[CSSimplify] Avoid simplifying dependent members until pack expansion… #84729
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…s in the based are bound
Dependent members cannot be simplified if base type contains unresolved
pack expansion type variables because they don't give enough information
to substitution logic to form a correct type. For example:
```
protocol P { associatedtype V }
struct S<each T> : P { typealias V = (repeat (each T)?) }
```
If pack expansion is represented as `$T1` and its pattern is `$T2`, a
reference to `V` would get a type `S<Pack{$T}>.V` and simplified version
would be `Optional<Pack{$T1}>` instead of `Pack{repeat Optional<$T2>}`
because `$T1` is treated as a substitution for `each T` until bound.
Resolves: rdar://161207705
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…s in the based are bound
Dependent members cannot be simplified if base type contains unresolved pack expansion type variables because they don't give enough information to substitution logic to form a correct type. For example:
If pack expansion is represented as
$T1and its pattern is$T2, a reference toVwould get a typeS<Pack{$T}>.Vand simplified version would beOptional<Pack{$T1}>instead ofPack{repeat Optional<$T2>}because$T1is treated as a substitution foreach Tuntil bound.Resolves: rdar://161207705