[Proposal]: Immediately Enumerated Collection Expressions

[RikkiGibson]

• Specification: https://github.com/dotnet/csharplang/blob/main/proposals/immediately-enumerated-collection-expressions.md
• Discussion: [Proposal Discussion]: Immediately Enumerated Collection Expressions #9755

Summary

Permit collection expressions in "immediately enumerated" contexts, without requiring a target type.

foreach (bool b in [true, false])
{
    doMyLogicWith(b);
}

string[] items1 = ["a", "b", .. ["c"]];
string[] items2 = ["a", "b", .. includeRest ? ["c", "d"] : []];

See also #9739.

Design meetings

• https://github.com/dotnet/csharplang/blob/main/meetings/2025/LDM-2025-10-13.md#immediately-enumerated-collection-expressions