From 1b1c34b90bb4bf3859b05b1da6db2dcb374996bb Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Sat, 4 May 2019 14:58:18 +0200
Subject: Move `Note`s into the spine of the AST

---
 dhall/src/normalize.rs         |  12 +--
 dhall/src/typecheck.rs         |   2 +-
 dhall_proc_macros/src/quote.rs |   4 +-
 dhall_syntax/src/core.rs       |  69 +++++-------
 dhall_syntax/src/parser.rs     |   2 +-
 dhall_syntax/src/printer.rs    |  10 +-
 dhall_syntax/src/visitor.rs    | 234 +++++++++--------------------------------
 7 files changed, 86 insertions(+), 247 deletions(-)

diff --git a/dhall/src/normalize.rs b/dhall/src/normalize.rs
index 4636859..4d87225 100644
--- a/dhall/src/normalize.rs
+++ b/dhall/src/normalize.rs
@@ -163,7 +163,7 @@ pub(crate) enum Value {
     UnionLit(Label, Thunk, BTreeMap<Label, Option<TypeThunk>>),
     TextLit(Vec<InterpolatedTextContents<Thunk>>),
     /// Invariant: This must not contain a value captured by one of the variants above.
-    PartialExpr(ExprF<Thunk, Label, X, X>),
+    PartialExpr(ExprF<Thunk, Label, X>),
 }
 
 impl Value {
@@ -497,7 +497,6 @@ impl Value {
                     |v| v.shift(delta, var),
                     |x, v| v.shift(delta, &var.shift(1, &x.into())),
                     X::clone,
-                    X::clone,
                     Label::clone,
                 ))
             }
@@ -607,7 +606,6 @@ impl Value {
                         )
                     },
                     X::clone,
-                    X::clone,
                     Label::clone,
                 ))
             }
@@ -1125,11 +1123,10 @@ fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> Value {
     }
 
     // Thunk subexpressions
-    let expr: ExprF<Thunk, Label, X, X> =
+    let expr: ExprF<Thunk, Label, X> =
         expr.as_ref().map_ref_with_special_handling_of_binders(
             |e| Thunk::new(ctx.clone(), e.clone()),
             |x, e| Thunk::new(ctx.skip(x), e.clone()),
-            X::clone,
             |_| unreachable!(),
             Label::clone,
         );
@@ -1137,7 +1134,7 @@ fn normalize_whnf(ctx: NormalizationContext, expr: InputSubExpr) -> Value {
     normalize_one_layer(expr)
 }
 
-fn normalize_one_layer(expr: ExprF<Thunk, Label, X, X>) -> Value {
+fn normalize_one_layer(expr: ExprF<Thunk, Label, X>) -> Value {
     use Value::{
         BoolLit, EmptyListLit, EmptyOptionalLit, Lam, NEListLit, NEOptionalLit,
         NaturalLit, Pi, RecordLit, RecordType, TextLit, UnionConstructor,
@@ -1149,7 +1146,7 @@ fn normalize_one_layer(expr: ExprF<Thunk, Label, X, X>) -> Value {
         RetValue(Value),
         RetThunk(Thunk),
         RetThunkRef(&'a Thunk),
-        RetExpr(ExprF<Thunk, Label, X, X>),
+        RetExpr(ExprF<Thunk, Label, X>),
     }
     use Ret::{RetExpr, RetThunk, RetThunkRef, RetValue};
 
@@ -1157,7 +1154,6 @@ fn normalize_one_layer(expr: ExprF<Thunk, Label, X, X>) -> Value {
         ExprF::Embed(_) => unreachable!(),
         ExprF::Var(_) => unreachable!(),
         ExprF::Annot(x, _) => RetThunk(x),
-        ExprF::Note(_, e) => RetThunk(e),
         ExprF::Lam(x, t, e) => RetValue(Lam(x, t, e)),
         ExprF::Pi(x, t, e) => {
             RetValue(Pi(x, TypeThunk::from_thunk(t), TypeThunk::from_thunk(e)))
diff --git a/dhall/src/typecheck.rs b/dhall/src/typecheck.rs
index 74de59b..ce4ca96 100644
--- a/dhall/src/typecheck.rs
+++ b/dhall/src/typecheck.rs
@@ -719,7 +719,7 @@ fn type_with(
 /// layer.
 fn type_last_layer(
     ctx: &TypecheckContext,
-    e: ExprF<Typed, Label, X, Normalized>,
+    e: ExprF<Typed, Label, Normalized>,
 ) -> Result<Ret, TypeError> {
     use dhall_syntax::BinOp::*;
     use dhall_syntax::Builtin::*;
diff --git a/dhall_proc_macros/src/quote.rs b/dhall_proc_macros/src/quote.rs
index c2323fa..e11bbaa 100644
--- a/dhall_proc_macros/src/quote.rs
+++ b/dhall_proc_macros/src/quote.rs
@@ -27,7 +27,7 @@ pub fn subexpr(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
 
 // Returns an expression of type ExprF<T, _, _>, where T is the
 // type of the subexpressions after interpolation.
-pub fn quote_exprf<TS>(expr: ExprF<TS, Label, X, X>) -> TokenStream
+pub fn quote_exprf<TS>(expr: ExprF<TS, Label, X>) -> TokenStream
 where
     TS: quote::ToTokens + std::fmt::Debug,
 {
@@ -103,7 +103,6 @@ fn quote_subexpr(
         |e| quote_subexpr(e, ctx),
         |l, e| quote_subexpr(e, &ctx.insert(l.clone(), ())),
         |_| unreachable!(),
-        |_| unreachable!(),
         Label::clone,
     ) {
         Var(V(ref s, n)) => {
@@ -138,7 +137,6 @@ fn quote_expr(expr: &Expr<X, X>, ctx: &Context<Label, ()>) -> TokenStream {
         |e| quote_subexpr(e, ctx),
         |l, e| quote_subexpr(e, &ctx.insert(l.clone(), ())),
         |_| unreachable!(),
-        |_| unreachable!(),
         Label::clone,
     ) {
         Var(V(ref s, n)) => {
diff --git a/dhall_syntax/src/core.rs b/dhall_syntax/src/core.rs
index 3db07dd..a81f96c 100644
--- a/dhall_syntax/src/core.rs
+++ b/dhall_syntax/src/core.rs
@@ -141,17 +141,25 @@ pub type ParsedExpr = SubExpr<X, Import>;
 pub type ResolvedExpr = SubExpr<X, X>;
 pub type DhallExpr = ResolvedExpr;
 
-#[derive(Debug, PartialEq, Eq)]
-pub struct SubExpr<Note, Embed>(pub Rc<Expr<Note, Embed>>);
+#[derive(Debug)]
+pub struct SubExpr<Note, Embed>(Rc<Expr<Note, Embed>>, Option<Note>);
 
-pub type Expr<Note, Embed> = ExprF<SubExpr<Note, Embed>, Label, Note, Embed>;
+impl<Note, Embed: PartialEq> std::cmp::PartialEq for SubExpr<Note, Embed> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0
+    }
+}
+
+impl<Note, Embed: Eq> std::cmp::Eq for SubExpr<Note, Embed> {}
+
+pub type Expr<Note, Embed> = ExprF<SubExpr<Note, Embed>, Label, Embed>;
 
 /// Syntax tree for expressions
 // Having the recursion out of the enum definition enables writing
 // much more generic code and improves pattern-matching behind
 // smart pointers.
 #[derive(Debug, Clone, PartialEq, Eq)]
-pub enum ExprF<SubExpr, Label, Note, Embed> {
+pub enum ExprF<SubExpr, Label, Embed> {
     Const(Const),
     ///  `x`
     ///  `x@n`
@@ -208,28 +216,25 @@ pub enum ExprF<SubExpr, Label, Note, Embed> {
     Field(SubExpr, Label),
     ///  `e.{ x, y, z }`
     Projection(SubExpr, Vec<Label>),
-    /// Annotation on the AST. Unused for now but could hold e.g. file location information
-    Note(Note, SubExpr),
     /// Embeds an import or the result of resolving the import
     Embed(Embed),
 }
 
-impl<SE, L, N, E> ExprF<SE, L, N, E> {
+impl<SE, L, E> ExprF<SE, L, E> {
     pub(crate) fn visit<'a, V, Return>(&'a self, v: V) -> Return
     where
-        V: visitor::GenericVisitor<&'a ExprF<SE, L, N, E>, Return>,
+        V: visitor::GenericVisitor<&'a ExprF<SE, L, E>, Return>,
     {
         v.visit(self)
     }
 
-    fn traverse_ref_with_special_handling_of_binders<'a, SE2, L2, N2, E2, Err>(
+    fn traverse_ref_with_special_handling_of_binders<'a, SE2, L2, E2, Err>(
         &'a self,
         visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
         visit_under_binder: impl FnOnce(&'a L, &'a SE) -> Result<SE2, Err>,
-        visit_note: impl FnOnce(&'a N) -> Result<N2, Err>,
         visit_embed: impl FnOnce(&'a E) -> Result<E2, Err>,
         visit_label: impl FnMut(&'a L) -> Result<L2, Err>,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Err>
+    ) -> Result<ExprF<SE2, L2, E2>, Err>
     where
         L: Ord,
         L2: Ord,
@@ -237,39 +242,35 @@ impl<SE, L, N, E> ExprF<SE, L, N, E> {
         self.visit(visitor::TraverseRefWithBindersVisitor {
             visit_subexpr,
             visit_under_binder,
-            visit_note,
             visit_embed,
             visit_label,
         })
     }
 
-    fn traverse_ref<'a, SE2, L2, N2, E2, Err>(
+    fn traverse_ref<'a, SE2, L2, E2, Err>(
         &'a self,
         visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
-        visit_note: impl FnOnce(&'a N) -> Result<N2, Err>,
         visit_embed: impl FnOnce(&'a E) -> Result<E2, Err>,
         visit_label: impl FnMut(&'a L) -> Result<L2, Err>,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Err>
+    ) -> Result<ExprF<SE2, L2, E2>, Err>
     where
         L: Ord,
         L2: Ord,
     {
         self.visit(visitor::TraverseRefVisitor {
             visit_subexpr,
-            visit_note,
             visit_embed,
             visit_label,
         })
     }
 
-    pub fn map_ref_with_special_handling_of_binders<'a, SE2, L2, N2, E2>(
+    pub fn map_ref_with_special_handling_of_binders<'a, SE2, L2, E2>(
         &'a self,
         mut map_subexpr: impl FnMut(&'a SE) -> SE2,
         mut map_under_binder: impl FnMut(&'a L, &'a SE) -> SE2,
-        map_note: impl FnOnce(&'a N) -> N2,
         map_embed: impl FnOnce(&'a E) -> E2,
         mut map_label: impl FnMut(&'a L) -> L2,
-    ) -> ExprF<SE2, L2, N2, E2>
+    ) -> ExprF<SE2, L2, E2>
     where
         L: Ord,
         L2: Ord,
@@ -277,26 +278,23 @@ impl<SE, L, N, E> ExprF<SE, L, N, E> {
         trivial_result(self.traverse_ref_with_special_handling_of_binders(
             |x| Ok(map_subexpr(x)),
             |l, x| Ok(map_under_binder(l, x)),
-            |x| Ok(map_note(x)),
             |x| Ok(map_embed(x)),
             |x| Ok(map_label(x)),
         ))
     }
 
-    pub fn map_ref<'a, SE2, L2, N2, E2>(
+    pub fn map_ref<'a, SE2, L2, E2>(
         &'a self,
         mut map_subexpr: impl FnMut(&'a SE) -> SE2,
-        map_note: impl FnOnce(&'a N) -> N2,
         map_embed: impl FnOnce(&'a E) -> E2,
         mut map_label: impl FnMut(&'a L) -> L2,
-    ) -> ExprF<SE2, L2, N2, E2>
+    ) -> ExprF<SE2, L2, E2>
     where
         L: Ord,
         L2: Ord,
     {
         trivial_result(self.traverse_ref(
             |x| Ok(map_subexpr(x)),
-            |x| Ok(map_note(x)),
             |x| Ok(map_embed(x)),
             |x| Ok(map_label(x)),
         ))
@@ -305,15 +303,13 @@ impl<SE, L, N, E> ExprF<SE, L, N, E> {
     pub fn traverse_ref_simple<'a, SE2, Err>(
         &'a self,
         visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
-    ) -> Result<ExprF<SE2, L, N, E>, Err>
+    ) -> Result<ExprF<SE2, L, E>, Err>
     where
         L: Ord + Clone,
-        N: Clone,
         E: Clone,
     {
         self.traverse_ref(
             visit_subexpr,
-            |x| Ok(N::clone(x)),
             |x| Ok(E::clone(x)),
             |x| Ok(L::clone(x)),
         )
@@ -322,13 +318,12 @@ impl<SE, L, N, E> ExprF<SE, L, N, E> {
     pub fn map_ref_simple<'a, SE2>(
         &'a self,
         map_subexpr: impl Fn(&'a SE) -> SE2,
-    ) -> ExprF<SE2, L, N, E>
+    ) -> ExprF<SE2, L, E>
     where
         L: Ord + Clone,
-        N: Clone,
         E: Clone,
     {
-        self.map_ref(map_subexpr, N::clone, E::clone, L::clone)
+        self.map_ref(map_subexpr, E::clone, L::clone)
     }
 }
 
@@ -413,19 +408,11 @@ impl<N, E> SubExpr<N, E> {
     ) -> Self {
         match self.as_ref() {
             ExprF::Embed(_) => SubExpr::clone(self),
-            // Recursive call
-            // TODO: don't discard the note !
-            ExprF::Note(_, e) => e
-                .map_subexprs_with_special_handling_of_binders(
-                    map_expr,
-                    map_under_binder,
-                ),
-            // Call ExprF::map_ref
+            // This calls ExprF::map_ref
             e => rc(e.map_ref_with_special_handling_of_binders(
                 map_expr,
                 map_under_binder,
                 |_| unreachable!(),
-                |_| unreachable!(),
                 Label::clone,
             )),
         }
@@ -491,13 +478,13 @@ impl<E: Clone> SubExpr<X, E> {
 
 impl<N, E> Clone for SubExpr<N, E> {
     fn clone(&self) -> Self {
-        SubExpr(Rc::clone(&self.0))
+        SubExpr(Rc::clone(&self.0), None)
     }
 }
 
 // Should probably rename this
 pub fn rc<N, E>(x: Expr<N, E>) -> SubExpr<N, E> {
-    SubExpr(Rc::new(x))
+    SubExpr(Rc::new(x), None)
 }
 
 /// Add an isize to an usize
diff --git a/dhall_syntax/src/parser.rs b/dhall_syntax/src/parser.rs
index 38e67a8..b5bf09d 100644
--- a/dhall_syntax/src/parser.rs
+++ b/dhall_syntax/src/parser.rs
@@ -29,7 +29,7 @@ fn rc(x: ParsedExpr) -> ParsedSubExpr {
     crate::rc(x)
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone)]
 pub struct Span {
     input: Rc<str>,
     /// # Safety
diff --git a/dhall_syntax/src/printer.rs b/dhall_syntax/src/printer.rs
index 704000a..e3b180b 100644
--- a/dhall_syntax/src/printer.rs
+++ b/dhall_syntax/src/printer.rs
@@ -3,7 +3,7 @@ use itertools::Itertools;
 use std::fmt::{self, Display};
 
 /// Generic instance that delegates to subexpressions
-impl<SE: Display + Clone, N, E: Display> Display for ExprF<SE, Label, N, E> {
+impl<SE: Display + Clone, E: Display> Display for ExprF<SE, Label, E> {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         use crate::ExprF::*;
         match self {
@@ -102,7 +102,6 @@ impl<SE: Display + Clone, N, E: Display> Display for ExprF<SE, Label, N, E> {
                 f.write_str(" >")?
             }
             Embed(a) => a.fmt(f)?,
-            Note(_, b) => b.fmt(f)?,
         }
         Ok(())
     }
@@ -143,7 +142,7 @@ impl<S: Clone, A: Display + Clone> Expr<S, A> {
     fn fmt_phase(
         &self,
         f: &mut fmt::Formatter,
-        mut phase: PrintPhase,
+        phase: PrintPhase,
     ) -> Result<(), fmt::Error> {
         use crate::ExprF::*;
         use PrintPhase::*;
@@ -170,10 +169,6 @@ impl<S: Clone, A: Display + Clone> Expr<S, A> {
             _ => false,
         };
 
-        if needs_paren {
-            phase = Base;
-        }
-
         // Annotate subexpressions with the appropriate phase, defaulting to Base
         let phased_self = match self.map_ref_simple(|e| PhasedExpr(e, Base)) {
             Pi(a, b, c) => {
@@ -200,7 +195,6 @@ impl<S: Clone, A: Display + Clone> Expr<S, A> {
             ExprF::App(f, a) => ExprF::App(f.phase(Import), a.phase(Import)),
             Field(a, b) => Field(a.phase(Primitive), b),
             Projection(e, ls) => Projection(e.phase(Primitive), ls),
-            Note(n, b) => Note(n, b.phase(phase)),
             e => e,
         };
 
diff --git a/dhall_syntax/src/visitor.rs b/dhall_syntax/src/visitor.rs
index caaefce..cbaa21e 100644
--- a/dhall_syntax/src/visitor.rs
+++ b/dhall_syntax/src/visitor.rs
@@ -18,11 +18,10 @@ pub trait GenericVisitor<Input, Return>: Sized {
 /// or just one, and Rust is ok with either. See for example TraverseRefVisitor
 /// and TraverseEmbedVisitor.
 /// This is very generic. For a more legible trait, see ExprFInFallibleVisitor
-pub trait ExprFVeryGenericVisitor<'a, Ret, SE1, L1, N1, E1>: Sized {
+pub trait ExprFVeryGenericVisitor<'a, Ret, SE1, L1, E1>: Sized {
     type Error;
     type SE2;
     type L2;
-    type N2;
     type E2;
 
     fn visit_subexpr(
@@ -39,27 +38,21 @@ pub trait ExprFVeryGenericVisitor<'a, Ret, SE1, L1, N1, E1>: Sized {
 
     fn visit_embed_squash(self, embed: &'a E1) -> Result<Ret, Self::Error>;
 
-    fn visit_note_squash(
-        self,
-        note: &'a N1,
-        subexpr: &'a SE1,
-    ) -> Result<Ret, Self::Error>;
-
-    // Called with the result of the map, in the non-embed/note case.
+    // Called with the result of the map, in the non-embed case.
     // Useful to change the result type, and/or avoid some loss of info
     fn visit_resulting_exprf(
-        result: ExprF<Self::SE2, Self::L2, Self::N2, Self::E2>,
+        result: ExprF<Self::SE2, Self::L2, Self::E2>,
     ) -> Result<Ret, Self::Error>;
 }
 
-impl<'a, T, Ret, SE1, L1, N1, E1>
-    GenericVisitor<&'a ExprF<SE1, L1, N1, E1>, Result<Ret, T::Error>> for T
+impl<'a, T, Ret, SE1, L1, E1>
+    GenericVisitor<&'a ExprF<SE1, L1, E1>, Result<Ret, T::Error>> for T
 where
     L1: Ord,
     T::L2: Ord,
-    T: ExprFVeryGenericVisitor<'a, Ret, SE1, L1, N1, E1>,
+    T: ExprFVeryGenericVisitor<'a, Ret, SE1, L1, E1>,
 {
-    fn visit(self, input: &'a ExprF<SE1, L1, N1, E1>) -> Result<Ret, T::Error> {
+    fn visit(self, input: &'a ExprF<SE1, L1, E1>) -> Result<Ret, T::Error> {
         fn vec<'a, T, U, Err, F: FnMut(&'a T) -> Result<U, Err>>(
             x: &'a [T],
             f: F,
@@ -75,27 +68,27 @@ where
                 None => None,
             })
         }
-        fn btmap<'a, V, Ret, SE, L, N, E>(
+        fn btmap<'a, V, Ret, SE, L, E>(
             x: &'a BTreeMap<L, SE>,
             mut v: V,
         ) -> Result<BTreeMap<V::L2, V::SE2>, V::Error>
         where
             L: Ord,
             V::L2: Ord,
-            V: ExprFVeryGenericVisitor<'a, Ret, SE, L, N, E>,
+            V: ExprFVeryGenericVisitor<'a, Ret, SE, L, E>,
         {
             x.iter()
                 .map(|(k, x)| Ok((v.visit_label(k)?, v.visit_subexpr(x)?)))
                 .collect()
         }
-        fn btoptmap<'a, V, Ret, SE, L, N, E>(
+        fn btoptmap<'a, V, Ret, SE, L, E>(
             x: &'a BTreeMap<L, Option<SE>>,
             mut v: V,
         ) -> Result<BTreeMap<V::L2, Option<V::SE2>>, V::Error>
         where
             L: Ord,
             V::L2: Ord,
-            V: ExprFVeryGenericVisitor<'a, Ret, SE, L, N, E>,
+            V: ExprFVeryGenericVisitor<'a, Ret, SE, L, E>,
         {
             x.iter()
                 .map(|(k, x)| {
@@ -171,7 +164,6 @@ where
             Projection(e, ls) => {
                 Projection(v.visit_subexpr(e)?, vec(ls, |l| v.visit_label(l))?)
             }
-            Note(n, e) => return v.visit_note_squash(n, e),
             Embed(a) => return v.visit_embed_squash(a),
         })
     }
@@ -179,14 +171,11 @@ where
 
 /// Like ExprFVeryGenericVisitor, but sets the return
 /// type to ExprF<_>
-pub trait ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>:
-    Sized
-{
+pub trait ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, E1, E2>: Sized {
     type Error;
 
     fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error>;
     fn visit_label(&mut self, label: &'a L1) -> Result<L2, Self::Error>;
-    fn visit_note(self, note: &'a N1) -> Result<N2, Self::Error>;
     fn visit_embed(self, embed: &'a E1) -> Result<E2, Self::Error>;
 
     fn visit_subexpr_under_binder(
@@ -211,30 +200,19 @@ pub trait ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>:
     fn visit_embed_squash(
         self,
         embed: &'a E1,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> {
+    ) -> Result<ExprF<SE2, L2, E2>, Self::Error> {
         Ok(ExprF::Embed(self.visit_embed(embed)?))
     }
-
-    fn visit_note_squash(
-        mut self,
-        note: &'a N1,
-        subexpr: &'a SE1,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> {
-        let subexpr = self.visit_subexpr(subexpr)?;
-        let note = self.visit_note(note)?;
-        Ok(ExprF::Note(note, subexpr))
-    }
 }
 
-impl<'a, T, SE1, SE2, L1, L2, N1, N2, E1, E2>
-    ExprFVeryGenericVisitor<'a, ExprF<SE2, L2, N2, E2>, SE1, L1, N1, E1> for T
+impl<'a, T, SE1, SE2, L1, L2, E1, E2>
+    ExprFVeryGenericVisitor<'a, ExprF<SE2, L2, E2>, SE1, L1, E1> for T
 where
-    T: ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>,
+    T: ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, E1, E2>,
 {
     type Error = T::Error;
     type SE2 = SE2;
     type L2 = L2;
-    type N2 = N2;
     type E2 = E2;
 
     fn visit_subexpr(
@@ -259,34 +237,23 @@ where
     fn visit_embed_squash(
         self,
         embed: &'a E1,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> {
+    ) -> Result<ExprF<SE2, L2, E2>, Self::Error> {
         self.visit_embed_squash(embed)
     }
 
-    fn visit_note_squash(
-        self,
-        note: &'a N1,
-        subexpr: &'a SE1,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> {
-        self.visit_note_squash(note, subexpr)
-    }
-
-    // Called with the result of the map, in the non-embed/note case.
+    // Called with the result of the map, in the non-embed case.
     // Useful to change the result type, and/or avoid some loss of info
     fn visit_resulting_exprf(
-        result: ExprF<Self::SE2, Self::L2, Self::N2, Self::E2>,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> {
+        result: ExprF<Self::SE2, Self::L2, Self::E2>,
+    ) -> Result<ExprF<SE2, L2, E2>, Self::Error> {
         Ok(result)
     }
 }
 
 /// Like ExprFFallibleVisitor, but without the error handling.
-pub trait ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>:
-    Sized
-{
+pub trait ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, E1, E2>: Sized {
     fn visit_subexpr(&mut self, subexpr: &'a SE1) -> SE2;
     fn visit_label(&mut self, label: &'a L1) -> L2;
-    fn visit_note(self, note: &'a N1) -> N2;
     fn visit_embed(self, embed: &'a E1) -> E2;
 
     fn visit_subexpr_under_binder(
@@ -304,28 +271,17 @@ pub trait ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>:
         )
     }
 
-    fn visit_embed_squash(self, embed: &'a E1) -> ExprF<SE2, L2, N2, E2> {
+    fn visit_embed_squash(self, embed: &'a E1) -> ExprF<SE2, L2, E2> {
         ExprF::Embed(self.visit_embed(embed))
     }
-
-    fn visit_note_squash(
-        mut self,
-        note: &'a N1,
-        subexpr: &'a SE1,
-    ) -> ExprF<SE2, L2, N2, E2> {
-        let subexpr = self.visit_subexpr(subexpr);
-        let note = self.visit_note(note);
-        ExprF::Note(note, subexpr)
-    }
 }
 
 struct InfallibleWrapper<T>(T);
 
-impl<'a, T, SE1, SE2, L1, L2, N1, N2, E1, E2>
-    ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>
-    for InfallibleWrapper<T>
+impl<'a, T, SE1, SE2, L1, L2, E1, E2>
+    ExprFFallibleVisitor<'a, SE1, SE2, L1, L2, E1, E2> for InfallibleWrapper<T>
 where
-    T: ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>,
+    T: ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, E1, E2>,
 {
     type Error = X;
 
@@ -335,9 +291,6 @@ where
     fn visit_label(&mut self, label: &'a L1) -> Result<L2, Self::Error> {
         Ok(self.0.visit_label(label))
     }
-    fn visit_note(self, note: &'a N1) -> Result<N2, Self::Error> {
-        Ok(self.0.visit_note(note))
-    }
     fn visit_embed(self, embed: &'a E1) -> Result<E2, Self::Error> {
         Ok(self.0.visit_embed(embed))
     }
@@ -353,55 +306,41 @@ where
     fn visit_embed_squash(
         self,
         embed: &'a E1,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> {
+    ) -> Result<ExprF<SE2, L2, E2>, Self::Error> {
         Ok(self.0.visit_embed_squash(embed))
     }
-
-    fn visit_note_squash(
-        self,
-        note: &'a N1,
-        subexpr: &'a SE1,
-    ) -> Result<ExprF<SE2, L2, N2, E2>, Self::Error> {
-        Ok(self.0.visit_note_squash(note, subexpr))
-    }
 }
 
-impl<'a, T, SE1, SE2, L1, L2, N1, N2, E1, E2>
-    GenericVisitor<&'a ExprF<SE1, L1, N1, E1>, ExprF<SE2, L2, N2, E2>> for T
+impl<'a, T, SE1, SE2, L1, L2, E1, E2>
+    GenericVisitor<&'a ExprF<SE1, L1, E1>, ExprF<SE2, L2, E2>> for T
 where
     L1: Ord,
     L2: Ord,
-    T: ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, N1, N2, E1, E2>,
+    T: ExprFInFallibleVisitor<'a, SE1, SE2, L1, L2, E1, E2>,
 {
-    fn visit(
-        self,
-        input: &'a ExprF<SE1, L1, N1, E1>,
-    ) -> ExprF<SE2, L2, N2, E2> {
+    fn visit(self, input: &'a ExprF<SE1, L1, E1>) -> ExprF<SE2, L2, E2> {
         trivial_result(InfallibleWrapper(self).visit(input))
     }
 }
 
-pub struct TraverseRefWithBindersVisitor<F1, F2, F3, F4, F5> {
+pub struct TraverseRefWithBindersVisitor<F1, F2, F4, F5> {
     pub visit_subexpr: F1,
     pub visit_under_binder: F2,
-    pub visit_note: F3,
     pub visit_embed: F4,
     pub visit_label: F5,
 }
 
-impl<'a, SE, L, N, E, SE2, L2, N2, E2, Err, F1, F2, F3, F4, F5>
-    ExprFFallibleVisitor<'a, SE, SE2, L, L2, N, N2, E, E2>
-    for TraverseRefWithBindersVisitor<F1, F2, F3, F4, F5>
+impl<'a, SE, L, E, SE2, L2, E2, Err, F1, F2, F4, F5>
+    ExprFFallibleVisitor<'a, SE, SE2, L, L2, E, E2>
+    for TraverseRefWithBindersVisitor<F1, F2, F4, F5>
 where
     SE: 'a,
     L: 'a,
-    N: 'a,
     E: 'a,
     L: Ord,
     L2: Ord,
     F1: FnMut(&'a SE) -> Result<SE2, Err>,
     F2: FnOnce(&'a L, &'a SE) -> Result<SE2, Err>,
-    F3: FnOnce(&'a N) -> Result<N2, Err>,
     F4: FnOnce(&'a E) -> Result<E2, Err>,
     F5: FnMut(&'a L) -> Result<L2, Err>,
 {
@@ -417,9 +356,6 @@ where
     ) -> Result<SE2, Self::Error> {
         (self.visit_under_binder)(label, subexpr)
     }
-    fn visit_note(self, note: &'a N) -> Result<N2, Self::Error> {
-        (self.visit_note)(note)
-    }
     fn visit_embed(self, embed: &'a E) -> Result<E2, Self::Error> {
         (self.visit_embed)(embed)
     }
@@ -428,25 +364,22 @@ where
     }
 }
 
-pub struct TraverseRefVisitor<F1, F2, F3, F4> {
+pub struct TraverseRefVisitor<F1, F3, F4> {
     pub visit_subexpr: F1,
-    pub visit_note: F2,
     pub visit_embed: F3,
     pub visit_label: F4,
 }
 
-impl<'a, SE, L, N, E, SE2, L2, N2, E2, Err, F1, F2, F3, F4>
-    ExprFFallibleVisitor<'a, SE, SE2, L, L2, N, N2, E, E2>
-    for TraverseRefVisitor<F1, F2, F3, F4>
+impl<'a, SE, L, E, SE2, L2, E2, Err, F1, F3, F4>
+    ExprFFallibleVisitor<'a, SE, SE2, L, L2, E, E2>
+    for TraverseRefVisitor<F1, F3, F4>
 where
     SE: 'a,
     L: 'a,
-    N: 'a,
     E: 'a,
     L: Ord,
     L2: Ord,
     F1: FnMut(&'a SE) -> Result<SE2, Err>,
-    F2: FnOnce(&'a N) -> Result<N2, Err>,
     F3: FnOnce(&'a E) -> Result<E2, Err>,
     F4: FnMut(&'a L) -> Result<L2, Err>,
 {
@@ -455,9 +388,6 @@ where
     fn visit_subexpr(&mut self, subexpr: &'a SE) -> Result<SE2, Self::Error> {
         (self.visit_subexpr)(subexpr)
     }
-    fn visit_note(self, note: &'a N) -> Result<N2, Self::Error> {
-        (self.visit_note)(note)
-    }
     fn visit_embed(self, embed: &'a E) -> Result<E2, Self::Error> {
         (self.visit_embed)(embed)
     }
@@ -469,17 +399,8 @@ where
 pub struct TraverseEmbedVisitor<F1>(pub F1);
 
 impl<'a, 'b, N, E, E2, Err, F1>
-    ExprFFallibleVisitor<
-        'a,
-        SubExpr<N, E>,
-        SubExpr<N, E2>,
-        Label,
-        Label,
-        N,
-        N,
-        E,
-        E2,
-    > for &'b mut TraverseEmbedVisitor<F1>
+    ExprFFallibleVisitor<'a, SubExpr<N, E>, SubExpr<N, E2>, Label, Label, E, E2>
+    for &'b mut TraverseEmbedVisitor<F1>
 where
     N: Clone + 'a,
     F1: FnMut(&E) -> Result<E2, Err>,
@@ -492,9 +413,6 @@ where
     ) -> Result<SubExpr<N, E2>, Self::Error> {
         Ok(rc(subexpr.as_ref().visit(&mut **self)?))
     }
-    fn visit_note(self, note: &'a N) -> Result<N, Self::Error> {
-        Ok(N::clone(note))
-    }
     fn visit_embed(self, embed: &'a E) -> Result<E2, Self::Error> {
         (self.0)(embed)
     }
@@ -506,7 +424,7 @@ where
 pub struct SquashEmbedVisitor<F1>(pub F1);
 
 impl<'a, 'b, N, E1, E2, F1>
-    ExprFVeryGenericVisitor<'a, SubExpr<N, E2>, SubExpr<N, E1>, Label, N, E1>
+    ExprFVeryGenericVisitor<'a, SubExpr<N, E2>, SubExpr<N, E1>, Label, E1>
     for &'b mut SquashEmbedVisitor<F1>
 where
     N: Clone + 'a,
@@ -515,7 +433,6 @@ where
     type Error = X;
     type SE2 = SubExpr<N, E2>;
     type L2 = Label;
-    type N2 = N;
     type E2 = E2;
 
     fn visit_subexpr(
@@ -547,20 +464,10 @@ where
         Ok((self.0)(embed))
     }
 
-    fn visit_note_squash(
-        mut self,
-        note: &'a N,
-        subexpr: &'a SubExpr<N, E1>,
-    ) -> Result<SubExpr<N, E2>, Self::Error> {
-        let subexpr = self.visit_subexpr(subexpr)?;
-        let note = N::clone(note);
-        Ok(rc(ExprF::Note(note, subexpr)))
-    }
-
-    // Called with the result of the map, in the non-embed/note case.
+    // Called with the result of the map, in the non-embed case.
     // Useful to change the result type, and/or avoid some loss of info
     fn visit_resulting_exprf(
-        result: ExprF<Self::SE2, Self::L2, Self::N2, Self::E2>,
+        result: ExprF<Self::SE2, Self::L2, Self::E2>,
     ) -> Result<SubExpr<N, E2>, Self::Error> {
         Ok(rc(result))
     }
@@ -569,33 +476,14 @@ where
 pub struct UnNoteVisitor;
 
 impl<'a, 'b, N, E>
-    ExprFInFallibleVisitor<
-        'a,
-        SubExpr<N, E>,
-        SubExpr<X, E>,
-        Label,
-        Label,
-        N,
-        X,
-        E,
-        E,
-    > for &'b mut UnNoteVisitor
+    ExprFInFallibleVisitor<'a, SubExpr<N, E>, SubExpr<X, E>, Label, Label, E, E>
+    for &'b mut UnNoteVisitor
 where
     E: Clone + 'a,
 {
     fn visit_subexpr(&mut self, subexpr: &'a SubExpr<N, E>) -> SubExpr<X, E> {
         rc(subexpr.as_ref().visit(&mut **self))
     }
-    fn visit_note(self, _: &'a N) -> X {
-        unreachable!()
-    }
-    fn visit_note_squash(
-        self,
-        _: &'a N,
-        subexpr: &'a SubExpr<N, E>,
-    ) -> Expr<X, E> {
-        subexpr.as_ref().visit(self)
-    }
     fn visit_embed(self, embed: &'a E) -> E {
         E::clone(embed)
     }
@@ -607,26 +495,14 @@ where
 pub struct NoteAbsurdVisitor;
 
 impl<'a, 'b, N, E>
-    ExprFInFallibleVisitor<
-        'a,
-        SubExpr<X, E>,
-        SubExpr<N, E>,
-        Label,
-        Label,
-        X,
-        N,
-        E,
-        E,
-    > for &'b mut NoteAbsurdVisitor
+    ExprFInFallibleVisitor<'a, SubExpr<X, E>, SubExpr<N, E>, Label, Label, E, E>
+    for &'b mut NoteAbsurdVisitor
 where
     E: Clone + 'a,
 {
     fn visit_subexpr(&mut self, subexpr: &'a SubExpr<X, E>) -> SubExpr<N, E> {
         rc(subexpr.as_ref().visit(&mut **self))
     }
-    fn visit_note(self, note: &'a X) -> N {
-        match *note {}
-    }
     fn visit_embed(self, embed: &'a E) -> E {
         E::clone(embed)
     }
@@ -638,26 +514,14 @@ where
 pub struct EmbedAbsurdVisitor;
 
 impl<'a, 'b, N, E>
-    ExprFInFallibleVisitor<
-        'a,
-        SubExpr<N, X>,
-        SubExpr<N, E>,
-        Label,
-        Label,
-        N,
-        N,
-        X,
-        E,
-    > for &'b mut EmbedAbsurdVisitor
+    ExprFInFallibleVisitor<'a, SubExpr<N, X>, SubExpr<N, E>, Label, Label, X, E>
+    for &'b mut EmbedAbsurdVisitor
 where
     N: Clone + 'a,
 {
     fn visit_subexpr(&mut self, subexpr: &'a SubExpr<N, X>) -> SubExpr<N, E> {
         rc(subexpr.as_ref().visit(&mut **self))
     }
-    fn visit_note(self, note: &'a N) -> N {
-        N::clone(note)
-    }
     fn visit_embed(self, embed: &'a X) -> E {
         match *embed {}
     }
-- 
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