Move token tree related lexer state to a separate struct

We only used a bunch of fields when tokenizing into a token tree,
so let's move them out of the base lexer

3 files changed, 71 insertions, 48 deletions

diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 2882acb0e78..60494a6a2bd 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -66,15 +66,7 @@ pub struct StringReader<'a> {
     span: Span,
     /// The raw source span which *does not* take `override_span` into account
     span_src_raw: Span,
-    /// Stack of open delimiters and their spans. Used for error message.
-    open_braces: Vec<(token::DelimToken, Span)>,
-    crate unmatched_braces: Vec<UnmatchedBrace>,
-    /// The type and spans for all braces
-    ///
-    /// Used only for error recovery when arriving to EOF with mismatched braces.
-    matching_delim_spans: Vec<(token::DelimToken, Span, Span)>,
-    crate override_span: Option<Span>,
-    last_unclosed_found_span: Option<Span>,
+    override_span: Option<Span>,
 }
 
 impl<'a> StringReader<'a> {
@@ -254,11 +246,7 @@ impl<'a> StringReader<'a> {
             token: token::Eof,
             span: syntax_pos::DUMMY_SP,
             span_src_raw: syntax_pos::DUMMY_SP,
-            open_braces: Vec::new(),
-            unmatched_braces: Vec::new(),
-            matching_delim_spans: Vec::new(),
             override_span,
-            last_unclosed_found_span: None,
         }
     }
 
diff --git a/src/libsyntax/parse/lexer/tokentrees.rs b/src/libsyntax/parse/lexer/tokentrees.rs
index 0db36c84cdf..a6e176c02a0 100644
--- a/src/libsyntax/parse/lexer/tokentrees.rs
+++ b/src/libsyntax/parse/lexer/tokentrees.rs
@@ -1,14 +1,42 @@
+use syntax_pos::Span;
+
 use crate::print::pprust::token_to_string;
 use crate::parse::lexer::{StringReader, UnmatchedBrace};
 use crate::parse::{token, PResult};
 use crate::tokenstream::{DelimSpan, IsJoint::*, TokenStream, TokenTree, TreeAndJoint};
 
 impl<'a> StringReader<'a> {
+    crate fn into_token_trees(self) -> (PResult<'a, TokenStream>, Vec<UnmatchedBrace>) {
+        let mut tt_reader = TokenTreesReader {
+            string_reader: self,
+            open_braces: Vec::new(),
+            unmatched_braces: Vec::new(),
+            matching_delim_spans: Vec::new(),
+            last_unclosed_found_span: None,
+        };
+        let res = tt_reader.parse_all_token_trees();
+        (res, tt_reader.unmatched_braces)
+    }
+}
+
+struct TokenTreesReader<'a> {
+    string_reader: StringReader<'a>,
+    /// Stack of open delimiters and their spans. Used for error message.
+    open_braces: Vec<(token::DelimToken, Span)>,
+    unmatched_braces: Vec<UnmatchedBrace>,
+    /// The type and spans for all braces
+    ///
+    /// Used only for error recovery when arriving to EOF with mismatched braces.
+    matching_delim_spans: Vec<(token::DelimToken, Span, Span)>,
+    last_unclosed_found_span: Option<Span>,
+}
+
+impl<'a> TokenTreesReader<'a> {
     // Parse a stream of tokens into a list of `TokenTree`s, up to an `Eof`.
-    crate fn parse_all_token_trees(&mut self) -> PResult<'a, TokenStream> {
+    fn parse_all_token_trees(&mut self) -> PResult<'a, TokenStream> {
         let mut tts = Vec::new();
 
-        while self.token != token::Eof {
+        while self.string_reader.token != token::Eof {
             tts.push(self.parse_token_tree()?);
         }
 
@@ -19,7 +47,7 @@ impl<'a> StringReader<'a> {
     fn parse_token_trees_until_close_delim(&mut self) -> TokenStream {
         let mut tts = vec![];
         loop {
-            if let token::CloseDelim(..) = self.token {
+            if let token::CloseDelim(..) = self.string_reader.token {
                 return TokenStream::new(tts);
             }
 
@@ -34,11 +62,12 @@ impl<'a> StringReader<'a> {
     }
 
     fn parse_token_tree(&mut self) -> PResult<'a, TreeAndJoint> {
-        let sm = self.sess.source_map();
-        match self.token {
+        let sm = self.string_reader.sess.source_map();
+        match self.string_reader.token {
             token::Eof => {
                 let msg = "this file contains an un-closed delimiter";
-                let mut err = self.sess.span_diagnostic.struct_span_err(self.span, msg);
+                let mut err = self.string_reader.sess.span_diagnostic
+                    .struct_span_err(self.span(), msg);
                 for &(_, sp) in &self.open_braces {
                     err.span_label(sp, "un-closed delimiter");
                 }
@@ -46,13 +75,12 @@ impl<'a> StringReader<'a> {
                 if let Some((delim, _)) = self.open_braces.last() {
                     if let Some((_, open_sp, close_sp)) = self.matching_delim_spans.iter()
                         .filter(|(d, open_sp, close_sp)| {
-
-                        if let Some(close_padding) = sm.span_to_margin(*close_sp) {
-                            if let Some(open_padding) = sm.span_to_margin(*open_sp) {
-                                return delim == d && close_padding != open_padding;
+                            if let Some(close_padding) = sm.span_to_margin(*close_sp) {
+                                if let Some(open_padding) = sm.span_to_margin(*open_sp) {
+                                    return delim == d && close_padding != open_padding;
+                                }
                             }
-                        }
-                        false
+                            false
                         }).next()  // these are in reverse order as they get inserted on close, but
                     {              // we want the last open/first close
                         err.span_label(
@@ -69,11 +97,11 @@ impl<'a> StringReader<'a> {
             },
             token::OpenDelim(delim) => {
                 // The span for beginning of the delimited section
-                let pre_span = self.span;
+                let pre_span = self.span();
 
                 // Parse the open delimiter.
-                self.open_braces.push((delim, self.span));
-                self.real_token();
+                self.open_braces.push((delim, self.span()));
+                self.string_reader.real_token();
 
                 // Parse the token trees within the delimiters.
                 // We stop at any delimiter so we can try to recover if the user
@@ -81,9 +109,9 @@ impl<'a> StringReader<'a> {
                 let tts = self.parse_token_trees_until_close_delim();
 
                 // Expand to cover the entire delimited token tree
-                let delim_span = DelimSpan::from_pair(pre_span, self.span);
+                let delim_span = DelimSpan::from_pair(pre_span, self.span());
 
-                match self.token {
+                match self.string_reader.token {
                     // Correct delimiter.
                     token::CloseDelim(d) if d == delim => {
                         let (open_brace, open_brace_span) = self.open_braces.pop().unwrap();
@@ -93,26 +121,26 @@ impl<'a> StringReader<'a> {
                             self.matching_delim_spans.clear();
                         } else {
                             self.matching_delim_spans.push(
-                                (open_brace, open_brace_span, self.span),
+                                (open_brace, open_brace_span, self.span()),
                             );
                         }
                         // Parse the close delimiter.
-                        self.real_token();
+                        self.string_reader.real_token();
                     }
                     // Incorrect delimiter.
                     token::CloseDelim(other) => {
                         let mut unclosed_delimiter = None;
                         let mut candidate = None;
-                        if self.last_unclosed_found_span != Some(self.span) {
+                        if self.last_unclosed_found_span != Some(self.span()) {
                             // do not complain about the same unclosed delimiter multiple times
-                            self.last_unclosed_found_span = Some(self.span);
+                            self.last_unclosed_found_span = Some(self.span());
                             // This is a conservative error: only report the last unclosed
                             // delimiter. The previous unclosed delimiters could actually be
                             // closed! The parser just hasn't gotten to them yet.
                             if let Some(&(_, sp)) = self.open_braces.last() {
                                 unclosed_delimiter = Some(sp);
                             };
-                            if let Some(current_padding) = sm.span_to_margin(self.span) {
+                            if let Some(current_padding) = sm.span_to_margin(self.span()) {
                                 for (brace, brace_span) in &self.open_braces {
                                     if let Some(padding) = sm.span_to_margin(*brace_span) {
                                         // high likelihood of these two corresponding
@@ -126,7 +154,7 @@ impl<'a> StringReader<'a> {
                             self.unmatched_braces.push(UnmatchedBrace {
                                 expected_delim: tok,
                                 found_delim: other,
-                                found_span: self.span,
+                                found_span: self.span(),
                                 unclosed_span: unclosed_delimiter,
                                 candidate_span: candidate,
                             });
@@ -142,7 +170,7 @@ impl<'a> StringReader<'a> {
                         //     bar(baz(
                         // }  // Incorrect delimiter but matches the earlier `{`
                         if !self.open_braces.iter().any(|&(b, _)| b == other) {
-                            self.real_token();
+                            self.string_reader.real_token();
                         }
                     }
                     token::Eof => {
@@ -162,22 +190,28 @@ impl<'a> StringReader<'a> {
             token::CloseDelim(_) => {
                 // An unexpected closing delimiter (i.e., there is no
                 // matching opening delimiter).
-                let token_str = token_to_string(&self.token);
+                let token_str = token_to_string(&self.string_reader.token);
                 let msg = format!("unexpected close delimiter: `{}`", token_str);
-                let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
-                err.span_label(self.span, "unexpected close delimiter");
+                let mut err = self.string_reader.sess.span_diagnostic
+                    .struct_span_err(self.span(), &msg);
+                err.span_label(self.span(), "unexpected close delimiter");
                 Err(err)
             },
             _ => {
-                let tt = TokenTree::Token(self.span, self.token.clone());
+                let tt = TokenTree::Token(self.span(), self.string_reader.token.clone());
                 // Note that testing for joint-ness here is done via the raw
                 // source span as the joint-ness is a property of the raw source
                 // rather than wanting to take `override_span` into account.
-                let raw = self.span_src_raw;
-                self.real_token();
-                let is_joint = raw.hi() == self.span_src_raw.lo() && token::is_op(&self.token);
+                let raw = self.string_reader.span_src_raw;
+                self.string_reader.real_token();
+                let is_joint = raw.hi() == self.string_reader.span_src_raw.lo()
+                    && token::is_op(&self.string_reader.token);
                 Ok((tt, if is_joint { Joint } else { NonJoint }))
             }
         }
     }
+
+    fn span(&self) -> Span {
+        self.string_reader.span
+    }
 }
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index be44b964ba5..1ddafb969c4 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -295,7 +295,7 @@ pub fn source_file_to_stream(
 }
 
 /// Given a source file, produces a sequence of token trees. Returns any buffered errors from
-/// parsing the token tream.
+/// parsing the token stream.
 pub fn maybe_file_to_stream(
     sess: &ParseSess,
     source_file: Lrc<SourceFile>,
@@ -303,14 +303,15 @@ pub fn maybe_file_to_stream(
 ) -> Result<(TokenStream, Vec<lexer::UnmatchedBrace>), Vec<Diagnostic>> {
     let mut srdr = lexer::StringReader::new_or_buffered_errs(sess, source_file, override_span)?;
     srdr.real_token();
+    let (token_trees, unmatched_braces) = srdr.into_token_trees();
 
-    match srdr.parse_all_token_trees() {
-        Ok(stream) => Ok((stream, srdr.unmatched_braces)),
+    match token_trees {
+        Ok(stream) => Ok((stream, unmatched_braces)),
         Err(err) => {
             let mut buffer = Vec::with_capacity(1);
             err.buffer(&mut buffer);
             // Not using `emit_unclosed_delims` to use `db.buffer`
-            for unmatched in srdr.unmatched_braces {
+            for unmatched in unmatched_braces {
                 let mut db = sess.span_diagnostic.struct_span_err(unmatched.found_span, &format!(
                     "incorrect close delimiter: `{}`",
                     token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),