diff --git a/Cargo.toml b/Cargo.toml index 350bf434..499bee1d 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -38,4 +38,4 @@ bench = [] dummy_match_byte = [] [workspace] -members = [".", "./macros", "./procedural-masquerade"] +members = [".", "./macros"] diff --git a/procedural-masquerade/Cargo.toml b/procedural-masquerade/Cargo.toml deleted file mode 100644 index 66638a31..00000000 --- a/procedural-masquerade/Cargo.toml +++ /dev/null @@ -1,12 +0,0 @@ -[package] -name = "procedural-masquerade" -version = "0.1.7" -authors = ["Simon Sapin "] -description = "macro_rules for making proc_macro_derive pretending to be proc_macro" -documentation = "https://docs.rs/procedural-masquerade/" -repository = "https://github.com/servo/rust-cssparser" -license = "MIT OR Apache-2.0" - -[lib] -path = "lib.rs" -doctest = false diff --git a/procedural-masquerade/LICENSE-APACHE b/procedural-masquerade/LICENSE-APACHE deleted file mode 100644 index 16fe87b0..00000000 --- a/procedural-masquerade/LICENSE-APACHE +++ /dev/null @@ -1,201 +0,0 @@ - Apache License - Version 2.0, January 2004 - http://www.apache.org/licenses/ - -TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION - -1. 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IN NO EVENT -SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY -CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION -OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR -IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER -DEALINGS IN THE SOFTWARE. diff --git a/procedural-masquerade/lib.rs b/procedural-masquerade/lib.rs deleted file mode 100644 index 53394044..00000000 --- a/procedural-masquerade/lib.rs +++ /dev/null @@ -1,286 +0,0 @@ -//! # Custom `derive` pretending to be functional procedural macros on Rust 1.15 -//! -//! This crate enables creating function-like macros (invoked as `foo!(...)`) -//! with a procedural component, -//! based on both custom `derive` (a.k.a. *Macros 1.1*) and `macro_rules!`. -//! -//! This convoluted mechanism enables such macros to run on stable Rust 1.15, -//! even though functional procedural macros (a.k.a. *Macros 2.0*) are not available yet. -//! -//! A library defining such a macro needs two crates: a “normal” one, and a `proc-macro` one. -//! In the example below we’ll call them `libfoo` and `libfoo-macros`, respectively. -//! -//! # Credits -//! -//! The trick that makes this crate work -//! is based on an idea from [David Tolnay](https://github.com/dtolnay). -//! Many thanks! -//! -//! # Example -//! -//! As a simple example, we’re going to re-implement the `stringify!` macro. -//! This is useless since `stringify!` already exists in the standard library, -//! and a bit absurd since this crate uses `stringify!` internally. -//! -//! Nevertheless, it serves as a simple example to demonstrate the use of this crate. -//! -//! ## The `proc-macro` crate -//! -//! The minimal `Cargo.toml` file is typical for Macros 1.1: -//! -//! ```toml -//! [package] -//! name = "libfoo-macros" -//! version = "1.0.0" -//! -//! [lib] -//! proc-macro = true -//! ``` -//! -//! In the code, we define the procedural part of our macro in a function. -//! This function will not be used directly by end users, -//! but it still needs to be re-exported to them -//! (because of limitations in `macro_rules!`). -//! -//! To avoid name collisions, we include a long and explicit prefix in the function’s name. -//! -//! The function takes a string containing arbitrary Rust tokens, -//! and returns a string that is parsed as *items*. -//! The returned string can contain constants, statics, functions, `impl`s, etc., -//! but not expressions directly. -//! -//! ```rust -//! #[macro_use] extern crate procedural_masquerade; -//! extern crate proc_macro; -//! -//! define_proc_macros! { -//! #[allow(non_snake_case)] -//! pub fn foo_internal__stringify_const(input: &str) -> String { -//! format!("const STRINGIFIED: &'static str = {:?};", input) -//! } -//! } -//! ``` -//! -//! A less trivial macro would probably use -//! the [`syn`](https://github.com/dtolnay/syn/) crate to parse its input -//! and the [`quote`](https://github.com/dtolnay/quote) crate to generate its output. -//! -//! ## The library crate -//! -//! ```toml -//! [package] -//! name = "libfoo" -//! version = "1.0.0" -//! -//! [dependencies] -//! libfoo-macros = {path = "./macros", version = "1.0"} -//! ``` -//! -//! ```rust -//! #[macro_use] extern crate libfoo_macros; // (1) -//! -//! pub use libfoo_macros::*; // (2) -//! -//! define_invoke_proc_macro!(libfoo__invoke_proc_macro); // (3) -//! -//! #[macro_export] -//! macro_rules! foo_stringify { // (4) -//! ( $( $tts: tt ) ) => { -//! { // (5) -//! libfoo__invoke_proc_macro! { // (6) -//! foo_internal__stringify_const!( $( $tts ) ) // (7) -//! } -//! STRINGIFIED // (8) -//! } -//! } -//! } -//! ``` -//! -//! Let’s go trough the numbered lines one by one: -//! -//! 1. `libfoo` depends on `libfoo-macros`, and imports its macros. -//! 2. Everything exported by `libfoo-macros` (which is one custom `derive`) -//! is re-exported to users of `libfoo`. -//! They’re not expected to use it directly, -//! but expansion of the `foo_stringify` macro needs it. -//! 3. This macro invocation defines yet another macro, called `libfoo__invoke_proc_macro`, -//! which is also exported. -//! This indirection is necessary -//! because re-exporting `macro_rules!` macros doesn’t work currently, -//! and once again it is used by the expansion of `foo_stringify`. -//! Again, we use a long prefix to avoid name collisions. -//! 4. Finally, we define the macro that we really want. -//! This one has a name that users will use. -//! 5. The expansion of this macro will define some items, -//! whose names are not hygienic in `macro_rules`. -//! So we wrap everything in an extra `{…}` block to prevent these names for leaking. -//! 6. Here we use the macro defined in (3), -//! which allows us to write something that look like invoking a functional procedural macro, -//! but really uses a custom `derive`. -//! This will define a type called `ProceduralMasqueradeDummyType`, -//! as a placeholder to use `derive`. -//! If `libfoo__invoke_proc_macro!` is to be used more than once, -//! each use needs to be nested in another block -//! so that the names of multiple dummy types don’t collide. -//! 7. In addition to the dummy type, -//! the items returned by our procedural component are inserted here. -//! (In this case the `STRINGIFIED` constant.) -//! 8. Finally, we write the expression that we want the macro to evaluate to. -//! This expression can use parts of `foo_stringify`’s input, -//! it can contain control-flow statements like `return` or `continue`, -//! and of course refer to procedurally-defined items. -//! -//! This macro can be used in an expression context. -//! It expands to a block-expression that contains some items (as an implementation detail) -//! and ends with another expression. -//! -//! ## For users -//! -//! Users of `libfoo` don’t need to worry about any of these implementation details. -//! They can use the `foo_stringify` macro as if it were a simle `macro_rules` macro: -//! -//! ```rust -//! #[macro_use] extern crate libfoo; -//! -//! fn main() { -//! do_something(foo_stringify!(1 + 2)); -//! } -//! -//! fn do_something(_: &str) { /* ... */ } -//! ``` -//! -//! # More -//! -//! To see a more complex example, look at -//! [`cssparser`’s `src/macros.rs`](https://github.com/servo/rust-cssparser/blob/master/src/macros.rs) -//! and -//! [`cssparser-macros`’s `macros/lib.rs`](https://github.com/servo/rust-cssparser/blob/master/macros/lib.rs). - -/// This macro wraps `&str -> String` functions -/// in custom `derive` implementations with `#[proc_macro_derive]`. -/// -/// See crate documentation for details. -#[macro_export] -macro_rules! define_proc_macros { - ( - $( - $( #[$attr:meta] )* - pub fn $proc_macro_name: ident ($input: ident : &str) -> String - $body: block - )+ - ) => { - $( - $( #[$attr] )* - #[proc_macro_derive($proc_macro_name)] - pub fn $proc_macro_name(derive_input: ::proc_macro::TokenStream) - -> ::proc_macro::TokenStream { - fn wrapped($input: &str) -> String { - $body - } - - // syn uses a huge amount of stack in debug mode. - let derive_input_string = derive_input.to_string(); - let handle = - ::std::thread::Builder::new().stack_size(128 * 1024 * 1024).spawn(move || { - wrapped($crate::_extract_input(&derive_input_string)) - }).unwrap(); - - handle.join().unwrap().parse().unwrap() - } - )+ - } -} - -/// Implementation detail of `define_proc_macros!`. -/// -/// **This function is not part of the public API. It can change or be removed between any versions.** -#[doc(hidden)] -pub fn _extract_input(derive_input: &str) -> &str { - let mut input = derive_input; - - for expected in &[ - "#", - "[", - "allow", - "(", - "unused", - ")", - "]", - "enum", - "ProceduralMasqueradeDummyType", - "{", - "Input", - "=", - "(", - "0", - ",", - "stringify", - "!", - "(", - ] { - input = input.trim_start(); - assert!( - input.starts_with(expected), - "expected prefix {:?} not found in {:?}", - expected, - derive_input - ); - input = &input[expected.len()..]; - } - - for expected in [")", ")", ".", "0", ",", "}"].iter().rev() { - input = input.trim_end(); - assert!( - input.ends_with(expected), - "expected suffix {:?} not found in {:?}", - expected, - derive_input - ); - let end = input.len() - expected.len(); - input = &input[..end]; - } - - input -} - -/// This macro expands to the definition of another macro (whose name is given as a parameter). -/// -/// See crate documentation for details. -#[macro_export] -macro_rules! define_invoke_proc_macro { - ($macro_name: ident) => { - /// Implementation detail of other macros in this crate. - #![rustfmt::skip] - #[doc(hidden)] - #[macro_export] - macro_rules! $macro_name { - ($proc_macro_name: ident ! $paren: tt) => { - #[derive($proc_macro_name)] - #[allow(unused)] - enum ProceduralMasqueradeDummyType { - // The magic happens here. - // - // We use an `enum` with an explicit discriminant - // because that is the only case where a type definition - // can contain a (const) expression. - // - // `(0, "foo").0` evalutes to 0, with the `"foo"` part ignored. - // - // By the time the `#[proc_macro_derive]` function - // implementing `#[derive($proc_macro_name)]` is called, - // `$paren` has already been replaced with the input of this inner macro, - // but `stringify!` has not been expanded yet. - // - // This how arbitrary tokens can be inserted - // in the input to the `#[proc_macro_derive]` function. - // - // Later, `stringify!(...)` is expanded into a string literal - // which is then ignored. - // Using `stringify!` enables passing arbitrary tokens - // rather than only what can be parsed as a const expression. - Input = (0, stringify! $paren ).0, - } - } - } - }; -}