Async @resultBuilder methods cause compiler crash (Swift 6.2.3)

Using Swift
1

I tried to mark result builder functions with async but compiler crashed.

/// Minimal reproduction: async result builder causes compiler crash
/// Swift 6.2.3 on Linux (Ubuntu 24.04)
/// 
/// To reproduce:
///   swiftc -parse-as-library main.swift
///
/// Expected: Compiler error explaining async is not supported in result builders
/// Actual:   Compiler crashes with SIGSEGV (signal 11)

@resultBuilder
public struct ParaBuild
{
    //                                      async causes compiler crash (SIGSEGV).
    //                                      The compiler does not reject async as invalid syntax,
    //                                      but crashes during LLVM code generation at
    //                                      llvm::ValueEnumerator::ValueEnumerator.
    public static func buildBlock(_ x: Int) /* async */ -> Int
    {
        return x
    }
}

struct ExampleBuild
{
    @ParaBuild var content: Int
    {
        42
    }
}

@main
struct Main
{
    static func main()
    {
        let example = ExampleBuild()
        print("Content: \(example.content)")
    }
}