Do you think God stays in heaven because he too lives in fear of what he's created? ~ Spy Kids 2

inspect

An experiment collecting information about types to be queried at run-time.

This can work for types containing references, and even those with non-static lifetime parameters; In the latter case the TypeId collected corresponds to the 'static version of the given type.

For now it is implemented for common primitive types, including numerics, pointers, references, slices, tuples (up to 8-tuples) and some types from std like Vec, PhantomData, Option, Result, &c.

TypeInfo contains the type_name, size, align, and TypeId of a types. For structs the names, offsets, and types of fields are available. For types like Vec<T>, Option<T>, [T] the type info of the generic item is available.

use ::inspect::TypeInfo;

#[derive(TypeInfo)]
struct MyStruct<T>(Option<Child<T>>);
#[derive(TypeInfo)]
struct Child<T>(usize, Option<Box<str>>, Box<[T]>);

let type_info = TypeInfo::of::<MyStruct<u32>>();
assert_eq!(
  format!("size: {:?}, align: {:?}", type_info.size(), type_info.align()),
  "size: Some(40), align: Some(8)"
);
assert_eq!(
  format!("{type_info:#}"),
"MyStruct<u32>(
    Option<Child<u32>(
        usize,
        Option<Box<str>>,
        Box<[u32]>,
    )>,
)",
  );

let type_info = TypeInfo::of::<[&'static Vec<u8>]>();
assert_eq!(
  format!("size: {:?}, align: {:?}", type_info.size(), type_info.align()),
  "size: None, align: None",
);
assert_eq!(
  format!("{type_info:#}"),
  "[&Vec<u8>]",
);

use ::core::marker::PhantomData;
let type_info = TypeInfo::of::<PhantomData<Vec<usize>>>();
assert_eq!(
  format!("size: {:?}, align: {:?}", type_info.size(), type_info.align()),
  "size: Some(0), align: Some(1)",
);
assert_eq!(
  format!("{type_info:#}"),
  "PhantomData<Vec<usize>>",
);