This crate is a collection of small tools for constructing identifiers inside macro_rules!
declarative macros. This can help reduce unnecessary use of the syn and quote crates.
This crate was originally inspired by a combination of the gensym and paste crates.
However, unlike gensym it does not use syn nor quote, and it is dumber than paste.
This crate instead implements a very basic expression evaluator which can combine commands.
Inside the macro body, # is used to identify a mident command. Commands output
either an identifier or a stream of tokens. Those which output an identifier can be combined
or nested, but those which output a token stream cannot.
The following commands output an identifier:
#rand-- will be replaced by__{uuid_v4_simple}#upcase ident-- converts ASCII letters to uppercase#downcase ident-- converts ASCII letters to lowercase#concat(ident_1, ident_2, ...)-- concatenates identifiers only#flatten(path)-- converts a type path into an identifier, replacing non-alphanumeric symbols with_{HEX}_#flatten_basename(path)-- same as#flatten, but strips everything before the last:(thus extracting only the type name)
The following commands output a token stream:
#ty_path(path)-- removes everything after the last:(thus returning the path to a type but not the type itself). Returns an empty token stream if there is no:in the input.
This crate only has visibility into tokens and does not have any information about types.
It cannot tell whether two types would be considered equivalent or coerce-able.
When using the #flatten command in multiple places, the output will only be an exact match
if they are spelled exactly the same (e.g. no type aliases or even differing qualified paths).
// Common macro which creates a variable
macro_rules! gen_ident_ {
($ty:path, $e:expr, $i:ident) => {
const $i: $ty = $e;
};
}
// Create a random identifier
macro_rules! rand_ident {
($ty:path, $e:expr) => {
mident::mident!{ gen_ident_!{$ty, $e, #rand} }
};
}
rand_ident!(u32, 123);
rand_ident!(u32, 123);
// Convert to lowercase
macro_rules! downcase_ident {
($a:ident, $ty:path, $e:expr) => {
mident::mident!{ gen_ident_!{$ty, $e, #downcase $a } }
};
}
downcase_ident!(FoO, u32, 123);
// The variable was created as `foo`
const baz: u32 = foo;
// Concatenate several pieces, while also using multiple mident operations
macro_rules! concat_ident {
($a:ident, $b:ident, $ty:path, $e:expr) => {
mident::mident!{ gen_ident_!{$ty, $e, #concat($a $b _ #upcase #concat($b $a)) } }
};
}
concat_ident!(foo, bar, u32, 123);
const qux: u32 = foobar_BARFOO;
// Example of using `flatten`
macro_rules! flatten_ident {
($a:path, $ty:path, $e:expr) => {
mident::mident!{ gen_ident_!{$ty, $e, #flatten_basename($a) } }
};
}
flatten_ident!(::some::long::path::to::FooStruct<'static, u32, 5, 'a'>, u32, 123);
const uwu: u32 = FooStruct_3C__27_static_2C_u32_2C_5_2C__27_a_27__3E_;
// Example of using `ty_path`
macro_rules! ty_path_test {
($a:path, $e:expr) => {
mident::mident!{
const #rand: #ty_path($a) Vec<u32> = $e;
}
};
}
ty_path_test!(::std::vec::this<'is, 'all, 'ignored, 'static, u32, (owo, uwu)>, Vec::new());