Check type of when expression

2 files changed, 66 insertions, 1 deletions

diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java
index c619409b..375b8923 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java
@@ -72,7 +72,7 @@ public class TypeCheckerIfTests {
     }
 
     @Test
-    public void whenBranchesHaveDifferentTypesThenTypeOfIfIsUnionOfBranchTypes() {
+    public void whenBranchesHaveDifferentTypesThenTypeOfIfIsCommonSuperTypeOfBranchTypes() {
         var untyped = Untyped.if_(
             List.of(
                 Untyped.conditionalBranch(
diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
index 4fdaf950..aec35c33 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
@@ -10,6 +10,7 @@ import java.util.Map;
 
 import static org.shedlang.compiler.ast.typed.TypedNodeMatchers.*;
 import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.equalTo;
 import static org.zwobble.precisely.Matchers.isSequence;
 
 public class TypeCheckerWhenTests {
@@ -65,4 +66,68 @@ public class TypeCheckerWhenTests {
             )
         ));
     }
+
+    @Test
+    public void whenCaseBodiesHaveSameTypeThenExpressionTypeIsThatType() {
+        var untyped = Untyped.when(
+            Untyped.reference("x"),
+            List.of(
+                Untyped.whenCase(
+                    Untyped.typeLevelReference(VARIANT_TYPE_1.name()),
+                    Untyped.block(List.of(
+                        Untyped.blockReturn(Untyped.stringLiteral("a"))
+                    ))
+                ),
+                Untyped.whenCase(
+                    Untyped.typeLevelReference(VARIANT_TYPE_2.name()),
+                    Untyped.block(List.of(
+                        Untyped.blockReturn(Untyped.stringLiteral("b"))
+                    ))
+                )
+            )
+        );
+        var context = TypeCheckerContext.EMPTY
+            .addSumTypeInfo(SUM_TYPE, new SumTypeInfo(P.orderedSet(VARIANT_TYPE_1, VARIANT_TYPE_2)))
+            .enterGlobal(P.map(
+                Map.entry("x", SUM_TYPE),
+                Map.entry(VARIANT_TYPE_1.name(), Types.metaType(VARIANT_TYPE_1)),
+                Map.entry(VARIANT_TYPE_2.name(), Types.metaType(VARIANT_TYPE_2))
+            ));
+
+        var result = TypeChecker.typeCheckExpression(untyped, context);
+
+        assertThat(result.value().type(), equalTo(Types.STRING));
+    }
+
+    @Test
+    public void whenCaseBodiesHaveDifferentTypesThenExpressionTypeIsCommonSuperType() {
+        var untyped = Untyped.when(
+            Untyped.reference("x"),
+            List.of(
+                Untyped.whenCase(
+                    Untyped.typeLevelReference(VARIANT_TYPE_1.name()),
+                    Untyped.block(List.of(
+                        Untyped.blockReturn(Untyped.stringLiteral("a"))
+                    ))
+                ),
+                Untyped.whenCase(
+                    Untyped.typeLevelReference(VARIANT_TYPE_2.name()),
+                    Untyped.block(List.of(
+                        Untyped.blockReturn(Untyped.intLiteral(42))
+                    ))
+                )
+            )
+        );
+        var context = TypeCheckerContext.EMPTY
+            .addSumTypeInfo(SUM_TYPE, new SumTypeInfo(P.orderedSet(VARIANT_TYPE_1, VARIANT_TYPE_2)))
+            .enterGlobal(P.map(
+                Map.entry("x", SUM_TYPE),
+                Map.entry(VARIANT_TYPE_1.name(), Types.metaType(VARIANT_TYPE_1)),
+                Map.entry(VARIANT_TYPE_2.name(), Types.metaType(VARIANT_TYPE_2))
+            ));
+
+        var result = TypeChecker.typeCheckExpression(untyped, context);
+
+        assertThat(result.value().type(), equalTo(Types.TOP));
+    }
 }