[Timon3]

I understand that you can define a restricted grammar that will stay parseable, as the embedded language would have to adapt to those rules. But that doesn't solve the question, as Typescript already has existing rules which overlap with JS syntax. The GP comment was:

> For example, the `as` keyword for casts has existed for a long time, and type stripping could strip everything after the `as` keyword with a minimal grammar.

My question is: what would a grammar like this look like in this specific case?

[bazoom42]

How about:

    TypeAssertion ::= Expression “as” TypeStuff
    TypeStuff ::= TypeStuffItem+
    TypeStuffItem ::= Block | any     token except , ; ) } ]
    Block ::= ParenBlock | CurlyBracketsBlock | SquareBracketsBlock | AngleBracketsBlock
    ParenBlock ::= ( ParenBlockItem* )
    ParenBlockItem ::= Block | any token except ( )

etc.