From d78f1088c8900d24e3391bd835ad80cb95756833 Mon Sep 17 00:00:00 2001
From: nub31 <oliverlhs@outlook.com>
Date: Fri, 12 Sep 2025 23:18:06 +0200
Subject: [PATCH] Better error messages for function parameter mismatch

---
 compiler/NubLang/TypeChecking/TypeChecker.cs | 23 +++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/compiler/NubLang/TypeChecking/TypeChecker.cs b/compiler/NubLang/TypeChecking/TypeChecker.cs
index 6154708..b1a7300 100644
--- a/compiler/NubLang/TypeChecking/TypeChecker.cs
+++ b/compiler/NubLang/TypeChecking/TypeChecker.cs
@@ -456,7 +456,10 @@ public sealed class TypeChecker
 
         if (expression.Parameters.Count != funcType.Parameters.Count)
         {
-            throw new TypeCheckerException(Diagnostic.Error($"Function {funcType} expects {funcType.Parameters} but got {expression.Parameters.Count} parameters").At(expression.Expression).Build());
+            throw new TypeCheckerException(Diagnostic
+                .Error($"Function {funcType} expects {funcType.Parameters.Count} parameters but got {expression.Parameters.Count}")
+                .At(expression.Parameters.LastOrDefault(expression))
+                .Build());
         }
 
         var parameters = new List<ExpressionNode>();
@@ -468,7 +471,10 @@ public sealed class TypeChecker
             var parameterExpression = CheckExpression(parameter, expectedType);
             if (parameterExpression.Type != expectedType)
             {
-                throw new TypeCheckerException(Diagnostic.Error($"Parameter {i + 1} does not match the type {expectedType} for function {funcType}").At(parameter).Build());
+                throw new TypeCheckerException(Diagnostic
+                    .Error($"Parameter {i + 1} does not match the type {expectedType} for function {funcType}")
+                    .At(parameter)
+                    .Build());
             }
 
             parameters.Add(parameterExpression);
@@ -489,6 +495,14 @@ public sealed class TypeChecker
                 throw new TypeCheckerException(Diagnostic.Error($"Function {expression.Name} not found on struct {structType}").At(expression).Build());
             }
 
+            if (expression.Parameters.Count != function.Type.Parameters.Count)
+            {
+                throw new TypeCheckerException(Diagnostic
+                    .Error($"Function {function.Type} expects {function.Type.Parameters.Count} parameters but got {expression.Parameters.Count}")
+                    .At(expression.Parameters.LastOrDefault(expression))
+                    .Build());
+            }
+
             var parameters = new List<ExpressionNode>();
             for (var i = 0; i < expression.Parameters.Count; i++)
             {
@@ -498,7 +512,10 @@ public sealed class TypeChecker
                 var parameterExpression = CheckExpression(parameter, expectedType);
                 if (parameterExpression.Type != expectedType)
                 {
-                    throw new TypeCheckerException(Diagnostic.Error($"Parameter {i + 1} does not match the type {expectedType} for function {function}").At(parameter).Build());
+                    throw new TypeCheckerException(Diagnostic
+                        .Error($"Parameter {i + 1} does not match the type {expectedType} for function {function}")
+                        .At(parameter)
+                        .Build());
                 }
 
                 parameters.Add(parameterExpression);