[BUG] Cppfront can not parse "\x{62}"

[MaxSagebaum]

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Cppfront produces the error:

main.cpp2(3,22): error: string literal "\" is missing its closing "
main.cpp2(5,32): error: local variable c cannot be used in its own initializer

while parsing ""\x{62}blub""

A reproducer on compiler explorer: https://cpp2.godbolt.org/z/h6e8vc1rv

One possible patch is:

diff --git a/source/lex.h b/source/lex.h
index bab314a..ba3be0e 100644
--- a/source/lex.h
+++ b/source/lex.h
@@ -939,10 +939,16 @@ auto lex_line(
         if (
             peek(  offset) == '\\'
             && peek(1+offset) == 'x'
-            && is_hexadecimal_digit(peek(2+offset))
+            && (is_hexadecimal_digit(peek(2+offset))
+              || (peek(2+offset) == '{' && is_hexadecimal_digit(peek(3+offset)))
             )
+        )
         {
+            bool has_bracket = peek(2+offset) == '{';
             auto j = 3;
+
+            if (has_bracket) { ++j; }
+
             while (
                 peek(j+offset)
                 && is_hexadecimal_digit(peek(j+offset))
@@ -950,6 +956,14 @@ auto lex_line(
             {
                 ++j;
             }
+
+            if (has_bracket) {
+                if (peek(j+offset) == '}') {
+                    ++j;
+                } else {
+                    return 0;
+                }
+            }
             return j;
         }
         return 0;

It seems that there is currently no regression test for the escapes.