Type checker fails when calling a function with an Optional<() -> Void> ternary expression as a parameter

[TheHarcker]

Description

No response

Reproduction

When compiling the following, the compiler fails with the error Type of expression is ambiguous without a type annotation

func takingAnOptionalClosure(closure: (() -> Void)?) {}
func someFunc() {}
func someOtherFunc() {
    let a = false ? someFunc : nil  // Fine
    takingAnOptionalClosure(closure: a)   // Fine
    takingAnOptionalClosure(closure: false ? someFunc : nil)  // Error
}

The above issue also leads to another diagnostic when the function call is within a SwiftUI ViewBuilder.

import SwiftUI
extension View {
    public func takingAnOptionalClosure(closure: (() -> Void)?) -> some View {
        self
    }
}
struct SwiftUIExample: View {
    func aFunc() {}

    var body: some View {
        Text("Hi")
        .takingAnOptionalClosure(closure: false ? aFunc : nil)
    }
}

Here the compiler returns the error Failed to produce diagnostic for expression; please submit a bug report (https://swift.org/contributing/#reporting-bugs) on the line of var body

POC swift package:
POC.zip

Expected behavior

I expected the code to successfully compile without any warnings or errors

Environment

The issues mentioned above happens when compiling the attached POC in Xcode 16.1 (16B40), Xcode 16.2 (16C5031c), and with swift build from the terminal. The problem does not seem to occur when compiling with swiftc

Output of swiftc -version:

swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.9 clang-1600.0.30.1)
Target: x86_64-apple-macosx15.0

Additional information

The problem first occurred in a file similar to the SwiftUI example above, after a class containing the equivalent of someFunc had been annotated with @ MainActor