[Proposal]: Support optional and named arguments in Expression trees

[333fred]

Support optional and named arguments in Expression trees

• Specification: https://github.com/dotnet/csharplang/blob/main/proposals/optional-and-named-parameters-in-expression-trees.md
• Discussion: [Proposal]: Support optional and named arguments in Expression trees #9190

Summary

Support optional and named arguments in method calls in Expression trees

Design meetings

• https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-03-12.md#optional-and-named-parameters-in-expression-trees