Simplify String rule in parser

[emanuele6]

Use a StringStart component that is either FORMAT QQSTRING_START or QQSTRING_START instead of having two similar rules for String.

This is simpler and avoids having to use an untyped mid-rule action component to copy FORMAT at the top of the stack before QQString, and having to use jv_free($<literal>3) instead of jv_free($1) just to make bison not complain about the "unused" mid-rule component.

[itchyny]

My first thought of skimming the rules is that including the format prefix in String is an unintended accident. .@html, {@html:.} are invalid but .@html"", {@html"":.} are valid. I think better rule is Term := String | Format | Format String | etc, which disallows unexpected formatted string usages around the syntax.

[emanuele6]

Why should you only be allowed to use a different format for a string literal in an expression, and not when using a string literal in a object constructor as key, or as ."string", or as path for import/include? What is the point of forcing the user to use "\(@foo "blah")" instead of just @foo "blah" if they want to do that?
In python, and javascript, you can use a f'' or `` string interpolation wherever you can use a string literal.

[nicowilliams]

I like this. It's easier to understand.

[nicowilliams]

LGTM. I really like this simplification. I'm not seeing what it might break either.

My first thought of skimming the rules is that including the format prefix in String is an unintended accident. .@html, {@html:.} are invalid but .@html"", {@html"":.} are valid. I think better rule is Term := String | Format | Format String | etc, which disallows unexpected formatted string usages around the syntax.

.@html, {@html:.} remain invalid with this patch, and .@html"", {@html"":.} remain valid with this patch. Today I learned that the format specifier is an integral part of the string literal, and... I think it makes sense.

So I think this is ready, unless there's any other objections. Changing nothing in the language while simplifying the parser is a win.

[itchyny]

Okay. Looks good.

[nicowilliams]

Thanks!