491 lines
18 KiB
Rust
491 lines
18 KiB
Rust
#![feature(let_chains)]
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#![feature(proc_macro_span)]
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#![allow(clippy::needless_if, dead_code)]
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extern crate proc_macro;
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use core::mem;
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use proc_macro::token_stream::IntoIter;
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use proc_macro::Delimiter::{self, Brace, Parenthesis};
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use proc_macro::Spacing::{self, Alone, Joint};
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use proc_macro::{Group, Ident, Literal, Punct, Span, TokenStream, TokenTree as TT};
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use syn::spanned::Spanned;
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type Result<T> = core::result::Result<T, TokenStream>;
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/// Make a `compile_error!` pointing to the given span.
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fn make_error(msg: &str, span: Span) -> TokenStream {
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TokenStream::from_iter([
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TT::Ident(Ident::new("compile_error", span)),
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TT::Punct(punct_with_span('!', Alone, span)),
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TT::Group({
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let mut msg = Literal::string(msg);
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msg.set_span(span);
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group_with_span(Parenthesis, TokenStream::from_iter([TT::Literal(msg)]), span)
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}),
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])
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}
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fn expect_tt<T>(tt: Option<TT>, f: impl FnOnce(TT) -> Option<T>, expected: &str, span: Span) -> Result<T> {
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match tt {
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None => Err(make_error(
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&format!("unexpected end of input, expected {expected}"),
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span,
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)),
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Some(tt) => {
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let span = tt.span();
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match f(tt) {
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Some(x) => Ok(x),
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None => Err(make_error(&format!("unexpected token, expected {expected}"), span)),
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}
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},
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}
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}
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fn punct_with_span(c: char, spacing: Spacing, span: Span) -> Punct {
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let mut p = Punct::new(c, spacing);
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p.set_span(span);
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p
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}
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fn group_with_span(delimiter: Delimiter, stream: TokenStream, span: Span) -> Group {
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let mut g = Group::new(delimiter, stream);
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g.set_span(span);
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g
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}
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/// Token used to escape the following token from the macro's span rules.
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const ESCAPE_CHAR: char = '$';
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/// Takes a single token followed by a sequence of tokens. Returns the sequence of tokens with their
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/// span set to that of the first token. Tokens may be escaped with either `$ident` or `$(tokens)`.
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#[proc_macro]
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pub fn with_span(input: TokenStream) -> TokenStream {
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let mut iter = input.into_iter();
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let span = iter.next().unwrap().span();
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let mut res = TokenStream::new();
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if let Err(e) = write_with_span(span, iter, &mut res) {
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e
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} else {
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res
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}
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}
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/// Takes a sequence of tokens and return the tokens with the span set such that they appear to be
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/// from an external macro. Tokens may be escaped with either `$ident` or `$(tokens)`.
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#[proc_macro]
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pub fn external(input: TokenStream) -> TokenStream {
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let mut res = TokenStream::new();
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if let Err(e) = write_with_span(Span::mixed_site(), input.into_iter(), &mut res) {
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e
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} else {
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res
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}
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}
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/// Copies all the tokens, replacing all their spans with the given span. Tokens can be escaped
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/// either by `$ident` or `$(tokens)`.
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fn write_with_span(s: Span, mut input: IntoIter, out: &mut TokenStream) -> Result<()> {
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while let Some(tt) = input.next() {
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match tt {
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TT::Punct(p) if p.as_char() == ESCAPE_CHAR => {
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expect_tt(
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input.next(),
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|tt| match tt {
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tt @ (TT::Ident(_) | TT::Literal(_)) => {
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out.extend([tt]);
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Some(())
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},
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TT::Punct(mut p) if p.as_char() == ESCAPE_CHAR => {
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p.set_span(s);
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out.extend([TT::Punct(p)]);
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Some(())
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},
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TT::Group(g) if g.delimiter() == Parenthesis => {
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out.extend([TT::Group(group_with_span(Delimiter::None, g.stream(), g.span()))]);
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Some(())
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},
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_ => None,
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},
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"an ident, a literal, or parenthesized tokens",
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p.span(),
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)?;
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},
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TT::Group(g) => {
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let mut stream = TokenStream::new();
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write_with_span(s, g.stream().into_iter(), &mut stream)?;
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out.extend([TT::Group(group_with_span(g.delimiter(), stream, s))]);
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},
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mut tt => {
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tt.set_span(s);
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out.extend([tt]);
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},
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}
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}
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Ok(())
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}
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/// Takes an array repeat expression such as `[0_u32; 2]`, and return the tokens with 10 times the
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/// original size, which turns to `[0_u32; 20]`.
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#[proc_macro]
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pub fn make_it_big(input: TokenStream) -> TokenStream {
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let mut expr_repeat = syn::parse_macro_input!(input as syn::ExprRepeat);
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let len_span = expr_repeat.len.span();
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if let syn::Expr::Lit(expr_lit) = &mut *expr_repeat.len {
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if let syn::Lit::Int(lit_int) = &expr_lit.lit {
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let orig_val = lit_int.base10_parse::<usize>().expect("not a valid length parameter");
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let new_val = orig_val.saturating_mul(10);
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expr_lit.lit = syn::parse_quote_spanned!( len_span => #new_val);
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}
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}
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quote::quote!(#expr_repeat).into()
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}
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/// Within the item this attribute is attached to, an `inline!` macro is available which expands the
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/// contained tokens as though they came from a macro expansion.
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///
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/// Within the `inline!` macro, any token preceded by `$` is passed as though it were an argument
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/// with an automatically chosen fragment specifier. `$ident` will be passed as `ident`, `$1` or
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/// `$"literal"` will be passed as `literal`, `$'lt` will be passed as `lifetime`, and `$(...)` will
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/// pass the contained tokens as a `tt` sequence (the wrapping parenthesis are removed). If another
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/// specifier is required it can be specified within parenthesis like `$(@expr ...)`. This will
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/// expand the remaining tokens as a single argument.
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///
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/// Multiple `inline!` macros may be nested within each other. This will expand as nested macro
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/// calls. However, any arguments will be passed as though they came from the outermost context.
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#[proc_macro_attribute]
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pub fn inline_macros(args: TokenStream, input: TokenStream) -> TokenStream {
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let mut args = args.into_iter();
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let mac_name = match args.next() {
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Some(TT::Ident(name)) => Some(name),
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Some(tt) => {
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return make_error(
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"unexpected argument, expected either an ident or no arguments",
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tt.span(),
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);
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},
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None => None,
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};
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if let Some(tt) = args.next() {
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return make_error(
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"unexpected argument, expected either an ident or no arguments",
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tt.span(),
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);
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};
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let mac_name = if let Some(mac_name) = mac_name {
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Ident::new(&format!("__inline_mac_{mac_name}"), Span::call_site())
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} else {
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let mut input = match LookaheadIter::new(input.clone().into_iter()) {
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Some(x) => x,
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None => return input,
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};
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loop {
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match input.next() {
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None => break Ident::new("__inline_mac", Span::call_site()),
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Some(TT::Ident(kind)) => match &*kind.to_string() {
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"impl" => break Ident::new("__inline_mac_impl", Span::call_site()),
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kind @ ("struct" | "enum" | "union" | "fn" | "mod" | "trait" | "type" | "const" | "static") => {
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if let TT::Ident(name) = &input.tt {
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break Ident::new(&format!("__inline_mac_{kind}_{name}"), Span::call_site());
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} else {
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break Ident::new(&format!("__inline_mac_{kind}"), Span::call_site());
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}
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},
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_ => {},
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},
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_ => {},
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}
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}
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};
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let mut expander = Expander::default();
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let mut mac = MacWriter::new(mac_name);
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if let Err(e) = expander.expand(input.into_iter(), &mut mac) {
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return e;
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}
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let mut out = TokenStream::new();
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mac.finish(&mut out);
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out.extend(expander.expn);
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out
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}
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/// Wraps a `TokenStream` iterator with a single token lookahead.
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struct LookaheadIter {
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tt: TT,
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iter: IntoIter,
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}
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impl LookaheadIter {
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fn new(mut iter: IntoIter) -> Option<Self> {
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iter.next().map(|tt| Self { tt, iter })
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}
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/// Get's the lookahead token, replacing it with the next token in the stream.
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/// Note: If there isn't a next token, this will not return the lookahead token.
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fn next(&mut self) -> Option<TT> {
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self.iter.next().map(|tt| mem::replace(&mut self.tt, tt))
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}
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}
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/// Builds the macro used to implement all the `inline!` macro calls.
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struct MacWriter {
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name: Ident,
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macros: TokenStream,
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next_idx: usize,
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}
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impl MacWriter {
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fn new(name: Ident) -> Self {
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Self {
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name,
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macros: TokenStream::new(),
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next_idx: 0,
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}
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}
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/// Inserts a new `inline!` call.
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fn insert(&mut self, name_span: Span, bang_span: Span, body: Group, expander: &mut Expander) -> Result<()> {
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let idx = self.next_idx;
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self.next_idx += 1;
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let mut inner = Expander::for_arm(idx);
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inner.expand(body.stream().into_iter(), self)?;
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let new_arm = inner.arm.unwrap();
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self.macros.extend([
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TT::Group(Group::new(Parenthesis, new_arm.args_def)),
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TT::Punct(Punct::new('=', Joint)),
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TT::Punct(Punct::new('>', Alone)),
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TT::Group(Group::new(Parenthesis, inner.expn)),
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TT::Punct(Punct::new(';', Alone)),
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]);
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expander.expn.extend([
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TT::Ident({
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let mut name = self.name.clone();
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name.set_span(name_span);
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name
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}),
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TT::Punct(punct_with_span('!', Alone, bang_span)),
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]);
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let mut call_body = TokenStream::from_iter([TT::Literal(Literal::usize_unsuffixed(idx))]);
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if let Some(arm) = expander.arm.as_mut() {
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if !new_arm.args.is_empty() {
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arm.add_sub_args(new_arm.args, &mut call_body);
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}
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} else {
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call_body.extend(new_arm.args);
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}
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let mut g = Group::new(body.delimiter(), call_body);
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g.set_span(body.span());
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expander.expn.extend([TT::Group(g)]);
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Ok(())
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}
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/// Creates the macro definition.
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fn finish(self, out: &mut TokenStream) {
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if self.next_idx != 0 {
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out.extend([
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TT::Ident(Ident::new("macro_rules", Span::call_site())),
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TT::Punct(Punct::new('!', Alone)),
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TT::Ident(self.name),
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TT::Group(Group::new(Brace, self.macros)),
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])
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}
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}
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}
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struct MacroArm {
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args_def: TokenStream,
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args: Vec<TT>,
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}
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impl MacroArm {
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fn add_single_arg_def(&mut self, kind: &str, dollar_span: Span, arg_span: Span, out: &mut TokenStream) {
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let mut name = Ident::new(&format!("_{}", self.args.len()), Span::call_site());
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self.args_def.extend([
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TT::Punct(Punct::new('$', Alone)),
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TT::Ident(name.clone()),
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TT::Punct(Punct::new(':', Alone)),
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TT::Ident(Ident::new(kind, Span::call_site())),
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]);
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name.set_span(arg_span);
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out.extend([TT::Punct(punct_with_span('$', Alone, dollar_span)), TT::Ident(name)]);
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}
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fn add_parenthesized_arg_def(&mut self, kind: Ident, dollar_span: Span, arg_span: Span, out: &mut TokenStream) {
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let mut name = Ident::new(&format!("_{}", self.args.len()), Span::call_site());
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self.args_def.extend([TT::Group(Group::new(
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Parenthesis,
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TokenStream::from_iter([
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TT::Punct(Punct::new('$', Alone)),
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TT::Ident(name.clone()),
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TT::Punct(Punct::new(':', Alone)),
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TT::Ident(kind),
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]),
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))]);
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name.set_span(arg_span);
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out.extend([TT::Punct(punct_with_span('$', Alone, dollar_span)), TT::Ident(name)]);
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}
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fn add_multi_arg_def(&mut self, dollar_span: Span, arg_span: Span, out: &mut TokenStream) {
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let mut name = Ident::new(&format!("_{}", self.args.len()), Span::call_site());
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self.args_def.extend([TT::Group(Group::new(
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Parenthesis,
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TokenStream::from_iter([
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TT::Punct(Punct::new('$', Alone)),
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TT::Group(Group::new(
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Parenthesis,
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TokenStream::from_iter([
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TT::Punct(Punct::new('$', Alone)),
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TT::Ident(name.clone()),
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TT::Punct(Punct::new(':', Alone)),
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TT::Ident(Ident::new("tt", Span::call_site())),
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]),
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)),
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TT::Punct(Punct::new('*', Alone)),
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]),
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))]);
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name.set_span(arg_span);
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out.extend([
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TT::Punct(punct_with_span('$', Alone, dollar_span)),
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TT::Group(group_with_span(
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Parenthesis,
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TokenStream::from_iter([TT::Punct(punct_with_span('$', Alone, dollar_span)), TT::Ident(name)]),
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dollar_span,
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)),
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TT::Punct(punct_with_span('*', Alone, dollar_span)),
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]);
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}
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fn add_arg(&mut self, dollar_span: Span, tt: TT, input: &mut IntoIter, out: &mut TokenStream) -> Result<()> {
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match tt {
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TT::Punct(p) if p.as_char() == ESCAPE_CHAR => out.extend([TT::Punct(p)]),
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TT::Punct(p) if p.as_char() == '\'' && p.spacing() == Joint => {
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let lt_name = expect_tt(
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input.next(),
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|tt| match tt {
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TT::Ident(x) => Some(x),
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_ => None,
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},
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"lifetime name",
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p.span(),
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)?;
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let arg_span = p.span().join(lt_name.span()).unwrap_or(p.span());
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self.add_single_arg_def("lifetime", dollar_span, arg_span, out);
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self.args.extend([TT::Punct(p), TT::Ident(lt_name)]);
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},
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TT::Ident(x) => {
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self.add_single_arg_def("ident", dollar_span, x.span(), out);
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self.args.push(TT::Ident(x));
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},
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TT::Literal(x) => {
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self.add_single_arg_def("literal", dollar_span, x.span(), out);
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self.args.push(TT::Literal(x));
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},
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TT::Group(g) if g.delimiter() == Parenthesis => {
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let mut inner = g.stream().into_iter();
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if let Some(TT::Punct(p)) = inner.next()
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&& p.as_char() == '@'
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{
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let kind = expect_tt(
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inner.next(),
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|tt| match tt {
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TT::Ident(kind) => Some(kind),
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_ => None,
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},
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"a macro fragment specifier",
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p.span(),
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)?;
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self.add_parenthesized_arg_def(kind, dollar_span, g.span(), out);
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self.args
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.push(TT::Group(group_with_span(Parenthesis, inner.collect(), g.span())))
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} else {
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self.add_multi_arg_def(dollar_span, g.span(), out);
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self.args.push(TT::Group(g));
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}
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},
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tt => return Err(make_error("unsupported escape", tt.span())),
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};
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Ok(())
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}
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fn add_sub_args(&mut self, args: Vec<TT>, out: &mut TokenStream) {
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self.add_multi_arg_def(Span::call_site(), Span::call_site(), out);
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self.args
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.extend([TT::Group(Group::new(Parenthesis, TokenStream::from_iter(args)))]);
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}
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}
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#[derive(Default)]
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struct Expander {
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arm: Option<MacroArm>,
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expn: TokenStream,
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}
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impl Expander {
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fn for_arm(idx: usize) -> Self {
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Self {
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arm: Some(MacroArm {
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args_def: TokenStream::from_iter([TT::Literal(Literal::usize_unsuffixed(idx))]),
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args: Vec::new(),
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}),
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expn: TokenStream::new(),
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}
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}
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fn write_tt(&mut self, tt: TT, mac: &mut MacWriter) -> Result<()> {
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match tt {
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TT::Group(g) => {
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let outer = mem::take(&mut self.expn);
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self.expand(g.stream().into_iter(), mac)?;
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let inner = mem::replace(&mut self.expn, outer);
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self.expn
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.extend([TT::Group(group_with_span(g.delimiter(), inner, g.span()))]);
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},
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tt => self.expn.extend([tt]),
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}
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Ok(())
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}
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fn expand(&mut self, input: IntoIter, mac: &mut MacWriter) -> Result<()> {
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let Some(mut input) = LookaheadIter::new(input) else {
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return Ok(());
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};
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while let Some(tt) = input.next() {
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if let TT::Punct(p) = &tt
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&& p.as_char() == ESCAPE_CHAR
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&& let Some(arm) = self.arm.as_mut()
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{
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arm.add_arg(
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p.span(),
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mem::replace(&mut input.tt, tt),
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&mut input.iter,
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&mut self.expn,
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)?;
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if input.next().is_none() {
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return Ok(());
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}
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} else if let TT::Punct(p) = &input.tt
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&& p.as_char() == '!'
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&& let TT::Ident(name) = &tt
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&& name.to_string() == "inline"
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{
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let g = expect_tt(
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input.iter.next(),
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|tt| match tt {
|
|
TT::Group(g) => Some(g),
|
|
_ => None,
|
|
},
|
|
"macro arguments",
|
|
p.span(),
|
|
)?;
|
|
mac.insert(name.span(), p.span(), g, self)?;
|
|
if input.next().is_none() {
|
|
return Ok(());
|
|
}
|
|
} else {
|
|
self.write_tt(tt, mac)?;
|
|
}
|
|
}
|
|
self.write_tt(input.tt, mac)
|
|
}
|
|
}
|