From bbc57bddb4dea75e3774673dbb173662e930c3dc Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 29 Dec 2023 11:22:55 +0000
Subject: Support subtyping for constructed sum types

---
 .../typechecker/TypeCheckerIsSubTypeTests.java     | 89 ++++++++++++++++++++++
 1 file changed, 89 insertions(+)

(limited to 'src/test/java')

diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
index 568256c2..ca3008f3 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
@@ -4,6 +4,8 @@ import org.junit.jupiter.api.Test;
 import org.shedlang.compiler.types.*;
 import org.shedlang.compiler.util.P;
 
+import java.util.List;
+
 import static org.shedlang.compiler.typechecker.TypeCheckerSubTyping.isSubType;
 import static org.zwobble.precisely.AssertThat.assertThat;
 import static org.zwobble.precisely.Matchers.equalTo;
@@ -137,6 +139,93 @@ public class TypeCheckerIsSubTypeTests {
         assertThat(isSubType(sumType, variantType2, context), equalTo(false));
     }
 
+    @Test
+    public void variantWithoutTypeLevelArgIsSubTypeOfConstructedSumType() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var sumType = Types.sum(namespaceName, "Sum");
+        var sumTypeConstructor = Types.typeConstructor(
+            List.of(TypeParam.forSumType(sumType, "T")),
+            sumType
+        );
+        var constructedSumType = Types.constructedType(
+            sumTypeConstructor,
+            List.of(Types.STRING)
+        );
+        var variantType1 = Types.struct(namespaceName, "Variant1");
+        var variantType2 = Types.struct(namespaceName, "Variant2");
+        var context = TypeCheckerContext.EMPTY
+            .addSumTypeInfo(sumType, new SumTypeInfo(P.orderedSet(
+                SumVariant.struct(variantType1),
+                SumVariant.struct(variantType2)
+            )));
+
+        assertThat(isSubType(variantType1, constructedSumType, context), equalTo(true));
+        assertThat(isSubType(variantType2, constructedSumType, context), equalTo(true));
+    }
+
+    @Test
+    public void variantWithTypeLevelArgIsSubTypeOfConstructedSumType() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var sumType = Types.sum(namespaceName, "Sum");
+        var sumTypeConstructor = Types.typeConstructor(
+            List.of(TypeParam.forSumType(sumType, "T")),
+            sumType
+        );
+        var constructedSumType = Types.constructedType(
+            sumTypeConstructor,
+            List.of(Types.STRING)
+        );
+        var variantType1 = Types.struct(namespaceName, "Variant1");
+        var variantTypeConstructor1 = Types.typeConstructor(
+            List.of(TypeParam.forStructType(variantType1, "T")),
+            variantType1
+        );
+        var constructedVariantType1 = Types.constructedType(
+            variantTypeConstructor1,
+            List.of(Types.STRING)
+        );
+        var variantType2 = Types.struct(namespaceName, "Variant2");
+        var context = TypeCheckerContext.EMPTY
+            .addSumTypeInfo(sumType, new SumTypeInfo(P.orderedSet(
+                SumVariant.constructedStruct(constructedVariantType1),
+                SumVariant.struct(variantType2)
+            )));
+
+        assertThat(isSubType(constructedVariantType1, constructedSumType, context), equalTo(true));
+        assertThat(
+            isSubType(
+                Types.constructedType(variantTypeConstructor1, List.of(Types.INT)),
+                constructedSumType,
+                context
+            ),
+            equalTo(false)
+        );
+    }
+
+    @Test
+    public void variantIsNotSuperTypeOfConstructedSumType() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var sumType = Types.sum(namespaceName, "Sum");
+        var sumTypeConstructor = Types.typeConstructor(
+            List.of(TypeParam.forSumType(sumType, "T")),
+            sumType
+        );
+        var constructedSumType = Types.constructedType(
+            sumTypeConstructor,
+            List.of(Types.STRING)
+        );
+        var variantType1 = Types.struct(namespaceName, "Variant1");
+        var variantType2 = Types.struct(namespaceName, "Variant2");
+        var context = TypeCheckerContext.EMPTY
+            .addSumTypeInfo(sumType, new SumTypeInfo(P.orderedSet(
+                SumVariant.struct(variantType1),
+                SumVariant.struct(variantType2)
+            )));
+
+        assertThat(isSubType(constructedSumType, variantType1, context), equalTo(false));
+        assertThat(isSubType(constructedSumType, variantType2, context), equalTo(false));
+    }
+
     @Test
     public void whenFunctionsHaveDifferentPositionalParamCountsThenTheyAreNotSubtypes() {
         var functionType1 = FunctionType.builder()
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