Macro block2::global_block

macro_rules! global_block {
    ($(#[$m : meta]) * $vis : vis static $name : ident = || $(-> $r : ty) ? $body
 : block) => { ... };
    ($(#[$m : meta]) * $vis : vis static $name : ident = |
 $($a : ident : $t : ty), * $(,) ? | $(-> $r : ty) ? $body : block) => { ... };
}

Construct a static GlobalBlock.

The syntax is similar to a static closure. Note that the block cannot capture it’s environment, and it’s argument types and return type must be Encode.

Examples

use block2::global_block;
global_block! {
    static MY_BLOCK = || -> i32 {
        42
    }
};
assert_eq!(unsafe { MY_BLOCK.call(()) }, 42);

use block2::global_block;
global_block! {
    static ADDER_BLOCK = |x: i32, y: i32| -> i32 {
        x + y
    }
};
assert_eq!(unsafe { ADDER_BLOCK.call((5, 7)) }, 12);

use block2::global_block;
global_block! {
    pub static MUTATING_BLOCK = |x: &mut i32| {
        *x = *x + 42;
    }
};
let mut x = 5;
unsafe { MUTATING_BLOCK.call((&mut x,)) };
assert_eq!(x, 47);

The following does not compile because Box is not Encode:

use block2::global_block;
global_block! {
    pub static INVALID_BLOCK = |b: Box<i32>| {}
};