Need help implementing Term for all std types

[fitzgen]

See a mostly complete list here:

scrapmetal/src/term_impls.rs

Lines 121 to 418 in b774152

	// TODO
	//
	// Below are all the stable `std` types that implement `Debug`, which I figure
	// is either all the stable `std` types, or pretty close to them. We need to
	// implement `Term` for all of these :)
	//
	// enum std::borrow::Cow
	// enum std::cmp::Ordering
	// enum std::collections::Bound
	// enum std::collections::btree_map::Entry
	// enum std::env::VarError
	// enum std::io::CharsError
	// enum std::io::ErrorKind
	// enum std::io::SeekFrom
	// enum std::net::IpAddr
	// enum std::net::Ipv6MulticastScope
	// enum std::net::Shutdown
	// enum std::net::SocketAddr
	// enum std::num::FpCategory
	// enum std::option::Option
	// enum std::os::raw::c_void
	// enum std::path::Component
	// enum std::path::Prefix
	// enum std::result::Result
	// enum std::str::pattern::SearchStep
	// enum std::string::ParseError
	// enum std::sync::TryLockError
	// enum std::sync::atomic::Ordering
	// enum std::sync::mpsc::RecvTimeoutError
	// enum std::sync::mpsc::TryRecvError
	// enum std::sync::mpsc::TrySendError
	// enum std::thread::LocalKeyState
	// struct std::any::TypeId
	// struct std::ascii::EscapeDefault
	// struct std::boxed::Box
	// struct std::cell::BorrowError
	// struct std::cell::BorrowMutError
	// struct std::cell::Cell
	// struct std::cell::Ref
	// struct std::cell::RefCell
	// struct std::cell::RefMut
	// struct std::cell::UnsafeCell
	// struct std::char::CharTryFromError
	// struct std::char::DecodeUtf16Error
	// struct std::char::DecodeUtf8
	// struct std::char::EscapeDebug
	// struct std::char::EscapeDefault
	// struct std::char::EscapeUnicode
	// struct std::cmp::Reverse
	// struct std::collections::HashMap
	// struct std::collections::HashSet
	// struct std::collections::binary_heap::BinaryHeap
	// struct std::collections::binary_heap::BinaryHeapPlace
	// struct std::collections::binary_heap::Drain
	// struct std::collections::binary_heap::IntoIter
	// struct std::collections::binary_heap::Iter
	// struct std::collections::binary_heap::PeekMut
	// struct std::collections::btree_map::BTreeMap
	// struct std::collections::btree_map::IntoIter
	// struct std::collections::btree_map::Iter
	// struct std::collections::btree_map::IterMut
	// struct std::collections::btree_map::Keys
	// struct std::collections::btree_map::OccupiedEntry
	// struct std::collections::btree_map::Range
	// struct std::collections::btree_map::RangeMut
	// struct std::collections::btree_map::VacantEntry
	// struct std::collections::btree_map::Values
	// struct std::collections::btree_map::ValuesMut
	// struct std::collections::btree_set::BTreeSet
	// struct std::collections::btree_set::Difference
	// struct std::collections::btree_set::Intersection
	// struct std::collections::btree_set::IntoIter
	// struct std::collections::btree_set::Iter
	// struct std::collections::btree_set::Range
	// struct std::collections::btree_set::SymmetricDifference
	// struct std::collections::btree_set::Union
	// struct std::collections::hash_map::DefaultHasher
	// struct std::collections::hash_map::Drain
	// struct std::collections::hash_map::IterMut
	// struct std::collections::hash_map::RandomState
	// struct std::collections::hash_map::ValuesMut
	// struct std::collections::hash_set::Difference
	// struct std::collections::hash_set::Intersection
	// struct std::collections::hash_set::SymmetricDifference
	// struct std::collections::hash_set::Union
	// struct std::collections::linked_list::BackPlace
	// struct std::collections::linked_list::FrontPlace
	// struct std::collections::linked_list::IntoIter
	// struct std::collections::linked_list::Iter
	// struct std::collections::linked_list::IterMut
	// struct std::collections::linked_list::LinkedList
	// struct std::collections::vec_deque::Drain
	// struct std::collections::vec_deque::IntoIter
	// struct std::collections::vec_deque::Iter
	// struct std::collections::vec_deque::IterMut
	// struct std::collections::vec_deque::PlaceBack
	// struct std::collections::vec_deque::PlaceFront
	// struct std::collections::vec_deque::VecDeque
	// struct std::env::Args
	// struct std::env::ArgsOs
	// struct std::env::JoinPathsError
	// struct std::env::SplitPaths
	// struct std::env::Vars
	// struct std::env::VarsOs
	// struct std::ffi::CStr
	// struct std::ffi::CString
	// struct std::ffi::FromBytesWithNulError
	// struct std::ffi::IntoStringError
	// struct std::ffi::NulError
	// struct std::ffi::OsStr
	// struct std::ffi::OsString
	// struct std::fmt::Arguments
	// struct std::fmt::Error
	// struct std::fs::DirBuilder
	// struct std::fs::DirEntry
	// struct std::fs::File
	// struct std::fs::FileType
	// struct std::fs::Metadata
	// struct std::fs::OpenOptions
	// struct std::fs::Permissions
	// struct std::fs::ReadDir
	// struct std::hash::BuildHasherDefault
	// struct std::hash::SipHasher
	// struct std::hash::SipHasher13
	// struct std::hash::SipHasher24
	// struct std::io::BufReader
	// struct std::io::Empty
	// struct std::io::Error
	// struct std::io::Repeat
	// struct std::io::Sink
	// struct std::io::Stderr
	// struct std::io::StderrLock
	// struct std::io::Stdin
	// struct std::io::StdinLock
	// struct std::io::Stdout
	// struct std::io::StdoutLock
	// struct std::iter::Chain
	// struct std::iter::Cloned
	// struct std::iter::Cycle
	// struct std::iter::DeprecatedStepBy
	// struct std::iter::Empty
	// struct std::iter::Enumerate
	// struct std::iter::Filter
	// struct std::iter::FilterMap
	// struct std::iter::FlatMap
	// struct std::iter::Fuse
	// struct std::iter::Inspect
	// struct std::iter::Map
	// struct std::iter::Once
	// struct std::iter::Peekable
	// struct std::iter::Repeat
	// struct std::iter::Rev
	// struct std::iter::Scan
	// struct std::iter::Skip
	// struct std::iter::SkipWhile
	// struct std::iter::StepBy
	// struct std::iter::Take
	// struct std::iter::TakeWhile
	// struct std::iter::Zip
	// struct std::marker::PhantomData
	// struct std::mem::Discriminant
	// struct std::net::AddrParseError
	// struct std::net::Incoming
	// struct std::net::Ipv4Addr
	// struct std::net::Ipv6Addr
	// struct std::net::LookupHost
	// struct std::net::SocketAddrV4
	// struct std::net::SocketAddrV6
	// struct std::net::TcpListener
	// struct std::net::TcpStream
	// struct std::net::UdpSocket
	// struct std::num::ParseFloatError
	// struct std::num::ParseIntError
	// struct std::num::TryFromIntError
	// struct std::num::Wrapping
	// struct std::ops::Range
	// struct std::ops::RangeFrom
	// struct std::ops::RangeFull
	// struct std::ops::RangeInclusive
	// struct std::ops::RangeTo
	// struct std::ops::RangeToInclusive
	// struct std::option::IntoIter
	// struct std::option::Iter
	// struct std::option::IterMut
	// struct std::os::unix::net::Incoming
	// struct std::os::unix::net::SocketAddr
	// struct std::os::unix::net::UnixDatagram
	// struct std::os::unix::net::UnixListener
	// struct std::os::unix::net::UnixStream
	// struct std::panic::Location
	// struct std::panic::PanicInfo
	// struct std::path::Components
	// struct std::path::Display
	// struct std::path::Iter
	// struct std::path::Path
	// struct std::path::PathBuf
	// struct std::path::PrefixComponent
	// struct std::path::StripPrefixError
	// struct std::process::Child
	// struct std::process::ChildStderr
	// struct std::process::ChildStdin
	// struct std::process::ChildStdout
	// struct std::process::Command
	// struct std::process::ExitStatus
	// struct std::process::Output
	// struct std::process::Stdio
	// struct std::rc::Rc
	// struct std::rc::Weak
	// struct std::result::IntoIter
	// struct std::result::Iter
	// struct std::result::IterMut
	// struct std::slice::Chunks
	// struct std::slice::ChunksMut
	// struct std::slice::Iter
	// struct std::slice::IterMut
	// struct std::slice::RSplit
	// struct std::slice::RSplitMut
	// struct std::slice::RSplitN
	// struct std::slice::RSplitNMut
	// struct std::slice::Split
	// struct std::slice::SplitMut
	// struct std::slice::SplitN
	// struct std::slice::SplitNMut
	// struct std::slice::Windows
	// struct std::str::Bytes
	// struct std::str::CharIndices
	// struct std::str::Chars
	// struct std::str::EncodeUtf16
	// struct std::str::Lines
	// struct std::str::LinesAny
	// struct std::str::MatchIndices
	// struct std::str::Matches
	// struct std::str::ParseBoolError
	// struct std::str::RMatchIndices
	// struct std::str::RMatches
	// struct std::str::RSplit
	// struct std::str::RSplitN
	// struct std::str::RSplitTerminator
	// struct std::str::Split
	// struct std::str::SplitN
	// struct std::str::SplitTerminator
	// struct std::str::Utf8Error
	// struct std::str::pattern::CharPredicateSearcher
	// struct std::str::pattern::CharSearcher
	// struct std::str::pattern::CharSliceSearcher
	// struct std::str::pattern::StrSearcher
	// struct std::string::Drain
	// struct std::string::FromUtf16Error
	// struct std::string::FromUtf8Error
	// struct std::string::Splice
	// struct std::string::String
	// struct std::sync::Arc
	// struct std::sync::Barrier
	// struct std::sync::BarrierWaitResult
	// struct std::sync::Condvar
	// struct std::sync::Once
	// struct std::sync::OnceState
	// struct std::sync::PoisonError
	// struct std::sync::WaitTimeoutResult
	// struct std::sync::Weak
	// struct std::sync::atomic::AtomicBool
	// struct std::sync::atomic::AtomicI16
	// struct std::sync::atomic::AtomicI32
	// struct std::sync::atomic::AtomicI64
	// struct std::sync::atomic::AtomicI8
	// struct std::sync::atomic::AtomicIsize
	// struct std::sync::atomic::AtomicPtr
	// struct std::sync::atomic::AtomicU16
	// struct std::sync::atomic::AtomicU32
	// struct std::sync::atomic::AtomicU64
	// struct std::sync::atomic::AtomicU8
	// struct std::sync::atomic::AtomicUsize
	// struct std::sync::mpsc::Receiver
	// struct std::sync::mpsc::RecvError
	// struct std::sync::mpsc::Select
	// struct std::sync::mpsc::SendError
	// struct std::sync::mpsc::Sender
	// struct std::sync::mpsc::SyncSender
	// struct std::thread::Builder
	// struct std::thread::JoinHandle
	// struct std::thread::LocalKey
	// struct std::thread::Thread
	// struct std::thread::ThreadId
	// struct std::time::Duration
	// struct std::time::Instant
	// struct std::time::SystemTime
	// struct std::time::SystemTimeError
	// struct std::vec::Drain
	// struct std::vec::IntoIter
	// struct std::vec::PlaceBack
	// struct std::vec::Splice
	// struct std::vec::Vec
	// trait std::any::Any
	// trait std::fmt::Debug
	// trait std::io::Write
	// trait std::marker::Send
	// trait std::marker::Sized
	// union std::mem::ManuallyDrop

Lots of work to be done here, easy to parallelize across multiple PRs from multiple folks :)

[JoeyEremondi]

I'd definitely be interested in helping one of these, I'm currently using your library to implement substitutions over terms for some programming-languages work I'm doing. I'm also looking to get in some PRs for Hacktoberfest.

What would you think of something like this:

impl<C,T,I> Term for C where
  C : IntoIter<Item = T, IntoIter =I> + FromIterator<T>,
  T : Term,
  I : Iterator<Item = T> {...
  //Bodies implemented using iter functions
} 

This would knock a bunch of collections off the list.

[fitzgen]

Hi @JoeyEremondi !

My concern is that we may want to special case Term for some collection and that this blanket implementation would preclude that. We could definitely write a macro_rules for this, and then we would just have a tiny bit of copy-pasting (or we could go even deeper to avoid even this).

Something like:

macro_rules! impl_term_for_collection {
    (
        $(
            $collection:ty ;
        )*
    ) => {
        $(
            impl Term for $collection {
                // ...
            }
        )*
    }
}

// And then use it...
impl_term_for_collection! {
    Vec<T>;
    HashMap<K, V>
}

(The macro would need to handle type parameters and their bounds too, which my sketch doesn't do.)

What do you think of this approach?