12.2.1 Expression classifications|General

[RexJaeschke]

In the list accompanying “An expression is classified as one of the following:”, v5std has

• A type. An expression with this classification can only appear as the left-hand side of a member_access (§12.7.5). In any other context, an expression classified as a type causes a compile-time error.”

while v6spec has

• A type. An expression with this classification can only appear as the left hand side of a member_access (Member access), or as an operand for the as operator (The as operator), the is operator (The is operator), or the typeof operator (The typeof operator). In any other context, an expression classified as a type causes a compile-time error.

What to do?

[jskeet]

I could be missing something here, but I think the standard is right. The is/as/typeof operators are defined using "type" directly rather than using "expression", so we don't need "an expression which is classified as a type" to be valid for their operands.

Proposal: stick with v5, but please validate carefully!

[gafter]

We should add that it can be the operand of a nameof operation too.

[jskeet]

Resolution:

• Leave v5 as it is
• For v6 we probably want to add nameof, but not the rest of them. (Reasoning: if the operand of nameof is just "expression" in the grammar, it needs to be included here - whereas the others are just "type" in the grammar.)

[RexJaeschke]

2020-06-25 Teleconference:

The v5 spec is correct; no change needed; review for v6.

[jskeet]

For nameof, this basically depends on the resolution of #10 - once we've firmed up the text there, we can work out whether we need a change here.

[Nigel-Ecma]

By the alternative PR #250, replacing #10, the operand of name is a named_entity and not an expression, so it looks like there is no need for a change here if #250 is accepted.

[Nigel-Ecma]

PR #250 has been accepted (pending @jskeet removing a tuple from an example and creating a PR for v7 to put it back) so there is nothing left to do here. Will close and remove discuss tag.