Procedural functionlike!() macros using only Macros 1.1
Did you think Macros 1.1 was only for custom derives? Think again.
This approach works with any Rust version >= 1.15.0.
Defining procedural macros
Two crates are required to define a macro.
The declaration crate
This crate is allowed to contain other public things if you need, for example traits or functions or ordinary macros.
extern crate proc_macro_hack; // This is what allows the users to depend on just your // declaration crate rather than both crates. extern crate demo_hack_impl; pub use *; proc_macro_expr_decl! proc_macro_item_decl!
The implementation crate
This crate must contain nothing but procedural macros. Private helper functions and private modules are fine but nothing can be public.
extern crate proc_macro_hack; proc_macro_expr_impl! proc_macro_item_impl!
Both crates depend on
 = "0.4"
Additionally, your implementation crate (but not your declaration crate) is a proc macro:
 = true
Using procedural macros
Users of your crate depend on your declaration crate (not your implementation crate), then use your procedural macros as though it were magic. They even get reasonable error messages if your procedural macro panics.
extern crate demo_hack; two_fn!;
Crates based on this approach
mashup– A stable approach to concatenating identifiers.
indoc– Macro that allows the content of string literals to be indented in source code.
structure– Macro that uses a format string to create strongly-typed data pack/unpack interfaces.
bstring– Macro for formatting byte strings.
net-literals– Macros for writing IP/socket address literals that are checked for validity at compile time.
wstr– Macros for compile-time UTF-16 (wide) string literals.
hexf– Macros that enable hexadecimal floating point literals.
binary_macros– Macros for decoding base64 and hexadecimal-like encodings from string literals to [u8] literals at compile time.
autoimpl– Macro to generate a default blanket impl for a generic trait.
- An item macro cannot be invoked multiple times within the same scope (#2).
- An expression macro cannot expand into recursive calls to itself (#4).
- The input to your macro cannot contain dollar signs (#8).
- Your macro must expand to either an expression or zero-or-more items, cannot sometimes be one or the other depending on input (#9).
- Type macros are not supported (#10).
- Input to an expression macro may not refer to hygienic identifiers of local variables (#15).
- An item macro cannot be used as an item in an impl block (#18).
- Macro output may not refer to the special metavariable
- Pattern macros are not supported (#20).
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this hack by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.