formatMessage

    fn formatMessage(self: FormatMessage, writer: *Writer) Writer.Error!void {
        switch (self.err) {
            .invalid_escape_character => |bad_index| try writer.print(
                "invalid escape character: '{c}'",
                .{self.raw_string[bad_index]},
            ),
            .expected_hex_digit => |bad_index| try writer.print(
                "expected hex digit, found '{c}'",
                .{self.raw_string[bad_index]},
            ),
            .empty_unicode_escape_sequence => try writer.writeAll(
                "empty unicode escape sequence",
            ),
            .expected_hex_digit_or_rbrace => |bad_index| try writer.print(
                "expected hex digit or '}}', found '{c}'",
                .{self.raw_string[bad_index]},
            ),
            .invalid_unicode_codepoint => try writer.writeAll(
                "unicode escape does not correspond to a valid unicode scalar value",
            ),
            .expected_lbrace => |bad_index| try writer.print(
                "expected '{{', found '{c}'",
                .{self.raw_string[bad_index]},
            ),
            .expected_rbrace => |bad_index| try writer.print(
                "expected '}}', found '{c}'",
                .{self.raw_string[bad_index]},
            ),
            .expected_single_quote => |bad_index| try writer.print(
                "expected single quote ('), found '{c}'",
                .{self.raw_string[bad_index]},
            ),
            .invalid_character => |bad_index| try writer.print(
                "invalid byte in string or character literal: '{c}'",
                .{self.raw_string[bad_index]},
            ),
            .empty_char_literal => try writer.writeAll(
                "empty character literal",
            ),
        }
    }