/2024/LDM-2024-05-08.md#readonly-for-primary-constructor-parameters