build(ariadne): vendor serde crates

third_party/crates/proc-macro2-1.0.107/src/wrapper.rs

@@ -0,0 +1,987 @@
+use crate::detection::inside_proc_macro;
+use crate::fallback::{self, FromStr2 as _};
+#[cfg(span_locations)]
+use crate::location::LineColumn;
+#[cfg(proc_macro_span)]
+use crate::probe::proc_macro_span;
+#[cfg(all(span_locations, proc_macro_span_file))]
+use crate::probe::proc_macro_span_file;
+#[cfg(all(span_locations, proc_macro_span_location))]
+use crate::probe::proc_macro_span_location;
+use crate::{Delimiter, Punct, Spacing, TokenTree};
+#[cfg(all(span_locations, not(proc_macro_span_file)))]
+use alloc::borrow::ToOwned as _;
+use alloc::string::{String, ToString as _};
+use alloc::vec::Vec;
+use core::ffi::CStr;
+use core::fmt::{self, Debug, Display};
+#[cfg(span_locations)]
+use core::ops::Range;
+use core::ops::RangeBounds;
+#[cfg(span_locations)]
+use std::path::PathBuf;
+
+#[derive(Clone)]
+pub(crate) enum TokenStream {
+    Compiler(DeferredTokenStream),
+    Fallback(fallback::TokenStream),
+}
+
+// Work around https://github.com/rust-lang/rust/issues/65080.
+// In `impl Extend<TokenTree> for TokenStream` which is used heavily by quote,
+// we hold on to the appended tokens and do proc_macro::TokenStream::extend as
+// late as possible to batch together consecutive uses of the Extend impl.
+#[derive(Clone)]
+pub(crate) struct DeferredTokenStream {
+    stream: proc_macro::TokenStream,
+    extra: Vec<proc_macro::TokenTree>,
+}
+
+pub(crate) enum LexError {
+    Compiler(proc_macro::LexError),
+    Fallback(fallback::LexError),
+
+    // Rustc was supposed to return a LexError, but it panicked instead.
+    // https://github.com/rust-lang/rust/issues/58736
+    CompilerPanic,
+}
+
+#[cold]
+fn mismatch(line: u32) -> ! {
+    #[cfg(procmacro2_backtrace)]
+    {
+        let backtrace = std::backtrace::Backtrace::force_capture();
+        panic!("compiler/fallback mismatch L{}\n\n{}", line, backtrace)
+    }
+    #[cfg(not(procmacro2_backtrace))]
+    {
+        panic!("compiler/fallback mismatch L{}", line)
+    }
+}
+
+impl DeferredTokenStream {
+    fn new(stream: proc_macro::TokenStream) -> Self {
+        DeferredTokenStream {
+            stream,
+            extra: Vec::new(),
+        }
+    }
+
+    fn is_empty(&self) -> bool {
+        self.stream.is_empty() && self.extra.is_empty()
+    }
+
+    fn evaluate_now(&mut self) {
+        // If-check provides a fast short circuit for the common case of `extra`
+        // being empty, which saves a round trip over the proc macro bridge.
+        // Improves macro expansion time in winrt by 6% in debug mode.
+        if !self.extra.is_empty() {
+            self.stream.extend(self.extra.drain(..));
+        }
+    }
+
+    fn into_token_stream(mut self) -> proc_macro::TokenStream {
+        self.evaluate_now();
+        self.stream
+    }
+}
+
+impl TokenStream {
+    pub(crate) fn new() -> Self {
+        if inside_proc_macro() {
+            TokenStream::Compiler(DeferredTokenStream::new(proc_macro::TokenStream::new()))
+        } else {
+            TokenStream::Fallback(fallback::TokenStream::new())
+        }
+    }
+
+    pub(crate) fn from_str_checked(src: &str) -> Result<Self, LexError> {
+        if inside_proc_macro() {
+            Ok(TokenStream::Compiler(DeferredTokenStream::new(
+                proc_macro::TokenStream::from_str_checked(src)?,
+            )))
+        } else {
+            Ok(TokenStream::Fallback(
+                fallback::TokenStream::from_str_checked(src)?,
+            ))
+        }
+    }
+
+    pub(crate) fn is_empty(&self) -> bool {
+        match self {
+            TokenStream::Compiler(tts) => tts.is_empty(),
+            TokenStream::Fallback(tts) => tts.is_empty(),
+        }
+    }
+
+    fn unwrap_nightly(self) -> proc_macro::TokenStream {
+        match self {
+            TokenStream::Compiler(s) => s.into_token_stream(),
+            TokenStream::Fallback(_) => mismatch(line!()),
+        }
+    }
+
+    fn unwrap_stable(self) -> fallback::TokenStream {
+        match self {
+            TokenStream::Compiler(_) => mismatch(line!()),
+            TokenStream::Fallback(s) => s,
+        }
+    }
+}
+
+impl Display for TokenStream {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TokenStream::Compiler(tts) => Display::fmt(&tts.clone().into_token_stream(), f),
+            TokenStream::Fallback(tts) => Display::fmt(tts, f),
+        }
+    }
+}
+
+impl From<proc_macro::TokenStream> for TokenStream {
+    fn from(inner: proc_macro::TokenStream) -> Self {
+        TokenStream::Compiler(DeferredTokenStream::new(inner))
+    }
+}
+
+impl From<TokenStream> for proc_macro::TokenStream {
+    fn from(inner: TokenStream) -> Self {
+        match inner {
+            TokenStream::Compiler(inner) => inner.into_token_stream(),
+            TokenStream::Fallback(inner) => {
+                proc_macro::TokenStream::from_str_unchecked(&inner.to_string())
+            }
+        }
+    }
+}
+
+impl From<fallback::TokenStream> for TokenStream {
+    fn from(inner: fallback::TokenStream) -> Self {
+        TokenStream::Fallback(inner)
+    }
+}
+
+// Assumes inside_proc_macro().
+fn into_compiler_token(token: TokenTree) -> proc_macro::TokenTree {
+    match token {
+        TokenTree::Group(tt) => proc_macro::TokenTree::Group(tt.inner.unwrap_nightly()),
+        TokenTree::Punct(tt) => {
+            let spacing = match tt.spacing() {
+                Spacing::Joint => proc_macro::Spacing::Joint,
+                Spacing::Alone => proc_macro::Spacing::Alone,
+            };
+            let mut punct = proc_macro::Punct::new(tt.as_char(), spacing);
+            punct.set_span(tt.span().inner.unwrap_nightly());
+            proc_macro::TokenTree::Punct(punct)
+        }
+        TokenTree::Ident(tt) => proc_macro::TokenTree::Ident(tt.inner.unwrap_nightly()),
+        TokenTree::Literal(tt) => proc_macro::TokenTree::Literal(tt.inner.unwrap_nightly()),
+    }
+}
+
+impl From<TokenTree> for TokenStream {
+    fn from(token: TokenTree) -> Self {
+        if inside_proc_macro() {
+            TokenStream::Compiler(DeferredTokenStream::new(proc_macro::TokenStream::from(
+                into_compiler_token(token),
+            )))
+        } else {
+            TokenStream::Fallback(fallback::TokenStream::from(token))
+        }
+    }
+}
+
+impl FromIterator<TokenTree> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenTree>>(tokens: I) -> Self {
+        if inside_proc_macro() {
+            TokenStream::Compiler(DeferredTokenStream::new(
+                tokens.into_iter().map(into_compiler_token).collect(),
+            ))
+        } else {
+            TokenStream::Fallback(tokens.into_iter().collect())
+        }
+    }
+}
+
+impl FromIterator<TokenStream> for TokenStream {
+    fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
+        let mut streams = streams.into_iter();
+        match streams.next() {
+            Some(TokenStream::Compiler(mut first)) => {
+                first.evaluate_now();
+                first.stream.extend(streams.map(|s| match s {
+                    TokenStream::Compiler(s) => s.into_token_stream(),
+                    TokenStream::Fallback(_) => mismatch(line!()),
+                }));
+                TokenStream::Compiler(first)
+            }
+            Some(TokenStream::Fallback(mut first)) => {
+                first.extend(streams.map(|s| match s {
+                    TokenStream::Fallback(s) => s,
+                    TokenStream::Compiler(_) => mismatch(line!()),
+                }));
+                TokenStream::Fallback(first)
+            }
+            None => TokenStream::new(),
+        }
+    }
+}
+
+impl Extend<TokenTree> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenTree>>(&mut self, tokens: I) {
+        match self {
+            TokenStream::Compiler(tts) => {
+                // Here is the reason for DeferredTokenStream.
+                for token in tokens {
+                    tts.extra.push(into_compiler_token(token));
+                }
+            }
+            TokenStream::Fallback(tts) => tts.extend(tokens),
+        }
+    }
+}
+
+impl Extend<TokenStream> for TokenStream {
+    fn extend<I: IntoIterator<Item = TokenStream>>(&mut self, streams: I) {
+        match self {
+            TokenStream::Compiler(tts) => {
+                tts.evaluate_now();
+                tts.stream
+                    .extend(streams.into_iter().map(TokenStream::unwrap_nightly));
+            }
+            TokenStream::Fallback(tts) => {
+                tts.extend(streams.into_iter().map(TokenStream::unwrap_stable));
+            }
+        }
+    }
+}
+
+impl Debug for TokenStream {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TokenStream::Compiler(tts) => Debug::fmt(&tts.clone().into_token_stream(), f),
+            TokenStream::Fallback(tts) => Debug::fmt(tts, f),
+        }
+    }
+}
+
+impl LexError {
+    pub(crate) fn span(&self) -> Span {
+        match self {
+            LexError::Compiler(_) | LexError::CompilerPanic => Span::call_site(),
+            LexError::Fallback(e) => Span::Fallback(e.span()),
+        }
+    }
+}
+
+impl From<proc_macro::LexError> for LexError {
+    fn from(e: proc_macro::LexError) -> Self {
+        LexError::Compiler(e)
+    }
+}
+
+impl From<fallback::LexError> for LexError {
+    fn from(e: fallback::LexError) -> Self {
+        LexError::Fallback(e)
+    }
+}
+
+impl Debug for LexError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            LexError::Compiler(e) => Debug::fmt(e, f),
+            LexError::Fallback(e) => Debug::fmt(e, f),
+            LexError::CompilerPanic => {
+                let fallback = fallback::LexError::call_site();
+                Debug::fmt(&fallback, f)
+            }
+        }
+    }
+}
+
+impl Display for LexError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            LexError::Compiler(e) => Display::fmt(e, f),
+            LexError::Fallback(e) => Display::fmt(e, f),
+            LexError::CompilerPanic => {
+                let fallback = fallback::LexError::call_site();
+                Display::fmt(&fallback, f)
+            }
+        }
+    }
+}
+
+#[derive(Clone)]
+pub(crate) enum TokenTreeIter {
+    Compiler(proc_macro::token_stream::IntoIter),
+    Fallback(fallback::TokenTreeIter),
+}
+
+impl IntoIterator for TokenStream {
+    type Item = TokenTree;
+    type IntoIter = TokenTreeIter;
+
+    fn into_iter(self) -> TokenTreeIter {
+        match self {
+            TokenStream::Compiler(tts) => {
+                TokenTreeIter::Compiler(tts.into_token_stream().into_iter())
+            }
+            TokenStream::Fallback(tts) => TokenTreeIter::Fallback(tts.into_iter()),
+        }
+    }
+}
+
+impl Iterator for TokenTreeIter {
+    type Item = TokenTree;
+
+    fn next(&mut self) -> Option<TokenTree> {
+        let token = match self {
+            TokenTreeIter::Compiler(iter) => iter.next()?,
+            TokenTreeIter::Fallback(iter) => return iter.next(),
+        };
+        Some(match token {
+            proc_macro::TokenTree::Group(tt) => {
+                TokenTree::Group(crate::Group::_new(Group::Compiler(tt)))
+            }
+            proc_macro::TokenTree::Punct(tt) => {
+                let spacing = match tt.spacing() {
+                    proc_macro::Spacing::Joint => Spacing::Joint,
+                    proc_macro::Spacing::Alone => Spacing::Alone,
+                };
+                let mut o = Punct::new(tt.as_char(), spacing);
+                o.set_span(crate::Span::_new(Span::Compiler(tt.span())));
+                TokenTree::Punct(o)
+            }
+            proc_macro::TokenTree::Ident(s) => {
+                TokenTree::Ident(crate::Ident::_new(Ident::Compiler(s)))
+            }
+            proc_macro::TokenTree::Literal(l) => {
+                TokenTree::Literal(crate::Literal::_new(Literal::Compiler(l)))
+            }
+        })
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        match self {
+            TokenTreeIter::Compiler(tts) => tts.size_hint(),
+            TokenTreeIter::Fallback(tts) => tts.size_hint(),
+        }
+    }
+}
+
+#[derive(Copy, Clone)]
+pub(crate) enum Span {
+    Compiler(proc_macro::Span),
+    Fallback(fallback::Span),
+}
+
+impl Span {
+    pub(crate) fn call_site() -> Self {
+        if inside_proc_macro() {
+            Span::Compiler(proc_macro::Span::call_site())
+        } else {
+            Span::Fallback(fallback::Span::call_site())
+        }
+    }
+
+    pub(crate) fn mixed_site() -> Self {
+        if inside_proc_macro() {
+            Span::Compiler(proc_macro::Span::mixed_site())
+        } else {
+            Span::Fallback(fallback::Span::mixed_site())
+        }
+    }
+
+    #[cfg(super_unstable)]
+    pub(crate) fn def_site() -> Self {
+        if inside_proc_macro() {
+            Span::Compiler(proc_macro::Span::def_site())
+        } else {
+            Span::Fallback(fallback::Span::def_site())
+        }
+    }
+
+    pub(crate) fn resolved_at(&self, other: Span) -> Span {
+        match (self, other) {
+            (Span::Compiler(a), Span::Compiler(b)) => Span::Compiler(a.resolved_at(b)),
+            (Span::Fallback(a), Span::Fallback(b)) => Span::Fallback(a.resolved_at(b)),
+            (Span::Compiler(_), Span::Fallback(_)) => mismatch(line!()),
+            (Span::Fallback(_), Span::Compiler(_)) => mismatch(line!()),
+        }
+    }
+
+    pub(crate) fn located_at(&self, other: Span) -> Span {
+        match (self, other) {
+            (Span::Compiler(a), Span::Compiler(b)) => Span::Compiler(a.located_at(b)),
+            (Span::Fallback(a), Span::Fallback(b)) => Span::Fallback(a.located_at(b)),
+            (Span::Compiler(_), Span::Fallback(_)) => mismatch(line!()),
+            (Span::Fallback(_), Span::Compiler(_)) => mismatch(line!()),
+        }
+    }
+
+    pub(crate) fn unwrap(self) -> proc_macro::Span {
+        match self {
+            Span::Compiler(s) => s,
+            Span::Fallback(_) => panic!("proc_macro::Span is only available in procedural macros"),
+        }
+    }
+
+    #[cfg(span_locations)]
+    pub(crate) fn byte_range(&self) -> Range<usize> {
+        match self {
+            #[cfg(proc_macro_span)]
+            Span::Compiler(s) => proc_macro_span::byte_range(s),
+            #[cfg(not(proc_macro_span))]
+            Span::Compiler(_) => 0..0,
+            Span::Fallback(s) => s.byte_range(),
+        }
+    }
+
+    #[cfg(span_locations)]
+    pub(crate) fn start(&self) -> LineColumn {
+        match self {
+            #[cfg(proc_macro_span_location)]
+            Span::Compiler(s) => LineColumn {
+                line: proc_macro_span_location::line(s),
+                column: proc_macro_span_location::column(s).saturating_sub(1),
+            },
+            #[cfg(not(proc_macro_span_location))]
+            Span::Compiler(_) => LineColumn { line: 0, column: 0 },
+            Span::Fallback(s) => s.start(),
+        }
+    }
+
+    #[cfg(span_locations)]
+    pub(crate) fn end(&self) -> LineColumn {
+        match self {
+            #[cfg(proc_macro_span_location)]
+            Span::Compiler(s) => {
+                let end = proc_macro_span_location::end(s);
+                LineColumn {
+                    line: proc_macro_span_location::line(&end),
+                    column: proc_macro_span_location::column(&end).saturating_sub(1),
+                }
+            }
+            #[cfg(not(proc_macro_span_location))]
+            Span::Compiler(_) => LineColumn { line: 0, column: 0 },
+            Span::Fallback(s) => s.end(),
+        }
+    }
+
+    #[cfg(span_locations)]
+    pub(crate) fn file(&self) -> String {
+        match self {
+            #[cfg(proc_macro_span_file)]
+            Span::Compiler(s) => proc_macro_span_file::file(s),
+            #[cfg(not(proc_macro_span_file))]
+            Span::Compiler(_) => "<token stream>".to_owned(),
+            Span::Fallback(s) => s.file(),
+        }
+    }
+
+    #[cfg(span_locations)]
+    pub(crate) fn local_file(&self) -> Option<PathBuf> {
+        match self {
+            #[cfg(proc_macro_span_file)]
+            Span::Compiler(s) => proc_macro_span_file::local_file(s),
+            #[cfg(not(proc_macro_span_file))]
+            Span::Compiler(_) => None,
+            Span::Fallback(s) => s.local_file(),
+        }
+    }
+
+    pub(crate) fn join(&self, other: Span) -> Option<Span> {
+        let ret = match (self, other) {
+            #[cfg(proc_macro_span)]
+            (Span::Compiler(a), Span::Compiler(b)) => Span::Compiler(proc_macro_span::join(a, b)?),
+            (Span::Fallback(a), Span::Fallback(b)) => Span::Fallback(a.join(b)?),
+            _ => return None,
+        };
+        Some(ret)
+    }
+
+    #[cfg(super_unstable)]
+    pub(crate) fn eq(&self, other: &Span) -> bool {
+        match (self, other) {
+            (Span::Compiler(a), Span::Compiler(b)) => a.eq(b),
+            (Span::Fallback(a), Span::Fallback(b)) => a.eq(b),
+            _ => false,
+        }
+    }
+
+    pub(crate) fn source_text(&self) -> Option<String> {
+        match self {
+            #[cfg(not(no_source_text))]
+            Span::Compiler(s) => s.source_text(),
+            #[cfg(no_source_text)]
+            Span::Compiler(_) => None,
+            Span::Fallback(s) => s.source_text(),
+        }
+    }
+
+    fn unwrap_nightly(self) -> proc_macro::Span {
+        match self {
+            Span::Compiler(s) => s,
+            Span::Fallback(_) => mismatch(line!()),
+        }
+    }
+}
+
+impl From<proc_macro::Span> for crate::Span {
+    fn from(proc_span: proc_macro::Span) -> Self {
+        crate::Span::_new(Span::Compiler(proc_span))
+    }
+}
+
+impl From<fallback::Span> for Span {
+    fn from(inner: fallback::Span) -> Self {
+        Span::Fallback(inner)
+    }
+}
+
+impl Debug for Span {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Span::Compiler(s) => Debug::fmt(s, f),
+            Span::Fallback(s) => Debug::fmt(s, f),
+        }
+    }
+}
+
+pub(crate) fn debug_span_field_if_nontrivial(debug: &mut fmt::DebugStruct, span: Span) {
+    match span {
+        Span::Compiler(s) => {
+            debug.field("span", &s);
+        }
+        Span::Fallback(s) => fallback::debug_span_field_if_nontrivial(debug, s),
+    }
+}
+
+#[derive(Clone)]
+pub(crate) enum Group {
+    Compiler(proc_macro::Group),
+    Fallback(fallback::Group),
+}
+
+impl Group {
+    pub(crate) fn new(delimiter: Delimiter, stream: TokenStream) -> Self {
+        match stream {
+            TokenStream::Compiler(tts) => {
+                let delimiter = match delimiter {
+                    Delimiter::Parenthesis => proc_macro::Delimiter::Parenthesis,
+                    Delimiter::Bracket => proc_macro::Delimiter::Bracket,
+                    Delimiter::Brace => proc_macro::Delimiter::Brace,
+                    Delimiter::None => proc_macro::Delimiter::None,
+                };
+                Group::Compiler(proc_macro::Group::new(delimiter, tts.into_token_stream()))
+            }
+            TokenStream::Fallback(stream) => {
+                Group::Fallback(fallback::Group::new(delimiter, stream))
+            }
+        }
+    }
+
+    pub(crate) fn delimiter(&self) -> Delimiter {
+        match self {
+            Group::Compiler(g) => match g.delimiter() {
+                proc_macro::Delimiter::Parenthesis => Delimiter::Parenthesis,
+                proc_macro::Delimiter::Bracket => Delimiter::Bracket,
+                proc_macro::Delimiter::Brace => Delimiter::Brace,
+                proc_macro::Delimiter::None => Delimiter::None,
+            },
+            Group::Fallback(g) => g.delimiter(),
+        }
+    }
+
+    pub(crate) fn stream(&self) -> TokenStream {
+        match self {
+            Group::Compiler(g) => TokenStream::Compiler(DeferredTokenStream::new(g.stream())),
+            Group::Fallback(g) => TokenStream::Fallback(g.stream()),
+        }
+    }
+
+    pub(crate) fn span(&self) -> Span {
+        match self {
+            Group::Compiler(g) => Span::Compiler(g.span()),
+            Group::Fallback(g) => Span::Fallback(g.span()),
+        }
+    }
+
+    pub(crate) fn span_open(&self) -> Span {
+        match self {
+            Group::Compiler(g) => Span::Compiler(g.span_open()),
+            Group::Fallback(g) => Span::Fallback(g.span_open()),
+        }
+    }
+
+    pub(crate) fn span_close(&self) -> Span {
+        match self {
+            Group::Compiler(g) => Span::Compiler(g.span_close()),
+            Group::Fallback(g) => Span::Fallback(g.span_close()),
+        }
+    }
+
+    pub(crate) fn set_span(&mut self, span: Span) {
+        match (self, span) {
+            (Group::Compiler(g), Span::Compiler(s)) => g.set_span(s),
+            (Group::Fallback(g), Span::Fallback(s)) => g.set_span(s),
+            (Group::Compiler(_), Span::Fallback(_)) => mismatch(line!()),
+            (Group::Fallback(_), Span::Compiler(_)) => mismatch(line!()),
+        }
+    }
+
+    fn unwrap_nightly(self) -> proc_macro::Group {
+        match self {
+            Group::Compiler(g) => g,
+            Group::Fallback(_) => mismatch(line!()),
+        }
+    }
+}
+
+impl From<fallback::Group> for Group {
+    fn from(g: fallback::Group) -> Self {
+        Group::Fallback(g)
+    }
+}
+
+impl Display for Group {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Group::Compiler(group) => Display::fmt(group, formatter),
+            Group::Fallback(group) => Display::fmt(group, formatter),
+        }
+    }
+}
+
+impl Debug for Group {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Group::Compiler(group) => Debug::fmt(group, formatter),
+            Group::Fallback(group) => Debug::fmt(group, formatter),
+        }
+    }
+}
+
+#[derive(Clone)]
+pub(crate) enum Ident {
+    Compiler(proc_macro::Ident),
+    Fallback(fallback::Ident),
+}
+
+impl Ident {
+    #[track_caller]
+    pub(crate) fn new_checked(string: &str, span: Span) -> Self {
+        match span {
+            Span::Compiler(s) => Ident::Compiler(proc_macro::Ident::new(string, s)),
+            Span::Fallback(s) => Ident::Fallback(fallback::Ident::new_checked(string, s)),
+        }
+    }
+
+    #[track_caller]
+    pub(crate) fn new_raw_checked(string: &str, span: Span) -> Self {
+        match span {
+            Span::Compiler(s) => Ident::Compiler(proc_macro::Ident::new_raw(string, s)),
+            Span::Fallback(s) => Ident::Fallback(fallback::Ident::new_raw_checked(string, s)),
+        }
+    }
+
+    pub(crate) fn span(&self) -> Span {
+        match self {
+            Ident::Compiler(t) => Span::Compiler(t.span()),
+            Ident::Fallback(t) => Span::Fallback(t.span()),
+        }
+    }
+
+    pub(crate) fn set_span(&mut self, span: Span) {
+        match (self, span) {
+            (Ident::Compiler(t), Span::Compiler(s)) => t.set_span(s),
+            (Ident::Fallback(t), Span::Fallback(s)) => t.set_span(s),
+            (Ident::Compiler(_), Span::Fallback(_)) => mismatch(line!()),
+            (Ident::Fallback(_), Span::Compiler(_)) => mismatch(line!()),
+        }
+    }
+
+    fn unwrap_nightly(self) -> proc_macro::Ident {
+        match self {
+            Ident::Compiler(s) => s,
+            Ident::Fallback(_) => mismatch(line!()),
+        }
+    }
+}
+
+impl From<fallback::Ident> for Ident {
+    fn from(inner: fallback::Ident) -> Self {
+        Ident::Fallback(inner)
+    }
+}
+
+impl PartialEq for Ident {
+    fn eq(&self, other: &Ident) -> bool {
+        match (self, other) {
+            (Ident::Compiler(t), Ident::Compiler(o)) => t.to_string() == o.to_string(),
+            (Ident::Fallback(t), Ident::Fallback(o)) => t == o,
+            (Ident::Compiler(_), Ident::Fallback(_)) => mismatch(line!()),
+            (Ident::Fallback(_), Ident::Compiler(_)) => mismatch(line!()),
+        }
+    }
+}
+
+impl<T> PartialEq<T> for Ident
+where
+    T: ?Sized + AsRef<str>,
+{
+    fn eq(&self, other: &T) -> bool {
+        let other = other.as_ref();
+        match self {
+            Ident::Compiler(t) => t.to_string() == other,
+            Ident::Fallback(t) => t == other,
+        }
+    }
+}
+
+impl Display for Ident {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Ident::Compiler(t) => Display::fmt(t, f),
+            Ident::Fallback(t) => Display::fmt(t, f),
+        }
+    }
+}
+
+impl Debug for Ident {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Ident::Compiler(t) => Debug::fmt(t, f),
+            Ident::Fallback(t) => Debug::fmt(t, f),
+        }
+    }
+}
+
+#[derive(Clone)]
+pub(crate) enum Literal {
+    Compiler(proc_macro::Literal),
+    Fallback(fallback::Literal),
+}
+
+macro_rules! suffixed_numbers {
+    ($($name:ident => $kind:ident,)*) => ($(
+        pub(crate) fn $name(n: $kind) -> Literal {
+            if inside_proc_macro() {
+                Literal::Compiler(proc_macro::Literal::$name(n))
+            } else {
+                Literal::Fallback(fallback::Literal::$name(n))
+            }
+        }
+    )*)
+}
+
+macro_rules! unsuffixed_integers {
+    ($($name:ident => $kind:ident,)*) => ($(
+        pub(crate) fn $name(n: $kind) -> Literal {
+            if inside_proc_macro() {
+                Literal::Compiler(proc_macro::Literal::$name(n))
+            } else {
+                Literal::Fallback(fallback::Literal::$name(n))
+            }
+        }
+    )*)
+}
+
+impl Literal {
+    pub(crate) fn from_str_checked(repr: &str) -> Result<Self, LexError> {
+        if inside_proc_macro() {
+            let literal = proc_macro::Literal::from_str_checked(repr)?;
+            Ok(Literal::Compiler(literal))
+        } else {
+            let literal = fallback::Literal::from_str_checked(repr)?;
+            Ok(Literal::Fallback(literal))
+        }
+    }
+
+    pub(crate) unsafe fn from_str_unchecked(repr: &str) -> Self {
+        if inside_proc_macro() {
+            Literal::Compiler(proc_macro::Literal::from_str_unchecked(repr))
+        } else {
+            Literal::Fallback(unsafe { fallback::Literal::from_str_unchecked(repr) })
+        }
+    }
+
+    suffixed_numbers! {
+        u8_suffixed => u8,
+        u16_suffixed => u16,
+        u32_suffixed => u32,
+        u64_suffixed => u64,
+        u128_suffixed => u128,
+        usize_suffixed => usize,
+        i8_suffixed => i8,
+        i16_suffixed => i16,
+        i32_suffixed => i32,
+        i64_suffixed => i64,
+        i128_suffixed => i128,
+        isize_suffixed => isize,
+
+        f32_suffixed => f32,
+        f64_suffixed => f64,
+    }
+
+    unsuffixed_integers! {
+        u8_unsuffixed => u8,
+        u16_unsuffixed => u16,
+        u32_unsuffixed => u32,
+        u64_unsuffixed => u64,
+        u128_unsuffixed => u128,
+        usize_unsuffixed => usize,
+        i8_unsuffixed => i8,
+        i16_unsuffixed => i16,
+        i32_unsuffixed => i32,
+        i64_unsuffixed => i64,
+        i128_unsuffixed => i128,
+        isize_unsuffixed => isize,
+    }
+
+    pub(crate) fn f32_unsuffixed(f: f32) -> Literal {
+        if inside_proc_macro() {
+            Literal::Compiler(proc_macro::Literal::f32_unsuffixed(f))
+        } else {
+            Literal::Fallback(fallback::Literal::f32_unsuffixed(f))
+        }
+    }
+
+    pub(crate) fn f64_unsuffixed(f: f64) -> Literal {
+        if inside_proc_macro() {
+            Literal::Compiler(proc_macro::Literal::f64_unsuffixed(f))
+        } else {
+            Literal::Fallback(fallback::Literal::f64_unsuffixed(f))
+        }
+    }
+
+    pub(crate) fn string(string: &str) -> Literal {
+        if inside_proc_macro() {
+            Literal::Compiler(proc_macro::Literal::string(string))
+        } else {
+            Literal::Fallback(fallback::Literal::string(string))
+        }
+    }
+
+    pub(crate) fn character(ch: char) -> Literal {
+        if inside_proc_macro() {
+            Literal::Compiler(proc_macro::Literal::character(ch))
+        } else {
+            Literal::Fallback(fallback::Literal::character(ch))
+        }
+    }
+
+    pub(crate) fn byte_character(byte: u8) -> Literal {
+        if inside_proc_macro() {
+            Literal::Compiler({
+                #[cfg(not(no_literal_byte_character))]
+                {
+                    proc_macro::Literal::byte_character(byte)
+                }
+
+                #[cfg(no_literal_byte_character)]
+                {
+                    let fallback = fallback::Literal::byte_character(byte);
+                    proc_macro::Literal::from_str_unchecked(&fallback.repr)
+                }
+            })
+        } else {
+            Literal::Fallback(fallback::Literal::byte_character(byte))
+        }
+    }
+
+    pub(crate) fn byte_string(bytes: &[u8]) -> Literal {
+        if inside_proc_macro() {
+            Literal::Compiler(proc_macro::Literal::byte_string(bytes))
+        } else {
+            Literal::Fallback(fallback::Literal::byte_string(bytes))
+        }
+    }
+
+    pub(crate) fn c_string(string: &CStr) -> Literal {
+        if inside_proc_macro() {
+            Literal::Compiler({
+                #[cfg(not(no_literal_c_string))]
+                {
+                    proc_macro::Literal::c_string(string)
+                }
+
+                #[cfg(no_literal_c_string)]
+                {
+                    let fallback = fallback::Literal::c_string(string);
+                    proc_macro::Literal::from_str_unchecked(&fallback.repr)
+                }
+            })
+        } else {
+            Literal::Fallback(fallback::Literal::c_string(string))
+        }
+    }
+
+    pub(crate) fn span(&self) -> Span {
+        match self {
+            Literal::Compiler(lit) => Span::Compiler(lit.span()),
+            Literal::Fallback(lit) => Span::Fallback(lit.span()),
+        }
+    }
+
+    pub(crate) fn set_span(&mut self, span: Span) {
+        match (self, span) {
+            (Literal::Compiler(lit), Span::Compiler(s)) => lit.set_span(s),
+            (Literal::Fallback(lit), Span::Fallback(s)) => lit.set_span(s),
+            (Literal::Compiler(_), Span::Fallback(_)) => mismatch(line!()),
+            (Literal::Fallback(_), Span::Compiler(_)) => mismatch(line!()),
+        }
+    }
+
+    pub(crate) fn subspan<R: RangeBounds<usize>>(&self, range: R) -> Option<Span> {
+        match self {
+            #[cfg(proc_macro_span)]
+            Literal::Compiler(lit) => proc_macro_span::subspan(lit, range).map(Span::Compiler),
+            #[cfg(not(proc_macro_span))]
+            Literal::Compiler(_lit) => None,
+            Literal::Fallback(lit) => lit.subspan(range).map(Span::Fallback),
+        }
+    }
+
+    fn unwrap_nightly(self) -> proc_macro::Literal {
+        match self {
+            Literal::Compiler(s) => s,
+            Literal::Fallback(_) => mismatch(line!()),
+        }
+    }
+}
+
+impl From<fallback::Literal> for Literal {
+    fn from(s: fallback::Literal) -> Self {
+        Literal::Fallback(s)
+    }
+}
+
+impl Display for Literal {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Literal::Compiler(t) => Display::fmt(t, f),
+            Literal::Fallback(t) => Display::fmt(t, f),
+        }
+    }
+}
+
+impl Debug for Literal {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Literal::Compiler(t) => Debug::fmt(t, f),
+            Literal::Fallback(t) => Debug::fmt(t, f),
+        }
+    }
+}
+
+#[cfg(span_locations)]
+pub(crate) fn invalidate_current_thread_spans() {
+    if inside_proc_macro() {
+        panic!(
+            "proc_macro2::extra::invalidate_current_thread_spans is not available in procedural macros"
+        );
+    }
+    crate::fallback::invalidate_current_thread_spans();
+}