checkaction=context calls user-defined toString-methods if defined. But those can throw an exception which masks the real assertion failure, e.g.: truct MayThrow { int i; string toString() { if (i == 1) throw new Exception("Error"); return "Some message"; } } assert(MayThrow(0) == MayThrow(1)); ==================================================== This test will report the exception from toString(), not the assertion failure.
@MoonlightSentinel created dlang/druntime pull request #3499 "Fix 22026 - Catch exceptions thrown by user-defined toString methods... " fixing this issue: - Fix 22026 - Catch exceptions thrown by user-defined toString methods... ... when formatting values for `-checkaction=context` and print the aggregate members as a fallback. This ensures that an unrelated error does not mask the assertion failure. https://github.com/dlang/druntime/pull/3499