[test] Add regression test for fn builders

Author: LucianoPAlmeida

validation-test/Sema/SwiftUI/issue-59716.swift

@@ -0,0 +1,31 @@
+// RUN: %target-typecheck-verify-swift -target %target-cpu-apple-macosx10.15 -swift-version 5 -enable-experimental-feature ResultBuilderASTTransform
+// REQUIRES: OS=macosx
+
+import SwiftUI
+
+protocol TestLayout {}
+extension TestLayout {
+  func callAsFunction<V: View>(_ f: () -> V) -> some View {
+    return f()
+  }
+}
+struct EqualWitdthHStack : TestLayout {}
+extension EqualWitdthHStack: View {
+  var body : some View {
+    Spacer()
+  }
+}
+
+struct EmptyView: View {
+  var body : some View { 
+    Spacer()
+  }
+}
+
+struct MyView: View {
+  var body : some View {
+    EqualWitdthHStack {
+      EmptyView()
+    }
+  }
+}