Don't handle refutable patterns in async transform

These aren't currently supported.

Author: hamishknight

lib/IDE/Refactoring.cpp

@@ -4988,6 +4988,11 @@ struct CallbackClassifier {
     if (!Cond.isValid())
       return None;
 
+    // If the condition involves a refutable pattern, we can't currently handle
+    // it.
+    if (Cond.BindPattern && Cond.BindPattern->isRefutablePattern())
+      return None;
+
     // For certain types of condition, they need to appear in certain lists.
     auto CondType = *Cond.Type;
     switch (CondType) {

test/refactoring/ConvertAsync/convert_pattern.swift

@@ -0,0 +1,45 @@
+// RUN: %empty-directory(%t)
+
+enum E : Error { case e }
+
+func anyCompletion(_ completion: (Any?, Error?) -> Void) {}
+
+// RUN: %refactor -convert-call-to-async-alternative -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=TEST-UNHANDLED %s
+anyCompletion { val, err in
+  if let x = val {
+    print("a")
+  }
+  if let _ = val {
+    print("b")
+  }
+  if case let x? = val {
+    print("c")
+  }
+  if case let _? = val {
+    print("d")
+  }
+  if case E.e? = val {
+    print("e")
+  }
+  if case (let x as String)? = val {
+    print("f")
+  }
+  if case let "" as String = val {
+    print("g")
+  }
+}
+
+// TEST-UNHANDLED:      let x = try await anyCompletion()
+// TEST-UNHANDLED-NEXT: print("a")
+// TEST-UNHANDLED-NEXT: print("b")
+// TEST-UNHANDLED-NEXT: print("c")
+// TEST-UNHANDLED-NEXT: print("d")
+// TEST-UNHANDLED-NEXT: if case E.e? = <#x#> {
+// TEST-UNHANDLED-NEXT:   print("e")
+// TEST-UNHANDLED-NEXT: }
+// TEST-UNHANDLED-NEXT: if case (let x as String)? = <#x#> {
+// TEST-UNHANDLED-NEXT:   print("f")
+// TEST-UNHANDLED-NEXT: }
+// TEST-UNHANDLED-NEXT: if case let "" as String = <#x#> {
+// TEST-UNHANDLED-NEXT:   print("g")
+// TEST-UNHANDLED-NEXT: }