bux-lang/examples/macro_unhygienic.bux

// Session 69 — unhygienic binders: `var $name` keeps the call-site identifier
// (not gensym'd). Hygienic template locals (`acc`) still get unique names.
import Std::Io::{PrintLine};
import Std::String::{String_FromInt};

// Introduce a binder named by the call-site ident; keep that name (unhygienic)
macro! let_mut {
    ( $name:ident, $init:literal ) => {
        var $name: int = $init;
        $name = $name + 1;
        $name
    }
}

// Hygienic local `acc` must not collide across two expansions
macro! double_acc {
    ( $start:literal ) => {
        var acc: int = $start;
        acc = acc + acc;
        acc
    }
}

// Mixed: unhygienic $name + hygienic scratch
macro! bump_named {
    ( $name:ident ) => {
        var $name: int = 0;
        var scratch: int = 1;
        $name = $name + scratch;
        $name
    }
}

func Main() -> int {
    // Unhygienic: binder becomes `counter` inside the expansion block
    let a: int = let_mut!(counter, 10);
    // 11
    let b: int = let_mut!(other, 20);
    // 21
    // Hygienic: two expansions with local `acc`
    let c: int = double_acc!(3);
    let d: int = double_acc!(5);
    // 6, 10
    let e: int = bump_named!(n);
    // 1
    PrintLine(String_FromInt(a));
    PrintLine(String_FromInt(b));
    PrintLine(String_FromInt(c));
    PrintLine(String_FromInt(d));
    PrintLine(String_FromInt(e));
    if a != 11 {
        PrintLine("FAIL let_mut counter");
        return 1;
    }
    if b != 21 {
        PrintLine("FAIL let_mut other");
        return 1;
    }
    if c != 6 {
        PrintLine("FAIL double_acc 3");
        return 1;
    }
    if d != 10 {
        PrintLine("FAIL double_acc 5");
        return 1;
    }
    if e != 1 {
        PrintLine("FAIL bump_named");
        return 1;
    }
    PrintLine("PASS macro_unhygienic");
    return 0;
}