sem: remove float analysis from sem/guards

[Clyybber]

Summary

Remove float analysis from sem/guards since it's currently unsound.

Details

sem/guards is only used for static bounds checking (
--staticBoundChecks ), not nil checking, warning for checked field
accesses ( --warning:ProveField ) and field accesses of fields
annotated with {.guard: ...} .
Since object variants with a float discriminator are invalid and
bound checks only concern integers, only conversions to float range
types would be affected under --staticBoundChecks .

It's not clear whether the analysis method here can work with floats
without special treatment in a lot of cases, due to float equality
lacking the subsitution and reflexivity property or the comparison
relations not being total.

[saem]

One minor typo.

So now we're using very simple symbol equality during tree equivalence checks in guards. Are we relying on guards outside of things like checked arithmetic which might be impacted?

[saem]

For the summary, the impact here would be not removing floating point operation checks in certain cases?

[Clyybber]

So now we're using very simple symbol equality during tree equivalence checks in guards. Are we relying on guards outside of things like checked arithmetic which might be impacted?
For the summary, the impact here would be not removing floating point operation checks in certain cases?

sem/guards is only used for static bounds checking (--staticBoundChecks), not nil checking and warning for checked field accesses (--warning:ProveField) and field accesses of fields annotated with {.guard: ...}, so it isn't actually used for optimization/removing checks.
Since object variants with a float kind are invalid and bound checks concern integers, only float range checks would be affected under --staticBoundChecks.
This PR doesn't actually change to use bit equality for floats (leaving that for #1238), but it does make it so that it shouldn't matter. (Although there are AFAICT other soundness issues in sem/guards so there might be cases where it does still matter)

[saem]

I moved the extra info into details, guards stuff seems so broken.

[saem]

/merge

[github-actions]

Merge requested by: @saem

Contents after the first section break of the PR description has been removed and preserved below:

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Notes for Reviewers

• Merging this before Don't use float equality for AST comparisons #1238 would allow the changes in that PR to be a bit cleaner

[saem]

/merge