Add test for duplicate param names

1 files changed, 23 insertions, 0 deletions

diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionDefinitionTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionDefinitionTests.java
index 78b89e90..00fa8e9e 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionDefinitionTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerFunctionDefinitionTests.java
@@ -4,6 +4,7 @@ import org.junit.jupiter.api.Test;
 import org.shedlang.compiler.ast.untyped.Untyped;
 import org.shedlang.compiler.ast.untyped.UntypedCallNode;
 import org.shedlang.compiler.ast.untyped.UntypedFunctionDefinitionNode;
+import org.shedlang.compiler.typechecker.errors.DuplicateVariableName;
 import org.shedlang.compiler.typechecker.errors.UnexpectedTypeError;
 import org.shedlang.compiler.typechecker.typesets.TypeSets;
 import org.shedlang.compiler.types.Effects;
@@ -80,6 +81,28 @@ public class TypeCheckerFunctionDefinitionTests {
     }
 
     @Test
+    public void paramsMustHaveUniqueNames() {
+        var untyped = UntypedFunctionDefinitionNode.builder()
+            .addPositionalParam("x", Untyped.typeLevelReference("String"))
+            .addPositionalParam("x", Untyped.typeLevelReference("Int"))
+            .withReturnType(Untyped.typeLevelReference("Unit"))
+            .build();
+        var context = TypeCheckerContext.EMPTY
+            .enterGlobal(P.map(
+                Map.entry("Int", Types.metaType(Types.INT)),
+                Map.entry("String", Types.metaType(Types.STRING)),
+                Map.entry("Unit", Types.metaType(Types.UNIT))
+            ));
+
+        var error = assertThrows(
+            DuplicateVariableName.class,
+            () -> typeCheckNamespaceStatement(untyped, context)
+        );
+
+        assertThat(error.variableName(), equalTo("x"));
+    }
+
+    @Test
     public void effectIsTypeChecked() {
         var untyped = UntypedFunctionDefinitionNode.builder()
             .withEffect(Untyped.typeLevelReference("Io"))