v7.x Q re throw expressions

[RexJaeschke]

In Draft PR #65, I've added almost all the edits to support the addition of throw expressions. Here's what's missing:

1. I've added the new section "The throw expression operator" to the the Expressions clause, but it needs to be "plugged into" the grammar, so it has precedence. (Also, for now, I've put this new section under primary expressions, but that might not be correct.)

[KalleOlaviNiemitalo]

The interaction of #65 and #213 does not allow a throw expression as an operand of a ref conditional expression:

ref int F(bool b, ref int i) => ref b ? ref i : ref throw null;

because "Both expressions shall be variables having the same type" and "A throw_expression has no type." I suppose this restriction is by design.

[BillWagner]

See PR #65

Note that instead of "primary", the throw expression precedence should be the same as the null coalescing question.

[jskeet]

@KalleOlaviNiemitalo: It's not clear to me from your comment whether this is how the compiler actually behaves, or whether this is an area you think this needs a spec change. I want to close this issue when #65 is merged, so please could you file a new issue if you believe we need to do more work on this?

[KalleOlaviNiemitalo]

@jskeet the standard text matches compiler behaviour and I think the behaviour is reasonable so no action is required.

[BillWagner]

@jskeet PR #65 has been merged. I think that the questions raised here have been answered.

Can we close this as fixed in #65

[jskeet]

Yes, I think so.