From facd2c587d96510c5a808f19d37b40c1fc2d2618 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Mon, 11 Nov 2019 17:20:48 +0000
Subject: Parse projection by expression

---
 dhall/src/phase/binary.rs    | 10 ++++++++++
 dhall/src/phase/normalize.rs |  1 +
 dhall/src/phase/typecheck.rs |  1 +
 3 files changed, 12 insertions(+)

(limited to 'dhall/src/phase')

diff --git a/dhall/src/phase/binary.rs b/dhall/src/phase/binary.rs
index b4f18da..464d71a 100644
--- a/dhall/src/phase/binary.rs
+++ b/dhall/src/phase/binary.rs
@@ -181,6 +181,15 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
                 let l = Label::from(l.as_str());
                 Field(x, l)
             }
+            [U64(10), x, Array(arr)] => {
+                let x = cbor_value_to_dhall(&x)?;
+                if let [y] = arr.as_slice() {
+                    let y = cbor_value_to_dhall(&y)?;
+                    ProjectionByExpr(x, y)
+                } else {
+                    Err(DecodeError::WrongFormatError("projection-by-expr".to_owned()))?
+                }
+            }
             [U64(10), x, rest @ ..] => {
                 let x = cbor_value_to_dhall(&x)?;
                 let labels = rest
@@ -577,6 +586,7 @@ where
                 .chain(once(expr(x)))
                 .chain(ls.iter().map(label)),
         ),
+        ProjectionByExpr(x, y) => ser_seq!(ser; tag(10), expr(x), vec![expr(y)]),
         Import(import) => serialize_import(ser, import),
         Embed(_) => unimplemented!(
             "An expression with resolved imports cannot be binary-encoded"
diff --git a/dhall/src/phase/normalize.rs b/dhall/src/phase/normalize.rs
index 0992f74..ae1aefe 100644
--- a/dhall/src/phase/normalize.rs
+++ b/dhall/src/phase/normalize.rs
@@ -738,6 +738,7 @@ pub(crate) fn normalize_one_layer(
                 }
             }
         }
+        ExprF::ProjectionByExpr(_, _) => unimplemented!("selection by expression"),
 
         ExprF::Merge(ref handlers, ref variant, _) => {
             let handlers_borrow = handlers.as_whnf();
diff --git a/dhall/src/phase/typecheck.rs b/dhall/src/phase/typecheck.rs
index 33919e4..265a20e 100644
--- a/dhall/src/phase/typecheck.rs
+++ b/dhall/src/phase/typecheck.rs
@@ -787,6 +787,7 @@ fn type_last_layer(
                 record_type.get_type()?,
             ))
         }
+        ProjectionByExpr(_, _) => unimplemented!("selection by expression"),
     };
 
     Ok(match ret {
-- 
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