With the advert of the numeric IntPtr feature, nint is an alias for System.IntPtr just like int is an alias for System.Int32. We should add analyzers and fixers to make it clear to user code, especially to those who think that IntPtr represents an opaque pointer-sized value. Here's what the analyzers should do:

• IDE0049 should be updated to suggest converting IntPtr to nint and UIntPtr to nuint.
• U?IntPtr.Zero ➡ 0 or (nu?int)0 if it would introduce ambiguity
• new U?IntPtr(x) ➡ x or (nu?int)x if it would introduce ambiguity, or unchecked((nu?int)x) if we are in a checked context.
• x.ToU?Int32() ➡ checked((u?int)x) or (u?int)x if we are in a checked context
• x.ToU?Int64() ➡ unchecked((u?long)x) or (u?long)x if we are in an unchecked context
• x.ToPointer() ➡ (void*) x
• Convert explicit casts between U?IntPtr and u?int or u?long, to nu?int, while taking the overflow checking context into account (too many to list).

These analyzers and fixers should be triggered only if the underlying runtime supports numeric IntPtr. Some of them might be legal even without it but it's not necessary to make it more complicated.