Auto merge of #60793 - Xanewok:raw-string-cleanup, r=petrochenkov

lexer: Disallow bare CR in raw byte strings

Handles bare CR ~but doesn't translate `\r\n` to `\n` yet in raw strings yet~ and translates CRLF to LF in raw strings.

As a side-note I think it'd be good to change the `unescape_` to return plain iterators to reduce some boilerplate (e.g. `has_error` could benefit from collecting `Result<T>` and aborting early on errors) but will do that separately, unless I missed something here that prevents it.

@matklad @petrochenkov thoughts?

4 files changed, 161 insertions, 128 deletions

diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 2f4c48d4bf9..9df2898696e 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -130,7 +130,7 @@ impl<'a> StringReader<'a> {
         self.ch.is_none()
     }
 
-    fn fail_unterminated_raw_string(&self, pos: BytePos, hash_count: u16) {
+    fn fail_unterminated_raw_string(&self, pos: BytePos, hash_count: u16) -> ! {
         let mut err = self.struct_span_fatal(pos, pos, "unterminated raw string");
         err.span_label(self.mk_sp(pos, pos), "unterminated raw string");
 
@@ -292,15 +292,6 @@ impl<'a> StringReader<'a> {
         self.sess.span_diagnostic.struct_span_fatal(self.mk_sp(from_pos, to_pos), &m[..])
     }
 
-    /// Report a lexical error spanning [`from_pos`, `to_pos`), appending an
-    /// escaped character to the error message
-    fn err_span_char(&self, from_pos: BytePos, to_pos: BytePos, m: &str, c: char) {
-        let mut m = m.to_string();
-        m.push_str(": ");
-        push_escaped_char(&mut m, c);
-        self.err_span_(from_pos, to_pos, &m[..]);
-    }
-
     /// Advance peek_token to refer to the next token, and
     /// possibly update the interner.
     fn advance_token(&mut self) -> Result<(), ()> {
@@ -1070,7 +1061,13 @@ impl<'a> StringReader<'a> {
                         self.validate_byte_str_escape(start_with_quote);
                         (token::ByteStr, symbol)
                     },
-                    Some('r') => self.scan_raw_byte_string(),
+                    Some('r') => {
+                        let (start, end, hash_count) = self.scan_raw_string();
+                        let symbol = self.name_from_to(start, end);
+                        self.validate_raw_byte_str_escape(start, end);
+
+                        (token::ByteStrRaw(hash_count), symbol)
+                    }
                     _ => unreachable!(),  // Should have been a token::Ident above.
                 };
                 let suffix = self.scan_optional_raw_name();
@@ -1086,79 +1083,9 @@ impl<'a> StringReader<'a> {
                 Ok(TokenKind::lit(token::Str, symbol, suffix))
             }
             'r' => {
-                let start_bpos = self.pos;
-                self.bump();
-                let mut hash_count: u16 = 0;
-                while self.ch_is('#') {
-                    if hash_count == 65535 {
-                        let bpos = self.next_pos;
-                        self.fatal_span_(start_bpos,
-                                         bpos,
-                                         "too many `#` symbols: raw strings may be \
-                                         delimited by up to 65535 `#` symbols").raise();
-                    }
-                    self.bump();
-                    hash_count += 1;
-                }
-
-                if self.is_eof() {
-                    self.fail_unterminated_raw_string(start_bpos, hash_count);
-                } else if !self.ch_is('"') {
-                    let last_bpos = self.pos;
-                    let curr_char = self.ch.unwrap();
-                    self.fatal_span_char(start_bpos,
-                                         last_bpos,
-                                         "found invalid character; only `#` is allowed \
-                                         in raw string delimitation",
-                                         curr_char).raise();
-                }
-                self.bump();
-                let content_start_bpos = self.pos;
-                let mut content_end_bpos;
-                let mut valid = true;
-                'outer: loop {
-                    if self.is_eof() {
-                        self.fail_unterminated_raw_string(start_bpos, hash_count);
-                    }
-                    // if self.ch_is('"') {
-                    // content_end_bpos = self.pos;
-                    // for _ in 0..hash_count {
-                    // self.bump();
-                    // if !self.ch_is('#') {
-                    // continue 'outer;
-                    let c = self.ch.unwrap();
-                    match c {
-                        '"' => {
-                            content_end_bpos = self.pos;
-                            for _ in 0..hash_count {
-                                self.bump();
-                                if !self.ch_is('#') {
-                                    continue 'outer;
-                                }
-                            }
-                            break;
-                        }
-                        '\r' => {
-                            if !self.nextch_is('\n') {
-                                let last_bpos = self.pos;
-                                self.err_span_(start_bpos,
-                                               last_bpos,
-                                               "bare CR not allowed in raw string, use \\r \
-                                                instead");
-                                valid = false;
-                            }
-                        }
-                        _ => (),
-                    }
-                    self.bump();
-                }
-
-                self.bump();
-                let symbol = if valid {
-                    self.name_from_to(content_start_bpos, content_end_bpos)
-                } else {
-                    Symbol::intern("??")
-                };
+                let (start, end, hash_count) = self.scan_raw_string();
+                let symbol = self.name_from_to(start, end);
+                self.validate_raw_str_escape(start, end);
                 let suffix = self.scan_optional_raw_name();
 
                 Ok(TokenKind::lit(token::StrRaw(hash_count), symbol, suffix))
@@ -1315,16 +1242,18 @@ impl<'a> StringReader<'a> {
         id
     }
 
-    fn scan_raw_byte_string(&mut self) -> (token::LitKind, Symbol) {
+    /// Scans a raw (byte) string, returning byte position range for `"<literal>"`
+    /// (including quotes) along with `#` character count in `(b)r##..."<literal>"##...`;
+    fn scan_raw_string(&mut self) -> (BytePos, BytePos, u16) {
         let start_bpos = self.pos;
         self.bump();
-        let mut hash_count = 0;
+        let mut hash_count: u16 = 0;
         while self.ch_is('#') {
             if hash_count == 65535 {
                 let bpos = self.next_pos;
                 self.fatal_span_(start_bpos,
                                  bpos,
-                                 "too many `#` symbols: raw byte strings may be \
+                                 "too many `#` symbols: raw strings may be \
                                  delimited by up to 65535 `#` symbols").raise();
             }
             self.bump();
@@ -1334,13 +1263,13 @@ impl<'a> StringReader<'a> {
         if self.is_eof() {
             self.fail_unterminated_raw_string(start_bpos, hash_count);
         } else if !self.ch_is('"') {
-            let pos = self.pos;
-            let ch = self.ch.unwrap();
+            let last_bpos = self.pos;
+            let curr_char = self.ch.unwrap();
             self.fatal_span_char(start_bpos,
-                                        pos,
-                                        "found invalid character; only `#` is allowed in raw \
-                                         string delimitation",
-                                        ch).raise();
+                                 last_bpos,
+                                 "found invalid character; only `#` is allowed \
+                                 in raw string delimitation",
+                                 curr_char).raise();
         }
         self.bump();
         let content_start_bpos = self.pos;
@@ -1360,19 +1289,14 @@ impl<'a> StringReader<'a> {
                     }
                     break;
                 }
-                Some(c) => {
-                    if c > '\x7F' {
-                        let pos = self.pos;
-                        self.err_span_char(pos, pos, "raw byte string must be ASCII", c);
-                    }
-                }
+                _ => (),
             }
             self.bump();
         }
 
         self.bump();
 
-        (token::ByteStrRaw(hash_count), self.name_from_to(content_start_bpos, content_end_bpos))
+        (content_start_bpos, content_end_bpos, hash_count)
     }
 
     fn validate_char_escape(&self, start_with_quote: BytePos) {
@@ -1422,6 +1346,40 @@ impl<'a> StringReader<'a> {
         });
     }
 
+    fn validate_raw_str_escape(&self, content_start: BytePos, content_end: BytePos) {
+        self.with_str_from_to(content_start, content_end, |lit: &str| {
+            unescape::unescape_raw_str(lit, &mut |range, c| {
+                if let Err(err) = c {
+                    emit_unescape_error(
+                        &self.sess.span_diagnostic,
+                        lit,
+                        self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                        unescape::Mode::Str,
+                        range,
+                        err,
+                    )
+                }
+            })
+        });
+    }
+
+    fn validate_raw_byte_str_escape(&self, content_start: BytePos, content_end: BytePos) {
+        self.with_str_from_to(content_start, content_end, |lit: &str| {
+            unescape::unescape_raw_byte_str(lit, &mut |range, c| {
+                if let Err(err) = c {
+                    emit_unescape_error(
+                        &self.sess.span_diagnostic,
+                        lit,
+                        self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                        unescape::Mode::ByteStr,
+                        range,
+                        err,
+                    )
+                }
+            })
+        });
+    }
+
     fn validate_byte_str_escape(&self, start_with_quote: BytePos) {
         self.with_str_from_to(start_with_quote + BytePos(1), self.pos - BytePos(1), |lit| {
             unescape::unescape_byte_str(lit, &mut |range, c| {
diff --git a/src/libsyntax/parse/literal.rs b/src/libsyntax/parse/literal.rs
index 84f7386235f..ef55bf6b929 100644
--- a/src/libsyntax/parse/literal.rs
+++ b/src/libsyntax/parse/literal.rs
@@ -4,7 +4,9 @@ use crate::ast::{self, Lit, LitKind};
 use crate::parse::parser::Parser;
 use crate::parse::PResult;
 use crate::parse::token::{self, Token, TokenKind};
-use crate::parse::unescape::{unescape_str, unescape_char, unescape_byte_str, unescape_byte};
+use crate::parse::unescape::{unescape_char, unescape_byte};
+use crate::parse::unescape::{unescape_str, unescape_byte_str};
+use crate::parse::unescape::{unescape_raw_str, unescape_raw_byte_str};
 use crate::print::pprust;
 use crate::symbol::{kw, sym, Symbol};
 use crate::tokenstream::{TokenStream, TokenTree};
@@ -141,7 +143,17 @@ impl LitKind {
                 // Ditto.
                 let s = symbol.as_str();
                 let symbol = if s.contains('\r') {
-                    Symbol::intern(&raw_str_lit(&s))
+                    let mut buf = String::with_capacity(s.len());
+                    let mut error = Ok(());
+                    unescape_raw_str(&s, &mut |_, unescaped_char| {
+                        match unescaped_char {
+                            Ok(c) => buf.push(c),
+                            Err(_) => error = Err(LitError::LexerError),
+                        }
+                    });
+                    error?;
+                    buf.shrink_to_fit();
+                    Symbol::intern(&buf)
                 } else {
                     symbol
                 };
@@ -161,7 +173,26 @@ impl LitKind {
                 buf.shrink_to_fit();
                 LitKind::ByteStr(Lrc::new(buf))
             }
-            token::ByteStrRaw(_) => LitKind::ByteStr(Lrc::new(symbol.to_string().into_bytes())),
+            token::ByteStrRaw(_) => {
+                let s = symbol.as_str();
+                let bytes = if s.contains('\r') {
+                    let mut buf = Vec::with_capacity(s.len());
+                    let mut error = Ok(());
+                    unescape_raw_byte_str(&s, &mut |_, unescaped_byte| {
+                        match unescaped_byte {
+                            Ok(c) => buf.push(c),
+                            Err(_) => error = Err(LitError::LexerError),
+                        }
+                    });
+                    error?;
+                    buf.shrink_to_fit();
+                    buf
+                } else {
+                    symbol.to_string().into_bytes()
+                };
+
+                LitKind::ByteStr(Lrc::new(bytes))
+            },
             token::Err => LitKind::Err(symbol),
         })
     }
@@ -353,29 +384,6 @@ crate fn expect_no_suffix(diag: &Handler, sp: Span, kind: &str, suffix: Option<S
     }
 }
 
-/// Parses a string representing a raw string literal into its final form. The
-/// only operation this does is convert embedded CRLF into a single LF.
-fn raw_str_lit(lit: &str) -> String {
-    debug!("raw_str_lit: {:?}", lit);
-    let mut res = String::with_capacity(lit.len());
-
-    let mut chars = lit.chars().peekable();
-    while let Some(c) = chars.next() {
-        if c == '\r' {
-            if *chars.peek().unwrap() != '\n' {
-                panic!("lexer accepted bare CR");
-            }
-            chars.next();
-            res.push('\n');
-        } else {
-            res.push(c);
-        }
-    }
-
-    res.shrink_to_fit();
-    res
-}
-
 // Checks if `s` looks like i32 or u1234 etc.
 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
     s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
diff --git a/src/libsyntax/parse/unescape.rs b/src/libsyntax/parse/unescape.rs
index 90ee549db01..22cce67b5ee 100644
--- a/src/libsyntax/parse/unescape.rs
+++ b/src/libsyntax/parse/unescape.rs
@@ -1,4 +1,4 @@
-//! Utilities for validating  string and char literals and turning them into
+//! Utilities for validating string and char literals and turning them into
 //! values they represent.
 
 use std::str::Chars;
@@ -12,6 +12,7 @@ pub(crate) enum EscapeError {
     LoneSlash,
     InvalidEscape,
     BareCarriageReturn,
+    BareCarriageReturnInRawString,
     EscapeOnlyChar,
 
     TooShortHexEscape,
@@ -29,6 +30,7 @@ pub(crate) enum EscapeError {
 
     UnicodeEscapeInByte,
     NonAsciiCharInByte,
+    NonAsciiCharInByteString,
 }
 
 /// Takes a contents of a char literal (without quotes), and returns an
@@ -66,6 +68,30 @@ where
     })
 }
 
+/// Takes a contents of a string literal (without quotes) and produces a
+/// sequence of characters or errors.
+/// NOTE: Raw strings do not perform any explicit character escaping, here we
+/// only translate CRLF to LF and produce errors on bare CR.
+pub(crate) fn unescape_raw_str<F>(literal_text: &str, callback: &mut F)
+where
+    F: FnMut(Range<usize>, Result<char, EscapeError>),
+{
+    unescape_raw_str_or_byte_str(literal_text, Mode::Str, callback)
+}
+
+/// Takes a contents of a string literal (without quotes) and produces a
+/// sequence of characters or errors.
+/// NOTE: Raw strings do not perform any explicit character escaping, here we
+/// only translate CRLF to LF and produce errors on bare CR.
+pub(crate) fn unescape_raw_byte_str<F>(literal_text: &str, callback: &mut F)
+where
+    F: FnMut(Range<usize>, Result<u8, EscapeError>),
+{
+    unescape_raw_str_or_byte_str(literal_text, Mode::ByteStr, &mut |range, char| {
+        callback(range, char.map(byte_from_char))
+    })
+}
+
 #[derive(Debug, Clone, Copy)]
 pub(crate) enum Mode {
     Char,
@@ -254,9 +280,40 @@ where
     }
 }
 
+/// Takes a contents of a string literal (without quotes) and produces a
+/// sequence of characters or errors.
+/// NOTE: Raw strings do not perform any explicit character escaping, here we
+/// only translate CRLF to LF and produce errors on bare CR.
+fn unescape_raw_str_or_byte_str<F>(literal_text: &str, mode: Mode, callback: &mut F)
+where
+    F: FnMut(Range<usize>, Result<char, EscapeError>),
+{
+    assert!(mode.in_double_quotes());
+    let initial_len = literal_text.len();
+
+    let mut chars = literal_text.chars();
+    while let Some(curr) = chars.next() {
+        let start = initial_len - chars.as_str().len() - curr.len_utf8();
+
+        let result = match (curr, chars.clone().next()) {
+            ('\r', Some('\n')) => {
+                chars.next();
+                Ok('\n')
+            },
+            ('\r', _) => Err(EscapeError::BareCarriageReturnInRawString),
+            (c, _) if mode.is_bytes() && !c.is_ascii() =>
+                Err(EscapeError::NonAsciiCharInByteString),
+            (c, _) => Ok(c),
+        };
+        let end = initial_len - chars.as_str().len();
+
+        callback(start..end, result);
+    }
+}
+
 fn byte_from_char(c: char) -> u8 {
     let res = c as u32;
-    assert!(res <= u8::max_value() as u32, "guaranteed because of Mode::Byte");
+    assert!(res <= u8::max_value() as u32, "guaranteed because of Mode::Byte(Str)");
     res as u8
 }
 
diff --git a/src/libsyntax/parse/unescape_error_reporting.rs b/src/libsyntax/parse/unescape_error_reporting.rs
index 22777c0884f..71b41161ad8 100644
--- a/src/libsyntax/parse/unescape_error_reporting.rs
+++ b/src/libsyntax/parse/unescape_error_reporting.rs
@@ -80,6 +80,11 @@ pub(crate) fn emit_unescape_error(
             };
             handler.span_err(span, msg);
         }
+        EscapeError::BareCarriageReturnInRawString => {
+            assert!(mode.in_double_quotes());
+            let msg = "bare CR not allowed in raw string";
+            handler.span_err(span, msg);
+        }
         EscapeError::InvalidEscape => {
             let (c, span) = last_char();
 
@@ -124,6 +129,11 @@ pub(crate) fn emit_unescape_error(
             handler.span_err(span, "byte constant must be ASCII. \
                                     Use a \\xHH escape for a non-ASCII byte")
         }
+        EscapeError::NonAsciiCharInByteString => {
+            assert!(mode.is_bytes());
+            let (_c, span) = last_char();
+            handler.span_err(span, "raw byte string must be ASCII")
+        }
         EscapeError::OutOfRangeHexEscape => {
             handler.span_err(span, "this form of character escape may only be used \
                                     with characters in the range [\\x00-\\x7f]")