[Feature request, Inlay Hints] Option for showing type size and padding in an inlay hint

[Alonely0]

Description

The purpose of this feature is to add a new inlay hint at the end of each type with its size and padding. When a type (a struct, an enum, etc) is bigger than a pointer, it is more efficient to pass it by reference where possible to avoid large copies. In rust this needs special attention since it is not very stack-efficient. This feature is trivial to implement, as the compiler already provides all the information required. In enums and structs, this could be added to every variant/field. The feature could also be extended to function arguments in function declarations.

Current solution

Manually calculating it or using -Zprint-type-sizes. Both are very cumbersome, the latter specially in files with lots of types, like massive lib.rss.

Possible settings

• Enable/Disable, obviously.
• Unit: bytes or bits. I would default to bytes, but personally I prefer bits.
• Size threshold: Only show for types bigger than a given size. A good default would be to show for size > sizeof(usize).
• Remove padding and size as separate labels and show the whole size in a single number. I actually think this should be the default.

[jonas-schievink]

Duplicate of #4091