[bgen] Support BindAs parameters in protocols - #26195

dalexsoto · 2026-07-20T15:04:06Z

Summary

allow parameter-level [BindAs] in [Protocol] and [Model] definitions while continuing to reject properties and return values
preserve native OriginalType metadata and messaging signatures, and resolve parameter attributes through mapped protocol methods in both registrars
use managed parameter types for trimming dependencies and generated XML documentation IDs
add generator, native callback, diagnostics, documentation, and XML-doc golden coverage

Context

This support was extracted from #26158 at @rolfbjarne’s request so that the generalized bgen/registrar feature lands in main independently of the Xcode 27 CoreSpotlight bindings. The deferred CoreSpotlight callback will be added after this change flows to xcode27.0.

Validation

make world with NO_XCODE=1 for the platform-independent main feature
full bgen suite: 399 passed, 1 skipped
XML documentation tests: 4 passed across iOS, tvOS, Mac Catalyst, and macOS

Allow parameter-level BindAs in Protocol and Model definitions while continuing to reject property and return-value usage. Preserve the native OriginalType through generated metadata and messaging signatures, resolve BindAs metadata through protocol interface maps in the static and managed registrars, and emit managed parameter types in DynamicDependency and XML documentation IDs. Add generator, registrar callback, diagnostic, documentation, and XML documentation coverage. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: b96fb7cb-f82d-4cd4-9b60-a7f899f3b42d

Move generalized parameter-level BindAs support for Protocol and Model definitions to #26195, which targets main as requested during review. Temporarily defer the protection-class searchable-items delegate callback and restore its targeted xtro todo entries until the feature flows from main to xcode27.0. Keep the CoreSpotlight compatibility fixes that hide incorrectly shipped APIs with Obsolete and EditorBrowsable attributes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: b96fb7cb-f82d-4cd4-9b60-a7f899f3b42d

Copilot

Pull request overview

This PR extends the binding generator (bgen) and both registrars to support parameter-level [BindAs] inside [Protocol] / [Model] definitions (while continuing to reject [BindAs] on protocol/model properties and return values). It also updates diagnostics, documentation, and adds/updates test coverage (including XML doc “golden” expectations) to validate the new behavior.

Changes:

Allow [BindAs] on protocol/model parameters and propagate the metadata correctly through generator + registrars (including mapped protocol/interface methods).
Adjust marshalling/doc-id generation to use the correct managed vs native parameter types where appropriate (trimming dependencies + XML doc IDs).
Add bindings-test + bgen test coverage and update user-facing docs/error messages to reflect the new constraints.

Reviewed changes

Copilot reviewed 21 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tools/dotnet-linker/Steps/ManagedRegistrarStep.cs	Resolves parameter `[BindAs]` via mapped protocol interface methods for the managed registrar step.
src/ObjCRuntime/Registrar.cs	Resolves parameter `[BindAs]` via mapped protocol interface methods in the runtime registrar.
src/bgen/Generator.cs	Permits protocol/model parameter `[BindAs]`, preserves `OriginalType`, and uses managed types for doc IDs/trimming metadata.
src/bgen/Models/MarshalInfo.cs	Uses `BindAsAttribute.OriginalType` when determining marshaling type info (native signature preservation).
src/bgen/DocumentationManager.cs	Adds an optional parameter-type provider to compute doc IDs using managed parameter types.
src/ObjCRuntime/BindAsAttribute.cs	Updates inline docs to describe parameter support in protocol/model definitions.
src/Resources.resx	Updates BI1050 message to match the new restriction (properties/return values only).
src/Resources.Designer.cs	Regenerates BI1050 designer comment to match updated resource string.
tests/bindings-test/ApiDefinition.cs	Adds a protocol/model method using parameter-level `[BindAs]` for runtime validation.
tests/bindings-test/ProtocolTest.cs	Adds a test that invokes the exported selector and asserts correct BindAs conversion in protocol implementation.
tests/bindings-test/Messaging.cs	Adds an `objc_msgSend` P/Invoke variant returning `void` used by the new protocol BindAs test.
tests/bgen/tests/bindastests.cs	Adds bgen test coverage for parameter `[BindAs]` inside `[Protocol]/[Model]`.
tests/bgen/tests/xmldocs.cs	Adds protocol method with parameter `[BindAs]` to exercise XML doc ID/type generation.
tests/bgen/tests/ExpectedXmlDocs.iOS.xml	Updates XML-doc golden output for BindAs-parameter doc IDs (iOS).
tests/bgen/tests/ExpectedXmlDocs.tvOS.xml	Updates XML-doc golden output for BindAs-parameter doc IDs (tvOS).
tests/bgen/tests/ExpectedXmlDocs.macOS.xml	Updates XML-doc golden output for BindAs-parameter doc IDs (macOS).
tests/bgen/tests/ExpectedXmlDocs.MacCatalyst.xml	Updates XML-doc golden output for BindAs-parameter doc IDs (Mac Catalyst).
tests/bgen/ErrorTests.cs	Updates BI1050 expected error text to match new restriction wording.
docs/website/generator-errors.md	Updates BI1050 documentation to match new restriction wording.
docs/website/binding_types_reference_guide.md	Updates BindAs docs to describe protocol/model parameter support and continued restrictions.
docs/website/binding_objc_libs.md	Updates BindAs docs to describe protocol/model parameter support and continued restrictions.
docs/api/ObjCRuntime/BindAsAttribute.xml	Adds API doc note clarifying protocol/model parameter-only support.

Files not reviewed (1)

src/Resources.Designer.cs: Generated file

Reuse the per-type protocol method map during normal registrar validation instead of rebuilding it for every parameter. Late signature evaluation prepares at most one local map per method, including null results. Thread one local map through each managed-registrar type without adding persistent runtime caches, and skip lookups for properties, constructors, and categories. Add native callback coverage for a protocol method with multiple BindAs parameters. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: b96fb7cb-f82d-4cd4-9b60-a7f899f3b42d

dalexsoto · 2026-07-20T16:22:33Z

Addressed the interface-map performance feedback in 6f41033 without adding persistent runtime caches. Normal registration reuses its existing per-type map, late evaluation builds at most one local map per method, and the managed registrar threads one local map through each type. Added a two-parameter native callback test; both callback tests pass under dynamic, static, and managed-static registrars on Xcode 27.

Update the tvOS and Mac Catalyst MonoVM interpreter preserved API baselines generated by CI for the protocol method-map reuse changes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: b96fb7cb-f82d-4cd4-9b60-a7f899f3b42d

dalexsoto · 2026-07-20T20:04:55Z

Updated the CI-generated tvOS and Mac Catalyst MonoVM interpreter preserved-API baselines in 86a3eeb. Both failed legs were app-size expectation drift from the registrar method-map changes; published NUnit results contained no functional test failures.

Update the iOS MonoVM interpreter preserved API baseline generated by CI for the protocol method-map reuse changes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: b96fb7cb-f82d-4cd4-9b60-a7f899f3b42d

dalexsoto · 2026-07-20T22:07:29Z

Added the CI-generated iOS MonoVM interpreter preserved-API baseline in 6d7b84e. This completes the app-size updates for all three affected platforms: iOS, tvOS, and Mac Catalyst.

dalexsoto · 2026-07-21T00:55:47Z

/azp run xamarin-macios-sim-pr-tests

azure-pipelines · 2026-07-21T00:56:04Z

Azure Pipelines: Successfully started running 1 pipeline(s).

dalexsoto · 2026-07-21T06:36:25Z

/azp run xamarin-macios-sim-pr-tests

azure-pipelines · 2026-07-21T06:36:44Z

Azure Pipelines: Successfully started running 1 pipeline(s).

dalexsoto · 2026-07-21T12:26:44Z

/azp run xamarin-macios-sim-pr-tests

dalexsoto · 2026-07-22T12:04:39Z

/apply-gist https://gist.github.com/vs-mobiletools-engineering-service2/13f6cf31106658c7f12e6a9581f2527d

Applied from gist: https://gist.github.com/vs-mobiletools-engineering-service2/13f6cf31106658c7f12e6a9581f2527d

github-actions · 2026-07-22T12:04:59Z

✅ Applied expected app size files from gist.

vs-mobiletools-engineering-service2 · 2026-07-22T16:42:55Z

⚠️ AppSizeTest expected files changed ⚠️

The AppSizeTest detected changes in the expected app size files.

To update the expected files, add a comment with the following command:

/apply-gist https://gist.github.com/vs-mobiletools-engineering-service2/3cf8ff719be49662de1febf84a2da537

Updated files

iOS-MonoVM-interpreter-preservedapis.txt
MacCatalyst-MonoVM-interpreter-preservedapis.txt
TVOS-MonoVM-interpreter-preservedapis.txt

Pipeline on Agent
Hash: e862a966741b114f303a0305ad01d38a78e3f395 [PR build]

dalexsoto · 2026-07-24T02:26:47Z

@copilot resolve the merge conflicts in this pull request

Resolve conflicts in TVOS and iOS MonoVM interpreter preservedapis expected files by accepting the updated content from main. Co-authored-by: dalexsoto <204671+dalexsoto@users.noreply.github.com>

Copilot · 2026-07-24T02:29:45Z

@copilot resolve the merge conflicts in this pull request

Resolved the merge conflicts in b283d7d. The conflicts were in TVOS-MonoVM-interpreter-preservedapis.txt and iOS-MonoVM-interpreter-preservedapis.txt — those files had been incorrectly emptied by the previously applied CI gist (commit e862a96). The merge takes the valid content from origin/main for both files.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: e9e228af-33c5-4ac3-ac5e-f8839d48f8bc

vs-mobiletools-engineering-service2 · 2026-07-24T06:11:37Z

✅ API diff for current PR / commit

NET (empty diffs)

iOS: vsdrops gist ( No breaking changes )
tvOS: vsdrops gist ( No breaking changes )
MacCatalyst: vsdrops gist ( No breaking changes )
macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

iOS: vsdrops gist ( No breaking changes )
tvOS: vsdrops gist ( No breaking changes )
MacCatalyst: vsdrops gist ( No breaking changes )
macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: 9c5f42720a0bf770a266a906dbe1be14a637ca13 [PR build]

vs-mobiletools-engineering-service2 · 2026-07-24T11:41:40Z

🚀 [CI Build #9c5f427] Test results 🚀

Test results

✅ All tests passed on VSTS: test results.

🎉 All 203 tests passed 🎉

Tests counts

✅ assembly-processing: All 1 tests passed. Html Report (VSDrops) Download
✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 4 tests passed. Html Report (VSDrops) Download
✅ linker (iOS): All 15 tests passed. Html Report (VSDrops) Download
✅ linker (MacCatalyst): All 15 tests passed. Html Report (VSDrops) Download
✅ linker (macOS): All 21 tests passed. Html Report (VSDrops) Download
✅ linker (tvOS): All 15 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 19 tests passed. Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 18 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 19 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 19 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ sharpie: All 1 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ windows: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

macOS tests

✅ Tests on macOS Monterey (12): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Ventura (13): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sonoma (14): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sequoia (15): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Tahoe (26): All 5 tests passed. Html Report (VSDrops) Download

Linux Build Verification

✅ Linux build succeeded

Pipeline on Agent
Hash: 9c5f42720a0bf770a266a906dbe1be14a637ca13 [PR build]

## Summary - Bind `CSSearchableIndexDelegate.searchableItemsForIdentifiers:protectionClass:searchableItemsHandler:` on iOS 27.0, macOS 27.0, and Mac Catalyst 27.0. - Reuse the existing searchable-items completion handler and preserve the native non-null contract. - Remove the resolved iOS, macOS, and Mac Catalyst CoreSpotlight xtro todo files. ## Temporary API shape The native `NSFileProtectionType` parameter is temporarily exposed as `NSString` because bgen still rejects parameter-level `[BindAs]` inside protocol/model definitions. Issue #26273 tracks changing it to `[BindAs (typeof (NSFileProtectionType))] NSString` before Xcode 27 GA, after #26195 lands. ## Validation - `make world` - Clean xtro generation/classification: sanity passed for all platforms - Clean cecil suite: passed - iOS 27 introspection: 44 passed, 0 failed - tvOS 27 introspection: 43 passed, 0 failed - macOS introspection: 32 passed, 0 failed, 2 host-version-gated - Mac Catalyst introspection: 39 passed, 0 failed, 4 expected ignores - Clean filtered `AppSizeTest`: 0 failed; 16 skipped because app-size baselines are disabled for beta Xcode Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 2883e233-aebe-4ada-932d-21a971c895e5

Copilot AI review requested due to automatic review settings July 20, 2026 15:04

dalexsoto requested a review from rolfbjarne as a code owner July 20, 2026 15:04

dalexsoto added the copilot label Jul 20, 2026

dalexsoto added this to the xcode27 milestone Jul 20, 2026

Copilot started reviewing on behalf of dalexsoto July 20, 2026 15:04 View session

dalexsoto mentioned this pull request Jul 20, 2026

[CoreSpotlight] Update bindings up to Xcode 27.0 Beta 3 #26158

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[tests] Update iOS expected app size file

6d7b84e

Update the iOS MonoVM interpreter preserved API baseline generated by CI for the protocol method-map reuse changes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: b96fb7cb-f82d-4cd4-9b60-a7f899f3b42d

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[tests] Update expected app size files

e862a96

Applied from gist: https://gist.github.com/vs-mobiletools-engineering-service2/13f6cf31106658c7f12e6a9581f2527d

github-actions Bot dismissed rolfbjarne’s stale review via e862a96 July 22, 2026 12:05

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This was referenced Jul 23, 2026

[CoreSpotlight] Strongly type the protection-class delegate parameter before Xcode 27 GA #26273

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[CoreSpotlight] Update bindings up to Xcode 27.0 Beta 4 #26279

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Copilot started work on behalf of dalexsoto July 24, 2026 02:27 View session

Merge origin/main into dev/alex/bindas-protocol-parameters

b283d7d

Resolve conflicts in TVOS and iOS MonoVM interpreter preservedapis expected files by accepting the updated content from main. Co-authored-by: dalexsoto <204671+dalexsoto@users.noreply.github.com>

Copilot finished work on behalf of dalexsoto July 24, 2026 02:29

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[tests] Update expected app size files

9c5f427

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: e9e228af-33c5-4ac3-ac5e-f8839d48f8bc

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dalexsoto mentioned this pull request Jul 24, 2026

[CI] Provisionator Xcode downloads at ~160 KB/s hit the 180-minute job limit #26212

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rolfbjarne approved these changes Jul 24, 2026

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dalexsoto merged commit 758a48d into main Jul 24, 2026
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dalexsoto deleted the dev/alex/bindas-protocol-parameters branch July 24, 2026 14:14

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vs-mobiletools-engineering-service2 commented Jul 22, 2026

⚠️ AppSizeTest expected files changed ⚠️

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🚀 [CI Build #9c5f427] Test results 🚀

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