From 6ce6049bbbfb609cb4d1acde3f4a5549aa3af9fc Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Wed, 25 Oct 2023 22:02:47 +0100
Subject: Check for duplicate named params in function type

---
 .../java/org/shedlang/compiler/typechecker/TypeChecker.java    | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index 3dd5e138..d7ad4627 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -651,6 +651,16 @@ public class TypeChecker {
             })
             .toList();
 
+        var seenParamNames = new HashSet<String>();
+        for (var untypedParamNode : untyped.params().named()) {
+            if (!seenParamNames.add(untypedParamNode.name())) {
+                throw new DuplicateVariableName(
+                    untypedParamNode.name(),
+                    untypedParamNode.source()
+                );
+            }
+        }
+
         var effect = untyped.effect()
             .map(untypedEffect -> typeCheckTypeLevelExpression(
                 TypeSets.EFFECT,
-- 
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