Support inferring return type from multiple return statements

1 files changed, 37 insertions, 3 deletions

diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionBodyTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionBodyTests.java
index 5e80c9a0..8b7bc4f6 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionBodyTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionBodyTests.java
@@ -217,7 +217,7 @@ public class TypeCheckerFunctionBodyTests {
     }
 
     @Test
-    public void givenNoExplicitReturnTypeWhenNoExplicitReturnsThenReturnTypeIsUnit() {
+    public void givenNoExplicitReturnTypeWhenNoReturnStatementsThenReturnTypeIsUnit() {
         var untyped = Untyped.block(List.of(
             Untyped.expressionStatement(Untyped.stringLiteral(""))
         ));
@@ -236,7 +236,7 @@ public class TypeCheckerFunctionBodyTests {
     }
 
     @Test
-    public void givenNoExplicitReturnTypeWhenThereAreExplicitReturnsThenAllBranchesMustReturn() {
+    public void givenNoExplicitReturnTypeWhenThereAreNonUnitReturnStatementsThenAllBranchesMustReturn() {
         var untyped = Untyped.block(List.of(
             Untyped.expressionStatement(Untyped.if_(
                 List.of(
@@ -268,7 +268,7 @@ public class TypeCheckerFunctionBodyTests {
     }
 
     @Test
-    public void givenNoExplicitReturnTypeWhenThereIsOneExplicitReturnThenReturnTypeIsTypeOfReturnExpression() {
+    public void givenNoExplicitReturnTypeWhenThereIsOneReturnStatementThenReturnTypeIsTypeOfReturnExpression() {
         var untyped = Untyped.block(List.of(
             Untyped.functionReturn(Untyped.stringLiteral(""))
         ));
@@ -287,6 +287,40 @@ public class TypeCheckerFunctionBodyTests {
     }
 
     @Test
+    public void givenNoExplicitReturnTypeWhenThereAreMultipleReturnStatementsThenReturnTypeIsCommonSupertypeOfReturnExpressions() {
+        var untyped = Untyped.block(List.of(
+            Untyped.expressionStatement(Untyped.if_(
+                List.of(
+                    Untyped.conditionalBranch(
+                        Untyped.reference("c"),
+                        Untyped.block(List.of(
+                            Untyped.functionReturn(Untyped.stringLiteral(""))
+                        ))
+                    )
+                ),
+                Untyped.block(List.of(
+                    Untyped.functionReturn(Untyped.intLiteral(0))
+                ))
+            ))
+        ));
+        var signature = TypedFunctionSignatureNode.builder()
+            .withoutReturnType()
+            .build();
+        var context = TypeCheckerContext.EMPTY
+            .enterGlobal(P.map(
+                Map.entry("c", Types.BOOL)
+            ));
+
+        var typed = typeCheckFunctionBody(untyped, signature, context);
+
+        assertThat(
+            typed.value(),
+            isTypedFunctionBodyNode()
+                .withType(Types.TOP)
+        );
+    }
+
+    @Test
     public void freeVariablesIncludeVariablesReferencedInFunctionButDefinedOutsideOfFunction() {
         var untyped = Untyped.block(List.of(
             Untyped.expressionStatement(Untyped.reference("y"))