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## Description This PR reimplements how `#[attribute]`s are parsed, defined, and checked. It fixes the following issues we had with attributes: - attributes were in general not checked for their expected and allowed usage. - when checked, checks were fixing particular reported issues and were scattered through various compilation phases: lexing, parsing, and tree conversion. - when checked, reported errors in some cases had bugs and were overalapping with other errors and warnings. - attribute handling was not centralized, but rahter scattered throught the whole code base, and mostly done at use sites. For concrete examples of these issues, see the list of closed issues below. The PR: - encapsulates the attributes handling within a single abstraction: `Attributes`. - assigns the following properties to every attribute: - _target_: what kind of elements an attribute can annotate. - _multiplicity_: if more then one attribute of the same kind can be applied to an element. - _arguments multiplicity_: a range defining how many arguments an attribute can or must have. - _arguments value expectation_: if attribute arguments are expected to have values. - validates those properties in a single place, during the `convert_parse_tree`. Note that this means that modules with attribute issues will now consistently not reach the type checking phase. This was previously the case for some of the issues with attributes where custom checks where done during the type checking phase. #6987 proposes to move those checks after the tree conversion phase, allowing the continuation of compilation. - adds the `AttributeKind::Unknow` to preserve unknown attributes in the typed tree. - removes redundant code related to attributes: specific warnings and errors, specialized parsing, repetitive and error-prone at use site checks, etc. - removes the unused `Doc` attribute. The PR also introduces a new pattern in emitting errors. The `attr_decls_to_attributes` function will always return `Attributes` even if they have errors, because: - we expect the compilation to continue even in the case of errors. - we expect those errors to be ignored if a valid `#[cfg]` attribute among those evaluates to false. - we expect them to be emitted with eventual other errors, or alone, at the end of the tree conversion of the annotated element. For more details, see the comment on `attr_decls_to_attributes` and `cfg_eval`. Closes #6880; closes #6913; closes #6914; closes #6915; closes #6916; closes #6917; closes #6918; closes #6931; closes #6981; closes #6983; closes #6984; closes #6985. ## Breaking changes Strictly seen, this PR can cause breaking changes, but only in the case of invalid existing attribute usage. We treat those breaking changes as bug fixes in the compiler and, thus, do not have them behind a feature flag. E.g., this kind of code was possible before, but will now emit and error: ```sway #[storage(read, write, read, write)] struct Struct {} ``` ## Checklist - [x] I have linked to any relevant issues. - [x] I have commented my code, particularly in hard-to-understand areas. - [ ] 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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