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The Sway compiler supports a list of attributes that perform various operations that are useful for building, testing and documenting Sway programs. Below is a list of all available attributes:

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The #[allow(...)] attribute overrides checks so that violations will go unreported. The following checks can be disabled:

  • #[allow(dead_code)] disable checks for dead code;
  • #[allow(deprecated)] disables checks for usage of deprecated structs, functions and other items.

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The #[doc(..)] attribute specifies documentation.

Line doc comments beginning with exactly three slashes ///, are interpreted as a special syntax for doc attributes. That is, they are equivalent to writing #[doc("...")] around the body of the comment, i.e., /// Foo turns into #[doc("Foo")]

Line comments beginning with //! are doc comments that apply to the module of the source file they are in. That is, they are equivalent to writing #![doc("...")] around the body of the comment. //! module level doc comments should be at the top of Sway files.

Documentation can be generated from doc attributes using forc doc.

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The inline attribute suggests that a copy of the attributed function should be placed in the caller, rather than generating code to call the function where it is defined.

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Note: The Sway compiler automatically inlines functions based on internal heuristics. Incorrectly inlining functions can make the program slower, so this attribute should be used with care.

The #[inline(never)] attribute suggests that an inline expansion should never be performed.

The #[inline(always)] attribute suggests that an inline expansion should always be performed.

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Note: #[inline(..)] in every form is a hint, with no requirements on the language to place a copy of the attributed function in the caller.

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The lack of #[payable] implies the method is non-payable. When calling an ABI method that is non-payable, the compiler emits an error if the amount of coins forwarded with the call is not guaranteed to be zero. Note that this is strictly a compile-time check and does not incur any runtime cost.

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In Sway, functions are pure by default but can be opted into impurity via the storage function attribute. The storage attribute may take read and/or write arguments indicating which type of access the function requires.

The #[storage(read)] attribute indicates that a function requires read access to the storage.

The #[storage(write)] attribute indicates that a function requires write access to the storage.

More details in Purity .

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The #[test] attribute marks a function to be executed as a test.

The #[test(should_revert)] attribute marks a function to be executed as a test that should revert.

More details in Unit Testing .

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The #[deprecated] attribute marks a item as deprecated and makes the compiler emit a warning for every usage of the deprecated item. This warning can be disabled using #[allow(deprecated)].

It is possible to improve the warning message with #[deprecated(note = "your message")]