Built-in Macros

Nitpick provides four built-in macros. They are always available — you do not need to import or declare them. They cannot be redefined.

assert!(condition)

Checks a boolean expression at compile time (static assertion).

assert!(1 == 1);         // always passes
assert!(true);           // always passes
assert!(some_const > 0); // passes if some_const > 0 is known at compile time

If the condition evaluates to false, the compiler emits an error:

error: assertion failed: 1 == 2

assert! works on constant expressions. For runtime checks, use the assert_rt! pattern (write an if with unreachable!()).

todo!()

Marks code that has not been implemented yet. The program compiles but the todo! site will panic at runtime.

func:load_config = string() {
    todo!();    // placeholder — implement later
};

At runtime, executing a todo!() site triggers a panic with the message:

not yet implemented

unreachable!()

Marks a code path that should never be reached. If the path is reached at runtime, the program panics.

func:classify = string(int32:n) {
    if (n > 0i32) { pass "positive"; }
    if (n < 0i32) { pass "negative"; }
    if (n == 0i32) { pass "zero"; }
    unreachable!();   // compiler appeased; runtime panics if somehow reached
};

Use unreachable!() at the end of exhaustive match-like chains to signal that you have covered all cases.

cfg!(platform)

Compiles a block conditionally based on the target platform.

cfg!(linux) {
    println("running on Linux");
};

cfg!(windows) {
    println("running on Windows");
};

Supported platform tokens: linux, windows, macos.

The block for the current compile target is included; all others are discarded during compilation.

Platform Detection Example

func:main = int32() {
    cfg!(linux) {
        exit(0);   // Linux: success
    };
    cfg!(windows) {
        exit(2);   // Windows: different code
    };
};
func:failsafe = int32(tbb32:e) { exit(1); };

Cannot Redefine Built-ins

Attempting to declare a macro with a built-in name is a compile error:

macro:assert = () { exit(0); };
// error: Cannot redefine built-in macro 'assert'