2 files changed, 9 insertions, 3 deletions
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index f3018fdb..af843021 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -3,11 +3,11 @@ package org.shedlang.compiler.typechecker;
 import org.shedlang.compiler.ast.typed.*;
 import org.shedlang.compiler.ast.untyped.*;
 import org.shedlang.compiler.sources.Source;
-import org.shedlang.compiler.sources.Sources;
 import org.shedlang.compiler.typechecker.errors.*;
 import org.shedlang.compiler.typechecker.typesets.TypeSetTypeLevelValue;
 import org.shedlang.compiler.typechecker.typesets.TypeSets;
 import org.shedlang.compiler.types.*;
+import org.shedlang.compiler.util.Iterables;
 import org.shedlang.compiler.util.P;
 import org.shedlang.compiler.util.PCollectors;
 
@@ -638,8 +638,10 @@ public class TypeChecker {
                 var subdependencies = deferredDependenciesByFunctionName.get(dependency.name());
 
                 if (subdependencies == null) {
-                    // TODO: fix source
-                    throw new ReferenceBeforeDefinitionError(dependency.name(), Sources.NULL);
+                    throw new ReferenceBeforeDefinitionError(
+                        dependency.name(),
+                        Iterables.first(dependency.referenceSources())
+                    );
                 }
 
                 for (var subdependency : subdependencies) {
diff --git a/src/main/java/org/shedlang/compiler/util/Iterables.java b/src/main/java/org/shedlang/compiler/util/Iterables.java
index ef392893..27fa3e8d 100644
--- a/src/main/java/org/shedlang/compiler/util/Iterables.java
+++ b/src/main/java/org/shedlang/compiler/util/Iterables.java
@@ -30,6 +30,10 @@ public class Iterables {
         return result;
     }
 
+    public static <T> T first(Iterable<T> iterable) {
+        return iterable.iterator().next();
+    }
+
     public static <T, E extends Exception> void forEachInterspersed(
         Iterable<T> values,
         OnElement<T, E> onElement,