Merge pull request #300115 from mumian/0520-bcp414

Document bcp414

Author: AnnaMHuff

articles/azure-resource-manager/bicep/bicep-core-diagnostics.md

@@ -389,7 +389,7 @@ If you need more information about a particular diagnostic code, select the **Fe
 | <a id='BCP410' />BCP410 | Error | Division by zero is not supported.     |
 | <a id='BCP411' />BCP411 | Error | The type `{type}` cannot be used in a type assignment because it does not fit within one of ARM's primitive type categories (string, int, bool, array, object). |
 | <a id='BCP412' />BCP412 | Error | The variable type is not valid. Please specify one of the following types: `{ToQuotedString(validTypes)}`. |
-| <a id='BCP414' />BCP414 | Error | The `^` indexing operator cannot be used on base expressions of type `{baseType}`.  |
+| <a id='BCP414' />[BCP414](./diagnostics/bcp414.md) | Error | The `^` indexing operator cannot be used on base expressions of type `{baseType}`.  |
 | <a id='BCP415' />BCP415 | Error | The `^` indexing operator cannot be used with index expressions of type `{indexType}`.     |
 | <a id='BCP416' />BCP416 | Error | The supplied string does not match the expected pattern of `{expectedPattern}`.   |
 | <a id='BCP417' />BCP417 | Error | The spread operator `{ellipsis}` cannot be used inside objects with property for-expressions.    |

articles/azure-resource-manager/bicep/diagnostics/bcp414.md

@@ -0,0 +1,47 @@
+---
+title: BCP414
+description: The `^` indexing operator can't be used on base expressions of type <data-type>.
+ms.topic: reference
+ms.custom: devx-track-bicep
+ms.date: 05/27/2025
+---
+
+# Bicep diagnostic code - BCP414
+
+This diagnostic occurs when the [reverse index operator (^)](../operators-access.md#reverse-index-accessor) is used on an expression of an unsupported type, such as object, bool, or int.
+
+## Description
+
+The `^` indexing operator can't be used on base expressions of type `<data-type>`.
+
+## Level
+
+Error
+
+## Examples
+
+The following code attempts to use the `^` operator on an object, which triggers BCP414.
+
+```bicep
+var config = {
+  name: 'example'
+  value: 42
+}
+
+output result any = config[^1] // Error: BCP414 - The "^" indexing operator cannot be used on base expressions of type "object".
+```
+
+Object properties aren't ordered, so they can't be accessed in reverse. The `^` operator also isn't supported when accessing properties with square bracket notation.
+
+```bicep
+var config = { 
+  'property name': 'example'
+  value: 42
+}
+
+output result string = config['property name']
+```
+
+## Next steps
+
+For more information about Bicep diagnostics, see [Bicep core diagnostics](../bicep-core-diagnostics.md).

articles/azure-resource-manager/bicep/toc.yml

@@ -737,5 +737,7 @@ items:
       href: diagnostics/bcp338.md      
     - name: BCP401
       href: diagnostics/bcp401.md
+    - name: BCP414
+      href: diagnostics/bcp414.md
   - name: Azure CLI
     href: /cli/azure/resource