Check for duplicate cases

1 files changed, 35 insertions, 0 deletions

diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
index 906e2cec..f593a710 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerWhenTests.java
@@ -2,6 +2,7 @@ package org.shedlang.compiler.typechecker;
 
 import org.junit.jupiter.api.Test;
 import org.shedlang.compiler.ast.untyped.Untyped;
+import org.shedlang.compiler.typechecker.errors.DuplicateWhenCaseError;
 import org.shedlang.compiler.typechecker.errors.UnhandledVariantError;
 import org.shedlang.compiler.typechecker.errors.UnreachableWhenCaseError;
 import org.shedlang.compiler.typechecker.errors.WhenExpressionIsNotInstanceOfSumTypeError;
@@ -108,6 +109,40 @@ public class TypeCheckerWhenTests {
     }
 
     @Test
+    public void whenCaseHasDuplicateCaseTypeThenErrorIsThrown() {
+        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_1.name()),
+                    Untyped.block(List.of(
+                        Untyped.blockReturn(Untyped.stringLiteral("a"))
+                    ))
+                )
+            )
+        );
+        var context = TypeCheckerContext.EMPTY
+            .addSumTypeInfo(SUM_TYPE, new SumTypeInfo(P.orderedSet(VARIANT_TYPE_1)))
+            .enterGlobal(P.map(
+                Map.entry("x", SUM_TYPE),
+                Map.entry(VARIANT_TYPE_1.name(), Types.metaType(VARIANT_TYPE_1))
+            ));
+
+        var error = assertThrows(
+            DuplicateWhenCaseError.class,
+            () -> TypeChecker.typeCheckExpression(untyped, context)
+        );
+
+        assertThat(error.caseType(), equalTo(VARIANT_TYPE_1));
+    }
+
+    @Test
     public void whenAllCasesAreHandledThenExpressionTypeChecks() {
         var untyped = Untyped.when(
             Untyped.reference("x"),