rust: proc-macro2: import crate

use core::sync::atomic::{AtomicUsize, Ordering};

use std::sync::Once;

static WORKS: AtomicUsize = AtomicUsize::new(0);

static INIT: Once = Once::new();

pub(crate) fn inside_proc_macro() -> bool {

    match WORKS.load(Ordering::Relaxed) {

        1 => return false,

        2 => return true,

        _ => {}

    }

    INIT.call_once(initialize);

    inside_proc_macro()

}

pub(crate) fn force_fallback() {

    WORKS.store(1, Ordering::Relaxed);

}

pub(crate) fn unforce_fallback() {

    initialize();

}

#[cfg(not(no_is_available))]

fn initialize() {

    let available = proc_macro::is_available();

    WORKS.store(available as usize + 1, Ordering::Relaxed);

}

// Swap in a null panic hook to avoid printing "thread panicked" to stderr,

// then use catch_unwind to determine whether the compiler's proc_macro is

// working. When proc-macro2 is used from outside of a procedural macro all

// of the proc_macro crate's APIs currently panic.

//

// The Once is to prevent the possibility of this ordering:

//

//     thread 1 calls take_hook, gets the user's original hook

//     thread 1 calls set_hook with the null hook

//     thread 2 calls take_hook, thinks null hook is the original hook

//     thread 2 calls set_hook with the null hook

//     thread 1 calls set_hook with the actual original hook

//     thread 2 calls set_hook with what it thinks is the original hook

//

// in which the user's hook has been lost.

//

// There is still a race condition where a panic in a different thread can

// happen during the interval that the user's original panic hook is

// unregistered such that their hook is incorrectly not called. This is

// sufficiently unlikely and less bad than printing panic messages to stderr

// on correct use of this crate. Maybe there is a libstd feature request

// here. For now, if a user needs to guarantee that this failure mode does

// not occur, they need to call e.g. `proc_macro2::Span::call_site()` from

// the main thread before launching any other threads.

#[cfg(no_is_available)]

fn initialize() {

    use std::panic::{self, PanicInfo};

    type PanicHook = dyn Fn(&PanicInfo) + Sync + Send + 'static;

    let null_hook: Box<PanicHook> = Box::new(|_panic_info| { /* ignore */ });

    let sanity_check = &*null_hook as *const PanicHook;

    let original_hook = panic::take_hook();

    panic::set_hook(null_hook);

    let works = panic::catch_unwind(proc_macro::Span::call_site).is_ok();

    WORKS.store(works as usize + 1, Ordering::Relaxed);

    let hopefully_null_hook = panic::take_hook();

    panic::set_hook(original_hook);

    if sanity_check != &*hopefully_null_hook {

        panic!("observed race condition in proc_macro2::inside_proc_macro");

    }

}

//! Items which do not have a correspondence to any API in the proc_macro crate,

//! but are necessary to include in proc-macro2.

use crate::fallback;

use crate::imp;

use crate::marker::{ProcMacroAutoTraits, MARKER};

use crate::Span;

use core::fmt::{self, Debug};

/// Invalidate any `proc_macro2::Span` that exist on the current thread.

///

/// The implementation of `Span` uses thread-local data structures and this

/// function clears them. Calling any method on a `Span` on the current thread

/// created prior to the invalidation will return incorrect values or crash.

///

/// This function is useful for programs that process more than 2<sup>32</sup>

/// bytes of Rust source code on the same thread. Just like rustc, proc-macro2

/// uses 32-bit source locations, and these wrap around when the total source

/// code processed by the same thread exceeds 2<sup>32</sup> bytes (4

/// gigabytes). After a wraparound, `Span` methods such as `source_text()` can

/// return wrong data.

///

/// # Example

///

/// As of late 2023, there is 200 GB of Rust code published on crates.io.

/// Looking at just the newest version of every crate, it is 16 GB of code. So a

/// workload that involves parsing it all would overflow a 32-bit source

/// location unless spans are being invalidated.

///

/// ```

/// use flate2::read::GzDecoder;

/// use std::ffi::OsStr;

/// use std::io::{BufReader, Read};

/// use std::str::FromStr;

/// use tar::Archive;

///

/// rayon::scope(|s| {

///     for krate in every_version_of_every_crate() {

///         s.spawn(move |_| {

///             proc_macro2::extra::invalidate_current_thread_spans();

///

///             let reader = BufReader::new(krate);

///             let tar = GzDecoder::new(reader);

///             let mut archive = Archive::new(tar);

///             for entry in archive.entries().unwrap() {

///                 let mut entry = entry.unwrap();

///                 let path = entry.path().unwrap();

///                 if path.extension() != Some(OsStr::new("rs")) {

///                     continue;

///                 }

///                 let mut content = String::new();

///                 entry.read_to_string(&mut content).unwrap();

///                 match proc_macro2::TokenStream::from_str(&content) {

///                     Ok(tokens) => {/* ... */},

///                     Err(_) => continue,

///                 }

///             }

///         });

///     }

/// });

/// #

/// # fn every_version_of_every_crate() -> Vec<std::fs::File> {

/// #     Vec::new()

/// # }

/// ```

///

/// # Panics

///

/// This function is not applicable to and will panic if called from a

/// procedural macro.

#[cfg(span_locations)]

#[cfg_attr(docsrs, doc(cfg(feature = "span-locations")))]

pub fn invalidate_current_thread_spans() {

    crate::imp::invalidate_current_thread_spans();

}

/// An object that holds a [`Group`]'s `span_open()` and `span_close()` together

/// in a more compact representation than holding those 2 spans individually.

///

/// [`Group`]: crate::Group

#[derive(Copy, Clone)]

pub struct DelimSpan {

    inner: DelimSpanEnum,

    _marker: ProcMacroAutoTraits,

}

#[derive(Copy, Clone)]

enum DelimSpanEnum {

    #[cfg(wrap_proc_macro)]

    Compiler {

        join: proc_macro::Span,

        open: proc_macro::Span,

        close: proc_macro::Span,

    },

    Fallback(fallback::Span),

}

impl DelimSpan {

    pub(crate) fn new(group: &imp::Group) -> Self {

        #[cfg(wrap_proc_macro)]

        let inner = match group {

            imp::Group::Compiler(group) => DelimSpanEnum::Compiler {

                join: group.span(),

                open: group.span_open(),

                close: group.span_close(),

            },

            imp::Group::Fallback(group) => DelimSpanEnum::Fallback(group.span()),

        };

        #[cfg(not(wrap_proc_macro))]

        let inner = DelimSpanEnum::Fallback(group.span());

        DelimSpan {

            inner,

            _marker: MARKER,

        }

    }

    /// Returns a span covering the entire delimited group.

    pub fn join(&self) -> Span {

        match &self.inner {

            #[cfg(wrap_proc_macro)]

            DelimSpanEnum::Compiler { join, .. } => Span::_new(imp::Span::Compiler(*join)),

            DelimSpanEnum::Fallback(span) => Span::_new_fallback(*span),

        }

    }

    /// Returns a span for the opening punctuation of the group only.

    pub fn open(&self) -> Span {

        match &self.inner {

            #[cfg(wrap_proc_macro)]

            DelimSpanEnum::Compiler { open, .. } => Span::_new(imp::Span::Compiler(*open)),

            DelimSpanEnum::Fallback(span) => Span::_new_fallback(span.first_byte()),

        }

    }

    /// Returns a span for the closing punctuation of the group only.

    pub fn close(&self) -> Span {

        match &self.inner {

            #[cfg(wrap_proc_macro)]

            DelimSpanEnum::Compiler { close, .. } => Span::_new(imp::Span::Compiler(*close)),

            DelimSpanEnum::Fallback(span) => Span::_new_fallback(span.last_byte()),

        }

    }

}

impl Debug for DelimSpan {

    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

        Debug::fmt(&self.join(), f)

    }

}

use core::cmp::Ordering;

/// A line-column pair representing the start or end of a `Span`.

///

/// This type is semver exempt and not exposed by default.

#[cfg_attr(docsrs, doc(cfg(feature = "span-locations")))]

#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]

pub struct LineColumn {

    /// The 1-indexed line in the source file on which the span starts or ends

    /// (inclusive).

    pub line: usize,

    /// The 0-indexed column (in UTF-8 characters) in the source file on which

    /// the span starts or ends (inclusive).

    pub column: usize,

}

impl Ord for LineColumn {

    fn cmp(&self, other: &Self) -> Ordering {

        self.line

            .cmp(&other.line)

            .then(self.column.cmp(&other.column))

    }

}

impl PartialOrd for LineColumn {

    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {

        Some(self.cmp(other))

    }

}