Extract and test isSubType()

1 files changed, 60 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
new file mode 100644
index 00000000..c80a861a
--- /dev/null
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIsSubTypeTests.java
@@ -0,0 +1,60 @@
+package org.shedlang.compiler.typechecker;
+
+import org.junit.jupiter.api.Test;
+import org.shedlang.compiler.types.NamespaceName;
+import org.shedlang.compiler.types.StructType;
+import org.shedlang.compiler.types.Types;
+
+import static org.shedlang.compiler.typechecker.TypeCheckerSubTyping.isSubType;
+import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.equalTo;
+
+public class TypeCheckerIsSubTypeTests {
+    @Test
+    public void typesAreSubTypesOfThemselves() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var context = TypeCheckerContext.EMPTY;
+
+        assertThat(isSubType(Types.INT, Types.INT, context), equalTo(true));
+        assertThat(
+            isSubType(
+                new StructType(namespaceName, "X"),
+                new StructType(namespaceName, "X"),
+                context
+            ),
+            equalTo(true)
+        );
+    }
+
+    @Test
+    public void unrelatedTypesAreNotSubTypes() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var context = TypeCheckerContext.EMPTY;
+
+        assertThat(isSubType(Types.INT, Types.STRING, context), equalTo(false));
+        assertThat(
+            isSubType(
+                new StructType(namespaceName, "X"),
+                new StructType(namespaceName, "Y"),
+                context
+            ),
+            equalTo(false)
+        );
+    }
+
+    @Test
+    public void topTypeIsSuperTypeOfAllTypes() {
+        var namespaceName = NamespaceName.of("Example", "Project");
+        var context = TypeCheckerContext.EMPTY;
+
+        assertThat(isSubType(Types.INT, Types.TOP, context), equalTo(true));
+        assertThat(
+            isSubType(
+                new StructType(namespaceName, "X"),
+                Types.TOP,
+                context
+            ),
+            equalTo(true)
+        );
+    }
+}