Cannot use @main with swift_binary srcs #913
Description
Summary
In newer versions of Swift its possible to define the main entry point using @main. The only requirement is the type has a public static main() method.
When using rules_swift to build a swift_binary that uses @main we get a compilation error:
example.swift:12:1: error: 'main' attribute cannot be used in a module that contains top-level code
@main
^
This happens when the example.swift is part of the swift_binary srcs attribute.
This same code works and is executable when using swift_library and adding it as a dep of swift_binary. However, if you do this then swift_library cannot be tested with swift_test because of: #911
Example
// example.swift
import Foundation
protocol DefinesMain {
}
extension DefinesMain {
public static func main() {
print("Hello, world!")
}
}
@main
struct Entry: DefinesMain {
}# BUILD.bazel
swift_binary(
name = "example",
srcs = ["example.swift"],
)