Kavon Farvardin 4964a66277 silgen: inherit eval scope for OpenExistentialExpr ...

We were not able to use an existential as the base
of an access that strictly borrows the existential,
because SILGen's RValue emission would establish
a fresh evaluation scope just for the existential's
opening, and then copy the opened value out.

This is problematic for noncopyable existentials.

So this patch moves & adds FormalEvaluationScope's
around so they're broad enough to enable a
borrow of an existential. The idea behind this
refactoring is to establish top-level
FormalEvaluationScopes when initially creating
RValue's for Expr's in SILGen. Any more-tightly
scoped operations will already establish their own
nested scope, so this is mostly adding safe-guards.

I've limited the existentials fix to noncopyables
for now.

part of rdar://159079818

2025-08-29 13:30:42 -07:00

63 KiB

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