From 08e1d8ece4314b56d64fa08595c2e043b97896d1 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 6 Apr 2020 17:19:31 +0100
Subject: Split off operations from main expr enum

---
 dhall/src/syntax/ast/visitor.rs | 100 ++++++++++++----------------------------
 1 file changed, 30 insertions(+), 70 deletions(-)

(limited to 'dhall/src/syntax/ast/visitor.rs')

diff --git a/dhall/src/syntax/ast/visitor.rs b/dhall/src/syntax/ast/visitor.rs
index 0a0c5ef..7244d0a 100644
--- a/dhall/src/syntax/ast/visitor.rs
+++ b/dhall/src/syntax/ast/visitor.rs
@@ -1,22 +1,13 @@
+use itertools::Itertools;
 use std::iter::FromIterator;
 
 use crate::syntax::*;
 
-fn vec<'a, T, U, Err>(
-    x: &'a [T],
-    f: impl FnMut(&'a T) -> Result<U, Err>,
-) -> Result<Vec<U>, Err> {
-    x.iter().map(f).collect()
-}
-
 fn opt<'a, T, U, Err>(
     x: &'a Option<T>,
     f: impl FnOnce(&'a T) -> Result<U, Err>,
 ) -> Result<Option<U>, Err> {
-    Ok(match x {
-        Some(x) => Some(f(x)?),
-        None => None,
-    })
+    x.as_ref().map(f).transpose()
 }
 
 fn dupmap<'a, SE1, SE2, T, Err>(
@@ -30,27 +21,6 @@ where
     x.into_iter().map(|(k, x)| Ok((k.clone(), f(x)?))).collect()
 }
 
-fn optdupmap<'a, SE1, SE2, T, Err>(
-    x: impl IntoIterator<Item = (&'a Label, &'a Option<SE1>)>,
-    mut f: impl FnMut(&'a SE1) -> Result<SE2, Err>,
-) -> Result<T, Err>
-where
-    SE1: 'a,
-    T: FromIterator<(Label, Option<SE2>)>,
-{
-    x.into_iter()
-        .map(|(k, x)| {
-            Ok((
-                k.clone(),
-                match x {
-                    Some(x) => Some(f(x)?),
-                    None => None,
-                },
-            ))
-        })
-        .collect()
-}
-
 pub fn visit_ref<'a, F, SE1, SE2, Err>(
     input: &'a ExprKind<SE1>,
     mut f: F,
@@ -60,54 +30,44 @@ where
 {
     // Can't use closures because of borrowing rules
     macro_rules! expr {
+        () => {
+            |e| Ok(expr!(e))
+        };
         ($e:expr) => {
-            f(None, $e)
+            f(None, $e)?
         };
         ($l:expr, $e:expr) => {
-            f(Some($l), $e)
+            f(Some($l), $e)?
+        };
+    }
+    macro_rules! opt {
+        () => {
+            |e| Ok(opt!(e))
+        };
+        ($e:expr) => {
+            opt($e, |e| Ok(expr!(e)))?
         };
     }
 
     use crate::syntax::ExprKind::*;
     Ok(match input {
         Var(v) => Var(v.clone()),
-        Lam(l, t, e) => {
-            let t = expr!(t)?;
-            let e = expr!(l, e)?;
-            Lam(l.clone(), t, e)
-        }
-        Pi(l, t, e) => {
-            let t = expr!(t)?;
-            let e = expr!(l, e)?;
-            Pi(l.clone(), t, e)
-        }
-        Let(l, t, a, e) => {
-            let t = opt(t, &mut |e| expr!(e))?;
-            let a = expr!(a)?;
-            let e = expr!(l, e)?;
-            Let(l.clone(), t, a, e)
-        }
-        App(f, a) => App(expr!(f)?, expr!(a)?),
-        Annot(x, t) => Annot(expr!(x)?, expr!(t)?),
+        Lam(l, t, e) => Lam(l.clone(), expr!(t), expr!(l, e)),
+        Pi(l, t, e) => Pi(l.clone(), expr!(t), expr!(l, e)),
+        Let(l, t, a, e) => Let(l.clone(), opt!(t), expr!(a), expr!(l, e)),
         Const(k) => Const(*k),
-        Builtin(v) => Builtin(*v),
         Num(n) => Num(n.clone()),
-        TextLit(t) => TextLit(t.traverse_ref(|e| expr!(e))?),
-        BinOp(o, x, y) => BinOp(*o, expr!(x)?, expr!(y)?),
-        BoolIf(b, t, f) => BoolIf(expr!(b)?, expr!(t)?, expr!(f)?),
-        EmptyListLit(t) => EmptyListLit(expr!(t)?),
-        NEListLit(es) => NEListLit(vec(es, |e| expr!(e))?),
-        SomeLit(e) => SomeLit(expr!(e)?),
-        RecordType(kts) => RecordType(dupmap(kts, |e| expr!(e))?),
-        RecordLit(kvs) => RecordLit(dupmap(kvs, |e| expr!(e))?),
-        UnionType(kts) => UnionType(optdupmap(kts, |e| expr!(e))?),
-        Merge(x, y, t) => Merge(expr!(x)?, expr!(y)?, opt(t, |e| expr!(e))?),
-        ToMap(x, t) => ToMap(expr!(x)?, opt(t, |e| expr!(e))?),
-        Field(e, l) => Field(expr!(e)?, l.clone()),
-        Projection(e, ls) => Projection(expr!(e)?, ls.clone()),
-        ProjectionByExpr(e, x) => ProjectionByExpr(expr!(e)?, expr!(x)?),
-        Completion(e, x) => Completion(expr!(e)?, expr!(x)?),
-        Assert(e) => Assert(expr!(e)?),
-        Import(i) => Import(i.traverse_ref(|e| expr!(e))?),
+        Builtin(v) => Builtin(*v),
+        TextLit(t) => TextLit(t.traverse_ref(expr!())?),
+        SomeLit(e) => SomeLit(expr!(e)),
+        EmptyListLit(t) => EmptyListLit(expr!(t)),
+        NEListLit(es) => NEListLit(es.iter().map(expr!()).try_collect()?),
+        RecordType(kts) => RecordType(dupmap(kts, expr!())?),
+        RecordLit(kvs) => RecordLit(dupmap(kvs, expr!())?),
+        UnionType(kts) => UnionType(dupmap(kts, opt!())?),
+        Op(op) => Op(op.traverse_ref(expr!())?),
+        Annot(x, t) => Annot(expr!(x), expr!(t)),
+        Assert(e) => Assert(expr!(e)),
+        Import(i) => Import(i.traverse_ref(expr!())?),
     })
 }
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