From ce8dfcfecd0937fbf2f4d5b941517f3750f29af2 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 30 Sep 2023 17:31:10 +0100
Subject: Add subtyping for bottom type

---
 .../typechecker/TypeCheckerIsSubTypeTests.java     | 48 ++++++++++++++++++++++
 1 file changed, 48 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 c80a861a..b7da683c 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
@@ -57,4 +57,52 @@ public class TypeCheckerIsSubTypeTests {
             equalTo(true)
         );
     }
+
+    @Test
+    public void topTypeIsSubTypeOfNoOtherTypes() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var context = TypeCheckerContext.EMPTY;
+
+        assertThat(isSubType(Types.TOP, Types.INT, context), equalTo(false));
+        assertThat(
+            isSubType(
+                Types.TOP,
+                new StructType(namespaceName, "X"),
+                context
+            ),
+            equalTo(false)
+        );
+    }
+
+    @Test
+    public void bottomTypeIsSubTypeOfAllTypes() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var context = TypeCheckerContext.EMPTY;
+
+        assertThat(isSubType(Types.BOTTOM, Types.INT, context), equalTo(true));
+        assertThat(
+            isSubType(
+                Types.BOTTOM,
+                new StructType(namespaceName, "X"),
+                context
+            ),
+            equalTo(true)
+        );
+    }
+
+    @Test
+    public void bottomTypeIsSuperTypeOfNoOtherTypes() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var context = TypeCheckerContext.EMPTY;
+
+        assertThat(isSubType(Types.INT, Types.BOTTOM, context), equalTo(false));
+        assertThat(
+            isSubType(
+                new StructType(namespaceName, "X"),
+                Types.BOTTOM,
+                context
+            ),
+            equalTo(false)
+        );
+    }
 }
-- 
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