2 files changed, 29 insertions, 8 deletions

diff --git a/dhall/src/core/value.rs b/dhall/src/core/value.rs
index b4b6b08..b6c156e 100644
--- a/dhall/src/core/value.rs
+++ b/dhall/src/core/value.rs
@@ -1,7 +1,7 @@
 use std::cell::{Ref, RefCell, RefMut};
 use std::rc::Rc;
 
-use dhall_syntax::{Builtin, Const};
+use dhall_syntax::{Builtin, Const, Span};
 
 use crate::core::context::TypecheckContext;
 use crate::core::valuef::ValueF;
@@ -36,6 +36,7 @@ struct ValueInternal {
     value: ValueF,
     /// This is None if and only if `value` is `Sort` (which doesn't have a type)
     ty: Option<Value>,
+    span: Span,
 }
 
 /// Stores a possibly unevaluated value. Gets (partially) normalized on-demand,
@@ -69,18 +70,21 @@ impl ValueInternal {
                 form: Unevaled,
                 value: ValueF::Const(Const::Type),
                 ty: None,
+                span: Span::Artificial,
             },
             |vint| match (&vint.form, &vint.ty) {
                 (Unevaled, Some(ty)) => ValueInternal {
                     form: WHNF,
                     value: normalize_whnf(vint.value, &ty),
                     ty: vint.ty,
+                    span: vint.span,
                 },
                 // `value` is `Sort`
                 (Unevaled, None) => ValueInternal {
                     form: NF,
                     value: ValueF::Const(Const::Sort),
                     ty: None,
+                    span: vint.span,
                 },
                 // Already in WHNF
                 (WHNF, _) | (NF, _) => vint,
@@ -113,11 +117,12 @@ impl ValueInternal {
 }
 
 impl Value {
-    fn new(value: ValueF, form: Form, ty: Value) -> Value {
+    fn new(value: ValueF, form: Form, ty: Value, span: Span) -> Value {
         ValueInternal {
             form,
             value,
             ty: Some(ty),
+            span,
         }
         .into_value()
     }
@@ -126,14 +131,22 @@ impl Value {
             form: NF,
             value: ValueF::Const(Const::Sort),
             ty: None,
+            span: Span::Artificial,
         }
         .into_value()
     }
     pub(crate) fn from_valuef_and_type(v: ValueF, t: Value) -> Value {
-        Value::new(v, Unevaled, t)
+        Value::new(v, Unevaled, t, Span::PlaceHolder)
+    }
+    pub(crate) fn from_valuef_and_type_and_span(
+        v: ValueF,
+        t: Value,
+        span: Span,
+    ) -> Value {
+        Value::new(v, Unevaled, t, span)
     }
     pub(crate) fn from_valuef_and_type_whnf(v: ValueF, t: Value) -> Value {
-        Value::new(v, WHNF, t)
+        Value::new(v, WHNF, t, Span::PlaceHolder)
     }
     pub(crate) fn from_const(c: Const) -> Self {
         const_to_value(c)
@@ -258,6 +271,7 @@ impl Shift for ValueInternal {
             form: self.form,
             value: self.value.shift(delta, var)?,
             ty: self.ty.shift(delta, var)?,
+            span: self.span.clone(),
         })
     }
 }
@@ -285,6 +299,7 @@ impl Subst<Value> for ValueInternal {
             form: Unevaled,
             value: self.value.subst_shift(var, val),
             ty: self.ty.subst_shift(var, val),
+            span: self.span.clone(),
         }
     }
 }
diff --git a/dhall/src/phase/typecheck.rs b/dhall/src/phase/typecheck.rs
index 4d8c7d3..63f5157 100644
--- a/dhall/src/phase/typecheck.rs
+++ b/dhall/src/phase/typecheck.rs
@@ -304,6 +304,7 @@ fn type_with(
     e: Expr<Normalized>,
 ) -> Result<Value, TypeError> {
     use dhall_syntax::ExprF::{Annot, Embed, Lam, Let, Pi, Var};
+    let span = e.span();
 
     Ok(match e.as_ref() {
         Lam(var, annot, body) => {
@@ -348,7 +349,7 @@ fn type_with(
                 |e| type_with(ctx, e.clone()),
                 |_, _| unreachable!(),
             )?;
-            type_last_layer(ctx, expr)?
+            type_last_layer(ctx, expr, span)?
         }
     })
 }
@@ -358,6 +359,7 @@ fn type_with(
 fn type_last_layer(
     ctx: &TypecheckContext,
     e: ExprF<Value, Normalized>,
+    span: Span,
 ) -> Result<Value, TypeError> {
     use crate::error::TypeMessage::*;
     use dhall_syntax::BinOp::*;
@@ -584,6 +586,7 @@ fn type_last_layer(
                 l.get_type()?,
                 r.get_type()?,
             ),
+            Span::PlaceHolder,
         )?),
         BinOp(RecursiveRecordTypeMerge, l, r) => {
             use crate::phase::normalize::merge_maps;
@@ -619,6 +622,7 @@ fn type_last_layer(
                             l.clone(),
                             r.clone(),
                         ),
+                        Span::PlaceHolder,
                     )
                 },
             )?;
@@ -786,9 +790,11 @@ fn type_last_layer(
     };
 
     Ok(match ret {
-        RetTypeOnly(typ) => {
-            Value::from_valuef_and_type(ValueF::PartialExpr(e), typ)
-        }
+        RetTypeOnly(typ) => Value::from_valuef_and_type_and_span(
+            ValueF::PartialExpr(e),
+            typ,
+            span,
+        ),
         RetWhole(v) => v,
     })
 }