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//! This crates provides a single, easy to use macro, that allows you to actually use concatenated
//! identifiers in Rust.
extern crate proc_macro;
use proc_macro::TokenStream;
use quote::quote;
use syn::{
Block, Ident, LitBool, LitByte, LitByteStr,
LitChar, LitFloat, LitInt, LitStr, parse_macro_input, Token, visit_mut,
};
use syn::parse::{self, Parse, ParseStream};
use syn::spanned::Spanned;
use syn::token::Underscore;
use syn::visit_mut::VisitMut;
#[cfg(test)]
mod tests {
#[test]
fn test() {
let t = trybuild::TestCases::new();
t.pass("tests/pass.rs");
t.compile_fail("tests/fail/*.rs");
}
}
/// A helper struct that implements [`Parse`] and extracts the `replace_ident`, the `concatenated_ident` and
/// the code `block` from the original macro input
/// ```text
/// concat_idents!(
/// ident = ident1, _, ident2 { /* code */ }
/// ^^^^^ ^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^
/// | | code block
/// | |
/// | concatenated-ident (in this case: 'ident1_ident2')
/// |
/// replace-ident
/// );
/// ```
struct InputParser {
replace_ident: Ident,
concatenated_ident: Ident,
block: Block,
}
impl Parse for InputParser {
fn parse(input: ParseStream) -> parse::Result<Self> {
let replace_ident: Ident = input.parse()?;
let _: Token![=] = input.parse()?;
let IdentParser(concatenated_ident) = input.parse()?;
let block: Block = input.parse()?;
Ok(InputParser {
replace_ident,
concatenated_ident,
block,
})
}
}
/// A helper struct that implements [`Parse`] and makes one [`Ident`] from a comma separated list
/// of idents, literals and underscores
/// ```text
/// ident1, ident2, _, 3, _, true
/// => ident1ident2_3_true
/// ```
struct IdentParser(Ident);
impl Parse for IdentParser {
fn parse(input: ParseStream) -> parse::Result<Self> {
let mut ident_parts = vec![];
while !input.peek(syn::token::Brace) {
ident_parts.push(IdentPart::parse(input)?);
if input.peek(Token![,]) {
input.parse::<Token![,]>()?;
} else {
break;
}
}
let span = match ident_parts.first() {
Some(IdentPart::Ident(i)) => i.span(),
Some(IdentPart::Underscore(u)) => u.span(),
Some(IdentPart::Str(s)) => s.span(),
Some(IdentPart::Char(c)) => c.span(),
Some(IdentPart::Bool(b)) if ident_parts.len() > 1 => b.span(),
Some(IdentPart::Bool(b)) => return Err(syn::Error::new(
b.span(),
"Identifiers cannot consist of only one bool",
)),
Some(IdentPart::Int(i)) if ident_parts.len() > 1 => return Err(syn::Error::new(
i.span(),
"Identifiers cannot start with integers",
)),
Some(IdentPart::Int(i)) => return Err(syn::Error::new(
i.span(),
"Identifiers cannot start nor consist only of integers with integers",
)),
None => return Err(syn::Error::new(
input.span(),
"Expected at least one identifier",
))
};
let mut ident = String::new();
for part in ident_parts {
match part {
IdentPart::Ident(i) => ident.push_str(i.to_string().trim_start_matches("r#")),
IdentPart::Underscore(_) => ident.push('_'),
IdentPart::Int(i) => ident.push_str(i.to_string().as_str()),
IdentPart::Bool(b) => ident.push_str(b.value.to_string().as_str()),
IdentPart::Str(s) => ident.push_str(s.value().as_str()),
IdentPart::Char(c) => ident.push(c.value())
}
}
Ok(Self(Ident::new(ident.as_str(), span)))
}
}
/// A helper struct, that represents a valid part of an identifier. Does not guarantee, that
/// this specific part is a fully qualified identifier.
///
/// ```text
/// ident1, ident2, _, 3, _, true
/// => ident1, ident2, _, 3, _, true
/// ```
enum IdentPart {
Underscore(Underscore),
Ident(Ident),
Int(LitInt),
Bool(LitBool),
Str(LitStr),
Char(LitChar),
}
impl Parse for IdentPart {
fn parse(input: ParseStream) -> parse::Result<Self> {
if input.peek(Ident) {
Ok(Self::Ident(input.parse()?))
} else if input.peek(Token![_]) {
Ok(Self::Underscore(input.parse()?))
} else if input.peek(LitInt) {
Ok(Self::Int(input.parse()?))
} else if input.peek(LitBool) {
Ok(Self::Bool(input.parse()?))
} else if input.peek(LitStr) {
let string = input.parse::<LitStr>()?;
if string.value().contains(|c: char| !c.is_ascii_alphanumeric() && c != '_') {
Err(syn::Error::new(
string.span(),
"Identifier parts can only contain [a-zA-Z0-9_]",
))
} else {
Ok(Self::Str(string))
}
} else if input.peek(LitChar) {
let char = input.parse::<LitChar>()?;
let c = char.value();
if !c.is_ascii_alphanumeric() && c != '_' {
Err(syn::Error::new(
char.span(),
"Identifier parts can only contain [a-zA-Z0-9_]",
))
} else {
Ok(Self::Char(char))
}
} else if input.peek(LitByteStr) {
Err(syn::Error::new(input.span(), "Identifiers cannot contain byte string"))
} else if input.peek(LitByte) {
Err(syn::Error::new(input.span(), "Identifiers cannot contain bytes"))
} else if input.peek(LitFloat) {
Err(syn::Error::new(input.span(), "Identifiers cannot contain floats"))
} else {
Err(syn::Error::new(
input.span(),
"Expected either an identifies, a `_`, an int, a bool, \
a string-literal, or a character-literal.\n\
Note: To create an Identifies from a reserved keywords like `struct`, or `return`, \
wrap it quotes, i.e. `\"struct\"`, or escape them with `r#`, i.e. `r#struct` .",
))
}
}
}
/// A helper struct that implements [`VisitMut`] and is responsible for replacing the `replace_ident`
/// with the `concatenated_ident`.
struct IdentReplacer {
replace_ident: Ident,
concatenated_ident: Ident,
code_block: Option<Block>,
}
impl IdentReplacer {
/// Creates a new Instance of IdentReplacer from an InputParser
fn from_input_parser(input_parser: InputParser) -> Self {
Self {
replace_ident: input_parser.replace_ident,
concatenated_ident: input_parser.concatenated_ident,
code_block: Some(input_parser.block),
}
}
/// Replaces all `replace_idents` in the `code_block` with the `concatenated_ident`
fn replace_idents(mut self) -> Self {
let mut code = self.code_block
.take()
.unwrap();
self.visit_block_mut(&mut code);
self.code_block = Some(code);
self
}
/// generates a TokenStream from the code-block
fn produce_token_stream(self) -> TokenStream {
let statements = self.code_block.unwrap().stmts;
(quote! { #( #statements )* }).into()
}
}
impl VisitMut for IdentReplacer {
fn visit_ident_mut(&mut self, node: &mut Ident) {
if *node == self.replace_ident {
*node = self.concatenated_ident.clone();
}
// Delegate to the default impl
visit_mut::visit_ident_mut(self, node);
}
}
/// This macros makes it possible to concatenate identifiers at compile time and use them as normal.
/// It's an extension/replacement of `std::concat_idents`, since in comprassion to the std-solution,
/// the idents here can be used everywhere.
///
/// # Usage:
/// ### Basic usage
/// ```
/// use concat_idents::concat_idents;
///
/// concat_idents!(fn_name = foo_, _, bar {
/// fn fn_name() {
/// // --snip--
/// }
/// });
///
/// foo__bar();
/// ```
///
/// ### Generating Tests
/// ```
///# use concat_idents::concat_idents;
///# use std::ops::{Add, Sub};
/// macro_rules! generate_test {
/// ($method:ident($lhs:ident, $rhs:ident)) => {
/// concat_idents!(test_name = $method, _, $lhs, _, $rhs {
/// #[test]
/// fn test_name() {
/// let _ = $lhs::default().$method($rhs::default());
/// }
/// });
/// };
/// }
///
/// #[derive(Default)]
/// struct S(i32);
/// impl Add<i32> for S {
/// // --snip--
///# type Output = S;
///# fn add(self,rhs: i32) -> Self::Output { S(self.0 + rhs) }
/// }
/// impl Sub<i32> for S {
/// // --snip--
///# type Output = S;
///# fn sub(self,rhs: i32) -> Self::Output { S(self.0 - rhs) }
/// }
///
/// generate_test!(add(S, i32));
/// generate_test!(sub(S, i32));
/// ```
#[proc_macro]
pub fn concat_idents(item: TokenStream) -> TokenStream {
let input_parser = parse_macro_input!(item as InputParser);
IdentReplacer::from_input_parser(input_parser)
.replace_idents()
.produce_token_stream()
}