Highlight strings more properly in Rust.

- Raw strings are now ``String`` rather than the unofficial ``String.Raw``
  which isn?t styled by default;

- Byte strings weren?t being handled at all;

- ``\x80`` and above aren?t valid in non-byte strings;

- ``\0`` is a thing, ``\777`` for octal 7 is *not* a thing, nor has it ever
  been, to the best of my knowledge. Not sure why that one was in there at all.

1 files changed, 11 insertions, 3 deletions

diff --git a/pygments/lexers/rust.py b/pygments/lexers/rust.py
index 78ecc305..c2bea123 100644
--- a/pygments/lexers/rust.py
+++ b/pygments/lexers/rust.py
@@ -85,7 +85,10 @@ class RustLexer(RegexLexer):
             # Labels
             (r'(break|continue)(\s*)(\'[A-Za-z_]\w*)?', bygroups(Keyword, Text.Whitespace, Name.Label)),
             # Character Literal
-            (r"""'(\\['"\\nrt]|\\x[0-9a-fA-F]{2}|\\[0-7]{1,3}"""
+            (r"""'(\\['"\\nrt]|\\x[0-7][0-9a-fA-F]|\\0"""
+             r"""|\\u[0-9a-fA-F]{4}|\\U[0-9a-fA-F]{8}|.)'""",
+             String.Char),
+            (r"""b'(\\['"\\nrt]|\\x[0-9a-fA-F]{2}|\\0"""
              r"""|\\u[0-9a-fA-F]{4}|\\U[0-9a-fA-F]{8}|.)'""",
              String.Char),
             # Binary Literal
@@ -99,8 +102,9 @@ class RustLexer(RegexLexer):
              r'\.[0-9_]*|[eE][+\-]?[0-9_]+)', Number.Float, 'number_lit'),
             (r'[0-9][0-9_]*', Number.Integer, 'number_lit'),
             # String Literal
+            (r'b"', String, 'bytestring'),
             (r'"', String, 'string'),
-            (r'r(#*)".*?"\1', String.Raw),
+            (r'b?r(#*)".*?"\1', String),
 
             # Lifetime
             (r"""'static""", Name.Builtin),
@@ -136,11 +140,15 @@ class RustLexer(RegexLexer):
         ],
         'string': [
             (r'"', String, '#pop'),
-            (r"""\\['"\\nrt]|\\x[0-9a-fA-F]{2}|\\[0-7]{1,3}"""
+            (r"""\\['"\\nrt]|\\x[0-7][0-9a-fA-F]|\\0"""
              r"""|\\u[0-9a-fA-F]{4}|\\U[0-9a-fA-F]{8}""", String.Escape),
             (r'[^\\"]+', String),
             (r'\\', String),
         ],
+        'bytestring': [
+            (r"""\\x[89a-fA-F][0-9a-fA-F]""", String.Escape),
+            include('string'),
+        ],
         'macro{': [
             (r'\{', Operator, '#push'),
             (r'\}', Operator, '#pop'),