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src/actions.rs

@@ -392,7 +392,9 @@ impl EGraph {
                             function.remove(args, self.timestamp);
                         }
                         Change::Subsume => {
-                            if function.decl.subtype != FunctionSubtype::Constructor {
+                            if function.decl.subtype != FunctionSubtype::Constructor
+                                && function.decl.subtype != FunctionSubtype::Relation
+                            {
                                 return Err(Error::SubsumeMergeError(*f));
                             }
                             function

tests/integration_test.rs

@@ -350,8 +350,9 @@ fn test_subsume() {
 }
 
 #[test]
-fn test_subsume_primitive() {
-    // Test that we can subsume a primitive
+fn test_subsume_custom() {
+    // Test that we can't subsume  a custom function
+    // Only relations and constructors are allowed to be subsumed
 
     let mut egraph = EGraph::default();
     let res = egraph.parse_and_run_program(
@@ -365,6 +366,29 @@ fn test_subsume_primitive() {
     assert!(res.is_err());
 }
 
+#[test]
+fn test_subsume_ok() {
+    let mut egraph = EGraph::default();
+    let res = egraph.parse_and_run_program(
+        None,
+        r#"
+        (sort E)
+        (constructor one () E)
+        (constructor two () E)
+        (one)
+        (subsume (one))
+        ;; subsuming a non-existent tuple
+        (subsume (two))
+
+        (relation R (i64))
+        (R 1)
+        (subsume (R 1))
+        (subsume (R 2))
+        "#,
+    );
+    assert!(res.is_ok());
+}
+
 #[test]
 fn test_cant_subsume_merge() {
     // Test that we can't subsume something with a merge function