From 7c34126993f49596ba425f54e44496599a5d25a2 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 29 Dec 2023 11:48:40 +0000
Subject: Check handling of case with wrong type arg in when expression

---
 .../compiler/typechecker/TypeCheckerWhenTests.java | 57 +++++++++++++++++++++-
 1 file changed, 56 insertions(+), 1 deletion(-)

(limited to 'src/test/java')

diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
index dcf0979d..9ed7b247 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
@@ -206,7 +206,6 @@ public class TypeCheckerWhenTests {
             List.of(TypeParam.forStructType(VARIANT_TYPE_1, "T")),
             VARIANT_TYPE_1
         );
-        // TODO: check type checking fails when constructed type arg for case is incorrect
         var constructedVariantType1 = Types.constructedType(
             variantTypeConstructor1,
             List.of(Types.STRING)
@@ -264,6 +263,62 @@ public class TypeCheckerWhenTests {
         ));
     }
 
+    @Test
+    public void whenCaseHasConstructedTypeWithWrongTypeArgThenErrorIsThrown() {
+        var variantTypeConstructor1 = Types.typeConstructor(
+            List.of(TypeParam.forStructType(VARIANT_TYPE_1, "T")),
+            VARIANT_TYPE_1
+        );
+        var constructedVariantType1 = Types.constructedType(
+            variantTypeConstructor1,
+            List.of(Types.STRING)
+        );
+        var untyped = Untyped.when(
+            Untyped.reference("x"),
+            List.of(
+                Untyped.whenCase(
+                    Untyped.constructedType(
+                        Untyped.typeLevelReference(VARIANT_TYPE_1.name()),
+                        List.of(Untyped.typeLevelReference("Int"))
+                    ),
+                    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(
+                SumVariant.constructedStruct(constructedVariantType1),
+                SumVariant.struct(VARIANT_TYPE_2)
+            )))
+            .enterGlobal(P.map(
+                Map.entry("Int", Types.metaType(Types.INT)),
+                Map.entry("x", SUM_TYPE),
+                Map.entry(VARIANT_TYPE_1.name(), Types.typeConstructorType(variantTypeConstructor1)),
+                Map.entry(VARIANT_TYPE_2.name(), Types.metaType(VARIANT_TYPE_2))
+            ));
+
+        var error = assertThrows(
+            UnreachableWhenCaseError.class,
+            () -> typeCheckExpression(untyped, context)
+        );
+
+        assertThat(
+            error.caseType(),
+            equalTo(Types.constructedType(
+                variantTypeConstructor1,
+                List.of(Types.INT)
+            ))
+        );
+    }
+
     @Test
     public void whenCaseBodiesHaveSameTypeThenExpressionTypeIsThatType() {
         var untyped = Untyped.when(
-- 
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