Rollup merge of #59671 - matklad:lexer, r=eddyb

Make some of lexer's API private

Lexer is a `pub` type, so it feels wrong that its fields are just pub (I guess it wasn't exported initially), so let's minimize visibility.

Context: I am looking into extracting rust-lexer into a library, which can be shared by rust-analyzer and rustc. I hope that a simple interface like `fn next_token(src: &str) -> (TokenKind, usize)` would work, but to try this out I need to understand what is the current API of the lexer.

Author: Centril

src/libsyntax/parse/lexer/mod.rs

@@ -43,16 +43,16 @@ pub struct UnmatchedBrace {
 }
 
 pub struct StringReader<'a> {
-    pub sess: &'a ParseSess,
+    crate sess: &'a ParseSess,
     /// The absolute offset within the source_map of the next character to read
-    pub next_pos: BytePos,
+    crate next_pos: BytePos,
     /// The absolute offset within the source_map of the current character
-    pub pos: BytePos,
+    crate pos: BytePos,
     /// The current character (which has been read from self.pos)
-    pub ch: Option<char>,
-    pub source_file: Lrc<syntax_pos::SourceFile>,
+    crate ch: Option<char>,
+    crate source_file: Lrc<syntax_pos::SourceFile>,
     /// Stop reading src at this index.
-    pub end_src_index: usize,
+    crate end_src_index: usize,
     // cached:
     peek_tok: token::Token,
     peek_span: Span,
@@ -126,7 +126,7 @@ impl<'a> StringReader<'a> {
     }
 
     /// Immutably extract string if found at current position with given delimiters
-    pub fn peek_delimited(&self, from_ch: char, to_ch: char) -> Option<String> {
+    fn peek_delimited(&self, from_ch: char, to_ch: char) -> Option<String> {
         let mut pos = self.pos;
         let mut idx = self.src_index(pos);
         let mut ch = char_at(&self.src, idx);
@@ -191,7 +191,7 @@ impl<'a> StringReader<'a> {
         self.fatal_span(self.peek_span, m)
     }
 
-    pub fn emit_fatal_errors(&mut self) {
+    crate fn emit_fatal_errors(&mut self) {
         for err in &mut self.fatal_errs {
             err.emit();
         }