From 696efe66336a268054c475fab9fe6505bdfc7b60 Mon Sep 17 00:00:00 2001
From: Nadrieril
Date: Sun, 4 Aug 2019 13:00:56 +0200
Subject: Add some new tests and implement import alternatives

---
 dhall_syntax/src/core/expr.rs    | 39 +++++++++++++++++++++++++++++++++++++++
 dhall_syntax/src/core/visitor.rs | 25 +++++++++++++++++++++++++
 2 files changed, 64 insertions(+)

(limited to 'dhall_syntax')

diff --git a/dhall_syntax/src/core/expr.rs b/dhall_syntax/src/core/expr.rs
index df2dc97..e33859b 100644
--- a/dhall_syntax/src/core/expr.rs
+++ b/dhall_syntax/src/core/expr.rs
@@ -307,6 +307,35 @@ impl<N, E> Expr<N, E> {
     {
         trivial_result(self.traverse_embed(|x| Ok(map_embed(x))))
     }
+
+    pub fn traverse_resolve<E2, Err>(
+        &self,
+        visit_embed: impl FnMut(&E) -> Result<E2, Err>,
+    ) -> Result<Expr<N, E2>, Err>
+    where
+        N: Clone,
+    {
+        self.traverse_resolve_with_visitor(&mut visitor::ResolveVisitor(
+            visit_embed,
+        ))
+    }
+
+    pub(crate) fn traverse_resolve_with_visitor<E2, Err, F1>(
+        &self,
+        visitor: &mut visitor::ResolveVisitor<F1>,
+    ) -> Result<Expr<N, E2>, Err>
+    where
+        N: Clone,
+        F1: FnMut(&E) -> Result<E2, Err>,
+    {
+        match self {
+            ExprF::BinOp(BinOp::ImportAlt, l, r) => l
+                .as_ref()
+                .traverse_resolve_with_visitor(visitor)
+                .or(r.as_ref().traverse_resolve_with_visitor(visitor)),
+            _ => self.visit(visitor),
+        }
+    }
 }
 
 impl Expr<X, X> {
@@ -383,6 +412,16 @@ impl<N, E> SubExpr<N, E> {
             )),
         }
     }
+
+    pub fn traverse_resolve<E2, Err>(
+        &self,
+        visit_embed: impl FnMut(&E) -> Result<E2, Err>,
+    ) -> Result<SubExpr<N, E2>, Err>
+    where
+        N: Clone,
+    {
+        Ok(self.rewrap(self.as_ref().traverse_resolve(visit_embed)?))
+    }
 }
 
 impl SubExpr<X, X> {
diff --git a/dhall_syntax/src/core/visitor.rs b/dhall_syntax/src/core/visitor.rs
index 1745fdb..b02544f 100644
--- a/dhall_syntax/src/core/visitor.rs
+++ b/dhall_syntax/src/core/visitor.rs
@@ -358,6 +358,31 @@ where
     }
 }
 
+pub struct ResolveVisitor<F1>(pub F1);
+
+impl<'a, 'b, N, E, E2, Err, F1>
+    ExprFFallibleVisitor<'a, SubExpr<N, E>, SubExpr<N, E2>, E, E2>
+    for &'b mut ResolveVisitor<F1>
+where
+    N: Clone + 'a,
+    F1: FnMut(&E) -> Result<E2, Err>,
+{
+    type Error = Err;
+
+    fn visit_subexpr(
+        &mut self,
+        subexpr: &'a SubExpr<N, E>,
+    ) -> Result<SubExpr<N, E2>, Self::Error> {
+        Ok(subexpr.rewrap(
+            subexpr
+                .as_ref()
+                .traverse_resolve_with_visitor(&mut **self)?,
+        ))
+    }
+    fn visit_embed(self, embed: &'a E) -> Result<E2, Self::Error> {
+        (self.0)(embed)
+    }
+}
 pub struct NoteAbsurdVisitor;
 
 impl<'a, 'b, N, E>
-- 
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