Attributes

An attribute attaches metadata to a declaration, written as @[Name(...)] on the line before the item it annotates. Attributes instruct the compiler — to link a foreign library, restrict an item to one platform, or flag a function at its call sites — without changing the declaration's own code.

@[Target("Windows")]
@[Import(lib: "Kernel32.dll")]
extern func Beep(freq: uint32, duration: uint32) -> bool32;

Multiple attributes may be stacked before a single declaration; each applies independently.

Available Attributes

Attribute	Purpose
@[Import]	Link an extern function to a dynamic library
@[Target]	Restrict a declaration to a specific operating system
@[Warn]	Emit a compiler warning at every call site
@[Error]	Emit a compiler error at every call site

See Also

• Foreign Function Interface — where @[Import] is used
• Functions — the declarations attributes most often annotate