[CodeCompletion] Add test case for SR-15502

Author: ahoppen

validation-test/IDE/crashers_2_fixed/sr15502.swift

@@ -0,0 +1,32 @@
+// RUN: %swift-ide-test --code-completion --code-completion-token COMPLETE --source-filename %s
+// Should not crash
+
+protocol View2 {}
+
+struct Foo {
+    init(closure: () -> Void) {}
+    func pnReceive(perform action: (MyResult) -> Void) -> some View2 {
+        fatalError()
+    }
+}
+
+struct SomeStruct {
+    var string: String
+}
+
+@resultBuilder public struct ViewBuilder2 {
+  public static func buildBlock<Content>(_ content: Content) -> Content where Content : View2 { fatalError() }
+}
+
+@ViewBuilder2 var body: some View2 {
+    Foo {}.pnReceive() { (value) in
+        switch value {
+        case let .success(#^COMPLETE^#raw, pretty):
+            break
+        }
+    }
+}
+
+enum MyResult {
+    case success(SomeStruct)
+}