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## Description This PR introduces the `panic` expression to the language, as defined in the [ABI Errors RFC](https://github.com/FuelLabs/sway-rfcs/blob/master/rfcs/0014-abi-errors.md#panic). The `panic` expression can be used without arguments, or accept an argument that implements the `std::marker::Error` trait. The `Error` trait is implemented by the compiler for the unit `()`, string slices, and `#[error_type]` enums. Using the `panic` expression without arguments gives the symetry with the `return` expression and acts in the same way as having unit as an argument. ``` panic; panic (); panic "This is some error."; panic Errors::SomeError(42); ``` Panicking without an argument or with unit as argument is discouraged to use. In the upcoming PR that finalizes the ABI errors feature, we will emit a warning if the `panic` is used without arguments or with unit as argument. `panic` expression is available in all program kinds. In predicates it currently compiles only to revert. Once `__dbg` intrinsic is implemented, we can consider compiling to it in predicates. In the upcoming PR, the `error_codes` entry in the ABI JSON will be available for all program kinds. The dead code analysis for the `panic` expression is implemented in the straightforward way, following the current approach of connecting reverts to the exit node. This will be revisted in a separate PR, together with the open TODOs in the DCA implementation of `Return`. Essentially, we want reverting/panicking to connect to program exit and implicit returns to the exit node. Additionally, the PR: - extends `forc test` CLI attributes with `--revert-codes` that prints revert codes even if tests are successful but revert. - updates outdated "Logs Inside Tests" chapter in the documentation on unit testing. - extends the snapshot testing infrastructure to support `forc test` in snapshot tests. - fixes #7072. Partially addresses #6765. ## Breaking Change `panic` is a new reserved keyword. Once the `error_type` feature becomes integrated, compiling any existing code containing a "panic" as an identifier will result in an "Identifiers cannot be a reserved keyword." error. In this PR, `panic` keyword is hidden behind the `error_type` feature flag. This prevents existing code from breaking, unless opted-in. Note that, although being behind a feature flag, `panic` cannot be used in conditional compilation, means in combination with the `#[cfg(experimental_error_type = true/false)]`. The reason is that `cfg` evaluation happens after parsing, and we can either parse `panic` as a keyword or identifier during the parsing, because we cannot distinguish ambiguous cases like `panic;` or just `panic`. This limitation means, that introducing `panic` to `std` can be done only once the `error_type` feature is fully integrated. In practice, this is not a serious limitation, because introducing `panic` in `std` would anyhow, due to effort and design decisions, happen after the feature is integrated. We will provide a migration for this breaking change that will migrate the existing "panic" identifiers to "r#panic". ## Checklist - [x] I have linked to any relevant issues. - [x] I have commented my code, particularly in hard-to-understand areas. - [x] I have updated the documentation where relevant (API docs, the reference, and the Sway book). - [ ] If my change requires substantial documentation changes, I have [requested support from the DevRel team](https://github.com/FuelLabs/devrel-requests/issues/new/choose) - [x] I have added tests that prove my fix is effective or that my feature works. - [x] I have added (or requested a maintainer to add) the necessary `Breaking*` or `New Feature` labels where relevant. - [x] I have done my best to ensure that my PR adheres to [the Fuel Labs Code Review Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md). - [x] I have requested a review from the relevant team or maintainers. |
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