From 5a2538d174fd36a8ed7f4fa344b9583fc48bd977 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 11 Feb 2020 13:12:13 +0000
Subject: Remove the Embed variant from ExprKind

---
 dhall/src/syntax/ast/expr.rs      | 58 +++++++++++++--------------------------
 dhall/src/syntax/ast/visitor.rs   | 30 ++++++++------------
 dhall/src/syntax/binary/decode.rs |  2 +-
 dhall/src/syntax/binary/encode.rs | 44 ++++++++++-------------------
 dhall/src/syntax/text/parser.rs   | 10 ++-----
 dhall/src/syntax/text/printer.rs  | 17 ++++++------
 6 files changed, 58 insertions(+), 103 deletions(-)

(limited to 'dhall/src/syntax')

diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 420df5b..722630f 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -96,19 +96,19 @@ pub enum Builtin {
 
 // Each node carries an annotation.
 #[derive(Debug, Clone)]
-pub struct Expr<Embed> {
-    kind: Box<ExprKind<Expr<Embed>, Embed>>,
+pub struct Expr {
+    kind: Box<ExprKind<Expr>>,
     span: Span,
 }
 
-pub type UnspannedExpr<Embed> = ExprKind<Expr<Embed>, Embed>;
+pub type UnspannedExpr = ExprKind<Expr>;
 
 /// 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, Hash)]
-pub enum ExprKind<SubExpr, Embed> {
+pub enum ExprKind<SubExpr> {
     Const(Const),
     ///  `x`
     ///  `x@n`
@@ -169,18 +169,13 @@ pub enum ExprKind<SubExpr, Embed> {
     Completion(SubExpr, SubExpr),
     /// `./some/path`
     Import(Import<SubExpr>),
-    /// Embeds the result of resolving an import
-    Embed(Embed),
 }
 
-impl<SE, E> ExprKind<SE, E> {
+impl<SE> ExprKind<SE> {
     pub fn traverse_ref_maybe_binder<'a, SE2, Err>(
         &'a self,
         visit: impl FnMut(Option<&'a Label>, &'a SE) -> Result<SE2, Err>,
-    ) -> Result<ExprKind<SE2, E>, Err>
-    where
-        E: Clone,
-    {
+    ) -> Result<ExprKind<SE2>, Err> {
         visitor::TraverseRefMaybeBinderVisitor(visit).visit(self)
     }
 
@@ -188,10 +183,7 @@ impl<SE, E> ExprKind<SE, E> {
         &'a self,
         mut visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
         mut visit_under_binder: impl FnMut(&'a Label, &'a SE) -> Result<SE2, Err>,
-    ) -> Result<ExprKind<SE2, E>, Err>
-    where
-        E: Clone,
-    {
+    ) -> Result<ExprKind<SE2>, Err> {
         self.traverse_ref_maybe_binder(|l, x| match l {
             None => visit_subexpr(x),
             Some(l) => visit_under_binder(l, x),
@@ -201,20 +193,14 @@ impl<SE, E> ExprKind<SE, E> {
     pub(crate) fn traverse_ref<'a, SE2, Err>(
         &'a self,
         mut visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
-    ) -> Result<ExprKind<SE2, E>, Err>
-    where
-        E: Clone,
-    {
+    ) -> Result<ExprKind<SE2>, Err> {
         self.traverse_ref_maybe_binder(|_, e| visit_subexpr(e))
     }
 
     pub fn map_ref_maybe_binder<'a, SE2>(
         &'a self,
         mut map: impl FnMut(Option<&'a Label>, &'a SE) -> SE2,
-    ) -> ExprKind<SE2, E>
-    where
-        E: Clone,
-    {
+    ) -> ExprKind<SE2> {
         trivial_result(self.traverse_ref_maybe_binder(|l, x| Ok(map(l, x))))
     }
 
@@ -222,10 +208,7 @@ impl<SE, E> ExprKind<SE, E> {
         &'a self,
         mut map_subexpr: impl FnMut(&'a SE) -> SE2,
         mut map_under_binder: impl FnMut(&'a Label, &'a SE) -> SE2,
-    ) -> ExprKind<SE2, E>
-    where
-        E: Clone,
-    {
+    ) -> ExprKind<SE2> {
         self.map_ref_maybe_binder(|l, x| match l {
             None => map_subexpr(x),
             Some(l) => map_under_binder(l, x),
@@ -235,33 +218,30 @@ impl<SE, E> ExprKind<SE, E> {
     pub fn map_ref<'a, SE2>(
         &'a self,
         mut map_subexpr: impl FnMut(&'a SE) -> SE2,
-    ) -> ExprKind<SE2, E>
-    where
-        E: Clone,
-    {
+    ) -> ExprKind<SE2> {
         self.map_ref_maybe_binder(|_, e| map_subexpr(e))
     }
 }
 
-impl<E> Expr<E> {
-    pub fn as_ref(&self) -> &UnspannedExpr<E> {
+impl Expr {
+    pub fn as_ref(&self) -> &UnspannedExpr {
         &self.kind
     }
-    pub fn kind(&self) -> &UnspannedExpr<E> {
+    pub fn kind(&self) -> &UnspannedExpr {
         &self.kind
     }
     pub fn span(&self) -> Span {
         self.span.clone()
     }
 
-    pub fn new(kind: UnspannedExpr<E>, span: Span) -> Self {
+    pub fn new(kind: UnspannedExpr, span: Span) -> Self {
         Expr {
             kind: Box::new(kind),
             span,
         }
     }
 
-    pub fn rewrap<E2>(&self, kind: UnspannedExpr<E2>) -> Expr<E2> {
+    pub fn rewrap(&self, kind: UnspannedExpr) -> Expr {
         Expr {
             kind: Box::new(kind),
             span: self.span.clone(),
@@ -317,15 +297,15 @@ impl From<Label> for V {
     }
 }
 
-impl<Embed: PartialEq> std::cmp::PartialEq for Expr<Embed> {
+impl std::cmp::PartialEq for Expr {
     fn eq(&self, other: &Self) -> bool {
         self.kind == other.kind
     }
 }
 
-impl<Embed: Eq> std::cmp::Eq for Expr<Embed> {}
+impl std::cmp::Eq for Expr {}
 
-impl<Embed: std::hash::Hash> std::hash::Hash for Expr<Embed> {
+impl std::hash::Hash for Expr {
     fn hash<H>(&self, state: &mut H)
     where
         H: std::hash::Hasher,
diff --git a/dhall/src/syntax/ast/visitor.rs b/dhall/src/syntax/ast/visitor.rs
index c09b8d4..fc90efd 100644
--- a/dhall/src/syntax/ast/visitor.rs
+++ b/dhall/src/syntax/ast/visitor.rs
@@ -10,11 +10,10 @@ use crate::syntax::*;
 /// preventing exactly this ! So we have to be more clever. The visitor pattern allows us to have
 /// only one mutable thing the whole time: the visitor itself. The visitor can then carry around
 /// multiple closures or just one, and Rust is ok with either. See for example TraverseRefVisitor.
-pub trait ExprKindVisitor<'a, SE1, SE2, E1, E2>: Sized {
+pub trait ExprKindVisitor<'a, SE1, SE2>: Sized {
     type Error;
 
     fn visit_subexpr(&mut self, subexpr: &'a SE1) -> Result<SE2, Self::Error>;
-    fn visit_embed(self, embed: &'a E1) -> Result<E2, Self::Error>;
 
     fn visit_subexpr_under_binder(
         mut self,
@@ -26,18 +25,18 @@ pub trait ExprKindVisitor<'a, SE1, SE2, E1, E2>: Sized {
 
     fn visit(
         self,
-        input: &'a ExprKind<SE1, E1>,
-    ) -> Result<ExprKind<SE2, E2>, Self::Error> {
+        input: &'a ExprKind<SE1>,
+    ) -> Result<ExprKind<SE2>, Self::Error> {
         visit_ref(self, input)
     }
 }
 
-fn visit_ref<'a, V, SE1, SE2, E1, E2>(
+fn visit_ref<'a, V, SE1, SE2>(
     mut v: V,
-    input: &'a ExprKind<SE1, E1>,
-) -> Result<ExprKind<SE2, E2>, V::Error>
+    input: &'a ExprKind<SE1>,
+) -> Result<ExprKind<SE2>, V::Error>
 where
-    V: ExprKindVisitor<'a, SE1, SE2, E1, E2>,
+    V: ExprKindVisitor<'a, SE1, SE2>,
 {
     fn vec<'a, T, U, Err, F: FnMut(&'a T) -> Result<U, Err>>(
         x: &'a [T],
@@ -54,27 +53,27 @@ where
             None => None,
         })
     }
-    fn dupmap<'a, V, SE1, SE2, E1, E2, T>(
+    fn dupmap<'a, V, SE1, SE2, T>(
         x: impl IntoIterator<Item = (&'a Label, &'a SE1)>,
         mut v: V,
     ) -> Result<T, V::Error>
     where
         SE1: 'a,
         T: FromIterator<(Label, SE2)>,
-        V: ExprKindVisitor<'a, SE1, SE2, E1, E2>,
+        V: ExprKindVisitor<'a, SE1, SE2>,
     {
         x.into_iter()
             .map(|(k, x)| Ok((k.clone(), v.visit_subexpr(x)?)))
             .collect()
     }
-    fn optdupmap<'a, V, SE1, SE2, E1, E2, T>(
+    fn optdupmap<'a, V, SE1, SE2, T>(
         x: impl IntoIterator<Item = (&'a Label, &'a Option<SE1>)>,
         mut v: V,
     ) -> Result<T, V::Error>
     where
         SE1: 'a,
         T: FromIterator<(Label, Option<SE2>)>,
-        V: ExprKindVisitor<'a, SE1, SE2, E1, E2>,
+        V: ExprKindVisitor<'a, SE1, SE2>,
     {
         x.into_iter()
             .map(|(k, x)| {
@@ -147,17 +146,15 @@ where
         }
         Assert(e) => Assert(v.visit_subexpr(e)?),
         Import(i) => Import(i.traverse_ref(|e| v.visit_subexpr(e))?),
-        Embed(a) => Embed(v.visit_embed(a)?),
     })
 }
 
 pub struct TraverseRefMaybeBinderVisitor<F>(pub F);
 
-impl<'a, SE, E, SE2, Err, F> ExprKindVisitor<'a, SE, SE2, E, E>
+impl<'a, SE, SE2, Err, F> ExprKindVisitor<'a, SE, SE2>
     for TraverseRefMaybeBinderVisitor<F>
 where
     SE: 'a,
-    E: 'a + Clone,
     F: FnMut(Option<&'a Label>, &'a SE) -> Result<SE2, Err>,
 {
     type Error = Err;
@@ -172,7 +169,4 @@ where
     ) -> Result<SE2, Self::Error> {
         (self.0)(Some(label), subexpr)
     }
-    fn visit_embed(self, embed: &'a E) -> Result<E, Self::Error> {
-        Ok(embed.clone())
-    }
 }
diff --git a/dhall/src/syntax/binary/decode.rs b/dhall/src/syntax/binary/decode.rs
index 52b699c..6fbcc10 100644
--- a/dhall/src/syntax/binary/decode.rs
+++ b/dhall/src/syntax/binary/decode.rs
@@ -19,7 +19,7 @@ pub(crate) fn decode(data: &[u8]) -> Result<DecodedExpr, DecodeError> {
 }
 
 // Should probably rename this
-fn rc<E>(x: UnspannedExpr<E>) -> Expr<E> {
+fn rc(x: UnspannedExpr) -> Expr {
     Expr::new(x, Span::Decoded)
 }
 
diff --git a/dhall/src/syntax/binary/encode.rs b/dhall/src/syntax/binary/encode.rs
index 5e79f2d..686f737 100644
--- a/dhall/src/syntax/binary/encode.rs
+++ b/dhall/src/syntax/binary/encode.rs
@@ -9,17 +9,16 @@ use crate::syntax::{
     Label, Scheme, V,
 };
 
-/// Warning: will fail if `expr` contains an `Embed` node.
-pub(crate) fn encode<E>(expr: &Expr<E>) -> Result<Vec<u8>, EncodeError> {
+pub(crate) fn encode(expr: &Expr) -> Result<Vec<u8>, EncodeError> {
     serde_cbor::ser::to_vec(&Serialize::Expr(expr))
         .map_err(|e| EncodeError::CBORError(e))
 }
 
-enum Serialize<'a, E> {
-    Expr(&'a Expr<E>),
+enum Serialize<'a> {
+    Expr(&'a Expr),
     CBOR(cbor::Value),
-    RecordMap(&'a DupTreeMap<Label, Expr<E>>),
-    UnionMap(&'a DupTreeMap<Label, Option<Expr<E>>>),
+    RecordMap(&'a DupTreeMap<Label, Expr>),
+    UnionMap(&'a DupTreeMap<Label, Option<Expr>>),
 }
 
 macro_rules! count {
@@ -39,7 +38,7 @@ macro_rules! ser_seq {
     }};
 }
 
-fn serialize_subexpr<S, E>(ser: S, e: &Expr<E>) -> Result<S::Ok, S::Error>
+fn serialize_subexpr<S>(ser: S, e: &Expr) -> Result<S::Ok, S::Error>
 where
     S: serde::ser::Serializer,
 {
@@ -49,11 +48,11 @@ where
     use syntax::ExprKind::*;
 
     use self::Serialize::{RecordMap, UnionMap};
-    fn expr<E>(x: &Expr<E>) -> self::Serialize<'_, E> {
+    fn expr(x: &Expr) -> self::Serialize<'_> {
         self::Serialize::Expr(x)
     }
     let cbor =
-        |v: cbor::Value| -> self::Serialize<'_, E> { self::Serialize::CBOR(v) };
+        |v: cbor::Value| -> self::Serialize<'_> { self::Serialize::CBOR(v) };
     let tag = |x: u64| cbor(U64(x));
     let null = || cbor(cbor::Value::Null);
     let label = |l: &Label| cbor(cbor::Value::String(l.into()));
@@ -166,16 +165,10 @@ where
         }
         Completion(x, y) => ser_seq!(ser; tag(3), tag(13), expr(x), expr(y)),
         Import(import) => serialize_import(ser, import),
-        Embed(_) => unimplemented!(
-            "An expression with resolved imports cannot be binary-encoded"
-        ),
     }
 }
 
-fn serialize_import<S, E>(
-    ser: S,
-    import: &Import<Expr<E>>,
-) -> Result<S::Ok, S::Error>
+fn serialize_import<S>(ser: S, import: &Import<Expr>) -> Result<S::Ok, S::Error>
 where
     S: serde::ser::Serializer,
 {
@@ -256,7 +249,7 @@ where
     ser_seq.end()
 }
 
-impl<'a, E> serde::ser::Serialize for Serialize<'a, E> {
+impl<'a> serde::ser::Serialize for Serialize<'a> {
     fn serialize<S>(&self, ser: S) -> Result<S::Ok, S::Error>
     where
         S: serde::ser::Serializer,
@@ -282,10 +275,8 @@ impl<'a, E> serde::ser::Serialize for Serialize<'a, E> {
     }
 }
 
-fn collect_nested_applications<'a, E>(
-    e: &'a Expr<E>,
-) -> (&'a Expr<E>, Vec<&'a Expr<E>>) {
-    fn go<'a, E>(e: &'a Expr<E>, vec: &mut Vec<&'a Expr<E>>) -> &'a Expr<E> {
+fn collect_nested_applications<'a>(e: &'a Expr) -> (&'a Expr, Vec<&'a Expr>) {
+    fn go<'a>(e: &'a Expr, vec: &mut Vec<&'a Expr>) -> &'a Expr {
         match e.as_ref() {
             ExprKind::App(f, a) => {
                 vec.push(a);
@@ -299,15 +290,10 @@ fn collect_nested_applications<'a, E>(
     (e, vec)
 }
 
-type LetBinding<'a, E> = (&'a Label, &'a Option<Expr<E>>, &'a Expr<E>);
+type LetBinding<'a> = (&'a Label, &'a Option<Expr>, &'a Expr);
 
-fn collect_nested_lets<'a, E>(
-    e: &'a Expr<E>,
-) -> (&'a Expr<E>, Vec<LetBinding<'a, E>>) {
-    fn go<'a, E>(
-        e: &'a Expr<E>,
-        vec: &mut Vec<LetBinding<'a, E>>,
-    ) -> &'a Expr<E> {
+fn collect_nested_lets<'a>(e: &'a Expr) -> (&'a Expr, Vec<LetBinding<'a>>) {
+    fn go<'a>(e: &'a Expr, vec: &mut Vec<LetBinding<'a>>) -> &'a Expr {
         match e.as_ref() {
             ExprKind::Let(l, t, v, e) => {
                 vec.push((l, t, v));
diff --git a/dhall/src/syntax/text/parser.rs b/dhall/src/syntax/text/parser.rs
index 8d571c0..0ff1363 100644
--- a/dhall/src/syntax/text/parser.rs
+++ b/dhall/src/syntax/text/parser.rs
@@ -5,23 +5,19 @@ use std::rc::Rc;
 
 use pest_consume::{match_nodes, Parser};
 
-use crate::syntax;
 use crate::syntax::map::{DupTreeMap, DupTreeSet};
 use crate::syntax::ExprKind::*;
 use crate::syntax::{
-    Double, FilePath, FilePrefix, Hash, ImportLocation, ImportMode, Integer,
-    InterpolatedText, InterpolatedTextContents, Label, NaiveDouble, Natural,
-    Scheme, Span, URL, V,
+    Double, Expr, FilePath, FilePrefix, Hash, ImportLocation, ImportMode,
+    Integer, InterpolatedText, InterpolatedTextContents, Label, NaiveDouble,
+    Natural, Scheme, Span, UnspannedExpr, URL, V,
 };
-use crate::Normalized;
 
 // This file consumes the parse tree generated by pest and turns it into
 // our own AST. All those custom macros should eventually moved into
 // their own crate because they are quite general and useful. For now they
 // are here and hopefully you can figure out how they work.
 
-type Expr = syntax::Expr<Normalized>;
-type UnspannedExpr = syntax::UnspannedExpr<Normalized>;
 type ParsedText = InterpolatedText<Expr>;
 type ParsedTextContents = InterpolatedTextContents<Expr>;
 type ParseInput<'input> = pest_consume::Node<'input, Rule, Rc<str>>;
diff --git a/dhall/src/syntax/text/printer.rs b/dhall/src/syntax/text/printer.rs
index 06dd70f..d1c9588 100644
--- a/dhall/src/syntax/text/printer.rs
+++ b/dhall/src/syntax/text/printer.rs
@@ -19,17 +19,17 @@ enum PrintPhase {
 // Wraps an Expr with a phase, so that phase selection can be done separate from the actual
 // printing.
 #[derive(Clone)]
-struct PhasedExpr<'a, E>(&'a Expr<E>, PrintPhase);
+struct PhasedExpr<'a>(&'a Expr, PrintPhase);
 
-impl<'a, E: Display + Clone> PhasedExpr<'a, E> {
-    fn phase(self, phase: PrintPhase) -> PhasedExpr<'a, E> {
+impl<'a> PhasedExpr<'a> {
+    fn phase(self, phase: PrintPhase) -> PhasedExpr<'a> {
         PhasedExpr(self.0, phase)
     }
 }
 
-impl<E: Display + Clone> UnspannedExpr<E> {
+impl UnspannedExpr {
     // Annotate subexpressions with the appropriate phase, defaulting to Base
-    fn annotate_with_phases<'a>(&'a self) -> ExprKind<PhasedExpr<'a, E>, E> {
+    fn annotate_with_phases<'a>(&'a self) -> ExprKind<PhasedExpr<'a>> {
         use crate::syntax::ExprKind::*;
         use PrintPhase::*;
         let with_base = self.map_ref(|e| PhasedExpr(e, Base));
@@ -134,7 +134,7 @@ where
 }
 
 /// Generic instance that delegates to subexpressions
-impl<SE: Display + Clone, E: Display> Display for ExprKind<SE, E> {
+impl<SE: Display + Clone> Display for ExprKind<SE> {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         use crate::syntax::ExprKind::*;
         match self {
@@ -232,19 +232,18 @@ impl<SE: Display + Clone, E: Display> Display for ExprKind<SE, E> {
                 write!(f, "{}::{}", a, b)?;
             }
             Import(a) => a.fmt(f)?,
-            Embed(a) => a.fmt(f)?,
         }
         Ok(())
     }
 }
 
-impl<E: Display + Clone> Display for Expr<E> {
+impl Display for Expr {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         self.as_ref().fmt_phase(f, PrintPhase::Base)
     }
 }
 
-impl<'a, E: Display + Clone> Display for PhasedExpr<'a, E> {
+impl<'a> Display for PhasedExpr<'a> {
     fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
         self.0.as_ref().fmt_phase(f, self.1)
     }
-- 
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