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Add rustfmt::skip to skip rustfmt for ProceduralMasqueradeDummyType enum #276

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merged 1 commit into from
Jun 22, 2020
Merged

Add rustfmt::skip to skip rustfmt for ProceduralMasqueradeDummyType enum #276

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57 changes: 29 additions & 28 deletions procedural-masquerade/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -250,36 +250,37 @@ pub fn _extract_input(derive_input: &str) -> &str {
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! $paren ).0,
}
}
}
($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,
}
}
}
};
}