zig fmt: properly check escape sequences

lib/std/zig/Ast/Render.zig

@@ -3167,7 +3167,7 @@ fn renderIdentifier(r: *Render, token_index: Ast.TokenIndex, space: Space, quote
                     },
                     .failure => return renderQuotedIdentifier(r, token_index, space, false),
                 }
-                contents_i += esc_offset;
+                contents_i = esc_offset;
                 continue;
             },
             else => return renderQuotedIdentifier(r, token_index, space, false),

lib/std/zig/parser_test.zig

@@ -6086,6 +6086,16 @@ test "zig fmt: seperate errors in error sets with comments" {
     );
 }
 
+test "zig fmt: proper escape checks" {
+    try testTransform(
+        \\@"\x41\x42\!"
+        \\
+    ,
+        \\@"AB\\!"
+        \\
+    );
+}
+
 test "zig fmt: field accesses on number literals" {
     try testCanonical(
         \\const a = 0xF .A;