swift

f10ca1c9 - [sil] Add convenience APIs to SILBoxType for generics safe field access

[sil] Add convenience APIs to SILBoxType for generics safe field access Before this patch it was easy to try to work with the types in a SILBoxType by accessing the layout of the SILBoxType... especially if one was working with mutability since there wasn't any comment/APIs on SILBoxType that pointed one at the appropriate API on SILType. To make this easier to use and self document, I added some new helper APIs onto SILBoxType that: 1. Let one grab the fields without touching the layout. The layout is an internal detail of SILBoxType that shouldn't be touched unless it is necessary. 2. Get a specific properly specialized SILType of a SILType for a given SILFunction. 3. Access the number of SILFIelds and also whether or not a specific SILField is mutable. 4. Yields a transform range that transform the SILFields in the SILBoxType into a range of properly specialized SILTypes. This should prevent these sorts of mistakes from happening in the future.