From 8d45d633dfa60e8d64c9e6e742de4e33496bf0fa Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Tue, 13 Aug 2019 22:11:45 +0200
Subject: Store Imports in their own node instead of in Embed

---
 dhall/src/phase/binary.rs    | 24 ++++++++++++++----------
 dhall/src/phase/mod.rs       |  8 +++++---
 dhall/src/phase/normalize.rs |  3 +++
 dhall/src/phase/typecheck.rs |  3 +++
 4 files changed, 25 insertions(+), 13 deletions(-)

(limited to 'dhall')

diff --git a/dhall/src/phase/binary.rs b/dhall/src/phase/binary.rs
index 3292617..b3a80aa 100644
--- a/dhall/src/phase/binary.rs
+++ b/dhall/src/phase/binary.rs
@@ -19,7 +19,6 @@ pub fn decode(data: &[u8]) -> Result<DecodedSubExpr, DecodeError> {
     }
 }
 
-//TODO: encode normalized expression too
 pub fn encode(expr: &ParsedSubExpr) -> Result<Vec<u8>, EncodeError> {
     serde_cbor::ser::to_vec(&Serialize::Expr(expr))
         .map_err(|e| EncodeError::CBORError(e))
@@ -264,7 +263,7 @@ fn cbor_value_to_dhall(
                             // TODO
                             // Some(x) => {
                             //     match cbor_value_to_dhall(&x)?.as_ref() {
-                            //         Embed(import) => Some(Box::new(
+                            //         Import(import) => Some(Box::new(
                             //             import.location_hashed.clone(),
                             //         )),
                             //         _ => Err(DecodeError::WrongFormatError(
@@ -340,7 +339,7 @@ fn cbor_value_to_dhall(
                         "import/type".to_owned(),
                     ))?,
                 };
-                Embed(Import {
+                Import(dhall_syntax::Import {
                     mode,
                     location_hashed: ImportHashed { hash, location },
                 })
@@ -573,7 +572,10 @@ where
                 .chain(once(expr(x)))
                 .chain(ls.iter().map(label)),
         ),
-        Embed(import) => serialize_import(ser, import),
+        Import(import) => serialize_import(ser, import),
+        Embed(_) => unimplemented!(
+            "An expression with resolved imports cannot be binary-encoded"
+        ),
     }
 }
 
@@ -631,12 +633,14 @@ where
         ImportLocation::Remote(url) => {
             match &url.headers {
                 None => ser_seq.serialize_element(&Null)?,
-                Some(location_hashed) => ser_seq.serialize_element(
-                    &self::Serialize::Expr(&rc(ExprF::Embed(Import {
-                        mode: ImportMode::Code,
-                        location_hashed: location_hashed.as_ref().clone(),
-                    }))),
-                )?,
+                Some(location_hashed) => {
+                    ser_seq.serialize_element(&self::Serialize::Expr(&rc(
+                        ExprF::Import(dhall_syntax::Import {
+                            mode: ImportMode::Code,
+                            location_hashed: location_hashed.as_ref().clone(),
+                        }),
+                    )))?
+                }
             };
             ser_seq.serialize_element(&url.authority)?;
             for p in &url.path {
diff --git a/dhall/src/phase/mod.rs b/dhall/src/phase/mod.rs
index 7364949..a1e3f29 100644
--- a/dhall/src/phase/mod.rs
+++ b/dhall/src/phase/mod.rs
@@ -2,7 +2,7 @@ use std::borrow::Cow;
 use std::fmt::Display;
 use std::path::Path;
 
-use dhall_syntax::{Const, Import, SubExpr};
+use dhall_syntax::{Const, SubExpr, Void};
 
 use crate::core::thunk::{Thunk, TypedThunk};
 use crate::core::value::Value;
@@ -17,8 +17,8 @@ pub(crate) mod parse;
 pub(crate) mod resolve;
 pub(crate) mod typecheck;
 
-pub type ParsedSubExpr = SubExpr<Import>;
-pub type DecodedSubExpr = SubExpr<Import>;
+pub type ParsedSubExpr = SubExpr<Void>;
+pub type DecodedSubExpr = SubExpr<Void>;
 pub type ResolvedSubExpr = SubExpr<Normalized>;
 pub type NormalizedSubExpr = SubExpr<Normalized>;
 
@@ -26,6 +26,8 @@ pub type NormalizedSubExpr = SubExpr<Normalized>;
 pub struct Parsed(ParsedSubExpr, ImportRoot);
 
 /// An expression where all imports have been resolved
+///
+/// Invariant: there must be no `Import` nodes or `ImportAlt` operations left.
 #[derive(Debug, Clone)]
 pub struct Resolved(ResolvedSubExpr);
 
diff --git a/dhall/src/phase/normalize.rs b/dhall/src/phase/normalize.rs
index 2970f5f..adbcb02 100644
--- a/dhall/src/phase/normalize.rs
+++ b/dhall/src/phase/normalize.rs
@@ -644,6 +644,9 @@ pub fn normalize_one_layer(expr: ExprF<Thunk, Normalized>) -> Value {
     };
 
     let ret = match expr {
+        ExprF::Import(_) => unreachable!(
+            "There should remain no imports in a resolved expression"
+        ),
         ExprF::Embed(_) => unreachable!(),
         ExprF::Var(_) => unreachable!(),
         ExprF::Annot(x, _) => Ret::Thunk(x),
diff --git a/dhall/src/phase/typecheck.rs b/dhall/src/phase/typecheck.rs
index e8b2544..89e2da8 100644
--- a/dhall/src/phase/typecheck.rs
+++ b/dhall/src/phase/typecheck.rs
@@ -407,6 +407,9 @@ fn type_last_layer(
     let mkerr = |msg: TypeMessage| TypeError::new(ctx, msg);
 
     match e {
+        Import(_) => unreachable!(
+            "There should remain no imports in a resolved expression"
+        ),
         Lam(_, _, _) | Pi(_, _, _) | Let(_, _, _, _) | Embed(_) | Var(_) => {
             unreachable!()
         }
-- 
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