analyzer: int2double doesn't work in const contexts

[MichaelRFairhurst]

This was thought to be #33441, but it turns out its its own issue:

const double x = 1; // inferred as 1.0
class C {
  const C() : assert(x is double); // false
}

The cause for this is actually very simple. The visitor that evaluates an AST node for const evaluation, does not look at the node's staticType at all, and simply creates an integer. This made sense when integer expressions were always integers.

It's not a bigger issue, like inference not having been run, as we thought behind #33441. It's really easy.

We have @failingTests for this in analyzer already.

[bwilkerson]

Partially fixed by https://dart-review.googlesource.com/c/sdk/+/87607, but still failing some cases.

[MichaelRFairhurst]

I just ran into something really weird

This now passes:

const C(double x) : assert(x is double);

where it didn't before.

But this still fails:

const double x = 0;
const C() : assert(x is double);

[bwilkerson]

The information needed by the first example is completely local. The information for the second isn't, and hence depends (IIRC) on having built a dependency graph so that x is evaluated before the initializer. I wonder whether the graph might not be getting built correctly for asserts in initializer lists.

[lrhn]

In either case is checks are not allowed in const contexts (yet), and th eexpression of a const constructor assert must be a potentially constant expression.
So, this should not compile anywhere.

[MichaelRFairhurst]

@lrhn there are other ways to reproduce the problem:

const double x = 0;
const C() : assert("$x" == "0.0");

However, these are just symptoms of the real problem, which is that x was given the wrong type.

Not only does it make it easier and more reliable to test this by turning on the const updates, it also makes it more important to have fixed before the new const behavior is released. So its all related.

[stereotype441]

@MichaelRFairhurst can we mark this as fixed now?

[MichaelRFairhurst]

Yes, thanks for the reminder!