Add E0747 error code

Author: GuillaumeGomez

src/librustc_error_codes/error_codes.rs

@@ -418,6 +418,7 @@ E0744: include_str!("./error_codes/E0744.md"),
 E0745: include_str!("./error_codes/E0745.md"),
 E0746: include_str!("./error_codes/E0746.md"),
 E0747: include_str!("./error_codes/E0747.md"),
+E0748: include_str!("./error_codes/E0748.md"),
 ;
 //  E0006, // merged with E0005
 //  E0008, // cannot bind by-move into a pattern guard

src/librustc_parse/lexer/mod.rs

@@ -1,5 +1,5 @@
 use rustc_data_structures::sync::Lrc;
-use rustc_errors::{DiagnosticBuilder, FatalError};
+use rustc_errors::{error_code, DiagnosticBuilder, FatalError};
 use rustc_lexer::unescape;
 use rustc_lexer::Base;
 use rustc_session::parse::ParseSess;
@@ -495,7 +495,11 @@ impl<'a> StringReader<'a> {
     }
 
     fn report_unterminated_raw_string(&self, start: BytePos, n_hashes: usize) -> ! {
-        let mut err = self.struct_span_fatal(start, start, "unterminated raw string");
+        let mut err = self.sess.span_diagnostic.struct_span_fatal_with_code(
+            self.mk_sp(start, start),
+            "unterminated raw string",
+            error_code!(E0748),
+        );
         err.span_label(self.mk_sp(start, start), "unterminated raw string");
 
         if n_hashes > 0 {