[Joker_vD]

I am pretty certain the following is a valid "for"-loop translation:

    block
        ;; code for "i = 0"
        loop
            ;; code for "i < 5"
            i32.eqz
            br_if 1
        
            i32.const 1
            loop
                if
                    ;; code for "i = i + 1"
                    br 2
                else
                end
        
                ;; code for "j = j * 2 + 1"

                i32.const 0
            end
        end
    end

It doesn't require cloning the lexer so probably would still fit in 500 lines? But yeah, in normal assembly it's way easier, even in one-pass:

        ;; code for "i = 0"
    .loop_test:
        ;; code for "i < 5"
        jz  .loop_end
        jmp .loop_body
    .loop_incr:
        ;; code for "i = i + 1"
        jmp .loop_test
    .loop_body:
        ;; code for "j = j * 2 + 1"
        jmp .loop_incr
    .loop_end:

Of course, normally you'd want to re-arrange things like so:

        ;; code for "i = 0"
        jmp .loop_test
    .loop_body:
        ;; code for "j = j * 2 + 1"
    .loop_incr:
        ;; code for "i = i + 1"
    .loop_test:
        ;; code for "i < 5"
        jnz .loop_body
    .loop_end:

I propose the better loop syntax for languages with one-pass implementations, then: "for (i = 0) { j = j * 2 + 1; } (i = i + 1; i < 5);" :)

[vgel]

Oh, interesting--I remember messing around with flags on the stack but was having issues with the WASM analyzer (it doesn't like possible inconsistencies with the number of parameters left on the stack between blocks). I think your solution might get around that, though!