goplus · xushiwei · Oct 9, 2025 · Oct 9, 2025 · Oct 9, 2025 · Oct 9, 2025
diff --git a/CLAUDE.md b/CLAUDE.md
@@ -32,6 +32,13 @@ When implementing new language syntax, follow this two-phase approach:
 - **Type Safety**: Leverage gogen's type information maintenance for semantic correctness
 - **Testing**: Add comprehensive test cases in `cl/_testgop/` covering various usage scenarios
 
+#### Phase 3: Documentation (Third Pull Request)
+**Scope**: User-facing documentation updates
+- **Quick Start Guide**: Add feature documentation to `doc/docs.md` with practical examples
+- **Table of Contents**: Update TOC in quick start to include new feature section
+- **Language Specification**: Update specification documents if needed (e.g., `doc/spec.md`)
+- **Examples**: Provide clear, runnable code examples demonstrating the feature
+
 ### Communication Protocol
 - When I request syntax additions, first confirm the exact grammar specification
 - Always consider backward compatibility with existing Go code
@@ -70,3 +77,7 @@ When implementing new language syntax, follow this two-phase approach:
   - Common usage scenarios
   - Edge cases and error conditions
   - Integration with existing type system
+- **Phase 3**: Documentation validation
+  - Ensure all code examples in documentation are runnable and correct
+  - Verify documentation accurately reflects implemented behavior
+  - Check that TOC links work correctly
diff --git a/doc/docs.md b/doc/docs.md
@@ -108,6 +108,7 @@ Here is my `Hello world` program:
     * [Error handling](#error-handling)
 * [Functions](#functions)
     * [Returning multiple values](#returning-multiple-values)
+    * [Optional parameters](#optional-parameters)
     * [Variadic parameters](#variadic-parameters)
     * [Higher order functions](#higher-order-functions)
     * [Lambda expressions](#lambda-expressions)
@@ -816,6 +817,41 @@ c, _ := foo() // ignore values using `_`
 <h5 align="right"><a href="#table-of-contents">⬆ back to toc</a></h5>
 
 
+### Optional parameters
+
+XGo supports optional parameters using the `T?` syntax. Optional parameters must have zero values as their defaults.
+
+```go
+func greet(name string, count int?) {
+    if count == 0 {
+        count = 1
+    }
+    for i := 0; i < count; i++ {
+        println "Hello,", name
+    }
+}
+
+greet "Alice", 3  // prints "Hello, Alice" three times
+greet "Bob"       // prints "Hello, Bob" once (default behavior)
+```
+
+Optional parameters are denoted by adding `?` after the parameter type. The default value is always the zero value of that type (e.g., `0` for integers, `""` for strings, `false` for booleans).
+
+```go
+func connect(host string, port int?, secure bool?) {
+    if port == 0 {
+        port = 80
+    }
+    println "Connecting to", host, "on port", port, "secure:", secure
+}
+
+connect "example.com", 443, true  // Connecting to example.com on port 443 secure: true
+connect "example.com"              // Connecting to example.com on port 80 secure: false
+```
+
+<h5 align="right"><a href="#table-of-contents">⬆ back to toc</a></h5>
+
+
 ### Variadic parameters
 
 ```go