Is there a way for Rust macros to act as text substitutions like in C?

Question

In C, if you wanted to, you could:

#define    do     {
#define    end    }

// ...

if (foo == bar) do
    foo += 5;
    bar /= foo;
end

Is there a way to do something like this in Rust?

Answer 1

No (thankfully). Rust macros must always expand to a complete AST node.

If you need textual substitution, use a tool suited for that job such as sed, awk, m4, the C preprocessor, etc. That can likely be driven by a build script.

Answer 2

There is a toy project that does this, in fact: slag. I have never tried it, though.

It comes with this helpful advice:

Should I use this?

No. Use the default rust syntax.