Check constraints are retained from sum subtype

1 files changed, 38 insertions, 0 deletions

diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
index 79b80179..7edff026 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
@@ -385,6 +385,44 @@ public class TypeCheckerIsSubTypeTests {
         ));
     }
 
+    @Test
+    public void constraintsFromSumSubtypeAreRetained() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var sumType = Types.sum(namespaceName, "Sum");
+        var variantType = Types.struct(namespaceName, "Variant2");
+        var variantTypeConstructor = Types.typeConstructor(
+            List.of(TypeParam.forStructType(variantType, "T")),
+            variantType
+        );
+        var typeInfos = TypeInfos.EMPTY
+            .addSumTypeInfo(sumType, new SumTypeInfo(P.orderedSet(
+                Types.constructedStructType(
+                    variantTypeConstructor,
+                    List.of(TypeParam.forSumType(sumType, "T"))
+                )
+            )));
+
+        var constraints = TypeCheckerSubTyping.constraints(
+            List.of(TypeParam.forSumType(sumType, "T")),
+            typeInfos
+        );
+        constraints = TypeCheckerSubTyping.addSubtypeConstraint(
+            sumType,
+            Types.constructedStructType(
+                variantTypeConstructor,
+                List.of(Types.STRING)
+            ),
+            Sources.NULL,
+            constraints
+        );
+
+        assertThat(constraints.typeBounds().get(TypeParam.forSumType(sumType, "T")), allOf(
+            has("lower", x -> x.lower(), isSequence(equalTo(Types.STRING))),
+            has("upper", x -> x.upper(), isSequence(equalTo(Types.STRING)))
+        ));
+    }
+
+
     // == Constructed types ==
 
     @Test