E146: An annotation the declaration under it cannot carry

@ownrship(acquires)pub extern fn malloc(size: int): void*;// ERROR [E146]: Unknown annotation '@ownrship'.//   Hint: Did you mean '@ownership'? The known annotations are: @ownership, @ffi.

An annotation, @name(arguments) written on the line before a function or an extern fn, tells the compiler a fact about that declaration. The compiler knows what a function does only because its declaration says so, never because of the function’s name: malloc is understood as an allocator because it says @ownership(acquires), and your own allocator is understood the same way when it says the same thing.

That is why a wrong annotation is an error rather than something quietly skipped. A misspelt one would otherwise switch off the very check it was written to turn on, and you would never find out.

There are two ways to get this error.

The name is not one the compiler knows. The message suggests the closest one and lists them all:

@ownership(acquires)                  // the double-free / use-after-free check@ffi(macos: malloc_size)              // which C symbol an extern binds to, per platform

The arguments do not fit the declaration. The message says what is wrong:

@ownership(acquires)fn count(): int { return 0; }// '@ownership(acquires)' says the function returns a fresh allocation,// but it does not return a pointer.@ownership(releases: q)pub extern fn free(p: void*): void;// 'q' is not a parameter of this function -- write 'releases: p'.@ffi(macos: malloc_size)fn helper(): int { return 0; }// '@ffi' can only sit on an 'extern fn'.

The fix is to correct the spelling, or to say what is actually true of the declaration, or to remove the annotation.

A malformed annotation – a missing ‘)’ or a number where a word belongs – is a syntax error instead, reported where the parser stopped.

Run turf --explain E146 in a terminal to read this again.