Kernel should have an AssertInitializer node

[johnniwinther]

Kernel should have an AssertInitializer node. The current encoding misuses the LocalInitializer and makes the feature unnecessarily convoluted.

[peter-ahe-google]

I disagree. Assert should be an expression.

[johnniwinther]

So do you want an ExpressionInitializer as well or do you prefer to hide the assert in an LocalInitializer of an unused local of a weird valid (a value of type void is presume) ?.

[rakudrama]

We need to omit the assert initializer when compile options dictate, so need to clearly match the entire thing, embedded side-effects and all.

We would like to avoid having to pattern-match inside some other initializer to attempt to identify the assert initializer. Perhaps an AssertInitializer contains an AssertExpression.

Whatever we do, we need something properly defined and described in kernel/lib/ast.dart in order to work on #30038 without having to go back for re-work as ideas change.

[peter-ahe-google]

I'd use LocalInitializer. That's more flexible.

[rakudrama]

@kmillikin As a first step, can we define in kernel/lib/ast.dart how an assert initializer will look?

Then the parser(s) can generate that tree, and the compilers can generate code for it.

The current form where dart2js sees a LocalInitializer containing a closure application is not suitable since it leaves residual code when assertions are not enabled.

[kmillikin]

As a first step:

AssertInitializer is an initializer that contains an AssertStatement. The representation is here: https://dart-review.googlesource.com/c/sdk/+/14760

Do you have any concerns with it?

[johnniwinther]

It clearly marks the initializer so I'm ok with it.