Merge pull request #5386 from Rageking8/expand-c2601-error-reference

Expand C2601 error reference

Author: v-dirichards

docs/error-messages/compiler-errors-2/compiler-error-c2601.md

@@ -1,28 +1,51 @@
 ---
-description: "Learn more about: Compiler Error C2601"
 title: "Compiler Error C2601"
-ms.date: "11/04/2016"
+description: "Learn more about: Compiler Error C2601"
+ms.date: 06/04/2025
 f1_keywords: ["C2601"]
 helpviewer_keywords: ["C2601"]
-ms.assetid: 88275582-5f37-45d7-807d-05f06ba00965
 ---
 # Compiler Error C2601
 
-'function' : local function definitions are illegal
+> '*function*': local function definitions are illegal
+
+## Remarks
 
 Code tries to define a function within a function.
 
-Or, there may be an extra brace in your source code before the location of the C2601 error.
+Or, there may be an extra/missing brace before the location of the C2601 error.
 
-The following sample generates C2601:
+## Examples
+
+### Define function within a function
+
+[Lambda Expressions](../../cpp/lambda-expressions-in-cpp.md) may be used to emulate the behavior of local functions:
 
 ```cpp
-// C2601.cpp
-int main() {
-   int i = 0;
+// C2601a.cpp
+int main()
+{
+    int increment(int value)   // C2601
+    {
+        return value + 1;
+    }
+
+    // Try the following line instead:
+    // auto increment = [](int value) { return value + 1; };
 
-   void funcname(int j) {   // C2601
-      j++;
-   }
+    int two = increment(1);
 }
 ```
+
+### Missing closing brace
+
+If a preceding function is missing a closing brace, the subsequent function is taken to be a local function:
+
+```cpp
+// C2601b.cpp
+void func()
+{
+// missing '}' brace here
+
+int main() {}   // C2601
+```