From eb6d9a49a803ee84c9f9aad7ca5657b4ded76941 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Sun, 21 Jun 2020 14:07:59 +0200
Subject: [PATCH 1/2] Add E0766 error for unterminated double quote byte string

---
 src/librustc_error_codes/error_codes.rs       |  1 +
 src/librustc_error_codes/error_codes/E0766.md | 13 +++++++++++++
 src/librustc_parse/lexer/mod.rs               | 15 +++++++++------
 3 files changed, 23 insertions(+), 6 deletions(-)
 create mode 100644 src/librustc_error_codes/error_codes/E0766.md

diff --git a/src/librustc_error_codes/error_codes.rs b/src/librustc_error_codes/error_codes.rs
index 6a5e23adafa53..162585360fbda 100644
--- a/src/librustc_error_codes/error_codes.rs
+++ b/src/librustc_error_codes/error_codes.rs
@@ -446,6 +446,7 @@ E0762: include_str!("./error_codes/E0762.md"),
 E0763: include_str!("./error_codes/E0763.md"),
 E0764: include_str!("./error_codes/E0764.md"),
 E0765: include_str!("./error_codes/E0765.md"),
+E0766: include_str!("./error_codes/E0766.md"),
 ;
 //  E0006, // merged with E0005
 //  E0008, // cannot bind by-move into a pattern guard
diff --git a/src/librustc_error_codes/error_codes/E0766.md b/src/librustc_error_codes/error_codes/E0766.md
new file mode 100644
index 0000000000000..4e775df2cac4d
--- /dev/null
+++ b/src/librustc_error_codes/error_codes/E0766.md
@@ -0,0 +1,13 @@
+A double quote byte string (`b"`) was not terminated.
+
+Erroneous code example:
+
+```compile_fail,E0766
+let s = b"; // error!
+```
+
+To fix this error, add the missing double quote at the end of the string:
+
+```
+let s = b""; // ok!
+```
diff --git a/src/librustc_parse/lexer/mod.rs b/src/librustc_parse/lexer/mod.rs
index 8e74c3847bc90..5050f03bea9b2 100644
--- a/src/librustc_parse/lexer/mod.rs
+++ b/src/librustc_parse/lexer/mod.rs
@@ -367,12 +367,15 @@ impl<'a> StringReader<'a> {
             }
             rustc_lexer::LiteralKind::ByteStr { terminated } => {
                 if !terminated {
-                    self.fatal_span_(
-                        start + BytePos(1),
-                        suffix_start,
-                        "unterminated double quote byte string",
-                    )
-                    .raise()
+                    self.sess
+                        .span_diagnostic
+                        .struct_span_fatal_with_code(
+                            self.mk_sp(start + BytePos(1), suffix_start),
+                            "unterminated double quote byte string",
+                            error_code!(E0766),
+                        )
+                        .emit();
+                    FatalError.raise();
                 }
                 (token::ByteStr, Mode::ByteStr, 2, 1) // b" "
             }

From 33302fa7d225a2d1152f0fe9a52e55fbd85d3017 Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Sun, 21 Jun 2020 14:08:06 +0200
Subject: [PATCH 2/2] Update UI test

---
 src/test/ui/parser/byte-string-literals.stderr | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/test/ui/parser/byte-string-literals.stderr b/src/test/ui/parser/byte-string-literals.stderr
index ca964cd4b8f21..9be9064414796 100644
--- a/src/test/ui/parser/byte-string-literals.stderr
+++ b/src/test/ui/parser/byte-string-literals.stderr
@@ -22,7 +22,7 @@ error: byte constant must be ASCII. Use a \xHH escape for a non-ASCII byte
 LL |     b"é";
    |       ^
 
-error: unterminated double quote byte string
+error[E0766]: unterminated double quote byte string
   --> $DIR/byte-string-literals.rs:7:6
    |
 LL |       b"a
@@ -32,3 +32,4 @@ LL | | }
 
 error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0766`.