In Rust, is it possible to accept arbitrary syntax in attribute macros? (just like other macros)

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In Rust, both declarative and procedural macros (macro_rules!) can accept arbitrary syntax which isn't necessarily valid Rust, provided that it parses. For instance, in the docs, this is used to create a macro which parses SQL queries from an SQL-like syntax.

However, when using attribute macros, this does not seem to be the case. For example:

#[my_attribute_macro]
fn example() {
    impl A {
        impl B {
            // This is invalid Rust code (nested `impl`s) which is parsable
        }
    }
}

Yields a compiler error because impls cannot be nested in valid Rust. Is there any way of working around this limitation, to get attribute macros which work more like other macros?

rust macros attributes
1 Answers

As far as I know, this is not possible today. The example you see in the docs is a function-like macro, not an attribute macro (proc-macro).

You can provide custom syntax to macros like this: sql!( CUSTOM SYNTAX )

But not to macros like this: #[sql] fn sql() { Custom Syntax }

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