[IDE] Add test case for SR-14708

SR-14708 is no longer happening in the stress tester. Add its test case to the test suite.

rdar://78781625

Author: ahoppen

validation-test/IDE/stress_tester_issues_fixed/sr14708.swift

@@ -0,0 +1,34 @@
+// RUN: %target-swift-ide-test --code-completion --source-filename %s --code-completion-token=COMPLETE | %FileCheck %s
+
+protocol View2 {}
+ 
+extension Never : View2 {}
+
+struct Text2: View2 {}
+
+@resultBuilder struct ViewBuilder2 {
+	static func buildBlock() -> Never { fatalError() }
+	static func buildBlock<Content>(_ content: Content) -> Content where Content : View2 { fatalError() }
+}
+
+struct MysteryIsland2 {
+    let chance: Int = 2
+}
+
+struct VStack2<Content> : View2 where Content : View2 {
+    init(@ViewBuilder2 content: () -> Content) { fatalError() }
+}
+
+struct MysteryIslandDetail {
+    let island: MysteryIsland2
+    
+    @ViewBuilder2 var body: some View2 {
+        let b = "\(island.#^COMPLETE^#chance)"
+        VStack2() {}
+    }
+}
+
+// CHECK: Begin completions, 2 items
+// CHECK-DAG: Keyword[self]/CurrNominal:          self[#MysteryIsland2#]; name=self
+// CHECK-DAG: Decl[InstanceVar]/CurrNominal/TypeRelation[Convertible]: chance[#Int#]; name=chance
+// CHECK: End completions