ymandel added a comment. In D61015#1478539 <https://reviews.llvm.org/D61015#1478539>, @ilya-biryukov wrote:
> Why would we consider this a legitimate failure, rather than a programming > error? > Same argument could be made about any form of format-string-like functions, > e.g. `llvm::formatv` or `sprintf`. > Yet, they return strings and not `Expected<string>` or their equivalent. It's not that it's a legitimate failure so much as an invalid argument -- that is, the caller caused it and therefore should handle the failure. For a standalone tool making the call, I'd argue they should treat it as a programming error and assert to crash. However, a server that takes the input from, say, a user will want to propagate that back to the user. As for `formatv` and `sprintf` -- I think the difference is that this has a more dynamic design. Both of those take explicit arguments at the callsite, vs. TextGenerator which takes a `MatchResult`. But, that's just a detail -- the key thing is that we're trying to support a usecase where the input may be flawed and we want to fail gracefully. We do so at the cost of the added complexity of `Expected<>`. Alternatives: 1. add a separate validation function. But, this will complicate the design since we'd need to pass two functions rather than one. That is, `TextGenerator` would need to be a pair of functions. 2. return an empty string on failure. This has the typical tradeoffs of using a sentinel value. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D61015/new/ https://reviews.llvm.org/D61015 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
