Language for testing the state of a production parameter is inconsistent

[gibson042]

Description:
A handful of sections test the state of production parameters, but they do so inconsistently. We should pick one pattern and standardize on it.

https://tc39.es/ecma262/#sec-identifiers-static-semantics-early-errors and https://tc39.es/ecma262/#sec-patterns-static-semantics-early-errors-annexb

• "if this production has a _[…] parameter"

https://tc39.es/ecma262/#sec-static-semantics-template-early-errors

• "if the _[…] parameter was not set"

https://tc39.es/ecma262/#sec-async-function-definitions and https://tc39.es/ecma262/#sec-regular-expressions-patterns

• "when the _[…] parameter is {present,absent}"
• "with the _[…] parameter present on [symbol]"

[jmdyck]

If you look at a parameterized production, such as:

StatementList[Return, In] : ...

and think of it as an abbreviation for 4 different productions:

StatementList : ...
StatementList_Return : ...
StatementList_In : ...
StatementList_Return_In : ...

then phrases such as "if this production has a [Return] parameter" or "if the [Return] parameter is present/absent" kind of make sense: you can think of it as "if this production's LHS has _Return in its name".

However, my guess is, most people don't think of it that way, they think of it as a production with parameters. In which case, these phrases are odd: you look at the production and it clearly has a [Return] parameter (the [Return] parameter is present), so how can it be a question of "if"?

So I think we should eliminate the phrasings:

• "if this production has a […] parameter"
• "when the […] parameter is {present,absent}"
• "with the […] parameter present on [symbol]"

That leaves

• "if the […] parameter was not set"

which is okay, but 5.1.5 Grammar Notation should clarify that (roughly speaking) "set" = "+" and "not set" = "~".

[gibson042]

Related: #2236