Test subtyping when supertype is bound type param

1 files changed, 24 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 88f93472..1ff85fea 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
@@ -1,10 +1,12 @@
 package org.shedlang.compiler.typechecker;
 
 import org.junit.jupiter.api.Test;
+import org.shedlang.compiler.sources.Sources;
 import org.shedlang.compiler.types.*;
 import org.shedlang.compiler.util.P;
 
 import java.util.List;
+import java.util.Map;
 
 import static org.shedlang.compiler.typechecker.TypeCheckerSubTyping.isSubType;
 import static org.zwobble.precisely.AssertThat.assertThat;
@@ -113,6 +115,28 @@ public class TypeCheckerIsSubTypeTests {
         );
     }
 
+    // == Type params ==
+
+    @Test
+    public void whenSupertypeIsBoundTypeParamThenLowerBoundIsAddedToType() {
+        var typeParam = TypeParam.forStructType(
+            Types.struct(NamespaceName.of("Example"), "Struct"),
+            "T"
+        );
+
+        var constraints = TypeCheckerSubTyping.addSubtypeConstraint(
+            Types.INT,
+            typeParam,
+            Sources.NULL,
+            TypeCheckerSubTyping.constraints(List.of(typeParam), TypeInfos.EMPTY)
+        );
+        var result = constraints.solve();
+
+        assertThat(result, equalTo(TypeSubstitutionMap.of(
+            Map.entry(typeParam, Types.INT)
+        )));
+    }
+
     // == Sum types ==
 
     @Test