From 10960f679c7b7d0558d6700857429149b1649000 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Fri, 3 May 2024 22:16:32 +0200
Subject: [PATCH 01/25] const LEN -> type LEN

---
 core/Cargo.toml   |  1 +
 core/src/hlist.rs | 43 +++++++++++++++++++++++++++++--------------
 2 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/core/Cargo.toml b/core/Cargo.toml
index afc58b1b..08005d5c 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -18,6 +18,7 @@ std = []
 
 [dependencies]
 serde = { version = "^1.0", optional = true, features = [ "derive" ] }
+typenum = { version = "1.17.0", default-features = false }
 
 [dev-dependencies.frunk_derives]
 path = "../derives"
diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 2fdee009..3d9cb92f 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -59,6 +59,8 @@ use crate::indices::{Here, Suffixed, There};
 use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
+use typenum::bit::B1;
+use typenum::{Unsigned, UInt, UTerm};
 
 use std::ops::Add;
 
@@ -67,8 +69,7 @@ use std::ops::Add;
 /// An HList is a heterogeneous list, one that is statically typed at compile time. In simple terms,
 /// it is just an arbitrarily-nested Tuple2.
 pub trait HList: Sized {
-    /// Returns the length of a given HList type without making use of any references, or
-    /// in fact, any values at all.
+    /// The type-level encapsulation of the lists length, using `typenum` under the hood.
     ///
     /// # Examples
     /// ```
@@ -76,10 +77,15 @@ pub trait HList: Sized {
     /// use frunk::prelude::*;
     /// use frunk_core::HList;
     ///
-    /// assert_eq!(<HList![i32, bool, f32]>::LEN, 3);
+    /// fn foo<T: typenum::IsEqual<U3>>() {}
+    /// let _ = foo::<HList![(), i32, bool]::Len>();
+    /// let byte: u32 = HList![bool, &str, String]::Len::UINT32;
+    ///
+    ///
+    /// assert_eq!(<HList![i32, bool, f32]>::Len, 3);
     /// # }
     /// ```
-    const LEN: usize;
+    type Len: Unsigned;
 
     /// Returns the length of a given HList
     ///
@@ -93,9 +99,10 @@ pub trait HList: Sized {
     /// assert_eq!(h.len(), 2);
     /// # }
     /// ```
+    #[deprecated(since = "0.5.0", note = "Please use Len::USIZE instead")]
     #[inline]
     fn len(&self) -> usize {
-        Self::LEN
+        <Self::Len as Unsigned>::USIZE
     }
 
     /// Returns whether a given HList is empty
@@ -112,7 +119,7 @@ pub trait HList: Sized {
     /// ```
     #[inline]
     fn is_empty(&self) -> bool {
-        Self::LEN == 0
+        <Self::Len as Unsigned>::USIZE == 0
     }
 
     /// Returns the length of a given HList type without making use of any references, or
@@ -127,7 +134,7 @@ pub trait HList: Sized {
     /// assert_eq!(<HList![i32, bool, f32]>::static_len(), 3);
     /// # }
     /// ```
-    #[deprecated(since = "0.1.31", note = "Please use LEN instead")]
+    #[deprecated(since = "0.1.31", note = "Please use Len::USIZE instead")]
     fn static_len() -> usize;
 
     /// Prepends an item to the current HList
@@ -168,9 +175,9 @@ pub trait HList: Sized {
 pub struct HNil;
 
 impl HList for HNil {
-    const LEN: usize = 0;
+    type Len = typenum::U0;
     fn static_len() -> usize {
-        Self::LEN
+        <Self::Len as Unsigned>::USIZE
     }
 }
 
@@ -183,10 +190,14 @@ pub struct HCons<H, T> {
     pub tail: T,
 }
 
-impl<H, T: HList> HList for HCons<H, T> {
-    const LEN: usize = 1 + <T as HList>::LEN;
+impl<H, T: HList> HList for HCons<H, T> 
+where 
+    <T as HList>::Len: Add<typenum::U1>,
+    <<T as HList>::Len as Add<typenum::U1>>::Output: Unsigned
+{
+    type Len = <<T as HList>::Len as Add<typenum::U1>>::Output;
     fn static_len() -> usize {
-        Self::LEN
+        <Self::Len as Unsigned>::USIZE
     }
 }
 
@@ -1123,6 +1134,8 @@ impl HZippable<HNil> for HNil {
 impl<H1, T1, H2, T2> HZippable<HCons<H2, T2>> for HCons<H1, T1>
 where
     T1: HZippable<T2>,
+    <<T1 as HZippable<T2>>::Zipped as HList>::Len: Add<UInt<UTerm, B1>>,
+    <<<T1 as HZippable<T2>>::Zipped as HList>::Len as Add<UInt<UTerm, B1>>>::Output: Unsigned,
 {
     type Zipped = HCons<(H1, H2), T1::Zipped>;
     fn zip(self, other: HCons<H2, T2>) -> Self::Zipped {
@@ -1438,11 +1451,13 @@ where
 impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
 where
     Tail: Into<Vec<H>> + HList,
+    <Tail as HList>::Len: Add<UInt<UTerm, B1>>,
+    <<Tail as HList>::Len as Add<UInt<UTerm, B1>>>::Output: Unsigned,
 {
     fn into(self) -> Vec<H> {
         let h = self.head;
         let t = self.tail;
-        let mut v = Vec::with_capacity(<Self as HList>::LEN);
+        let mut v = Vec::with_capacity(<<Self as HList>::Len as Unsigned>::USIZE);
         v.push(h);
         let mut t_vec: Vec<H> = t.into();
         v.append(&mut t_vec);
@@ -1905,7 +1920,7 @@ mod tests {
 
     #[test]
     fn test_len_const() {
-        assert_eq!(<HList![usize, &str, f32] as HList>::LEN, 3);
+        assert_eq!(<HList![usize, &str, f32] as HList>::Len::USIZE, 3);
     }
 
     #[test]

From 56781742d190dbc6bb91f76c714f690704292e0d Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Fri, 3 May 2024 22:17:04 +0200
Subject: [PATCH 02/25] deprecate len() for Self::Len + version-bump

---
 Cargo.toml                    | 4 ++--
 core/Cargo.toml               | 4 ++--
 laws/Cargo.toml               | 2 +-
 proc-macro-helpers/Cargo.toml | 2 +-
 proc-macros/Cargo.toml        | 2 +-
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index dab64399..4cf4331b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "frunk"
 edition = "2021"
-version = "0.4.2"
+version = "0.5.0"
 authors = ["Lloyd <lloydmeta@gmail.com>"]
 description = "Frunk provides developers with a number of functional programming tools like HList, Coproduct, Generic, LabelledGeneric, Validated, Monoid, Semigroup and friends."
 license = "MIT"
@@ -19,7 +19,7 @@ time = "0.3"
 [dependencies.frunk_core]
 path = "core"
 default-features = false
-version = "0.4.2"
+version = "0.5.0"
 
 [dependencies.frunk_proc_macros]
 path = "proc-macros"
diff --git a/core/Cargo.toml b/core/Cargo.toml
index 08005d5c..be695e6a 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "frunk_core"
 edition = "2021"
-version = "0.4.2"
+version = "0.5.0"
 authors = ["Lloyd <lloydmeta@gmail.com>"]
 description = "Frunk core provides developers with HList, Coproduct, LabelledGeneric and Generic"
 license = "MIT"
@@ -28,7 +28,7 @@ version = "0.4.1"
 [dev-dependencies.frunk]
 path = ".."
 default-features = false
-version = "0.4.2"
+version = "0.5.0"
 
 [dev-dependencies.frunk_proc_macros]
 path = "../proc-macros"
diff --git a/laws/Cargo.toml b/laws/Cargo.toml
index 576948b6..42280264 100644
--- a/laws/Cargo.toml
+++ b/laws/Cargo.toml
@@ -15,7 +15,7 @@ travis-ci = { repository = "lloydmeta/frunk" }
 [dependencies.frunk]
 path = ".."
 default-features = false
-version = "0.4.2"
+version = "0.5.0"
 
 [dependencies]
 quickcheck = "1.0.3"
diff --git a/proc-macro-helpers/Cargo.toml b/proc-macro-helpers/Cargo.toml
index a58542f5..67fd7558 100644
--- a/proc-macro-helpers/Cargo.toml
+++ b/proc-macro-helpers/Cargo.toml
@@ -20,4 +20,4 @@ proc-macro2 = "1"
 [dependencies.frunk_core]
 path = "../core"
 default-features = false
-version = "0.4.2"
+version = "0.5.0"
diff --git a/proc-macros/Cargo.toml b/proc-macros/Cargo.toml
index b190ef27..1c2b3070 100644
--- a/proc-macros/Cargo.toml
+++ b/proc-macros/Cargo.toml
@@ -23,7 +23,7 @@ proc-macro = true
 [dependencies.frunk_core]
 path = "../core"
 default-features = false
-version = "0.4.2"
+version = "0.5.0"
 
 [dependencies.frunk_proc_macro_helpers]
 path = "../proc-macro-helpers"

From 001a667f417e7b6c84bbdd15aa91c22296b31f0b Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Fri, 3 May 2024 22:39:31 +0200
Subject: [PATCH 03/25] Correct doc-test.

---
 core/src/hlist.rs | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 3d9cb92f..31a24ac5 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -74,15 +74,18 @@ pub trait HList: Sized {
     /// # Examples
     /// ```
     /// # fn main() {
+    /// use typenum::Unsigned;
     /// use frunk::prelude::*;
     /// use frunk_core::HList;
     ///
-    /// fn foo<T: typenum::IsEqual<U3>>() {}
-    /// let _ = foo::<HList![(), i32, bool]::Len>();
-    /// let byte: u32 = HList![bool, &str, String]::Len::UINT32;
+    /// type LenThree = HList![bool, (), u8];
+    /// fn foo<T: typenum::IsEqual<typenum::U3>>() {}
     ///
+    /// let _ = foo::<<LenThree as HList>::Len>();
+    /// let byte: u8 = <<LenThree as HList>::Len>::U8;
     ///
-    /// assert_eq!(<HList![i32, bool, f32]>::Len, 3);
+    ///
+    /// assert_eq!(<LenThree as HList>::Len::USIZE, 3);
     /// # }
     /// ```
     type Len: Unsigned;

From bdad2d17bfe8898b073c40b58baca27174f76ce1 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Fri, 3 May 2024 22:57:56 +0200
Subject: [PATCH 04/25] add "teaser-trailer" of using typnum internally

---
 core/src/hlist.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 31a24ac5..ed5859fc 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -102,7 +102,7 @@ pub trait HList: Sized {
     /// assert_eq!(h.len(), 2);
     /// # }
     /// ```
-    #[deprecated(since = "0.5.0", note = "Please use Len::USIZE instead")]
+    #[deprecated(since = "0.5.0", note = "Please use <Self as HList>::Len::[USIZE | U8 | U32 | ... ] instead")]
     #[inline]
     fn len(&self) -> usize {
         <Self::Len as Unsigned>::USIZE
@@ -266,6 +266,9 @@ macro_rules! gen_inherent_methods {
             pub fn len(&self) -> usize
             where Self: HList,
             {
+                // this is how it's done at the type-level
+                // <Self as HList>::Len::USIZE
+                #[allow(deprecated)]
                 HList::len(self)
             }
 
@@ -286,6 +289,8 @@ macro_rules! gen_inherent_methods {
             where Self: HList,
             {
                 HList::is_empty(self)
+                // this is how it's done at the type-level
+                // <<<Self as HList>::Len as typenum::IsEqual<typenum::U0>>::Output as typenum::Bit>::BOOL
             }
 
             /// Prepend an item to the current HList

From a024384e5ecd63a9c6ba01f6603d98c9baeb514c Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 09:23:23 +0200
Subject: [PATCH 05/25] cargo fmt

---
 core/src/hlist.rs | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index ed5859fc..af93d9a5 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -60,7 +60,7 @@ use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 use typenum::bit::B1;
-use typenum::{Unsigned, UInt, UTerm};
+use typenum::{UInt, UTerm, Unsigned};
 
 use std::ops::Add;
 
@@ -102,7 +102,10 @@ pub trait HList: Sized {
     /// assert_eq!(h.len(), 2);
     /// # }
     /// ```
-    #[deprecated(since = "0.5.0", note = "Please use <Self as HList>::Len::[USIZE | U8 | U32 | ... ] instead")]
+    #[deprecated(
+        since = "0.5.0",
+        note = "Please use <Self as HList>::Len::[USIZE | U8 | U32 | ... ] instead"
+    )]
     #[inline]
     fn len(&self) -> usize {
         <Self::Len as Unsigned>::USIZE
@@ -193,10 +196,10 @@ pub struct HCons<H, T> {
     pub tail: T,
 }
 
-impl<H, T: HList> HList for HCons<H, T> 
-where 
+impl<H, T: HList> HList for HCons<H, T>
+where
     <T as HList>::Len: Add<typenum::U1>,
-    <<T as HList>::Len as Add<typenum::U1>>::Output: Unsigned
+    <<T as HList>::Len as Add<typenum::U1>>::Output: Unsigned,
 {
     type Len = <<T as HList>::Len as Add<typenum::U1>>::Output;
     fn static_len() -> usize {

From f2ff09c2ee609be1a6c5856d0a5fedb6c6ac274d Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 14:03:40 +0200
Subject: [PATCH 06/25] update length-get support

---
 core/src/hlist.rs | 25 -------------------------
 1 file changed, 25 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index af93d9a5..200951f0 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -102,10 +102,6 @@ pub trait HList: Sized {
     /// assert_eq!(h.len(), 2);
     /// # }
     /// ```
-    #[deprecated(
-        since = "0.5.0",
-        note = "Please use <Self as HList>::Len::[USIZE | U8 | U32 | ... ] instead"
-    )]
     #[inline]
     fn len(&self) -> usize {
         <Self::Len as Unsigned>::USIZE
@@ -128,21 +124,6 @@ pub trait HList: Sized {
         <Self::Len as Unsigned>::USIZE == 0
     }
 
-    /// Returns the length of a given HList type without making use of any references, or
-    /// in fact, any values at all.
-    ///
-    /// # Examples
-    /// ```
-    /// # fn main() {
-    /// use frunk::prelude::*;
-    /// use frunk_core::HList;
-    ///
-    /// assert_eq!(<HList![i32, bool, f32]>::static_len(), 3);
-    /// # }
-    /// ```
-    #[deprecated(since = "0.1.31", note = "Please use Len::USIZE instead")]
-    fn static_len() -> usize;
-
     /// Prepends an item to the current HList
     ///
     /// # Examples
@@ -182,9 +163,6 @@ pub struct HNil;
 
 impl HList for HNil {
     type Len = typenum::U0;
-    fn static_len() -> usize {
-        <Self::Len as Unsigned>::USIZE
-    }
 }
 
 /// Represents the most basic non-empty HList. Its value is held in `head`
@@ -202,9 +180,6 @@ where
     <<T as HList>::Len as Add<typenum::U1>>::Output: Unsigned,
 {
     type Len = <<T as HList>::Len as Add<typenum::U1>>::Output;
-    fn static_len() -> usize {
-        <Self::Len as Unsigned>::USIZE
-    }
 }
 
 impl<H, T> HCons<H, T> {

From 91f4442ac087ee5bbd0fc85b1e42540403d8c8ea Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 14:10:41 +0200
Subject: [PATCH 07/25] retain the const-generic

---
 core/src/hlist.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 200951f0..3fd4896f 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -90,6 +90,8 @@ pub trait HList: Sized {
     /// ```
     type Len: Unsigned;
 
+    const LEN: usize;
+
     /// Returns the length of a given HList
     ///
     /// # Examples
@@ -163,6 +165,8 @@ pub struct HNil;
 
 impl HList for HNil {
     type Len = typenum::U0;
+
+    const LEN: usize = 0;
 }
 
 /// Represents the most basic non-empty HList. Its value is held in `head`
@@ -180,6 +184,8 @@ where
     <<T as HList>::Len as Add<typenum::U1>>::Output: Unsigned,
 {
     type Len = <<T as HList>::Len as Add<typenum::U1>>::Output;
+
+    const LEN: usize = 0;
 }
 
 impl<H, T> HCons<H, T> {

From e0783fcf814dd744ff06fcc14d9aa3427bdb6f21 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 14:27:00 +0200
Subject: [PATCH 08/25] Refine doc-comments.

---
 core/src/hlist.rs | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 3fd4896f..fb68f374 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -62,6 +62,7 @@ use serde::{Deserialize, Serialize};
 use typenum::bit::B1;
 use typenum::{UInt, UTerm, Unsigned};
 
+
 use std::ops::Add;
 
 /// Typeclass for HList-y behaviour
@@ -74,22 +75,35 @@ pub trait HList: Sized {
     /// # Examples
     /// ```
     /// # fn main() {
-    /// use typenum::Unsigned;
+    /// use frunk_core::typenum::Unsigned;
     /// use frunk::prelude::*;
     /// use frunk_core::HList;
     ///
     /// type LenThree = HList![bool, (), u8];
-    /// fn foo<T: typenum::IsEqual<typenum::U3>>() {}
+    /// type LenTwo = HList![bool, ()];
+    ///
+    /// // Attach a constraint that ensures constraints are met at type-check time
+    /// fn type_len_constraint<T: typenum::IsLessThan<typenum::U3>>() {}
+    ///
     ///
-    /// let _ = foo::<<LenThree as HList>::Len>();
+    /// 
+    /// // Won't compile: the length of LenThree doesn't meet the less-than-3 requirement
+    /// // let _ = type_len_constraint::<<LenThree as HList>::Len>();
+    ///
+    /// // ...this works, though
+    /// let _ = type_len_constraint::<<LenTwo as HList>::Len>();
+    ///
+    /// // Pull out the length of the list in the word-size of your choosing.
     /// let byte: u8 = <<LenThree as HList>::Len>::U8;
+    /// let u_16: u16 = <<LenThree as HList>::Len>::U16;
     ///
     ///
-    /// assert_eq!(<LenThree as HList>::Len::USIZE, 3);
+    /// assert_eq!(<LenThree as HList>::Len::U8, 3u8);
     /// # }
     /// ```
     type Len: Unsigned;
 
+    /// Length as a usize const generic. Is equivilent to `<Self as HList>::LEN::USIZE`
     const LEN: usize;
 
     /// Returns the length of a given HList
@@ -184,7 +198,6 @@ where
     <<T as HList>::Len as Add<typenum::U1>>::Output: Unsigned,
 {
     type Len = <<T as HList>::Len as Add<typenum::U1>>::Output;
-
     const LEN: usize = 0;
 }
 

From b1521ae8e7db4b5844b6a7e0c0e824ba626e0896 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 19:04:00 +0200
Subject: [PATCH 09/25] Clean some things up

---
 core/src/hlist.rs | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index fb68f374..998f877d 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -59,8 +59,9 @@ use crate::indices::{Here, Suffixed, There};
 use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
-use typenum::bit::B1;
-use typenum::{UInt, UTerm, Unsigned};
+
+use typenum::{Add1, bit::B1, Unsigned};
+pub use typenum;
 
 
 use std::ops::Add;
@@ -75,7 +76,7 @@ pub trait HList: Sized {
     /// # Examples
     /// ```
     /// # fn main() {
-    /// use frunk_core::typenum::Unsigned;
+    /// use frunk_core::hlist::typenum::Unsigned;
     /// use frunk::prelude::*;
     /// use frunk_core::HList;
     ///
@@ -83,7 +84,7 @@ pub trait HList: Sized {
     /// type LenTwo = HList![bool, ()];
     ///
     /// // Attach a constraint that ensures constraints are met at type-check time
-    /// fn type_len_constraint<T: typenum::IsLessThan<typenum::U3>>() {}
+    /// fn type_len_constraint<T: typenum::IsLess<typenum::U3>>() {}
     ///
     ///
     /// 
@@ -194,10 +195,10 @@ pub struct HCons<H, T> {
 
 impl<H, T: HList> HList for HCons<H, T>
 where
-    <T as HList>::Len: Add<typenum::U1>,
-    <<T as HList>::Len as Add<typenum::U1>>::Output: Unsigned,
+    <T as HList>::Len: Add<B1>,
+    Add1<<T as HList>::Len>: Unsigned,
 {
-    type Len = <<T as HList>::Len as Add<typenum::U1>>::Output;
+    type Len = Add1<<T as HList>::Len>;
     const LEN: usize = 0;
 }
 
@@ -1139,8 +1140,8 @@ impl HZippable<HNil> for HNil {
 impl<H1, T1, H2, T2> HZippable<HCons<H2, T2>> for HCons<H1, T1>
 where
     T1: HZippable<T2>,
-    <<T1 as HZippable<T2>>::Zipped as HList>::Len: Add<UInt<UTerm, B1>>,
-    <<<T1 as HZippable<T2>>::Zipped as HList>::Len as Add<UInt<UTerm, B1>>>::Output: Unsigned,
+    <<T1 as HZippable<T2>>::Zipped as HList>::Len: Add<B1>,
+    Add1<<<T1 as HZippable<T2>>::Zipped as HList>::Len>: Unsigned,
 {
     type Zipped = HCons<(H1, H2), T1::Zipped>;
     fn zip(self, other: HCons<H2, T2>) -> Self::Zipped {
@@ -1456,8 +1457,8 @@ where
 impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
 where
     Tail: Into<Vec<H>> + HList,
-    <Tail as HList>::Len: Add<UInt<UTerm, B1>>,
-    <<Tail as HList>::Len as Add<UInt<UTerm, B1>>>::Output: Unsigned,
+    <Tail as HList>::Len: Add<B1>,
+    Add1<<Tail as HList>::Len>: Unsigned,
 {
     fn into(self) -> Vec<H> {
         let h = self.head;

From 053516a7bad0fdd56993ba162ef87d47bd63265a Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 19:04:21 +0200
Subject: [PATCH 10/25] cargo fmt

---
 core/src/hlist.rs | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 998f877d..3a4b9834 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -60,9 +60,8 @@ use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
-use typenum::{Add1, bit::B1, Unsigned};
 pub use typenum;
-
+use typenum::{bit::B1, Add1, Unsigned};
 
 use std::ops::Add;
 
@@ -87,7 +86,7 @@ pub trait HList: Sized {
     /// fn type_len_constraint<T: typenum::IsLess<typenum::U3>>() {}
     ///
     ///
-    /// 
+    ///
     /// // Won't compile: the length of LenThree doesn't meet the less-than-3 requirement
     /// // let _ = type_len_constraint::<<LenThree as HList>::Len>();
     ///

From 327efd15c9b71f68e9b2754a5f986d863b6e200f Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 19:49:39 +0200
Subject: [PATCH 11/25] fix obo error

---
 core/src/hlist.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 3a4b9834..19ebaa2b 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -193,12 +193,12 @@ pub struct HCons<H, T> {
 }
 
 impl<H, T: HList> HList for HCons<H, T>
-where
+where 
     <T as HList>::Len: Add<B1>,
-    Add1<<T as HList>::Len>: Unsigned,
+    <<T as HList>::Len as Add<B1>>::Output: Unsigned
 {
-    type Len = Add1<<T as HList>::Len>;
-    const LEN: usize = 0;
+    type Len = <<T as HList>::Len as Add<B1>>::Output;
+    const LEN: usize = 1 + <T as HList>::LEN;
 }
 
 impl<H, T> HCons<H, T> {

From e3995ca6021f318ddf81307a6492f606de1266eb Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 19:51:04 +0200
Subject: [PATCH 12/25] Use Self::LEN internally

---
 core/src/hlist.rs | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 19ebaa2b..8cb7101f 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -61,7 +61,7 @@ use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 use serde::{Deserialize, Serialize};
 
 pub use typenum;
-use typenum::{bit::B1, Add1, Unsigned};
+use typenum::{U0, bit::B1, Add1, Unsigned};
 
 use std::ops::Add;
 
@@ -120,7 +120,7 @@ pub trait HList: Sized {
     /// ```
     #[inline]
     fn len(&self) -> usize {
-        <Self::Len as Unsigned>::USIZE
+        Self::LEN
     }
 
     /// Returns whether a given HList is empty
@@ -137,7 +137,7 @@ pub trait HList: Sized {
     /// ```
     #[inline]
     fn is_empty(&self) -> bool {
-        <Self::Len as Unsigned>::USIZE == 0
+        Self::LEN == 0
     }
 
     /// Prepends an item to the current HList
@@ -178,7 +178,7 @@ pub trait HList: Sized {
 pub struct HNil;
 
 impl HList for HNil {
-    type Len = typenum::U0;
+    type Len = U0;
 
     const LEN: usize = 0;
 }
@@ -1136,6 +1136,22 @@ impl HZippable<HNil> for HNil {
     }
 }
 
+//#[cfg(feature = "typenum")]
+//impl<H1, T1, H2, T2> HZippable<HCons<H2, T2>> for HCons<H1, T1>
+//where
+//    T1: HZippable<T2>,
+//    <<T1 as HZippable<T2>>::Zipped as HList>::Len: Add<B1>,
+//    Add1<<<T1 as HZippable<T2>>::Zipped as HList>::Len>: Unsigned,
+//{
+//    type Zipped = HCons<(H1, H2), T1::Zipped>;
+//    fn zip(self, other: HCons<H2, T2>) -> Self::Zipped {
+//        HCons {
+//            head: (self.head, other.head),
+//            tail: self.tail.zip(other.tail),
+//        }
+//    }
+//}
+// #[cfg(not(feature = "typenum"))]
 impl<H1, T1, H2, T2> HZippable<HCons<H2, T2>> for HCons<H1, T1>
 where
     T1: HZippable<T2>,
@@ -1457,12 +1473,12 @@ impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
 where
     Tail: Into<Vec<H>> + HList,
     <Tail as HList>::Len: Add<B1>,
-    Add1<<Tail as HList>::Len>: Unsigned,
+    Add1<<Tail as HList>::Len>: Unsigned
 {
     fn into(self) -> Vec<H> {
         let h = self.head;
         let t = self.tail;
-        let mut v = Vec::with_capacity(<<Self as HList>::Len as Unsigned>::USIZE);
+        let mut v = Vec::with_capacity(<Self as HList>::LEN);
         v.push(h);
         let mut t_vec: Vec<H> = t.into();
         v.append(&mut t_vec);
@@ -1925,7 +1941,9 @@ mod tests {
 
     #[test]
     fn test_len_const() {
+        // #[cfg(feature = "typenum")]
         assert_eq!(<HList![usize, &str, f32] as HList>::Len::USIZE, 3);
+        assert_eq!(<HList![usize, &str, f32] as HList>::LEN, 3);
     }
 
     #[test]

From cb668a90731587e38c0b1ce419a74b4569cf5745 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 20:06:18 +0200
Subject: [PATCH 13/25] hide the use of typenum behind feature gate

---
 core/Cargo.toml   |  3 ++-
 core/src/hlist.rs | 44 +++++++++++++++++++++++++-------------------
 2 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/core/Cargo.toml b/core/Cargo.toml
index be695e6a..e88d8923 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -15,10 +15,11 @@ travis-ci = { repository = "lloydmeta/frunk" }
 [features]
 default = ["std"]
 std = []
+typenum = ["dep:typenum"]
 
 [dependencies]
 serde = { version = "^1.0", optional = true, features = [ "derive" ] }
-typenum = { version = "1.17.0", default-features = false }
+typenum = { version = "1.17.0", optional = true, default-features = false, features = ["no_std"] }
 
 [dev-dependencies.frunk_derives]
 path = "../derives"
diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 8cb7101f..e2d1c072 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -60,7 +60,9 @@ use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+#[cfg(feature = "typenum")]
 pub use typenum;
+#[cfg(feature = "typenum")]
 use typenum::{U0, bit::B1, Add1, Unsigned};
 
 use std::ops::Add;
@@ -101,6 +103,7 @@ pub trait HList: Sized {
     /// assert_eq!(<LenThree as HList>::Len::U8, 3u8);
     /// # }
     /// ```
+    #[cfg(feature = "typenum")]
     type Len: Unsigned;
 
     /// Length as a usize const generic. Is equivilent to `<Self as HList>::LEN::USIZE`
@@ -178,6 +181,7 @@ pub trait HList: Sized {
 pub struct HNil;
 
 impl HList for HNil {
+    #[cfg(feature = "typenum")]
     type Len = U0;
 
     const LEN: usize = 0;
@@ -192,6 +196,7 @@ pub struct HCons<H, T> {
     pub tail: T,
 }
 
+#[cfg(feature = "typenum")]
 impl<H, T: HList> HList for HCons<H, T>
 where 
     <T as HList>::Len: Add<B1>,
@@ -200,6 +205,11 @@ where
     type Len = <<T as HList>::Len as Add<B1>>::Output;
     const LEN: usize = 1 + <T as HList>::LEN;
 }
+#[cfg(not(feature = "typenum"))]
+impl<H, T: HList> HList for HCons<H, T>
+{
+    const LEN: usize = 1 + <T as HList>::LEN;
+}
 
 impl<H, T> HCons<H, T> {
     /// Returns the head of the list and the tail of the list as a tuple2.
@@ -1136,22 +1146,20 @@ impl HZippable<HNil> for HNil {
     }
 }
 
-//#[cfg(feature = "typenum")]
-//impl<H1, T1, H2, T2> HZippable<HCons<H2, T2>> for HCons<H1, T1>
-//where
-//    T1: HZippable<T2>,
-//    <<T1 as HZippable<T2>>::Zipped as HList>::Len: Add<B1>,
-//    Add1<<<T1 as HZippable<T2>>::Zipped as HList>::Len>: Unsigned,
-//{
-//    type Zipped = HCons<(H1, H2), T1::Zipped>;
-//    fn zip(self, other: HCons<H2, T2>) -> Self::Zipped {
-//        HCons {
-//            head: (self.head, other.head),
-//            tail: self.tail.zip(other.tail),
-//        }
-//    }
-//}
-// #[cfg(not(feature = "typenum"))]
+#[cfg(not(feature = "typenum"))]
+impl<H1, T1, H2, T2> HZippable<HCons<H2, T2>> for HCons<H1, T1>
+where
+    T1: HZippable<T2>,
+{
+    type Zipped = HCons<(H1, H2), T1::Zipped>;
+    fn zip(self, other: HCons<H2, T2>) -> Self::Zipped {
+        HCons {
+            head: (self.head, other.head),
+            tail: self.tail.zip(other.tail),
+        }
+    }
+}
+#[cfg(feature = "typenum")]
 impl<H1, T1, H2, T2> HZippable<HCons<H2, T2>> for HCons<H1, T1>
 where
     T1: HZippable<T2>,
@@ -1472,8 +1480,6 @@ where
 impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
 where
     Tail: Into<Vec<H>> + HList,
-    <Tail as HList>::Len: Add<B1>,
-    Add1<<Tail as HList>::Len>: Unsigned
 {
     fn into(self) -> Vec<H> {
         let h = self.head;
@@ -1941,7 +1947,7 @@ mod tests {
 
     #[test]
     fn test_len_const() {
-        // #[cfg(feature = "typenum")]
+        #[cfg(feature = "typenum")]
         assert_eq!(<HList![usize, &str, f32] as HList>::Len::USIZE, 3);
         assert_eq!(<HList![usize, &str, f32] as HList>::LEN, 3);
     }

From 56484d5b61d93de4060baf0e48fea5c3b353f2c5 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 20:13:10 +0200
Subject: [PATCH 14/25] In root, `cargo test --all` pass with/without typenum

---
 core/src/hlist.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index e2d1c072..688f44a5 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -1475,12 +1475,34 @@ where
     }
 }
 
+#[cfg(feature = "typenum")]
 #[cfg(feature = "std")]
 #[allow(clippy::from_over_into)]
 impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
 where
     Tail: Into<Vec<H>> + HList,
+    <Tail as HList>::Len: Add<B1>,
+    Add1<<Tail as HList>::Len>: Unsigned
 {
+
+    fn into(self) -> Vec<H>  {
+        let h = self.head;
+        let t = self.tail;
+        let mut v = Vec::with_capacity(<Self as HList>::LEN);
+        v.push(h);
+        let mut t_vec: Vec<H> = t.into();
+        v.append(&mut t_vec);
+        v
+    }
+}
+#[cfg(not(feature = "typenum"))]
+#[cfg(feature = "std")]
+#[allow(clippy::from_over_into)]
+impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
+where
+    Tail: Into<Vec<H>> + HList,
+{
+
     fn into(self) -> Vec<H> {
         let h = self.head;
         let t = self.tail;

From 8f83135b29d9533bf6207d524cbfa44b7aa054de Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 20:13:24 +0200
Subject: [PATCH 15/25] cargo fmt

---
 core/src/hlist.rs | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 688f44a5..cc1455b2 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -63,7 +63,7 @@ use serde::{Deserialize, Serialize};
 #[cfg(feature = "typenum")]
 pub use typenum;
 #[cfg(feature = "typenum")]
-use typenum::{U0, bit::B1, Add1, Unsigned};
+use typenum::{bit::B1, Add1, Unsigned, U0};
 
 use std::ops::Add;
 
@@ -198,16 +198,15 @@ pub struct HCons<H, T> {
 
 #[cfg(feature = "typenum")]
 impl<H, T: HList> HList for HCons<H, T>
-where 
+where
     <T as HList>::Len: Add<B1>,
-    <<T as HList>::Len as Add<B1>>::Output: Unsigned
+    <<T as HList>::Len as Add<B1>>::Output: Unsigned,
 {
     type Len = <<T as HList>::Len as Add<B1>>::Output;
     const LEN: usize = 1 + <T as HList>::LEN;
 }
 #[cfg(not(feature = "typenum"))]
-impl<H, T: HList> HList for HCons<H, T>
-{
+impl<H, T: HList> HList for HCons<H, T> {
     const LEN: usize = 1 + <T as HList>::LEN;
 }
 
@@ -1482,10 +1481,9 @@ impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
 where
     Tail: Into<Vec<H>> + HList,
     <Tail as HList>::Len: Add<B1>,
-    Add1<<Tail as HList>::Len>: Unsigned
+    Add1<<Tail as HList>::Len>: Unsigned,
 {
-
-    fn into(self) -> Vec<H>  {
+    fn into(self) -> Vec<H> {
         let h = self.head;
         let t = self.tail;
         let mut v = Vec::with_capacity(<Self as HList>::LEN);
@@ -1502,7 +1500,6 @@ impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
 where
     Tail: Into<Vec<H>> + HList,
 {
-
     fn into(self) -> Vec<H> {
         let h = self.head;
         let t = self.tail;

From 8d687fe260bd9be338c09c81e6691d7300666245 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 21:41:59 +0200
Subject: [PATCH 16/25] Render feature-gate in built docs

---
 core/Cargo.toml   | 1 +
 core/src/hlist.rs | 9 ++++-----
 core/src/lib.rs   | 7 ++++++-
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/core/Cargo.toml b/core/Cargo.toml
index e88d8923..8b6b7a82 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -16,6 +16,7 @@ travis-ci = { repository = "lloydmeta/frunk" }
 default = ["std"]
 std = []
 typenum = ["dep:typenum"]
+nightly = []
 
 [dependencies]
 serde = { version = "^1.0", optional = true, features = [ "derive" ] }
diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index cc1455b2..6e2f6fe9 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -60,6 +60,7 @@ use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
+#[doc(cfg(feature = "typenum"))]
 #[cfg(feature = "typenum")]
 pub use typenum;
 #[cfg(feature = "typenum")]
@@ -72,6 +73,7 @@ use std::ops::Add;
 /// An HList is a heterogeneous list, one that is statically typed at compile time. In simple terms,
 /// it is just an arbitrarily-nested Tuple2.
 pub trait HList: Sized {
+    #[doc(cfg(feature = "typenum"))]
     /// The type-level encapsulation of the lists length, using `typenum` under the hood.
     ///
     /// # Examples
@@ -272,9 +274,6 @@ macro_rules! gen_inherent_methods {
             pub fn len(&self) -> usize
             where Self: HList,
             {
-                // this is how it's done at the type-level
-                // <Self as HList>::Len::USIZE
-                #[allow(deprecated)]
                 HList::len(self)
             }
 
@@ -295,8 +294,6 @@ macro_rules! gen_inherent_methods {
             where Self: HList,
             {
                 HList::is_empty(self)
-                // this is how it's done at the type-level
-                // <<<Self as HList>::Len as typenum::IsEqual<typenum::U0>>::Output as typenum::Bit>::BOOL
             }
 
             /// Prepend an item to the current HList
@@ -1474,6 +1471,7 @@ where
     }
 }
 
+#[cfg_attr(feature = "nightly", doc(cfg(feature = "std")))]
 #[cfg(feature = "typenum")]
 #[cfg(feature = "std")]
 #[allow(clippy::from_over_into)]
@@ -1494,6 +1492,7 @@ where
     }
 }
 #[cfg(not(feature = "typenum"))]
+#[cfg_attr(feature = "nightly", doc(cfg(feature = "std")))]
 #[cfg(feature = "std")]
 #[allow(clippy::from_over_into)]
 impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
diff --git a/core/src/lib.rs b/core/src/lib.rs
index bc16035f..38b7c057 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -1,4 +1,9 @@
-#![cfg_attr(not(feature = "std"), no_std)]
+// This feature allows `cargo +nightly doc --F $GATED_FEATURES` to include 
+// said features as well as show that they are behind a feature gate, like so:
+// #[doc(cfg(feature = "$GATED_FEATURE"))]
+// ...without adding nightly requirement to non-doc builds
+#![cfg_attr(feature = "nightly", feature(doc_cfg))]
+
 #![doc(html_playground_url = "https://play.rust-lang.org/")]
 //! Frunk Core
 //!

From 6a86de848259dd89ee3922b7ccfc7f3e2f433727 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 21:43:36 +0200
Subject: [PATCH 17/25] modify doc-publish to build (just docs) with nightly

---
 .github/workflows/rustdoc.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/rustdoc.yml b/.github/workflows/rustdoc.yml
index f61a8ab5..1b3fc367 100644
--- a/.github/workflows/rustdoc.yml
+++ b/.github/workflows/rustdoc.yml
@@ -15,7 +15,7 @@ jobs:
 
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
+          toolchain: nightly
           override: true
 
       - uses: Swatinem/rust-cache@v2
@@ -23,8 +23,8 @@ jobs:
       - uses: actions-rs/cargo@v1
         name: build docs
         with:
-          command: doc
-          args: --all --no-deps
+          command: +nightly doc
+          args: --all --no-deps --features nightly,typenum
 
       - uses: peaceiris/actions-gh-pages@v4
         name: push docs

From 02bbdf8528b7a977d31c30444c36a064762ece55 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 21:54:04 +0200
Subject: [PATCH 18/25] include typenum feature in ci doc-check

---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8d7c8083..4b42143b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -146,4 +146,4 @@ jobs:
           RUSTDOCFLAGS: '-D warnings'
         with:
           command: doc
-          args: --all --no-deps  --document-private-items
+          args: --all --no-deps  --document-private-items --features typenum

From 8a9775ab1ebdb01a25d9d547756b094ce4310c72 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 22:07:18 +0200
Subject: [PATCH 19/25] nightly features only used with -F nightly

---
 core/src/hlist.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 6e2f6fe9..9f4c6528 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -60,7 +60,7 @@ use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
-#[doc(cfg(feature = "typenum"))]
+#[cfg_attr(feature = "nightly", doc(cfg(feature = "typenum")))]
 #[cfg(feature = "typenum")]
 pub use typenum;
 #[cfg(feature = "typenum")]
@@ -73,7 +73,7 @@ use std::ops::Add;
 /// An HList is a heterogeneous list, one that is statically typed at compile time. In simple terms,
 /// it is just an arbitrarily-nested Tuple2.
 pub trait HList: Sized {
-    #[doc(cfg(feature = "typenum"))]
+    #[cfg_attr(feature = "nightly", doc(cfg(feature = "typenum")))]
     /// The type-level encapsulation of the lists length, using `typenum` under the hood.
     ///
     /// # Examples
@@ -1510,6 +1510,7 @@ where
     }
 }
 
+#[cfg_attr(feature = "nightly", doc(cfg(feature = "std")))]
 #[cfg(feature = "std")]
 #[allow(clippy::from_over_into)]
 impl<T> Into<Vec<T>> for HNil {

From f39266f2df815799b37366ad365d8c507ea8eb63 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Sat, 4 May 2024 22:14:14 +0200
Subject: [PATCH 20/25] cargo fmt --all

---
 core/src/lib.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/core/src/lib.rs b/core/src/lib.rs
index 38b7c057..9290d2f1 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -1,9 +1,8 @@
-// This feature allows `cargo +nightly doc --F $GATED_FEATURES` to include 
+// This feature allows `cargo +nightly doc --F $GATED_FEATURES` to include
 // said features as well as show that they are behind a feature gate, like so:
 // #[doc(cfg(feature = "$GATED_FEATURE"))]
 // ...without adding nightly requirement to non-doc builds
 #![cfg_attr(feature = "nightly", feature(doc_cfg))]
-
 #![doc(html_playground_url = "https://play.rust-lang.org/")]
 //! Frunk Core
 //!

From ce74350067da1a77c468f05f3af8ae092050e26b Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Mon, 6 May 2024 12:51:27 +0200
Subject: [PATCH 21/25] Revert nightly stuff. Let error+suggestions help.

---
 .github/workflows/rustdoc.yml | 6 +++---
 core/Cargo.toml               | 1 -
 core/src/hlist.rs             | 5 -----
 core/src/lib.rs               | 5 -----
 4 files changed, 3 insertions(+), 14 deletions(-)

diff --git a/.github/workflows/rustdoc.yml b/.github/workflows/rustdoc.yml
index 1b3fc367..83923d17 100644
--- a/.github/workflows/rustdoc.yml
+++ b/.github/workflows/rustdoc.yml
@@ -15,7 +15,7 @@ jobs:
 
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: stable
           override: true
 
       - uses: Swatinem/rust-cache@v2
@@ -23,8 +23,8 @@ jobs:
       - uses: actions-rs/cargo@v1
         name: build docs
         with:
-          command: +nightly doc
-          args: --all --no-deps --features nightly,typenum
+          command: doc
+          args: --all --no-deps --features typenum
 
       - uses: peaceiris/actions-gh-pages@v4
         name: push docs
diff --git a/core/Cargo.toml b/core/Cargo.toml
index 8b6b7a82..e88d8923 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -16,7 +16,6 @@ travis-ci = { repository = "lloydmeta/frunk" }
 default = ["std"]
 std = []
 typenum = ["dep:typenum"]
-nightly = []
 
 [dependencies]
 serde = { version = "^1.0", optional = true, features = [ "derive" ] }
diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 9f4c6528..e0c694aa 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -60,7 +60,6 @@ use crate::traits::{Func, IntoReverse, Poly, ToMut, ToRef};
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
-#[cfg_attr(feature = "nightly", doc(cfg(feature = "typenum")))]
 #[cfg(feature = "typenum")]
 pub use typenum;
 #[cfg(feature = "typenum")]
@@ -73,7 +72,6 @@ use std::ops::Add;
 /// An HList is a heterogeneous list, one that is statically typed at compile time. In simple terms,
 /// it is just an arbitrarily-nested Tuple2.
 pub trait HList: Sized {
-    #[cfg_attr(feature = "nightly", doc(cfg(feature = "typenum")))]
     /// The type-level encapsulation of the lists length, using `typenum` under the hood.
     ///
     /// # Examples
@@ -1471,7 +1469,6 @@ where
     }
 }
 
-#[cfg_attr(feature = "nightly", doc(cfg(feature = "std")))]
 #[cfg(feature = "typenum")]
 #[cfg(feature = "std")]
 #[allow(clippy::from_over_into)]
@@ -1492,7 +1489,6 @@ where
     }
 }
 #[cfg(not(feature = "typenum"))]
-#[cfg_attr(feature = "nightly", doc(cfg(feature = "std")))]
 #[cfg(feature = "std")]
 #[allow(clippy::from_over_into)]
 impl<H, Tail> Into<Vec<H>> for HCons<H, Tail>
@@ -1510,7 +1506,6 @@ where
     }
 }
 
-#[cfg_attr(feature = "nightly", doc(cfg(feature = "std")))]
 #[cfg(feature = "std")]
 #[allow(clippy::from_over_into)]
 impl<T> Into<Vec<T>> for HNil {
diff --git a/core/src/lib.rs b/core/src/lib.rs
index 9290d2f1..02956918 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -1,8 +1,3 @@
-// This feature allows `cargo +nightly doc --F $GATED_FEATURES` to include
-// said features as well as show that they are behind a feature gate, like so:
-// #[doc(cfg(feature = "$GATED_FEATURE"))]
-// ...without adding nightly requirement to non-doc builds
-#![cfg_attr(feature = "nightly", feature(doc_cfg))]
 #![doc(html_playground_url = "https://play.rust-lang.org/")]
 //! Frunk Core
 //!

From 906c499f6890f2cf86da9dceb74d1dcdc753f8ad Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Mon, 6 May 2024 13:08:05 +0200
Subject: [PATCH 22/25] Simplify typnum inclusion

---
 core/Cargo.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/core/Cargo.toml b/core/Cargo.toml
index e88d8923..bb8dbc97 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -19,7 +19,7 @@ typenum = ["dep:typenum"]
 
 [dependencies]
 serde = { version = "^1.0", optional = true, features = [ "derive" ] }
-typenum = { version = "1.17.0", optional = true, default-features = false, features = ["no_std"] }
+typenum = { version = "1.17.0", optional = true }
 
 [dev-dependencies.frunk_derives]
 path = "../derives"

From 7cb70529df5b8444066ac752d8d61c025158ffa4 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Mon, 6 May 2024 13:28:29 +0200
Subject: [PATCH 23/25] Restore the core no_std

---
 core/src/lib.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/core/src/lib.rs b/core/src/lib.rs
index 02956918..bc16035f 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -1,3 +1,4 @@
+#![cfg_attr(not(feature = "std"), no_std)]
 #![doc(html_playground_url = "https://play.rust-lang.org/")]
 //! Frunk Core
 //!

From fb310a6667f72cbf8302f75a82a7804cd152ee87 Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Mon, 6 May 2024 13:28:43 +0200
Subject: [PATCH 24/25] refine doc-test

---
 core/src/hlist.rs | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index e0c694aa..5284ae29 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -77,7 +77,7 @@ pub trait HList: Sized {
     /// # Examples
     /// ```
     /// # fn main() {
-    /// use frunk_core::hlist::typenum::Unsigned;
+    /// use frunk_core::hlist::typenum::{self, Unsigned };
     /// use frunk::prelude::*;
     /// use frunk_core::HList;
     ///
@@ -85,15 +85,13 @@ pub trait HList: Sized {
     /// type LenTwo = HList![bool, ()];
     ///
     /// // Attach a constraint that ensures constraints are met at type-check time
-    /// fn type_len_constraint<T: typenum::IsLess<typenum::U3>>() {}
+    /// fn type_len_constraint<T: typenum::IsLess<typenum::U3, Output = typenum::True>>() {}
     ///
     ///
     ///
     /// // Won't compile: the length of LenThree doesn't meet the less-than-3 requirement
-    /// // let _ = type_len_constraint::<<LenThree as HList>::Len>();
-    ///
-    /// // ...this works, though
-    /// let _ = type_len_constraint::<<LenTwo as HList>::Len>();
+    /// // let _fail = type_len_constraint::<<LenThree as HList>::Len>();
+    /// let _is_good = type_len_constraint::<<LenTwo   as HList>::Len>();
     ///
     /// // Pull out the length of the list in the word-size of your choosing.
     /// let byte: u8 = <<LenThree as HList>::Len>::U8;
@@ -103,6 +101,25 @@ pub trait HList: Sized {
     /// assert_eq!(<LenThree as HList>::Len::U8, 3u8);
     /// # }
     /// ```
+    ///
+    /// ```compile_fail
+    /// # fn main() {
+    /// use frunk_core::hlist::typenum::{self, Unsigned };
+    /// use frunk::prelude::*;
+    /// use frunk_core::HList;
+    ///
+    /// type LenThree = HList![bool, (), u8];
+    /// type LenTwo = HList![bool, ()];
+    ///
+    /// // Attach a constraint that ensures constraints are met at type-check time
+    /// fn type_len_constraint<T: typenum::IsLess<typenum::U3, Output = typenum::True>>() {}
+    ///
+    ///
+    ///
+    /// // Won't compile: the length of LenThree doesn't meet the less-than-3 requirement
+    /// let _ = type_len_constraint::<<LenThree as HList>::Len>();
+    /// # }
+    /// ```
     #[cfg(feature = "typenum")]
     type Len: Unsigned;
 

From 424d7699dd655bac8394e1aac6651bf3a7c00c6d Mon Sep 17 00:00:00 2001
From: Ben PHL <benphawke@gmail.com>
Date: Mon, 6 May 2024 14:31:30 +0200
Subject: [PATCH 25/25] Lift the typenum feature to root toml

---
 Cargo.toml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Cargo.toml b/Cargo.toml
index 4cf4331b..b1e3cdb6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -45,6 +45,7 @@ default = ["validated", "proc-macros"]
 validated = ["std"]
 proc-macros = ["frunk_proc_macros"]
 std = ["frunk_core/std"]
+typenum = ["frunk_core/typenum"]
 
 [profile.bench]
 opt-level = 3