Fix non-determinism in Regex source generator

[stephentoub]

The source generator enumerates a Hashtable to write out its contents. When the keys of the Hashtable are strings, string hash code randomization may result in the order of that enumeration being different in different processes, leading to non-deterministic ordering of values written out and thus non-deterministic source generator output.

Fixes#76774 (though we'll want to backport this to release/7.0)
cc: @MichalStrehovsky, @ViktorHofer, @joperezr

@jaredpar, another source of non-determinism for your list.

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Issue Details

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The source generator enumerates a Hashtable to write out its contents. When the keys of the Hashtable are strings, string hash code randomization may result in the order of that enumeration being different in different processes, leading to non-deterministic ordering of values written out and thus non-deterministic source generator output.

Fixes #76774
cc: @MichalStrehovsky, @ViktorHofer, @joperezr

@jaredpar, another source of non-determinism for your list.

Author:	stephentoub
Assignees:	-
Labels:	area-System.Text.RegularExpressions
Milestone:	-

[joperezr]

LGTM

[stephentoub]

/backport to release/7.0

[github-actions]

Started backporting to release/7.0: https://github.com/dotnet/runtime/actions/runs/3436073260