src/libsyntax/ext/proc_macro_server.rs - third_party/rust - Git at Google

 use crate::ast;
 use crate::ext::base::ExtCtxt;
 use crate::parse::{self, token, ParseSess};
 use crate::parse::lexer::comments;
 use crate::tokenstream::{self, DelimSpan, IsJoint::*, TokenStream, TreeAndJoint};

 use errors::{Diagnostic, DiagnosticBuilder};
 use rustc_data_structures::sync::Lrc;
 use syntax_pos::{BytePos, FileName, MultiSpan, Pos, SourceFile, Span};
 use syntax_pos::hygiene::{SyntaxContext, Transparency};
 use syntax_pos::symbol::{kw, sym, Symbol};

 use proc_macro::{Delimiter, Level, LineColumn, Spacing};
 use proc_macro::bridge::{server, TokenTree};
 use std::{ascii, panic};
 use std::ops::Bound;

 trait FromInternal<T> {
     fn from_internal(x: T) -> Self;
 }

 trait ToInternal<T> {
     fn to_internal(self) -> T;
 }

 impl FromInternal<token::DelimToken> for Delimiter {
     fn from_internal(delim: token::DelimToken) -> Delimiter {
         match delim {
             token::Paren => Delimiter::Parenthesis,
             token::Brace => Delimiter::Brace,
             token::Bracket => Delimiter::Bracket,
             token::NoDelim => Delimiter::None,
         }
     }
 }

 impl ToInternal<token::DelimToken> for Delimiter {
     fn to_internal(self) -> token::DelimToken {
         match self {
             Delimiter::Parenthesis => token::Paren,
             Delimiter::Brace => token::Brace,
             Delimiter::Bracket => token::Bracket,
             Delimiter::None => token::NoDelim,
         }
     }
 }

 impl FromInternal<(TreeAndJoint, &'_ ParseSess, &'_ mut Vec<Self>)>
     for TokenTree<Group, Punct, Ident, Literal>
 {
     fn from_internal(((tree, is_joint), sess, stack): (TreeAndJoint, &ParseSess, &mut Vec<Self>))
                     -> Self {
         use crate::parse::token::*;

         let joint = is_joint == Joint;
         let Token { kind, span } = match tree {
             tokenstream::TokenTree::Delimited(span, delim, tts) => {
                 let delimiter = Delimiter::from_internal(delim);
                 return TokenTree::Group(Group {
                     delimiter,
                     stream: tts.into(),
                     span,
                 });
             }
             tokenstream::TokenTree::Token(token) => token,
         };

         macro_rules! tt {
             ($ty:ident { $($field:ident $(: $value:expr)*),+ $(,)? }) => (
                 TokenTree::$ty(self::$ty {
                     $($field $(: $value)*,)+
                     span,
                 })
             );
             ($ty:ident::$method:ident($($value:expr),*)) => (
                 TokenTree::$ty(self::$ty::$method($($value,)* span))
             );
         }
         macro_rules! op {
             ($a:expr) => {
                 tt!(Punct::new($a, joint))
             };
             ($a:expr, $b:expr) => {{
                 stack.push(tt!(Punct::new($b, joint)));
                 tt!(Punct::new($a, true))
             }};
             ($a:expr, $b:expr, $c:expr) => {{
                 stack.push(tt!(Punct::new($c, joint)));
                 stack.push(tt!(Punct::new($b, true)));
                 tt!(Punct::new($a, true))
             }};
         }

         match kind {
             Eq => op!('='),
             Lt => op!('<'),
             Le => op!('<', '='),
             EqEq => op!('=', '='),
             Ne => op!('!', '='),
             Ge => op!('>', '='),
             Gt => op!('>'),
             AndAnd => op!('&', '&'),
             OrOr => op!('|', '|'),
             Not => op!('!'),
             Tilde => op!('~'),
             BinOp(Plus) => op!('+'),
             BinOp(Minus) => op!('-'),
             BinOp(Star) => op!('*'),
             BinOp(Slash) => op!('/'),
             BinOp(Percent) => op!('%'),
             BinOp(Caret) => op!('^'),
             BinOp(And) => op!('&'),
             BinOp(Or) => op!('|'),
             BinOp(Shl) => op!('<', '<'),
             BinOp(Shr) => op!('>', '>'),
             BinOpEq(Plus) => op!('+', '='),
             BinOpEq(Minus) => op!('-', '='),
             BinOpEq(Star) => op!('*', '='),
             BinOpEq(Slash) => op!('/', '='),
             BinOpEq(Percent) => op!('%', '='),
             BinOpEq(Caret) => op!('^', '='),
             BinOpEq(And) => op!('&', '='),
             BinOpEq(Or) => op!('|', '='),
             BinOpEq(Shl) => op!('<', '<', '='),
             BinOpEq(Shr) => op!('>', '>', '='),
             At => op!('@'),
             Dot => op!('.'),
             DotDot => op!('.', '.'),
             DotDotDot => op!('.', '.', '.'),
             DotDotEq => op!('.', '.', '='),
             Comma => op!(','),
             Semi => op!(';'),
             Colon => op!(':'),
             ModSep => op!(':', ':'),
             RArrow => op!('-', '>'),
             LArrow => op!('<', '-'),
             FatArrow => op!('=', '>'),
             Pound => op!('#'),
             Dollar => op!('$'),
             Question => op!('?'),
             SingleQuote => op!('\''),

             Ident(name, false) if name == kw::DollarCrate => tt!(Ident::dollar_crate()),
             Ident(name, is_raw) => tt!(Ident::new(name, is_raw)),
             Lifetime(name) => {
                 let ident = ast::Ident::new(name, span).without_first_quote();
                 stack.push(tt!(Ident::new(ident.name, false)));
                 tt!(Punct::new('\'', true))
             }
             Literal(lit) => tt!(Literal { lit }),
             DocComment(c) => {
                 let style = comments::doc_comment_style(&c.as_str());
                 let stripped = comments::strip_doc_comment_decoration(&c.as_str());
                 let mut escaped = String::new();
                 for ch in stripped.chars() {
                     escaped.extend(ch.escape_debug());
                 }
                 let stream = vec![
                     Ident(sym::doc, false),
                     Eq,
                     TokenKind::lit(token::Str, Symbol::intern(&escaped), None),
                 ]
                 .into_iter()
                 .map(|kind| tokenstream::TokenTree::token(kind, span))
                 .collect();
                 stack.push(TokenTree::Group(Group {
                     delimiter: Delimiter::Bracket,
                     stream,
                     span: DelimSpan::from_single(span),
                 }));
                 if style == ast::AttrStyle::Inner {
                     stack.push(tt!(Punct::new('!', false)));
                 }
                 tt!(Punct::new('#', false))
             }

             Interpolated(nt) => {
                 let stream = nt.to_tokenstream(sess, span);
                 TokenTree::Group(Group {
                     delimiter: Delimiter::None,
                     stream,
                     span: DelimSpan::from_single(span),
                 })
             }

             OpenDelim(..) | CloseDelim(..) => unreachable!(),
             Whitespace | Comment | Shebang(..) | Unknown(..) | Eof => unreachable!(),
         }
     }
 }

 impl ToInternal<TokenStream> for TokenTree<Group, Punct, Ident, Literal> {
     fn to_internal(self) -> TokenStream {
         use crate::parse::token::*;

         let (ch, joint, span) = match self {
             TokenTree::Punct(Punct { ch, joint, span }) => (ch, joint, span),
             TokenTree::Group(Group {
                 delimiter,
                 stream,
                 span,
             }) => {
                 return tokenstream::TokenTree::Delimited(
                     span,
                     delimiter.to_internal(),
                     stream.into(),
                 )
                 .into();
             }
             TokenTree::Ident(self::Ident { sym, is_raw, span }) => {
                 return tokenstream::TokenTree::token(Ident(sym, is_raw), span).into();
             }
             TokenTree::Literal(self::Literal {
                 lit: token::Lit { kind: token::Integer, symbol, suffix },
                 span,
             }) if symbol.as_str().starts_with("-") => {
                 let minus = BinOp(BinOpToken::Minus);
                 let symbol = Symbol::intern(&symbol.as_str()[1..]);
                 let integer = TokenKind::lit(token::Integer, symbol, suffix);
                 let a = tokenstream::TokenTree::token(minus, span);
                 let b = tokenstream::TokenTree::token(integer, span);
                 return vec![a, b].into_iter().collect();
             }
             TokenTree::Literal(self::Literal {
                 lit: token::Lit { kind: token::Float, symbol, suffix },
                 span,
             }) if symbol.as_str().starts_with("-") => {
                 let minus = BinOp(BinOpToken::Minus);
                 let symbol = Symbol::intern(&symbol.as_str()[1..]);
                 let float = TokenKind::lit(token::Float, symbol, suffix);
                 let a = tokenstream::TokenTree::token(minus, span);
                 let b = tokenstream::TokenTree::token(float, span);
                 return vec![a, b].into_iter().collect();
             }
             TokenTree::Literal(self::Literal { lit, span }) => {
                 return tokenstream::TokenTree::token(Literal(lit), span).into()
             }
         };

         let kind = match ch {
             '=' => Eq,
             '<' => Lt,
             '>' => Gt,
             '!' => Not,
             '~' => Tilde,
             '+' => BinOp(Plus),
             '-' => BinOp(Minus),
             '*' => BinOp(Star),
             '/' => BinOp(Slash),
             '%' => BinOp(Percent),
             '^' => BinOp(Caret),
             '&' => BinOp(And),
             '|' => BinOp(Or),
             '@' => At,
             '.' => Dot,
             ',' => Comma,
             ';' => Semi,
             ':' => Colon,
             '#' => Pound,
             '$' => Dollar,
             '?' => Question,
             '\'' => SingleQuote,
             _ => unreachable!(),
         };

         let tree = tokenstream::TokenTree::token(kind, span);
         TokenStream::new(vec![(tree, if joint { Joint } else { NonJoint })])
     }
 }

 impl ToInternal<errors::Level> for Level {
     fn to_internal(self) -> errors::Level {
         match self {
             Level::Error => errors::Level::Error,
             Level::Warning => errors::Level::Warning,
             Level::Note => errors::Level::Note,
             Level::Help => errors::Level::Help,
             _ => unreachable!("unknown proc_macro::Level variant: {:?}", self),
         }
     }
 }

 #[derive(Clone)]
 pub struct TokenStreamIter {
     cursor: tokenstream::Cursor,
     stack: Vec<TokenTree<Group, Punct, Ident, Literal>>,
 }

 #[derive(Clone)]
 pub struct Group {
     delimiter: Delimiter,
     stream: TokenStream,
     span: DelimSpan,
 }

 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct Punct {
     ch: char,
     // NB. not using `Spacing` here because it doesn't implement `Hash`.
     joint: bool,
     span: Span,
 }

 impl Punct {
     fn new(ch: char, joint: bool, span: Span) -> Punct {
         const LEGAL_CHARS: &[char] = &['=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^',
                                        '&', '|', '@', '.', ',', ';', ':', '#', '$', '?', '\''];
         if !LEGAL_CHARS.contains(&ch) {
             panic!("unsupported character `{:?}`", ch)
         }
         Punct { ch, joint, span }
     }
 }

 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub struct Ident {
     sym: Symbol,
     is_raw: bool,
     span: Span,
 }

 impl Ident {
     fn is_valid(string: &str) -> bool {
         let mut chars = string.chars();
         if let Some(start) = chars.next() {
             (start == '_' || start.is_xid_start())
                 && chars.all(|cont| cont == '_' || cont.is_xid_continue())
         } else {
             false
         }
     }
     fn new(sym: Symbol, is_raw: bool, span: Span) -> Ident {
         let string = sym.as_str();
         if !Self::is_valid(&string) {
             panic!("`{:?}` is not a valid identifier", string)
         }
         // Get rid of gensyms to conservatively check rawness on the string contents only.
         if is_raw && !sym.as_interned_str().as_symbol().can_be_raw() {
             panic!("`{}` cannot be a raw identifier", string);
         }
         Ident { sym, is_raw, span }
     }
     fn dollar_crate(span: Span) -> Ident {
         // `$crate` is accepted as an ident only if it comes from the compiler.
         Ident { sym: kw::DollarCrate, is_raw: false, span }
     }
 }

 // FIXME(eddyb) `Literal` should not expose internal `Debug` impls.
 #[derive(Clone, Debug)]
 pub struct Literal {
     lit: token::Lit,
     span: Span,
 }

 pub(crate) struct Rustc<'a> {
     sess: &'a ParseSess,
     def_site: Span,
     call_site: Span,
 }

 impl<'a> Rustc<'a> {
     pub fn new(cx: &'a ExtCtxt<'_>) -> Self {
         // No way to determine def location for a proc macro right now, so use call location.
         let location = cx.current_expansion.id.expn_info().unwrap().call_site;
         let to_span = |transparency| {
             location.with_ctxt(
                 SyntaxContext::empty()
                     .apply_mark_with_transparency(cx.current_expansion.id, transparency),
             )
         };
         Rustc {
             sess: cx.parse_sess,
             def_site: to_span(Transparency::Opaque),
             call_site: to_span(Transparency::Transparent),
         }
     }

     fn lit(&mut self, kind: token::LitKind, symbol: Symbol, suffix: Option<Symbol>) -> Literal {
         Literal {
             lit: token::Lit::new(kind, symbol, suffix),
             span: server::Span::call_site(self),
         }
     }
 }

 impl server::Types for Rustc<'_> {
     type TokenStream = TokenStream;
     type TokenStreamBuilder = tokenstream::TokenStreamBuilder;
     type TokenStreamIter = TokenStreamIter;
     type Group = Group;
     type Punct = Punct;
     type Ident = Ident;
     type Literal = Literal;
     type SourceFile = Lrc<SourceFile>;
     type MultiSpan = Vec<Span>;
     type Diagnostic = Diagnostic;
     type Span = Span;
 }

 impl server::TokenStream for Rustc<'_> {
     fn new(&mut self) -> Self::TokenStream {
         TokenStream::empty()
     }
     fn is_empty(&mut self, stream: &Self::TokenStream) -> bool {
         stream.is_empty()
     }
     fn from_str(&mut self, src: &str) -> Self::TokenStream {
         parse::parse_stream_from_source_str(
             FileName::proc_macro_source_code(src),
             src.to_string(),
             self.sess,
             Some(self.call_site),
         )
     }
     fn to_string(&mut self, stream: &Self::TokenStream) -> String {
         stream.to_string()
     }
     fn from_token_tree(
         &mut self,
         tree: TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>,
     ) -> Self::TokenStream {
         tree.to_internal()
     }
     fn into_iter(&mut self, stream: Self::TokenStream) -> Self::TokenStreamIter {
         TokenStreamIter {
             cursor: stream.trees(),
             stack: vec![],
         }
     }
 }

 impl server::TokenStreamBuilder for Rustc<'_> {
     fn new(&mut self) -> Self::TokenStreamBuilder {
         tokenstream::TokenStreamBuilder::new()
     }
     fn push(&mut self, builder: &mut Self::TokenStreamBuilder, stream: Self::TokenStream) {
         builder.push(stream);
     }
     fn build(&mut self, builder: Self::TokenStreamBuilder) -> Self::TokenStream {
         builder.build()
     }
 }

 impl server::TokenStreamIter for Rustc<'_> {
     fn next(
         &mut self,
         iter: &mut Self::TokenStreamIter,
     ) -> Option<TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>> {
         loop {
             let tree = iter.stack.pop().or_else(|| {
                 let next = iter.cursor.next_with_joint()?;
                 Some(TokenTree::from_internal((next, self.sess, &mut iter.stack)))
             })?;
             // HACK: The condition "dummy span + group with empty delimiter" represents an AST
             // fragment approximately converted into a token stream. This may happen, for
             // example, with inputs to proc macro attributes, including derives. Such "groups"
             // need to flattened during iteration over stream's token trees.
             // Eventually this needs to be removed in favor of keeping original token trees
             // and not doing the roundtrip through AST.
             if let TokenTree::Group(ref group) = tree {
                 if group.delimiter == Delimiter::None && group.span.entire().is_dummy() {
                     iter.cursor.append(group.stream.clone());
                     continue;
                 }
             }
             return Some(tree);
         }
     }
 }

 impl server::Group for Rustc<'_> {
     fn new(&mut self, delimiter: Delimiter, stream: Self::TokenStream) -> Self::Group {
         Group {
             delimiter,
             stream,
             span: DelimSpan::from_single(server::Span::call_site(self)),
         }
     }
     fn delimiter(&mut self, group: &Self::Group) -> Delimiter {
         group.delimiter
     }
     fn stream(&mut self, group: &Self::Group) -> Self::TokenStream {
         group.stream.clone()
     }
     fn span(&mut self, group: &Self::Group) -> Self::Span {
         group.span.entire()
     }
     fn span_open(&mut self, group: &Self::Group) -> Self::Span {
         group.span.open
     }
     fn span_close(&mut self, group: &Self::Group) -> Self::Span {
         group.span.close
     }
     fn set_span(&mut self, group: &mut Self::Group, span: Self::Span) {
         group.span = DelimSpan::from_single(span);
     }
 }

 impl server::Punct for Rustc<'_> {
     fn new(&mut self, ch: char, spacing: Spacing) -> Self::Punct {
         Punct::new(ch, spacing == Spacing::Joint, server::Span::call_site(self))
     }
     fn as_char(&mut self, punct: Self::Punct) -> char {
         punct.ch
     }
     fn spacing(&mut self, punct: Self::Punct) -> Spacing {
         if punct.joint {
             Spacing::Joint
         } else {
             Spacing::Alone
         }
     }
     fn span(&mut self, punct: Self::Punct) -> Self::Span {
         punct.span
     }
     fn with_span(&mut self, punct: Self::Punct, span: Self::Span) -> Self::Punct {
         Punct { span, ..punct }
     }
 }

 impl server::Ident for Rustc<'_> {
     fn new(&mut self, string: &str, span: Self::Span, is_raw: bool) -> Self::Ident {
         Ident::new(Symbol::intern(string), is_raw, span)
     }
     fn span(&mut self, ident: Self::Ident) -> Self::Span {
         ident.span
     }
     fn with_span(&mut self, ident: Self::Ident, span: Self::Span) -> Self::Ident {
         Ident { span, ..ident }
     }
 }

 impl server::Literal for Rustc<'_> {
     // FIXME(eddyb) `Literal` should not expose internal `Debug` impls.
     fn debug(&mut self, literal: &Self::Literal) -> String {
         format!("{:?}", literal)
     }
     fn integer(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Integer, Symbol::intern(n), None)
     }
     fn typed_integer(&mut self, n: &str, kind: &str) -> Self::Literal {
         self.lit(token::Integer, Symbol::intern(n), Some(Symbol::intern(kind)))
     }
     fn float(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Float, Symbol::intern(n), None)
     }
     fn f32(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Float, Symbol::intern(n), Some(sym::f32))
     }
     fn f64(&mut self, n: &str) -> Self::Literal {
         self.lit(token::Float, Symbol::intern(n), Some(sym::f64))
     }
     fn string(&mut self, string: &str) -> Self::Literal {
         let mut escaped = String::new();
         for ch in string.chars() {
             escaped.extend(ch.escape_debug());
         }
         self.lit(token::Str, Symbol::intern(&escaped), None)
     }
     fn character(&mut self, ch: char) -> Self::Literal {
         let mut escaped = String::new();
         escaped.extend(ch.escape_unicode());
         self.lit(token::Char, Symbol::intern(&escaped), None)
     }
     fn byte_string(&mut self, bytes: &[u8]) -> Self::Literal {
         let string = bytes
             .iter()
             .cloned()
             .flat_map(ascii::escape_default)
             .map(Into::<char>::into)
             .collect::<String>();
         self.lit(token::ByteStr, Symbol::intern(&string), None)
     }
     fn span(&mut self, literal: &Self::Literal) -> Self::Span {
         literal.span
     }
     fn set_span(&mut self, literal: &mut Self::Literal, span: Self::Span) {
         literal.span = span;
     }
     fn subspan(
         &mut self,
         literal: &Self::Literal,
         start: Bound<usize>,
         end: Bound<usize>,
     ) -> Option<Self::Span> {
         let span = literal.span;
         let length = span.hi().to_usize() - span.lo().to_usize();

         let start = match start {
             Bound::Included(lo) => lo,
             Bound::Excluded(lo) => lo + 1,
             Bound::Unbounded => 0,
         };

         let end = match end {
             Bound::Included(hi) => hi + 1,
             Bound::Excluded(hi) => hi,
             Bound::Unbounded => length,
         };

         // Bounds check the values, preventing addition overflow and OOB spans.
         if start > u32::max_value() as usize
             || end > u32::max_value() as usize
             || (u32::max_value() - start as u32) < span.lo().to_u32()
             || (u32::max_value() - end as u32) < span.lo().to_u32()
             || start >= end
             || end > length
         {
             return None;
         }

         let new_lo = span.lo() + BytePos::from_usize(start);
         let new_hi = span.lo() + BytePos::from_usize(end);
         Some(span.with_lo(new_lo).with_hi(new_hi))
     }
 }

 impl server::SourceFile for Rustc<'_> {
     fn eq(&mut self, file1: &Self::SourceFile, file2: &Self::SourceFile) -> bool {
         Lrc::ptr_eq(file1, file2)
     }
     fn path(&mut self, file: &Self::SourceFile) -> String {
         match file.name {
             FileName::Real(ref path) => path
                 .to_str()
                 .expect("non-UTF8 file path in `proc_macro::SourceFile::path`")
                 .to_string(),
             _ => file.name.to_string(),
         }
     }
     fn is_real(&mut self, file: &Self::SourceFile) -> bool {
         file.is_real_file()
     }
 }

 impl server::MultiSpan for Rustc<'_> {
     fn new(&mut self) -> Self::MultiSpan {
         vec![]
     }
     fn push(&mut self, spans: &mut Self::MultiSpan, span: Self::Span) {
         spans.push(span)
     }
 }

 impl server::Diagnostic for Rustc<'_> {
     fn new(&mut self, level: Level, msg: &str, spans: Self::MultiSpan) -> Self::Diagnostic {
         let mut diag = Diagnostic::new(level.to_internal(), msg);
         diag.set_span(MultiSpan::from_spans(spans));
         diag
     }
     fn sub(
         &mut self,
         diag: &mut Self::Diagnostic,
         level: Level,
         msg: &str,
         spans: Self::MultiSpan,
     ) {
         diag.sub(level.to_internal(), msg, MultiSpan::from_spans(spans), None);
     }
     fn emit(&mut self, diag: Self::Diagnostic) {
         DiagnosticBuilder::new_diagnostic(&self.sess.span_diagnostic, diag).emit()
     }
 }

 impl server::Span for Rustc<'_> {
     fn debug(&mut self, span: Self::Span) -> String {
         format!("{:?} bytes({}..{})", span.ctxt(), span.lo().0, span.hi().0)
     }
     fn def_site(&mut self) -> Self::Span {
         self.def_site
     }
     fn call_site(&mut self) -> Self::Span {
         self.call_site
     }
     fn source_file(&mut self, span: Self::Span) -> Self::SourceFile {
         self.sess.source_map().lookup_char_pos(span.lo()).file
     }
     fn parent(&mut self, span: Self::Span) -> Option<Self::Span> {
         span.ctxt().outer_expn_info().map(|i| i.call_site)
     }
     fn source(&mut self, span: Self::Span) -> Self::Span {
         span.source_callsite()
     }
     fn start(&mut self, span: Self::Span) -> LineColumn {
         let loc = self.sess.source_map().lookup_char_pos(span.lo());
         LineColumn {
             line: loc.line,
             column: loc.col.to_usize(),
         }
     }
     fn end(&mut self, span: Self::Span) -> LineColumn {
         let loc = self.sess.source_map().lookup_char_pos(span.hi());
         LineColumn {
             line: loc.line,
             column: loc.col.to_usize(),
         }
     }
     fn join(&mut self, first: Self::Span, second: Self::Span) -> Option<Self::Span> {
         let self_loc = self.sess.source_map().lookup_char_pos(first.lo());
         let other_loc = self.sess.source_map().lookup_char_pos(second.lo());

         if self_loc.file.name != other_loc.file.name {
             return None;
         }

         Some(first.to(second))
     }
     fn resolved_at(&mut self, span: Self::Span, at: Self::Span) -> Self::Span {
         span.with_ctxt(at.ctxt())
     }
     fn source_text(&mut self,  span: Self::Span) -> Option<String> {
         self.sess.source_map().span_to_snippet(span).ok()
     }
 }
	use crate::ast;
	use crate::ext::base::ExtCtxt;
	use crate::parse::{self, token, ParseSess};
	use crate::parse::lexer::comments;
	use crate::tokenstream::{self, DelimSpan, IsJoint::*, TokenStream, TreeAndJoint};

	use errors::{Diagnostic, DiagnosticBuilder};
	use rustc_data_structures::sync::Lrc;
	use syntax_pos::{BytePos, FileName, MultiSpan, Pos, SourceFile, Span};
	use syntax_pos::hygiene::{SyntaxContext, Transparency};
	use syntax_pos::symbol::{kw, sym, Symbol};

	use proc_macro::{Delimiter, Level, LineColumn, Spacing};
	use proc_macro::bridge::{server, TokenTree};
	use std::{ascii, panic};
	use std::ops::Bound;

	trait FromInternal<T> {
	fn from_internal(x: T) -> Self;
	}

	trait ToInternal<T> {
	fn to_internal(self) -> T;
	}

	impl FromInternal<token::DelimToken> for Delimiter {
	fn from_internal(delim: token::DelimToken) -> Delimiter {
	match delim {
	token::Paren => Delimiter::Parenthesis,
	token::Brace => Delimiter::Brace,
	token::Bracket => Delimiter::Bracket,
	token::NoDelim => Delimiter::None,
	}
	}
	}

	impl ToInternal<token::DelimToken> for Delimiter {
	fn to_internal(self) -> token::DelimToken {
	match self {
	Delimiter::Parenthesis => token::Paren,
	Delimiter::Brace => token::Brace,
	Delimiter::Bracket => token::Bracket,
	Delimiter::None => token::NoDelim,
	}
	}
	}

	impl FromInternal<(TreeAndJoint, &'_ ParseSess, &'_ mut Vec<Self>)>
	for TokenTree<Group, Punct, Ident, Literal>
	{
	fn from_internal(((tree, is_joint), sess, stack): (TreeAndJoint, &ParseSess, &mut Vec<Self>))
	-> Self {
	use crate::parse::token::*;

	let joint = is_joint == Joint;
	let Token { kind, span } = match tree {
	tokenstream::TokenTree::Delimited(span, delim, tts) => {
	let delimiter = Delimiter::from_internal(delim);
	return TokenTree::Group(Group {
	delimiter,
	stream: tts.into(),
	span,
	});
	}
	tokenstream::TokenTree::Token(token) => token,
	};

	macro_rules! tt {
	($ty:ident { $($field:ident $(: $value:expr)*),+ $(,)? }) => (
	TokenTree::$ty(self::$ty {
	$($field $(: $value)*,)+
	span,
	})
	);
	($ty:ident::$method:ident($($value:expr),*)) => (
	TokenTree::$ty(self::$ty::$method($($value,)* span))
	);
	}
	macro_rules! op {
	($a:expr) => {
	tt!(Punct::new($a, joint))
	};
	($a:expr, $b:expr) => {{
	stack.push(tt!(Punct::new($b, joint)));
	tt!(Punct::new($a, true))
	}};
	($a:expr, $b:expr, $c:expr) => {{
	stack.push(tt!(Punct::new($c, joint)));
	stack.push(tt!(Punct::new($b, true)));
	tt!(Punct::new($a, true))
	}};
	}

	match kind {
	Eq => op!('='),
	Lt => op!('<'),
	Le => op!('<', '='),
	EqEq => op!('=', '='),
	Ne => op!('!', '='),
	Ge => op!('>', '='),
	Gt => op!('>'),
	AndAnd => op!('&', '&'),
	OrOr => op!('\|', '\|'),
	Not => op!('!'),
	Tilde => op!('~'),
	BinOp(Plus) => op!('+'),
	BinOp(Minus) => op!('-'),
	BinOp(Star) => op!('*'),
	BinOp(Slash) => op!('/'),
	BinOp(Percent) => op!('%'),
	BinOp(Caret) => op!('^'),
	BinOp(And) => op!('&'),
	BinOp(Or) => op!('\|'),
	BinOp(Shl) => op!('<', '<'),
	BinOp(Shr) => op!('>', '>'),
	BinOpEq(Plus) => op!('+', '='),
	BinOpEq(Minus) => op!('-', '='),
	BinOpEq(Star) => op!('*', '='),
	BinOpEq(Slash) => op!('/', '='),
	BinOpEq(Percent) => op!('%', '='),
	BinOpEq(Caret) => op!('^', '='),
	BinOpEq(And) => op!('&', '='),
	BinOpEq(Or) => op!('\|', '='),
	BinOpEq(Shl) => op!('<', '<', '='),
	BinOpEq(Shr) => op!('>', '>', '='),
	At => op!('@'),
	Dot => op!('.'),
	DotDot => op!('.', '.'),
	DotDotDot => op!('.', '.', '.'),
	DotDotEq => op!('.', '.', '='),
	Comma => op!(','),
	Semi => op!(';'),
	Colon => op!(':'),
	ModSep => op!(':', ':'),
	RArrow => op!('-', '>'),
	LArrow => op!('<', '-'),
	FatArrow => op!('=', '>'),
	Pound => op!('#'),
	Dollar => op!('$'),
	Question => op!('?'),
	SingleQuote => op!('\''),

	Ident(name, false) if name == kw::DollarCrate => tt!(Ident::dollar_crate()),
	Ident(name, is_raw) => tt!(Ident::new(name, is_raw)),
	Lifetime(name) => {
	let ident = ast::Ident::new(name, span).without_first_quote();
	stack.push(tt!(Ident::new(ident.name, false)));
	tt!(Punct::new('\'', true))
	}
	Literal(lit) => tt!(Literal { lit }),
	DocComment(c) => {
	let style = comments::doc_comment_style(&c.as_str());
	let stripped = comments::strip_doc_comment_decoration(&c.as_str());
	let mut escaped = String::new();
	for ch in stripped.chars() {
	escaped.extend(ch.escape_debug());
	}
	let stream = vec![
	Ident(sym::doc, false),
	Eq,
	TokenKind::lit(token::Str, Symbol::intern(&escaped), None),
	]
	.into_iter()
	.map(\|kind\| tokenstream::TokenTree::token(kind, span))
	.collect();
	stack.push(TokenTree::Group(Group {
	delimiter: Delimiter::Bracket,
	stream,
	span: DelimSpan::from_single(span),
	}));
	if style == ast::AttrStyle::Inner {
	stack.push(tt!(Punct::new('!', false)));
	}
	tt!(Punct::new('#', false))
	}

	Interpolated(nt) => {
	let stream = nt.to_tokenstream(sess, span);
	TokenTree::Group(Group {
	delimiter: Delimiter::None,
	stream,
	span: DelimSpan::from_single(span),
	})
	}

	OpenDelim(..) \| CloseDelim(..) => unreachable!(),
	Whitespace \| Comment \| Shebang(..) \| Unknown(..) \| Eof => unreachable!(),
	}
	}
	}

	impl ToInternal<TokenStream> for TokenTree<Group, Punct, Ident, Literal> {
	fn to_internal(self) -> TokenStream {
	use crate::parse::token::*;

	let (ch, joint, span) = match self {
	TokenTree::Punct(Punct { ch, joint, span }) => (ch, joint, span),
	TokenTree::Group(Group {
	delimiter,
	stream,
	span,
	}) => {
	return tokenstream::TokenTree::Delimited(
	span,
	delimiter.to_internal(),
	stream.into(),
	)
	.into();
	}
	TokenTree::Ident(self::Ident { sym, is_raw, span }) => {
	return tokenstream::TokenTree::token(Ident(sym, is_raw), span).into();
	}
	TokenTree::Literal(self::Literal {
	lit: token::Lit { kind: token::Integer, symbol, suffix },
	span,
	}) if symbol.as_str().starts_with("-") => {
	let minus = BinOp(BinOpToken::Minus);
	let symbol = Symbol::intern(&symbol.as_str()[1..]);
	let integer = TokenKind::lit(token::Integer, symbol, suffix);
	let a = tokenstream::TokenTree::token(minus, span);
	let b = tokenstream::TokenTree::token(integer, span);
	return vec![a, b].into_iter().collect();
	}
	TokenTree::Literal(self::Literal {
	lit: token::Lit { kind: token::Float, symbol, suffix },
	span,
	}) if symbol.as_str().starts_with("-") => {
	let minus = BinOp(BinOpToken::Minus);
	let symbol = Symbol::intern(&symbol.as_str()[1..]);
	let float = TokenKind::lit(token::Float, symbol, suffix);
	let a = tokenstream::TokenTree::token(minus, span);
	let b = tokenstream::TokenTree::token(float, span);
	return vec![a, b].into_iter().collect();
	}
	TokenTree::Literal(self::Literal { lit, span }) => {
	return tokenstream::TokenTree::token(Literal(lit), span).into()
	}
	};

	let kind = match ch {
	'=' => Eq,
	'<' => Lt,
	'>' => Gt,
	'!' => Not,
	'~' => Tilde,
	'+' => BinOp(Plus),
	'-' => BinOp(Minus),
	'*' => BinOp(Star),
	'/' => BinOp(Slash),
	'%' => BinOp(Percent),
	'^' => BinOp(Caret),
	'&' => BinOp(And),
	'\|' => BinOp(Or),
	'@' => At,
	'.' => Dot,
	',' => Comma,
	';' => Semi,
	':' => Colon,
	'#' => Pound,
	'$' => Dollar,
	'?' => Question,
	'\'' => SingleQuote,
	_ => unreachable!(),
	};

	let tree = tokenstream::TokenTree::token(kind, span);
	TokenStream::new(vec![(tree, if joint { Joint } else { NonJoint })])
	}
	}

	impl ToInternal<errors::Level> for Level {
	fn to_internal(self) -> errors::Level {
	match self {
	Level::Error => errors::Level::Error,
	Level::Warning => errors::Level::Warning,
	Level::Note => errors::Level::Note,
	Level::Help => errors::Level::Help,
	_ => unreachable!("unknown proc_macro::Level variant: {:?}", self),
	}
	}
	}

	#[derive(Clone)]
	pub struct TokenStreamIter {
	cursor: tokenstream::Cursor,
	stack: Vec<TokenTree<Group, Punct, Ident, Literal>>,
	}

	#[derive(Clone)]
	pub struct Group {
	delimiter: Delimiter,
	stream: TokenStream,
	span: DelimSpan,
	}

	#[derive(Copy, Clone, PartialEq, Eq, Hash)]
	pub struct Punct {
	ch: char,
	// NB. not using `Spacing` here because it doesn't implement `Hash`.
	joint: bool,
	span: Span,
	}

	impl Punct {
	fn new(ch: char, joint: bool, span: Span) -> Punct {
	const LEGAL_CHARS: &[char] = &['=', '<', '>', '!', '~', '+', '-', '*', '/', '%', '^',
	'&', '\|', '@', '.', ',', ';', ':', '#', '$', '?', '\''];
	if !LEGAL_CHARS.contains(&ch) {
	panic!("unsupported character `{:?}`", ch)
	}
	Punct { ch, joint, span }
	}
	}

	#[derive(Copy, Clone, PartialEq, Eq, Hash)]
	pub struct Ident {
	sym: Symbol,
	is_raw: bool,
	span: Span,
	}

	impl Ident {
	fn is_valid(string: &str) -> bool {
	let mut chars = string.chars();
	if let Some(start) = chars.next() {
	(start == '_' \|\| start.is_xid_start())
	&& chars.all(\|cont\| cont == '_' \|\| cont.is_xid_continue())
	} else {
	false
	}
	}
	fn new(sym: Symbol, is_raw: bool, span: Span) -> Ident {
	let string = sym.as_str();
	if !Self::is_valid(&string) {
	panic!("`{:?}` is not a valid identifier", string)
	}
	// Get rid of gensyms to conservatively check rawness on the string contents only.
	if is_raw && !sym.as_interned_str().as_symbol().can_be_raw() {
	panic!("`{}` cannot be a raw identifier", string);
	}
	Ident { sym, is_raw, span }
	}
	fn dollar_crate(span: Span) -> Ident {
	// `$crate` is accepted as an ident only if it comes from the compiler.
	Ident { sym: kw::DollarCrate, is_raw: false, span }
	}
	}

	// FIXME(eddyb) `Literal` should not expose internal `Debug` impls.
	#[derive(Clone, Debug)]
	pub struct Literal {
	lit: token::Lit,
	span: Span,
	}

	pub(crate) struct Rustc<'a> {
	sess: &'a ParseSess,
	def_site: Span,
	call_site: Span,
	}

	impl<'a> Rustc<'a> {
	pub fn new(cx: &'a ExtCtxt<'_>) -> Self {
	// No way to determine def location for a proc macro right now, so use call location.
	let location = cx.current_expansion.id.expn_info().unwrap().call_site;
	let to_span = \|transparency\| {
	location.with_ctxt(
	SyntaxContext::empty()
	.apply_mark_with_transparency(cx.current_expansion.id, transparency),
	)
	};
	Rustc {
	sess: cx.parse_sess,
	def_site: to_span(Transparency::Opaque),
	call_site: to_span(Transparency::Transparent),
	}
	}

	fn lit(&mut self, kind: token::LitKind, symbol: Symbol, suffix: Option<Symbol>) -> Literal {
	Literal {
	lit: token::Lit::new(kind, symbol, suffix),
	span: server::Span::call_site(self),
	}
	}
	}

	impl server::Types for Rustc<'_> {
	type TokenStream = TokenStream;
	type TokenStreamBuilder = tokenstream::TokenStreamBuilder;
	type TokenStreamIter = TokenStreamIter;
	type Group = Group;
	type Punct = Punct;
	type Ident = Ident;
	type Literal = Literal;
	type SourceFile = Lrc<SourceFile>;
	type MultiSpan = Vec<Span>;
	type Diagnostic = Diagnostic;
	type Span = Span;
	}

	impl server::TokenStream for Rustc<'_> {
	fn new(&mut self) -> Self::TokenStream {
	TokenStream::empty()
	}
	fn is_empty(&mut self, stream: &Self::TokenStream) -> bool {
	stream.is_empty()
	}
	fn from_str(&mut self, src: &str) -> Self::TokenStream {
	parse::parse_stream_from_source_str(
	FileName::proc_macro_source_code(src),
	src.to_string(),
	self.sess,
	Some(self.call_site),
	)
	}
	fn to_string(&mut self, stream: &Self::TokenStream) -> String {
	stream.to_string()
	}
	fn from_token_tree(
	&mut self,
	tree: TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>,
	) -> Self::TokenStream {
	tree.to_internal()
	}
	fn into_iter(&mut self, stream: Self::TokenStream) -> Self::TokenStreamIter {
	TokenStreamIter {
	cursor: stream.trees(),
	stack: vec![],
	}
	}
	}

	impl server::TokenStreamBuilder for Rustc<'_> {
	fn new(&mut self) -> Self::TokenStreamBuilder {
	tokenstream::TokenStreamBuilder::new()
	}
	fn push(&mut self, builder: &mut Self::TokenStreamBuilder, stream: Self::TokenStream) {
	builder.push(stream);
	}
	fn build(&mut self, builder: Self::TokenStreamBuilder) -> Self::TokenStream {
	builder.build()
	}
	}

	impl server::TokenStreamIter for Rustc<'_> {
	fn next(
	&mut self,
	iter: &mut Self::TokenStreamIter,
	) -> Option<TokenTree<Self::Group, Self::Punct, Self::Ident, Self::Literal>> {
	loop {
	let tree = iter.stack.pop().or_else(\|\| {
	let next = iter.cursor.next_with_joint()?;
	Some(TokenTree::from_internal((next, self.sess, &mut iter.stack)))
	})?;
	// HACK: The condition "dummy span + group with empty delimiter" represents an AST
	// fragment approximately converted into a token stream. This may happen, for
	// example, with inputs to proc macro attributes, including derives. Such "groups"
	// need to flattened during iteration over stream's token trees.
	// Eventually this needs to be removed in favor of keeping original token trees
	// and not doing the roundtrip through AST.
	if let TokenTree::Group(ref group) = tree {
	if group.delimiter == Delimiter::None && group.span.entire().is_dummy() {
	iter.cursor.append(group.stream.clone());
	continue;
	}
	}
	return Some(tree);
	}
	}
	}

	impl server::Group for Rustc<'_> {
	fn new(&mut self, delimiter: Delimiter, stream: Self::TokenStream) -> Self::Group {
	Group {
	delimiter,
	stream,
	span: DelimSpan::from_single(server::Span::call_site(self)),
	}
	}
	fn delimiter(&mut self, group: &Self::Group) -> Delimiter {
	group.delimiter
	}
	fn stream(&mut self, group: &Self::Group) -> Self::TokenStream {
	group.stream.clone()
	}
	fn span(&mut self, group: &Self::Group) -> Self::Span {
	group.span.entire()
	}
	fn span_open(&mut self, group: &Self::Group) -> Self::Span {
	group.span.open
	}
	fn span_close(&mut self, group: &Self::Group) -> Self::Span {
	group.span.close
	}
	fn set_span(&mut self, group: &mut Self::Group, span: Self::Span) {
	group.span = DelimSpan::from_single(span);
	}
	}

	impl server::Punct for Rustc<'_> {
	fn new(&mut self, ch: char, spacing: Spacing) -> Self::Punct {
	Punct::new(ch, spacing == Spacing::Joint, server::Span::call_site(self))
	}
	fn as_char(&mut self, punct: Self::Punct) -> char {
	punct.ch
	}
	fn spacing(&mut self, punct: Self::Punct) -> Spacing {
	if punct.joint {
	Spacing::Joint
	} else {
	Spacing::Alone
	}
	}
	fn span(&mut self, punct: Self::Punct) -> Self::Span {
	punct.span
	}
	fn with_span(&mut self, punct: Self::Punct, span: Self::Span) -> Self::Punct {
	Punct { span, ..punct }
	}
	}

	impl server::Ident for Rustc<'_> {
	fn new(&mut self, string: &str, span: Self::Span, is_raw: bool) -> Self::Ident {
	Ident::new(Symbol::intern(string), is_raw, span)
	}
	fn span(&mut self, ident: Self::Ident) -> Self::Span {
	ident.span
	}
	fn with_span(&mut self, ident: Self::Ident, span: Self::Span) -> Self::Ident {
	Ident { span, ..ident }
	}
	}

	impl server::Literal for Rustc<'_> {
	// FIXME(eddyb) `Literal` should not expose internal `Debug` impls.
	fn debug(&mut self, literal: &Self::Literal) -> String {
	format!("{:?}", literal)
	}
	fn integer(&mut self, n: &str) -> Self::Literal {
	self.lit(token::Integer, Symbol::intern(n), None)
	}
	fn typed_integer(&mut self, n: &str, kind: &str) -> Self::Literal {
	self.lit(token::Integer, Symbol::intern(n), Some(Symbol::intern(kind)))
	}
	fn float(&mut self, n: &str) -> Self::Literal {
	self.lit(token::Float, Symbol::intern(n), None)
	}
	fn f32(&mut self, n: &str) -> Self::Literal {
	self.lit(token::Float, Symbol::intern(n), Some(sym::f32))
	}
	fn f64(&mut self, n: &str) -> Self::Literal {
	self.lit(token::Float, Symbol::intern(n), Some(sym::f64))
	}
	fn string(&mut self, string: &str) -> Self::Literal {
	let mut escaped = String::new();
	for ch in string.chars() {
	escaped.extend(ch.escape_debug());
	}
	self.lit(token::Str, Symbol::intern(&escaped), None)
	}
	fn character(&mut self, ch: char) -> Self::Literal {
	let mut escaped = String::new();
	escaped.extend(ch.escape_unicode());
	self.lit(token::Char, Symbol::intern(&escaped), None)
	}
	fn byte_string(&mut self, bytes: &[u8]) -> Self::Literal {
	let string = bytes
	.iter()
	.cloned()
	.flat_map(ascii::escape_default)
	.map(Into::<char>::into)
	.collect::<String>();
	self.lit(token::ByteStr, Symbol::intern(&string), None)
	}
	fn span(&mut self, literal: &Self::Literal) -> Self::Span {
	literal.span
	}
	fn set_span(&mut self, literal: &mut Self::Literal, span: Self::Span) {
	literal.span = span;
	}
	fn subspan(
	&mut self,
	literal: &Self::Literal,
	start: Bound<usize>,
	end: Bound<usize>,
	) -> Option<Self::Span> {
	let span = literal.span;
	let length = span.hi().to_usize() - span.lo().to_usize();

	let start = match start {
	Bound::Included(lo) => lo,
	Bound::Excluded(lo) => lo + 1,
	Bound::Unbounded => 0,
	};

	let end = match end {
	Bound::Included(hi) => hi + 1,
	Bound::Excluded(hi) => hi,
	Bound::Unbounded => length,
	};

	// Bounds check the values, preventing addition overflow and OOB spans.
	if start > u32::max_value() as usize
	\|\| end > u32::max_value() as usize
	\|\| (u32::max_value() - start as u32) < span.lo().to_u32()
	\|\| (u32::max_value() - end as u32) < span.lo().to_u32()
	\|\| start >= end
	\|\| end > length
	{
	return None;
	}

	let new_lo = span.lo() + BytePos::from_usize(start);
	let new_hi = span.lo() + BytePos::from_usize(end);
	Some(span.with_lo(new_lo).with_hi(new_hi))
	}
	}

	impl server::SourceFile for Rustc<'_> {
	fn eq(&mut self, file1: &Self::SourceFile, file2: &Self::SourceFile) -> bool {
	Lrc::ptr_eq(file1, file2)
	}
	fn path(&mut self, file: &Self::SourceFile) -> String {
	match file.name {
	FileName::Real(ref path) => path
	.to_str()
	.expect("non-UTF8 file path in `proc_macro::SourceFile::path`")
	.to_string(),
	_ => file.name.to_string(),
	}
	}
	fn is_real(&mut self, file: &Self::SourceFile) -> bool {
	file.is_real_file()
	}
	}

	impl server::MultiSpan for Rustc<'_> {
	fn new(&mut self) -> Self::MultiSpan {
	vec![]
	}
	fn push(&mut self, spans: &mut Self::MultiSpan, span: Self::Span) {
	spans.push(span)
	}
	}

	impl server::Diagnostic for Rustc<'_> {
	fn new(&mut self, level: Level, msg: &str, spans: Self::MultiSpan) -> Self::Diagnostic {
	let mut diag = Diagnostic::new(level.to_internal(), msg);
	diag.set_span(MultiSpan::from_spans(spans));
	diag
	}
	fn sub(
	&mut self,
	diag: &mut Self::Diagnostic,
	level: Level,
	msg: &str,
	spans: Self::MultiSpan,
	) {
	diag.sub(level.to_internal(), msg, MultiSpan::from_spans(spans), None);
	}
	fn emit(&mut self, diag: Self::Diagnostic) {
	DiagnosticBuilder::new_diagnostic(&self.sess.span_diagnostic, diag).emit()
	}
	}

	impl server::Span for Rustc<'_> {
	fn debug(&mut self, span: Self::Span) -> String {
	format!("{:?} bytes({}..{})", span.ctxt(), span.lo().0, span.hi().0)
	}
	fn def_site(&mut self) -> Self::Span {
	self.def_site
	}
	fn call_site(&mut self) -> Self::Span {
	self.call_site
	}
	fn source_file(&mut self, span: Self::Span) -> Self::SourceFile {
	self.sess.source_map().lookup_char_pos(span.lo()).file
	}
	fn parent(&mut self, span: Self::Span) -> Option<Self::Span> {
	span.ctxt().outer_expn_info().map(\|i\| i.call_site)
	}
	fn source(&mut self, span: Self::Span) -> Self::Span {
	span.source_callsite()
	}
	fn start(&mut self, span: Self::Span) -> LineColumn {
	let loc = self.sess.source_map().lookup_char_pos(span.lo());
	LineColumn {
	line: loc.line,
	column: loc.col.to_usize(),
	}
	}
	fn end(&mut self, span: Self::Span) -> LineColumn {
	let loc = self.sess.source_map().lookup_char_pos(span.hi());
	LineColumn {
	line: loc.line,
	column: loc.col.to_usize(),
	}
	}
	fn join(&mut self, first: Self::Span, second: Self::Span) -> Option<Self::Span> {
	let self_loc = self.sess.source_map().lookup_char_pos(first.lo());
	let other_loc = self.sess.source_map().lookup_char_pos(second.lo());

	if self_loc.file.name != other_loc.file.name {
	return None;
	}

	Some(first.to(second))
	}
	fn resolved_at(&mut self, span: Self::Span, at: Self::Span) -> Self::Span {
	span.with_ctxt(at.ctxt())
	}
	fn source_text(&mut self, span: Self::Span) -> Option<String> {
	self.sess.source_map().span_to_snippet(span).ok()
	}
	}