Improve F# nameof pattern documentation with practical examples

[Copilot]

Problem

The existing documentation for the F# nameof pattern didn't clearly demonstrate its usefulness. The example showed:

let f (str: string) =
    match str with
    | nameof str -> "It's 'str'!"
    | _ -> "It is not 'str'!"

This appeared to work identically to using a string literal "str", making it unclear why developers should use nameof instead of plain strings.

Solution

Updated both pattern-matching.md and nameof.md to include:

1. A practical, real-world example showing event deserialization with discriminated unions:

type EventType =
    | OrderCreated
    | OrderShipped
    | OrderDelivered

let handleEvent eventName data =
    match eventName with
    | nameof OrderCreated -> printfn "Processing order creation: %s" data
    | nameof OrderShipped -> printfn "Processing order shipment: %s" data
    | nameof OrderDelivered -> printfn "Processing order delivery: %s" data
    | _ -> printfn "Unknown event type: %s" eventName

2. Clear explanation of benefits:

   • Automatic updates when refactoring (if you rename OrderCreated to OrderPlaced, the pattern automatically updates)
   • Compiler validation prevents typos by ensuring the symbol exists
   • Code remains consistent during refactoring

3. Kept the original simple example for completeness, but moved it after the more compelling use case

The new examples make it immediately clear why nameof pattern is better than hardcoded string literals, especially in scenarios like message deserialization, event handling, and API routing where string values represent type or case names.

Testing

• ✅ All markdown linting passes (markdownlint-cli2)
• ✅ F# code examples compile and execute successfully
• ✅ Changes follow repository documentation guidelines

Original prompt

---

This section details on the original issue you should resolve

<issue_title>usefulness of the nameof pattern is not clear</issue_title>
<issue_description>A compelling use for the nameof pattern is not presented. I can’t see the usefulness from the example given.

let f (str: string) =
    match str with
    | nameof str -> "It's 'str'!"
    | _ -> "It is not 'str'!"

seems to work identically to this:

let f2 (s: string) =
    match s with
    | "str" -> "It's 'str'!"
    | _ -> "It is not 'str'!"

The page linked does not help to clarify.

---

Document Details

⚠ Do not edit this section. It is required for learn.microsoft.com ➟ GitHub issue linking.

• ID: 8a3ed054-03c9-375f-403b-68f0356d5870
• Version Independent ID: 3c167003-13e8-359b-e919-693258e7f48b
• Content: Pattern Matching - F#
• Content Source: docs/fsharp/language-reference/pattern-matching.md
• Product: dotnet-fsharp
• GitHub Login: @cartermp
• Microsoft Alias: dotnetcontent</issue_description>

Comments on the Issue (you are @copilot in this section)

@BillWagner tagging @vzarytovskii for recommendation on the best fix.

Fixes #36396

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Internal previews

📄 File	🔗 Preview link
docs/fsharp/language-reference/nameof.md	docs/fsharp/language-reference/nameof
docs/fsharp/language-reference/pattern-matching.md	docs/fsharp/language-reference/pattern-matching

[BillWagner]

This one is ready for final review.

[Copilot]

Pull Request Overview

This PR addresses feedback about the F# nameof pattern documentation by adding practical, real-world examples that clearly demonstrate its usefulness over string literals. The changes improve developer understanding by showing compelling use cases for the nameof pattern in event handling and message deserialization scenarios.

• Added a practical event handling example using discriminated unions that demonstrates the refactoring safety benefits of nameof patterns
• Explained the specific advantages of using nameof over string literals (automatic updates during refactoring, compiler validation, consistency)
• Added AI usage disclosure frontmatter to both documentation files

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
docs/fsharp/language-reference/pattern-matching.md	Enhanced nameof pattern section with practical event handling example and clear benefit explanations
docs/fsharp/language-reference/nameof.md	Updated nameof pattern matching section with the same practical example and benefits