https://issues.dlang.org/show_bug.cgi?id=20122

          Issue ID: 20122
           Summary: core.atomic.cas discards result on failure
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: druntime
          Assignee: nobody@puremagic.com
          Reporter: turkeyman@gmail.com

The implementation of `cas` discards the result when the compare fails. This is a strange choice, and not desirable.

There needs to be additional overloads that actually return the result.

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