1 files changed, 38 insertions, 29 deletions

diff --git a/dhall/src/phase/binary.rs b/dhall/src/phase/binary.rs
index 5110241..7f72e80 100644
--- a/dhall/src/phase/binary.rs
+++ b/dhall/src/phase/binary.rs
@@ -1,5 +1,6 @@
 use itertools::Itertools;
 use serde_cbor::value::value as cbor;
+use std::iter::FromIterator;
 
 use dhall_syntax::{
     rc, ExprF, FilePrefix, Hash, Import, ImportHashed, ImportLocation,
@@ -131,11 +132,11 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<ParsedExpr, DecodeError> {
                 Merge(x, y, Some(z))
             }
             [U64(7), Object(map)] => {
-                let map = cbor_map_to_dhall_map(map.iter())?;
+                let map = cbor_map_to_dhall_map(map)?;
                 RecordType(map)
             }
             [U64(8), Object(map)] => {
-                let map = cbor_map_to_dhall_map(map.iter())?;
+                let map = cbor_map_to_dhall_map(map)?;
                 RecordLit(map)
             }
             [U64(9), x, String(l)] => {
@@ -144,11 +145,11 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<ParsedExpr, DecodeError> {
                 Field(x, l)
             }
             [U64(11), Object(map)] => {
-                let map = cbor_map_to_dhall_opt_map(map.iter())?;
+                let map = cbor_map_to_dhall_opt_map(map)?;
                 UnionType(map)
             }
             [U64(12), String(l), x, Object(map)] => {
-                let map = cbor_map_to_dhall_opt_map(map.iter())?;
+                let map = cbor_map_to_dhall_opt_map(map)?;
                 let x = cbor_value_to_dhall(&x)?;
                 let l = Label::from(l.as_str());
                 UnionLit(l, x, map)
@@ -331,31 +332,39 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<ParsedExpr, DecodeError> {
     }))
 }
 
-fn cbor_map_to_dhall_map<'a>(
-    map: impl Iterator<Item = (&'a cbor::ObjectKey, &'a cbor::Value)>,
-) -> Result<Vec<(Label, ParsedExpr)>, DecodeError> {
-    map.map(|(k, v)| -> Result<(_, _), _> {
-        let k = k.as_string().ok_or_else(|| {
-            DecodeError::WrongFormatError("map/key".to_owned())
-        })?;
-        let v = cbor_value_to_dhall(v)?;
-        Ok((Label::from(k.as_ref()), v))
-    })
-    .collect::<Result<_, _>>()
+fn cbor_map_to_dhall_map<'a, T>(
+    map: impl IntoIterator<Item = (&'a cbor::ObjectKey, &'a cbor::Value)>,
+) -> Result<T, DecodeError>
+where
+    T: FromIterator<(Label, ParsedExpr)>,
+{
+    map.into_iter()
+        .map(|(k, v)| -> Result<(_, _), _> {
+            let k = k.as_string().ok_or_else(|| {
+                DecodeError::WrongFormatError("map/key".to_owned())
+            })?;
+            let v = cbor_value_to_dhall(v)?;
+            Ok((Label::from(k.as_ref()), v))
+        })
+        .collect::<Result<_, _>>()
 }
 
-fn cbor_map_to_dhall_opt_map<'a>(
-    map: impl Iterator<Item = (&'a cbor::ObjectKey, &'a cbor::Value)>,
-) -> Result<Vec<(Label, Option<ParsedExpr>)>, DecodeError> {
-    map.map(|(k, v)| -> Result<(_, _), _> {
-        let k = k.as_string().ok_or_else(|| {
-            DecodeError::WrongFormatError("map/key".to_owned())
-        })?;
-        let v = match v {
-            cbor::Value::Null => None,
-            _ => Some(cbor_value_to_dhall(v)?),
-        };
-        Ok((Label::from(k.as_ref()), v))
-    })
-    .collect::<Result<_, _>>()
+fn cbor_map_to_dhall_opt_map<'a, T>(
+    map: impl IntoIterator<Item = (&'a cbor::ObjectKey, &'a cbor::Value)>,
+) -> Result<T, DecodeError>
+where
+    T: FromIterator<(Label, Option<ParsedExpr>)>,
+{
+    map.into_iter()
+        .map(|(k, v)| -> Result<(_, _), _> {
+            let k = k.as_string().ok_or_else(|| {
+                DecodeError::WrongFormatError("map/key".to_owned())
+            })?;
+            let v = match v {
+                cbor::Value::Null => None,
+                _ => Some(cbor_value_to_dhall(v)?),
+            };
+            Ok((Label::from(k.as_ref()), v))
+        })
+        .collect::<Result<_, _>>()
 }