1 //! Items which do not have a correspondence to any API in the proc_macro crate,
2 //! but are necessary to include in proc-macro2.
3
4 use crate::fallback;
5 use crate::imp;
6 use crate::marker::{ProcMacroAutoTraits, MARKER};
7 use crate::Span;
8 use core::fmt::{self, Debug};
9
10 /// Invalidate any `proc_macro2::Span` that exist on the current thread.
11 ///
12 /// The implementation of `Span` uses thread-local data structures and this
13 /// function clears them. Calling any method on a `Span` on the current thread
14 /// created prior to the invalidation will return incorrect values or crash.
15 ///
16 /// This function is useful for programs that process more than 2<sup>32</sup>
17 /// bytes of Rust source code on the same thread. Just like rustc, proc-macro2
18 /// uses 32-bit source locations, and these wrap around when the total source
19 /// code processed by the same thread exceeds 2<sup>32</sup> bytes (4
20 /// gigabytes). After a wraparound, `Span` methods such as `source_text()` can
21 /// return wrong data.
22 ///
23 /// # Example
24 ///
25 /// As of late 2023, there is 200 GB of Rust code published on crates.io.
26 /// Looking at just the newest version of every crate, it is 16 GB of code. So a
27 /// workload that involves parsing it all would overflow a 32-bit source
28 /// location unless spans are being invalidated.
29 ///
30 /// ```
31 /// use flate2::read::GzDecoder;
32 /// use std::ffi::OsStr;
33 /// use std::io::{BufReader, Read};
34 /// use std::str::FromStr;
35 /// use tar::Archive;
36 ///
37 /// rayon::scope(|s| {
38 /// for krate in every_version_of_every_crate() {
39 /// s.spawn(move |_| {
40 /// proc_macro2::extra::invalidate_current_thread_spans();
41 ///
42 /// let reader = BufReader::new(krate);
43 /// let tar = GzDecoder::new(reader);
44 /// let mut archive = Archive::new(tar);
45 /// for entry in archive.entries().unwrap() {
46 /// let mut entry = entry.unwrap();
47 /// let path = entry.path().unwrap();
48 /// if path.extension() != Some(OsStr::new("rs")) {
49 /// continue;
50 /// }
51 /// let mut content = String::new();
52 /// entry.read_to_string(&mut content).unwrap();
53 /// match proc_macro2::TokenStream::from_str(&content) {
54 /// Ok(tokens) => {/* ... */},
55 /// Err(_) => continue,
56 /// }
57 /// }
58 /// });
59 /// }
60 /// });
61 /// #
62 /// # fn every_version_of_every_crate() -> Vec<std::fs::File> {
63 /// # Vec::new()
64 /// # }
65 /// ```
66 ///
67 /// # Panics
68 ///
69 /// This function is not applicable to and will panic if called from a
70 /// procedural macro.
71 #[cfg(span_locations)]
72 #[cfg_attr(docsrs, doc(cfg(feature = "span-locations")))]
invalidate_current_thread_spans()73 pub fn invalidate_current_thread_spans() {
74 crate::imp::invalidate_current_thread_spans();
75 }
76
77 /// An object that holds a [`Group`]'s `span_open()` and `span_close()` together
78 /// in a more compact representation than holding those 2 spans individually.
79 ///
80 /// [`Group`]: crate::Group
81 #[derive(Copy, Clone)]
82 pub struct DelimSpan {
83 inner: DelimSpanEnum,
84 _marker: ProcMacroAutoTraits,
85 }
86
87 #[derive(Copy, Clone)]
88 enum DelimSpanEnum {
89 #[cfg(wrap_proc_macro)]
90 Compiler {
91 join: proc_macro::Span,
92 open: proc_macro::Span,
93 close: proc_macro::Span,
94 },
95 Fallback(fallback::Span),
96 }
97
98 impl DelimSpan {
new(group: &imp::Group) -> Self99 pub(crate) fn new(group: &imp::Group) -> Self {
100 #[cfg(wrap_proc_macro)]
101 let inner = match group {
102 imp::Group::Compiler(group) => DelimSpanEnum::Compiler {
103 join: group.span(),
104 open: group.span_open(),
105 close: group.span_close(),
106 },
107 imp::Group::Fallback(group) => DelimSpanEnum::Fallback(group.span()),
108 };
109
110 #[cfg(not(wrap_proc_macro))]
111 let inner = DelimSpanEnum::Fallback(group.span());
112
113 DelimSpan {
114 inner,
115 _marker: MARKER,
116 }
117 }
118
119 /// Returns a span covering the entire delimited group.
join(&self) -> Span120 pub fn join(&self) -> Span {
121 match &self.inner {
122 #[cfg(wrap_proc_macro)]
123 DelimSpanEnum::Compiler { join, .. } => Span::_new(imp::Span::Compiler(*join)),
124 DelimSpanEnum::Fallback(span) => Span::_new_fallback(*span),
125 }
126 }
127
128 /// Returns a span for the opening punctuation of the group only.
open(&self) -> Span129 pub fn open(&self) -> Span {
130 match &self.inner {
131 #[cfg(wrap_proc_macro)]
132 DelimSpanEnum::Compiler { open, .. } => Span::_new(imp::Span::Compiler(*open)),
133 DelimSpanEnum::Fallback(span) => Span::_new_fallback(span.first_byte()),
134 }
135 }
136
137 /// Returns a span for the closing punctuation of the group only.
close(&self) -> Span138 pub fn close(&self) -> Span {
139 match &self.inner {
140 #[cfg(wrap_proc_macro)]
141 DelimSpanEnum::Compiler { close, .. } => Span::_new(imp::Span::Compiler(*close)),
142 DelimSpanEnum::Fallback(span) => Span::_new_fallback(span.last_byte()),
143 }
144 }
145 }
146
147 impl Debug for DelimSpan {
fmt(&self, f: &mut fmt::Formatter) -> fmt::Result148 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
149 Debug::fmt(&self.join(), f)
150 }
151 }
152