Don't suggest using \r in raw strings

src/libsyntax/parse/unescape.rs

@@ -12,6 +12,7 @@ pub(crate) enum EscapeError {
     LoneSlash,
     InvalidEscape,
     BareCarriageReturn,
+    BareCarriageReturnInRawString,
     EscapeOnlyChar,
 
     TooShortHexEscape,
@@ -299,7 +300,7 @@ fn unescape_raw_str_or_byte_str<F>(literal_text: &str, mode: Mode, callback: &mu
                 chars.next();
                 Ok('\n')
             },
-            ('\r', _) => Err(EscapeError::BareCarriageReturn),
+            ('\r', _) => Err(EscapeError::BareCarriageReturnInRawString),
             (c, _) if mode.is_bytes() && !c.is_ascii() =>
                 Err(EscapeError::NonAsciiCharInByteString),
             (c, _) => Ok(c),

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();
 

src/test/ui/parser/lex-bare-cr-string-literal-doc-comment.rs

@@ -21,7 +21,7 @@ fn main() {
     let _s = "foo
bar"; //~ ERROR: bare CR not allowed in string
 
     // the following string literal has a bare CR in it
-    let _s = r"bar
foo"; //~ ERROR: bare CR not allowed in string
+    let _s = r"bar
foo"; //~ ERROR: bare CR not allowed in raw string
 
     // the following string literal has a bare CR in it
     let _s = "foo\
bar"; //~ ERROR: unknown character escape: \r

src/test/ui/parser/lex-bare-cr-string-literal-doc-comment.stderr

@@ -28,7 +28,7 @@ error: bare CR not allowed in string, use \r instead
 LL |     let _s = "foo
bar";
    |                  ^
 
-error: bare CR not allowed in string, use \r instead
+error: bare CR not allowed in raw string
   --> $DIR/lex-bare-cr-string-literal-doc-comment.rs:24:19
    |
 LL |     let _s = r"bar
foo";

src/test/ui/parser/raw-byte-string-literals.rs

 // ignore-tidy-cr
 // compile-flags: -Z continue-parse-after-error
 pub fn main() {
-    br"a
"; //~ ERROR bare CR not allowed in string
+    br"a
"; //~ ERROR bare CR not allowed in raw string
     br"é";  //~ ERROR raw byte string must be ASCII
     br##~"a"~##;  //~ ERROR only `#` is allowed in raw string delimitation
 }

src/test/ui/parser/raw-byte-string-literals.stderr

-error: bare CR not allowed in string, use \r instead
+error: bare CR not allowed in raw string
   --> $DIR/raw-byte-string-literals.rs:4:9
    |
 LL |     br"a
";