Import 'proc-macro-hack' rust crate version 0.5.12
Bug: b/151760391
Test: m crosvm.experimental
Change-Id: I70ccc8c3a5640eab38ce5bcfea97feedad7e972d
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..e9b80e6
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,657 @@
+//! As of Rust 1.30, the language supports user-defined function-like procedural
+//! macros. However these can only be invoked in item position, not in
+//! statements or expressions.
+//!
+//! This crate implements an alternative type of procedural macro that can be
+//! invoked in statement or expression position.
+//!
+//! # Defining procedural macros
+//!
+//! Two crates are required to define a procedural macro.
+//!
+//! ## The implementation crate
+//!
+//! This crate must contain nothing but procedural macros. Private helper
+//! functions and private modules are fine but nothing can be public.
+//!
+//! [> example of an implementation crate][demo-hack-impl]
+//!
+//! Just like you would use a #\[proc_macro\] attribute to define a natively
+//! supported procedural macro, use proc-macro-hack's #\[proc_macro_hack\]
+//! attribute to define a procedural macro that works in expression position.
+//! The function signature is the same as for ordinary function-like procedural
+//! macros.
+//!
+//! ```
+//! extern crate proc_macro;
+//!
+//! use proc_macro::TokenStream;
+//! use proc_macro_hack::proc_macro_hack;
+//! use quote::quote;
+//! use syn::{parse_macro_input, Expr};
+//!
+//! # const IGNORE: &str = stringify! {
+//! #[proc_macro_hack]
+//! # };
+//! pub fn add_one(input: TokenStream) -> TokenStream {
+//! let expr = parse_macro_input!(input as Expr);
+//! TokenStream::from(quote! {
+//! 1 + (#expr)
+//! })
+//! }
+//! #
+//! # fn main() {}
+//! ```
+//!
+//! ## The declaration crate
+//!
+//! This crate is allowed to contain other public things if you need, for
+//! example traits or functions or ordinary macros.
+//!
+//! [> example of a declaration crate][demo-hack]
+//!
+//! Within the declaration crate there needs to be a re-export of your
+//! procedural macro from the implementation crate. The re-export also carries a
+//! \#\[proc_macro_hack\] attribute.
+//!
+//! ```
+//! use proc_macro_hack::proc_macro_hack;
+//!
+//! /// Add one to an expression.
+//! ///
+//! /// (Documentation goes here on the re-export, not in the other crate.)
+//! #[proc_macro_hack]
+//! pub use demo_hack_impl::add_one;
+//! #
+//! # fn main() {}
+//! ```
+//!
+//! Both crates depend on `proc-macro-hack`:
+//!
+//! ```toml
+//! [dependencies]
+//! proc-macro-hack = "0.5"
+//! ```
+//!
+//! Additionally, your implementation crate (but not your declaration crate) is
+//! a proc macro crate:
+//!
+//! ```toml
+//! [lib]
+//! proc-macro = true
+//! ```
+//!
+//! # Using procedural macros
+//!
+//! Users of your crate depend on your declaration crate (not your
+//! implementation crate), then use your procedural macros as usual.
+//!
+//! [> example of a downstream crate][example]
+//!
+//! ```
+//! use demo_hack::add_one;
+//!
+//! fn main() {
+//! let two = 2;
+//! let nine = add_one!(two) + add_one!(2 + 3);
+//! println!("nine = {}", nine);
+//! }
+//! ```
+//!
+//! [demo-hack-impl]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack-impl
+//! [demo-hack]: https://github.com/dtolnay/proc-macro-hack/tree/master/demo-hack
+//! [example]: https://github.com/dtolnay/proc-macro-hack/tree/master/example
+//!
+//! # Limitations
+//!
+//! - Only proc macros in expression position are supported. Proc macros in
+//! pattern position ([#20]) are not supported.
+//!
+//! - By default, nested invocations are not supported i.e. the code emitted by
+//! a proc-macro-hack macro invocation cannot contain recursive calls to the
+//! same proc-macro-hack macro nor calls to any other proc-macro-hack macros.
+//! Use [`proc-macro-nested`] if you require support for nested invocations.
+//!
+//! - By default, hygiene is structured such that the expanded code can't refer
+//! to local variables other than those passed by name somewhere in the macro
+//! input. If your macro must refer to *local* variables that don't get named
+//! in the macro input, use `#[proc_macro_hack(fake_call_site)]` on the
+//! re-export in your declaration crate. *Most macros won't need this.*
+//!
+//! [#10]: https://github.com/dtolnay/proc-macro-hack/issues/10
+//! [#20]: https://github.com/dtolnay/proc-macro-hack/issues/20
+//! [`proc-macro-nested`]: https://docs.rs/proc-macro-nested
+
+#![recursion_limit = "512"]
+#![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
+#![cfg_attr(feature = "cargo-clippy", allow(needless_pass_by_value))]
+
+extern crate proc_macro;
+
+use proc_macro2::{Span, TokenStream, TokenTree};
+use quote::{format_ident, quote, ToTokens};
+use std::fmt::Write;
+use syn::ext::IdentExt;
+use syn::parse::{Parse, ParseStream, Result};
+use syn::{braced, bracketed, parenthesized, parse_macro_input, token, Ident, LitInt, Token};
+
+type Visibility = Option<Token![pub]>;
+
+enum Input {
+ Export(Export),
+ Define(Define),
+}
+
+// pub use demo_hack_impl::{m1, m2 as qrst};
+struct Export {
+ attrs: TokenStream,
+ vis: Visibility,
+ from: Ident,
+ macros: Vec<Macro>,
+}
+
+// pub fn m1(input: TokenStream) -> TokenStream { ... }
+struct Define {
+ attrs: TokenStream,
+ name: Ident,
+ body: TokenStream,
+}
+
+struct Macro {
+ name: Ident,
+ export_as: Ident,
+}
+
+impl Parse for Input {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let ahead = input.fork();
+ parse_attributes(&ahead)?;
+ ahead.parse::<Visibility>()?;
+
+ if ahead.peek(Token![use]) {
+ input.parse().map(Input::Export)
+ } else if ahead.peek(Token![fn]) {
+ input.parse().map(Input::Define)
+ } else {
+ Err(input.error("unexpected input to #[proc_macro_hack]"))
+ }
+ }
+}
+
+impl Parse for Export {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let attrs = input.call(parse_attributes)?;
+ let vis: Visibility = input.parse()?;
+ input.parse::<Token![use]>()?;
+ input.parse::<Option<Token![::]>>()?;
+ let from: Ident = input.parse()?;
+ input.parse::<Token![::]>()?;
+
+ let mut macros = Vec::new();
+ if input.peek(token::Brace) {
+ let content;
+ braced!(content in input);
+ loop {
+ macros.push(content.parse()?);
+ if content.is_empty() {
+ break;
+ }
+ content.parse::<Token![,]>()?;
+ if content.is_empty() {
+ break;
+ }
+ }
+ } else {
+ macros.push(input.parse()?);
+ }
+
+ input.parse::<Token![;]>()?;
+ Ok(Export {
+ attrs,
+ vis,
+ from,
+ macros,
+ })
+ }
+}
+
+impl Parse for Define {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let attrs = input.call(parse_attributes)?;
+ let vis: Visibility = input.parse()?;
+ if vis.is_none() {
+ return Err(input.error("functions tagged with `#[proc_macro_hack]` must be `pub`"));
+ }
+
+ input.parse::<Token![fn]>()?;
+ let name: Ident = input.parse()?;
+ let body: TokenStream = input.parse()?;
+ Ok(Define { attrs, name, body })
+ }
+}
+
+impl Parse for Macro {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let name: Ident = input.parse()?;
+ let renamed: Option<Token![as]> = input.parse()?;
+ let export_as = if renamed.is_some() {
+ input.parse()?
+ } else {
+ name.clone()
+ };
+ Ok(Macro { name, export_as })
+ }
+}
+
+fn parse_attributes(input: ParseStream) -> Result<TokenStream> {
+ let mut attrs = TokenStream::new();
+ while input.peek(Token![#]) {
+ let pound: Token![#] = input.parse()?;
+ pound.to_tokens(&mut attrs);
+ let content;
+ let bracket_token = bracketed!(content in input);
+ let content: TokenStream = content.parse()?;
+ bracket_token.surround(&mut attrs, |tokens| content.to_tokens(tokens));
+ }
+ Ok(attrs)
+}
+
+#[proc_macro_attribute]
+pub fn proc_macro_hack(
+ args: proc_macro::TokenStream,
+ input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+ proc_macro::TokenStream::from(match parse_macro_input!(input) {
+ Input::Export(export) => {
+ let args = parse_macro_input!(args as ExportArgs);
+ expand_export(export, args)
+ }
+ Input::Define(define) => {
+ parse_macro_input!(args as DefineArgs);
+ expand_define(define)
+ }
+ })
+}
+
+mod kw {
+ syn::custom_keyword!(derive);
+ syn::custom_keyword!(fake_call_site);
+ syn::custom_keyword!(internal_macro_calls);
+ syn::custom_keyword!(support_nested);
+}
+
+struct ExportArgs {
+ support_nested: bool,
+ internal_macro_calls: u16,
+ fake_call_site: bool,
+}
+
+impl Parse for ExportArgs {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let mut args = ExportArgs {
+ support_nested: false,
+ internal_macro_calls: 0,
+ fake_call_site: false,
+ };
+
+ while !input.is_empty() {
+ let ahead = input.lookahead1();
+ if ahead.peek(kw::support_nested) {
+ input.parse::<kw::support_nested>()?;
+ args.support_nested = true;
+ } else if ahead.peek(kw::internal_macro_calls) {
+ input.parse::<kw::internal_macro_calls>()?;
+ input.parse::<Token![=]>()?;
+ let calls = input.parse::<LitInt>()?.base10_parse()?;
+ args.internal_macro_calls = calls;
+ } else if ahead.peek(kw::fake_call_site) {
+ input.parse::<kw::fake_call_site>()?;
+ args.fake_call_site = true;
+ } else {
+ return Err(ahead.error());
+ }
+ if input.is_empty() {
+ break;
+ }
+ input.parse::<Token![,]>()?;
+ }
+
+ Ok(args)
+ }
+}
+
+struct DefineArgs;
+
+impl Parse for DefineArgs {
+ fn parse(_input: ParseStream) -> Result<Self> {
+ Ok(DefineArgs)
+ }
+}
+
+struct EnumHack {
+ token_stream: TokenStream,
+}
+
+impl Parse for EnumHack {
+ fn parse(input: ParseStream) -> Result<Self> {
+ input.parse::<Token![enum]>()?;
+ input.parse::<Ident>()?;
+
+ let braces;
+ braced!(braces in input);
+ braces.parse::<Ident>()?;
+ braces.parse::<Token![=]>()?;
+
+ let parens;
+ parenthesized!(parens in braces);
+ parens.parse::<Ident>()?;
+ parens.parse::<Token![!]>()?;
+
+ let inner;
+ braced!(inner in parens);
+ let token_stream: TokenStream = inner.parse()?;
+
+ parens.parse::<Token![,]>()?;
+ parens.parse::<TokenTree>()?;
+ braces.parse::<Token![.]>()?;
+ braces.parse::<TokenTree>()?;
+ braces.parse::<Token![,]>()?;
+
+ Ok(EnumHack { token_stream })
+ }
+}
+
+#[doc(hidden)]
+#[proc_macro_derive(ProcMacroHack)]
+pub fn enum_hack(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+ let inner = parse_macro_input!(input as EnumHack);
+ proc_macro::TokenStream::from(inner.token_stream)
+}
+
+struct FakeCallSite {
+ derive: Ident,
+ rest: TokenStream,
+}
+
+impl Parse for FakeCallSite {
+ fn parse(input: ParseStream) -> Result<Self> {
+ input.parse::<Token![#]>()?;
+ let attr;
+ bracketed!(attr in input);
+ attr.parse::<kw::derive>()?;
+ let path;
+ parenthesized!(path in attr);
+ Ok(FakeCallSite {
+ derive: path.parse()?,
+ rest: input.parse()?,
+ })
+ }
+}
+
+#[doc(hidden)]
+#[proc_macro_attribute]
+pub fn fake_call_site(
+ args: proc_macro::TokenStream,
+ input: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+ let args = TokenStream::from(args);
+ let span = match args.into_iter().next() {
+ Some(token) => token.span(),
+ None => return input,
+ };
+
+ let input = parse_macro_input!(input as FakeCallSite);
+ let mut derive = input.derive;
+ derive.set_span(span);
+ let rest = input.rest;
+
+ let expanded = quote! {
+ #[derive(#derive)]
+ #rest
+ };
+
+ proc_macro::TokenStream::from(expanded)
+}
+
+fn expand_export(export: Export, args: ExportArgs) -> TokenStream {
+ let dummy = dummy_name_for_export(&export);
+
+ let attrs = export.attrs;
+ let vis = export.vis;
+ let macro_export = match vis {
+ Some(_) => quote!(#[macro_export]),
+ None => quote!(),
+ };
+ let crate_prefix = vis.map(|_| quote!($crate::));
+ let enum_variant = if args.support_nested {
+ if args.internal_macro_calls == 0 {
+ quote!(Nested)
+ } else {
+ format_ident!("Nested{}", args.internal_macro_calls).to_token_stream()
+ }
+ } else {
+ quote!(Value)
+ };
+
+ let from = export.from;
+ let rules = export
+ .macros
+ .into_iter()
+ .map(|Macro { name, export_as }| {
+ let actual_name = actual_proc_macro_name(&name);
+ let dispatch = dispatch_macro_name(&name);
+ let call_site = call_site_macro_name(&name);
+
+ let export_dispatch = if args.support_nested {
+ quote! {
+ #[doc(hidden)]
+ #vis use proc_macro_nested::dispatch as #dispatch;
+ }
+ } else {
+ quote!()
+ };
+
+ let proc_macro_call = if args.support_nested {
+ let extra_bangs = (0..args.internal_macro_calls).map(|_| quote!(!));
+ quote! {
+ #crate_prefix #dispatch! { ($($proc_macro)*) #(#extra_bangs)* }
+ }
+ } else {
+ quote! {
+ proc_macro_call!()
+ }
+ };
+
+ let export_call_site = if args.fake_call_site {
+ quote! {
+ #[doc(hidden)]
+ #vis use proc_macro_hack::fake_call_site as #call_site;
+ }
+ } else {
+ quote!()
+ };
+
+ let do_derive = if !args.fake_call_site {
+ quote! {
+ #[derive(#crate_prefix #actual_name)]
+ }
+ } else if crate_prefix.is_some() {
+ quote! {
+ use #crate_prefix #actual_name;
+ #[#crate_prefix #call_site ($($proc_macro)*)]
+ #[derive(#actual_name)]
+ }
+ } else {
+ quote! {
+ #[#call_site ($($proc_macro)*)]
+ #[derive(#actual_name)]
+ }
+ };
+
+ quote! {
+ #[doc(hidden)]
+ #vis use #from::#actual_name;
+
+ #export_dispatch
+ #export_call_site
+
+ #attrs
+ #macro_export
+ macro_rules! #export_as {
+ ($($proc_macro:tt)*) => {{
+ #do_derive
+ enum ProcMacroHack {
+ #enum_variant = (stringify! { $($proc_macro)* }, 0).1,
+ }
+ #proc_macro_call
+ }};
+ }
+ }
+ })
+ .collect();
+
+ wrap_in_enum_hack(dummy, rules)
+}
+
+fn expand_define(define: Define) -> TokenStream {
+ let attrs = define.attrs;
+ let name = define.name;
+ let dummy = actual_proc_macro_name(&name);
+ let body = define.body;
+
+ quote! {
+ mod #dummy {
+ extern crate proc_macro;
+ pub use self::proc_macro::*;
+ }
+
+ #attrs
+ #[proc_macro_derive(#dummy)]
+ pub fn #dummy(input: #dummy::TokenStream) -> #dummy::TokenStream {
+ use std::iter::FromIterator;
+
+ let mut iter = input.into_iter();
+ iter.next().unwrap(); // `enum`
+ iter.next().unwrap(); // `ProcMacroHack`
+
+ let mut braces = match iter.next().unwrap() {
+ #dummy::TokenTree::Group(group) => group.stream().into_iter(),
+ _ => unimplemented!(),
+ };
+ let variant = braces.next().unwrap(); // `Value` or `Nested`
+ let varname = variant.to_string();
+ let support_nested = varname.starts_with("Nested");
+ braces.next().unwrap(); // `=`
+
+ let mut parens = match braces.next().unwrap() {
+ #dummy::TokenTree::Group(group) => group.stream().into_iter(),
+ _ => unimplemented!(),
+ };
+ parens.next().unwrap(); // `stringify`
+ parens.next().unwrap(); // `!`
+
+ let inner = match parens.next().unwrap() {
+ #dummy::TokenTree::Group(group) => group.stream(),
+ _ => unimplemented!(),
+ };
+
+ let output: #dummy::TokenStream = #name(inner.clone());
+
+ fn count_bangs(input: #dummy::TokenStream) -> usize {
+ let mut count = 0;
+ for token in input {
+ match token {
+ #dummy::TokenTree::Punct(punct) => {
+ if punct.as_char() == '!' {
+ count += 1;
+ }
+ }
+ #dummy::TokenTree::Group(group) => {
+ count += count_bangs(group.stream());
+ }
+ _ => {}
+ }
+ }
+ count
+ }
+
+ // macro_rules! proc_macro_call {
+ // () => { #output }
+ // }
+ #dummy::TokenStream::from_iter(vec![
+ #dummy::TokenTree::Ident(
+ #dummy::Ident::new("macro_rules", #dummy::Span::call_site()),
+ ),
+ #dummy::TokenTree::Punct(
+ #dummy::Punct::new('!', #dummy::Spacing::Alone),
+ ),
+ #dummy::TokenTree::Ident(
+ #dummy::Ident::new(
+ &if support_nested {
+ let extra_bangs = if varname == "Nested" {
+ 0
+ } else {
+ varname["Nested".len()..].parse().unwrap()
+ };
+ format!("proc_macro_call_{}", extra_bangs + count_bangs(inner))
+ } else {
+ String::from("proc_macro_call")
+ },
+ #dummy::Span::call_site(),
+ ),
+ ),
+ #dummy::TokenTree::Group(
+ #dummy::Group::new(#dummy::Delimiter::Brace, #dummy::TokenStream::from_iter(vec![
+ #dummy::TokenTree::Group(
+ #dummy::Group::new(#dummy::Delimiter::Parenthesis, #dummy::TokenStream::new()),
+ ),
+ #dummy::TokenTree::Punct(
+ #dummy::Punct::new('=', #dummy::Spacing::Joint),
+ ),
+ #dummy::TokenTree::Punct(
+ #dummy::Punct::new('>', #dummy::Spacing::Alone),
+ ),
+ #dummy::TokenTree::Group(
+ #dummy::Group::new(#dummy::Delimiter::Brace, output),
+ ),
+ ])),
+ ),
+ ])
+ }
+
+ fn #name #body
+ }
+}
+
+fn actual_proc_macro_name(conceptual: &Ident) -> Ident {
+ format_ident!("proc_macro_hack_{}", conceptual)
+}
+
+fn dispatch_macro_name(conceptual: &Ident) -> Ident {
+ format_ident!("proc_macro_call_{}", conceptual)
+}
+
+fn call_site_macro_name(conceptual: &Ident) -> Ident {
+ format_ident!("proc_macro_fake_call_site_{}", conceptual)
+}
+
+fn dummy_name_for_export(export: &Export) -> String {
+ let mut dummy = String::new();
+ let from = export.from.unraw().to_string();
+ write!(dummy, "_{}{}", from.len(), from).unwrap();
+ for m in &export.macros {
+ let name = m.name.unraw().to_string();
+ write!(dummy, "_{}{}", name.len(), name).unwrap();
+ }
+ dummy
+}
+
+fn wrap_in_enum_hack(dummy: String, inner: TokenStream) -> TokenStream {
+ let dummy = Ident::new(&dummy, Span::call_site());
+ quote! {
+ #[derive(proc_macro_hack::ProcMacroHack)]
+ enum #dummy {
+ Value = (stringify! { #inner }, 0).1,
+ }
+ }
+}