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Diffstat (limited to 'third_party/rust/synstructure/src/macros.rs')
| -rw-r--r-- | third_party/rust/synstructure/src/macros.rs | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/third_party/rust/synstructure/src/macros.rs b/third_party/rust/synstructure/src/macros.rs new file mode 100644 index 0000000000..5b6557b7c7 --- /dev/null +++ b/third_party/rust/synstructure/src/macros.rs @@ -0,0 +1,250 @@ +//! This module provides two utility macros for testing custom derives. They can +//! be used together to eliminate some of the boilerplate required in order to +//! declare and test custom derive implementations. + +// Re-exports used by the decl_derive! and test_derive! +pub use proc_macro2::TokenStream as TokenStream2; +pub use syn::{parse_str, DeriveInput}; + +#[cfg(all( + not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "wasi"))), + feature = "proc-macro" +))] +pub use proc_macro::TokenStream; +#[cfg(all( + not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "wasi"))), + feature = "proc-macro" +))] +pub use syn::parse; + +/// The `decl_derive!` macro declares a custom derive wrapper. It will parse the +/// incoming `TokenStream` into a `synstructure::Structure` object, and pass it +/// into the inner function. +/// +/// Your inner function should take a `synstructure::Structure` by value, and +/// return a type implementing `synstructure::MacroResult`, for example: +/// +/// ``` +/// fn derive_simple(input: synstructure::Structure) -> proc_macro2::TokenStream { +/// unimplemented!() +/// } +/// +/// fn derive_result(input: synstructure::Structure) +/// -> syn::Result<proc_macro2::TokenStream> +/// { +/// unimplemented!() +/// } +/// ``` +/// +/// # Usage +/// +/// ### Without Attributes +/// ``` +/// fn derive_interesting(_input: synstructure::Structure) -> proc_macro2::TokenStream { +/// quote::quote! { ... } +/// } +/// +/// # const _IGNORE: &'static str = stringify! { +/// decl_derive!([Interesting] => derive_interesting); +/// # }; +/// ``` +/// +/// ### With Attributes +/// ``` +/// # fn main() {} +/// fn derive_interesting(_input: synstructure::Structure) -> proc_macro2::TokenStream { +/// quote::quote! { ... } +/// } +/// +/// # const _IGNORE: &'static str = stringify! { +/// decl_derive!([Interesting, attributes(interesting_ignore)] => derive_interesting); +/// # }; +/// ``` +/// +/// ### Decl Attributes & Doc Comments +/// ``` +/// # fn main() {} +/// fn derive_interesting(_input: synstructure::Structure) -> proc_macro2::TokenStream { +/// quote::quote! { ... } +/// } +/// +/// # const _IGNORE: &'static str = stringify! { +/// decl_derive! { +/// [Interesting] => +/// #[allow(some_lint)] +/// /// Documentation Comments +/// derive_interesting +/// } +/// # }; +/// ``` +/// +/// *This macro is available if `synstructure` is built with the `"proc-macro"` +/// feature.* +#[cfg(all( + not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "wasi"))), + feature = "proc-macro" +))] +#[macro_export] +macro_rules! decl_derive { + // XXX: Switch to using this variant everywhere? + ([$derives:ident $($derive_t:tt)*] => $(#[$($attrs:tt)*])* $inner:path) => { + #[proc_macro_derive($derives $($derive_t)*)] + #[allow(non_snake_case)] + $(#[$($attrs)*])* + pub fn $derives( + i: $crate::macros::TokenStream + ) -> $crate::macros::TokenStream { + match $crate::macros::parse::<$crate::macros::DeriveInput>(i) { + Ok(p) => { + match $crate::Structure::try_new(&p) { + Ok(s) => $crate::MacroResult::into_stream($inner(s)), + Err(e) => e.to_compile_error().into(), + } + } + Err(e) => e.to_compile_error().into(), + } + } + }; +} + +/// The `decl_attribute!` macro declares a custom attribute wrapper. It will +/// parse the incoming `TokenStream` into a `synstructure::Structure` object, +/// and pass it into the inner function. +/// +/// Your inner function should have the following type: +/// +/// ``` +/// fn attribute( +/// attr: proc_macro2::TokenStream, +/// structure: synstructure::Structure, +/// ) -> proc_macro2::TokenStream { +/// unimplemented!() +/// } +/// ``` +/// +/// # Usage +/// +/// ``` +/// fn attribute_interesting( +/// _attr: proc_macro2::TokenStream, +/// _structure: synstructure::Structure, +/// ) -> proc_macro2::TokenStream { +/// quote::quote! { ... } +/// } +/// +/// # const _IGNORE: &'static str = stringify! { +/// decl_attribute!([interesting] => attribute_interesting); +/// # }; +/// ``` +/// +/// *This macro is available if `synstructure` is built with the `"proc-macro"` +/// feature.* +#[cfg(all( + not(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "wasi"))), + feature = "proc-macro" +))] +#[macro_export] +macro_rules! decl_attribute { + ([$attribute:ident] => $(#[$($attrs:tt)*])* $inner:path) => { + #[proc_macro_attribute] + $(#[$($attrs)*])* + pub fn $attribute( + attr: $crate::macros::TokenStream, + i: $crate::macros::TokenStream, + ) -> $crate::macros::TokenStream { + match $crate::macros::parse::<$crate::macros::DeriveInput>(i) { + Ok(p) => match $crate::Structure::try_new(&p) { + Ok(s) => $crate::MacroResult::into_stream($inner(attr.into(), s)), + Err(e) => e.to_compile_error().into(), + }, + Err(e) => e.to_compile_error().into(), + } + } + }; +} + +/// Run a test on a custom derive. This macro expands both the original struct +/// and the expansion to ensure that they compile correctly, and confirms that +/// feeding the original struct into the named derive will produce the written +/// output. +/// +/// You can add `no_build` to the end of the macro invocation to disable +/// checking that the written code compiles. This is useful in contexts where +/// the procedural macro cannot depend on the crate where it is used during +/// tests. +/// +/// # Usage +/// +/// ``` +/// fn test_derive_example(_s: synstructure::Structure) +/// -> Result<proc_macro2::TokenStream, syn::Error> +/// { +/// Ok(quote::quote! { const YOUR_OUTPUT: &'static str = "here"; }) +/// } +/// +/// fn main() { +/// synstructure::test_derive!{ +/// test_derive_example { +/// struct A; +/// } +/// expands to { +/// const YOUR_OUTPUT: &'static str = "here"; +/// } +/// } +/// } +/// ``` +#[macro_export] +macro_rules! test_derive { + ($name:path { $($i:tt)* } expands to { $($o:tt)* }) => { + { + #[allow(dead_code)] + fn ensure_compiles() { + $($i)* + $($o)* + } + + $crate::test_derive!($name { $($i)* } expands to { $($o)* } no_build); + } + }; + + ($name:path { $($i:tt)* } expands to { $($o:tt)* } no_build) => { + { + let i = stringify!( $($i)* ); + let parsed = $crate::macros::parse_str::<$crate::macros::DeriveInput>(i) + .expect(concat!( + "Failed to parse input to `#[derive(", + stringify!($name), + ")]`", + )); + + let raw_res = $name($crate::Structure::new(&parsed)); + let res = $crate::MacroResult::into_result(raw_res) + .expect(concat!( + "Procedural macro failed for `#[derive(", + stringify!($name), + ")]`", + )); + + let expected = stringify!( $($o)* ) + .parse::<$crate::macros::TokenStream2>() + .expect("output should be a valid TokenStream"); + let mut expected_toks = $crate::macros::TokenStream2::from(expected); + if res.to_string() != expected_toks.to_string() { + panic!("\ +test_derive failed: +expected: +``` +{} +``` + +got: +``` +{} +```\n", + $crate::unpretty_print(&expected_toks), + $crate::unpretty_print(&res), + ); + } + } + }; +} |