Editorial: instead of the [Tagged] parameter

[jmdyck]

The [Tagged] grammatical parameter doesn't actually alter the grammar -- there are no right-hand-sides preceded by [+Tagged] or [~Tagged]. Its purpose appears to be: for a given TemplateLiteral, capture whether it belongs to a tagged template, and then convey that fact to the TemplateLiteral's literal components, so that they know whether or not to raise a Syntax Error on NotEscapeSequence.

But if that's the case, then we don't need to use a grammatical parameter, we could just say things like:

TemplateMiddle :: `}` TemplateCharacters? `${`
    It is a Syntax Error if |TemplateCharacters| Contains |NotEscapeSequence| and
    the |TemplateLiteral| that most closely contains |TemplateMiddle| is a |PrimaryExpression|.

Note that we use similar 'context-examining' formulations in the early error rules for 'break' and 'continue', for uninitialized constant-decls, and (kind of) whenever an EE rule says "if [something] is contained in strict mode code".

(You could do it in a single early error rule:

TemplateCharacter :: `\` NotEscapeSequence
    It is a Syntax Error if the |TemplateLiteral| that most closely contains
    this |TemplateCharacter| is a |PrimaryExpression|

but that makes an assumption about the syntactic/lexical boundary that we may not want to make.)