Parser gets confused by stray commas

Example:

L.FOO = "something",
L.BAR = "something else"

This triggers two unexpected diagnostics: err-equal-as-assign and redundant-value which is a bit confusing.

The reason is that it interprets this as that the user's intent was to write FOO, (some other var) = "something", BAR == "something else"

However, the actual error is a stray comma after the first line.

This error may sound a bit obscure, because why would add someone a stray comma? The answer is that this happened in a localization files where people who are not necessarily familiar with Lua are contributing translations. Sometimes these translations are given in table literals where they need to add commas after each line and sometimes they are given as a list of setfield statements...

This is probably not easy to fix because the parser's interpretation is completely valid until it encounteres the assignment...

首先复现包含两条赋值语句的 Lua 示例，并检查生成 err-equal-as-assign 和 redundant-value 的 parser 路径。当多余的逗号被报告为相关错误，而不是产生这些令人困惑的诊断时，该问题就得到了解决。