Embedded compilation issue

[ainame]

I've got a relatively smaller repro project with elementary-ui.
https://github.com/ainame/elementary-ui-embedded-bug-repro

With this, I see below compilation error when compiling the project with wasm-embedded SDK.

ElementaryUI/Views/Function/_FunctionView.swift:30:14:
error: cannot specialize generic function or default protocol method in this context [#EmbeddedRestrictions]
node.patch(view, tx: &tx)

classes cannot have a non-final, generic method 'runUpdate(tx:)' in embedded Swift
classes cannot have a non-final, generic method 'progressAnimation(tx:)' in embedded Swift
ElementaryUI/Views/Function/_FunctionNode.swift:150:13:
error: classes cannot have a non-final, generic method 'SchedulableFunction' in embedded Swift

Full logs

Details

% make
swift build \
                --swift-sdk swift-6.3.2-RELEASE_wasm-embedded \
                --configuration release \
                --product WebApp
[1/1] Planning build
Building for production...
/path/to/elementary-ui-embedded-bug-repro/.build/checkouts/elementary-ui/Sources/ElementaryUI/Views/Function/_FunctionView.swift:30:14: error: cannot specialize generic function or default protocol method in this context [#EmbeddedRestrictions]
28 |         tx: inout _TransactionContext
29 |     ) {
30 |         node.patch(view, tx: &tx)
   |              `- error: cannot specialize generic function or default protocol method in this context [#EmbeddedRestrictions]
31 |     }
32 | }

<unknown>:0: note: generic specialization called here
<unknown>:0: note: generic specialization called here
<unknown>:0: note: generic specialization called here
<unknown>:0: note: generic specialization called here
<unknown>:0: note: generic specialization called here
<unknown>:0: note: generic specialization called here
/path/to/elementary-ui-embedded-bug-repro/Sources/WebApp/App.swift:7:9: note: generic specialization called here
 5 |   static func main() {
 6 |     let app = Application(RootView())
 7 |     app.mount(in: "#app")
   |         `- note: generic specialization called here
 8 |   }
 9 | }

<unknown>:0: error: classes cannot have a non-final, generic method 'runUpdate(tx:)' in embedded Swift [#EmbeddedRestrictions]
<unknown>:0: error: classes cannot have a non-final, generic method 'progressAnimation(tx:)' in embedded Swift [#EmbeddedRestrictions]
<unknown>:0: error: classes cannot have a non-final, generic method 'init(child:animatedValue:wiredValue:depthInTree:)' in embedded Swift [#EmbeddedRestrictions]
<unknown>:0: error: classes cannot have a non-final, generic method 'deinit' in embedded Swift [#EmbeddedRestrictions]
/path/to/elementary-ui-embedded-bug-repro/.build/checkouts/elementary-ui/Sources/ElementaryUI/Views/Function/_FunctionNode.swift:150:13: error: classes cannot have a non-final, generic method 'SchedulableFunction' in embedded Swift [#EmbeddedRestrictions]
148 | }
149 |
150 | final class SchedulableFunction<
    |             `- error: classes cannot have a non-final, generic method 'SchedulableFunction' in embedded Swift [#EmbeddedRestrictions]
151 |     Value: __FunctionView,
152 |     Child: _Mountable,

<unknown>:0: error: classes cannot have a non-final, generic method 'runUpdate(tx:)' in embedded Swift [#EmbeddedRestrictions]
<unknown>:0: error: classes cannot have a non-final, generic method 'progressAnimation(tx:)' in embedded Swift [#EmbeddedRestrictions]
<unknown>:0: error: classes cannot have a non-final, generic method 'init(child:animatedValue:wiredValue:depthInTree:)' in embedded Swift [#EmbeddedRestrictions]
<unknown>:0: error: classes cannot have a non-final, generic method 'deinit' in embedded Swift [#EmbeddedRestrictions]
/path/to/elementary-ui-embedded-bug-repro/.build/checkouts/elementary-ui/Sources/ElementaryUI/Views/Function/_FunctionNode.swift:150:13: error: classes cannot have a non-final, generic method 'SchedulableFunction' in embedded Swift [#EmbeddedRestrictions]
148 | }
149 |
150 | final class SchedulableFunction<
    |             `- error: classes cannot have a non-final, generic method 'SchedulableFunction' in embedded Swift [#EmbeddedRestrictions]
151 |     Value: __FunctionView,
152 |     Child: _Mountable,

[#EmbeddedRestrictions]: <https://docs.swift.org/compiler/documentation/diagnostics/embedded-restrictions>

make: *** [build] Error 1

Environment

• OS: macOS 26.5
• Swift: Apple Swift version 6.3.2 (swift-6.3.2-RELEASE) installed via swiftly
• Embedded Swift SDK: swift-6.3.2-RELEASE_wasm-embedded
• elementary-ui: 0.2.3
• elementary: 0.7.1

Originally reported on Swift WASM discord:
https://discord.com/channels/780838335798706197/973525316272279552/1505722359494086738

[sliemeobn]

I played a bit with it and I saw that when removing any conditional "up the chain" (like the if let, or the switch) things compile.
my best guess ATM is that we hit some weird Swift compiler limitation that prevents specialization if the type gets "too complicated" (pure gut feel).
need to investigate further....

[sliemeobn]

the plot thickens: we seem to run into some pretty weird compiler bugs.
I hope to get swiftlang/swift issues reported and ideally picked into 6.4.

there may also be a way to navigate around this by altering a few optimizer attributes in the existing codebase for 6.3. I'll try my best to get a fix in...

[sliemeobn]

this reproducer is a gift that keeps on giving:
when building on the current main-snapshot we run into different troubles - so at the moment I cannot say if the embedded specialization bug is fixed on main or not.

swiftlang/swift#89255
swiftlang/swift#89257

[sliemeobn]

swift issue: swiftlang/swift#89291

[sliemeobn]

swift issue was fixed (and cherry picked into 6.4 branch)

we should wait for new snapshot builds of Swift (main, 6.4) and verify that this reproducer actually builds correctly now.