Add Unicode out-of-range example to CS1009 compiler error documentation (#47963)

Copilot · BillWagner · web-flow · commit a6cb49629477 · 2025-08-22T20:39:57.000-04:00
* Initial plan

* Add Unicode out-of-range example to CS1009 documentation

Co-authored-by: BillWagner &lt;493969+BillWagner@users.noreply.github.com&gt;

---------

Co-authored-by: copilot-swe-agent[bot] &lt;198982749+Copilot@users.noreply.github.com&gt;
Co-authored-by: BillWagner &lt;493969+BillWagner@users.noreply.github.com&gt;
diff --git a/docs/csharp/language-reference/compiler-messages/cs1009.md b/docs/csharp/language-reference/compiler-messages/cs1009.md
@@ -34,6 +34,8 @@ class MyClass
       string hexEscapeSequence = '\X061';
       // CS1009; an uppercase \U-style Unicode escape sequence must have exactly 8 hex digits
       string uppercaseUnicodeEscape = '\U0061';
+      // CS1009; Unicode code points above U+10FFFF are invalid (well-formed but out of range)
+      string outOfRangeUnicode = "\U00110000";
    }  
 }  
 ```  

Original file line number	Diff line number	Diff line change
`@@ -34,6 +34,8 @@ class MyClass`
`34`	`34`	`string hexEscapeSequence = '\X061';`
`35`	`35`	`// CS1009; an uppercase \U-style Unicode escape sequence must have exactly 8 hex digits`
`36`	`36`	`string uppercaseUnicodeEscape = '\U0061';`
	`37`	`+ // CS1009; Unicode code points above U+10FFFF are invalid (well-formed but out of range)`
	`38`	`+ string outOfRangeUnicode = "\U00110000";`
`37`	`39`	`}`
`38`	`40`	`}`
`39`	`41`	```