Crate fn_meta

Returns metadata about a function at runtime.

Currently this includes the TypeIds of function parameters.

This includes a FnMetadata struct and FnMetadataExt trait. FnMetadataExt adds the .metadata() function on functions and closures to return a FnMetadata, whose implementation returns function metadata at runtime.

Usage

Add the following to Cargo.toml

fn_meta = "0.8.0"

# or
fn_meta = { version = "0.8.0", features = ["fn_meta_ext"] }

Code:

use fn_meta::{FnMetaDyn, FnMetadataExt};

fn f1(_: &S0, _: &mut S1, _: &S2) -> () {}

let fn_metadata = f1.metadata();

assert_eq!(
    [TypeId::of::<S0>(), TypeId::of::<S2>()],
    fn_metadata.borrows().as_slice()
);
assert_eq!([TypeId::of::<S1>()], fn_metadata.borrow_muts().as_slice());

Features

"fn_meta_ext":

Enables the FnMeta and FnMetaExt traits. FnMetaExt adds the .meta() function on functions and closures to return a Box<dyn FnMeta>, which is the dynamic dispatch analog to FnMetadata.

"high_arg_count":

Raises the number of arguments that FnMetaExt and FnMetadataExt are implemented for from 6 to 8.

This is feature gated because compilation time increasing significantly with higher numbers of arguments – as much as from 1.5 seconds for 6 arguments to 8 seconds for 8 arguments.

Structs

FnMetadata

Metadata about a function

Traits

FnMeta

Any type that tracks metadata about a function.

FnMetaDyn

Any type that tracks metadata about a function.

FnMetaExt

Extension to return Box<dyn FnMetaDyn> for a function.

FnMetadataExt

Extension to return FnMetadata for a function.

Type Aliases

TypeIds

Array of TypeIds.