[Refactoring] Support refactoring for case let patterns

Previously we only supported `case` patterns that bound with a `let` inside the associated value like `case .success(let value)`. With this change, we also support `case let .success(value)`.

Fixes rdar://79279846 [SR-14772]

Author: ahoppen

lib/IDE/Refactoring.cpp

@@ -4571,7 +4571,8 @@ struct CallbackCondition {
   /// }
   /// ```
   CallbackCondition(const Decl *Subject, const CaseLabelItem *CaseItem) {
-    if (auto *EEP = dyn_cast<EnumElementPattern>(CaseItem->getPattern())) {
+    if (auto *EEP = dyn_cast<EnumElementPattern>(
+            CaseItem->getPattern()->getSemanticsProvidingPattern())) {
       // `case .<func>(let <bind>)`
       initFromEnumPattern(Subject, EEP);
     }

test/refactoring/ConvertAsync/convert_pattern.swift

@@ -265,6 +265,16 @@ func testPatterns() async throws {
   // STRING-TUPLE-RESULT-NEXT:   print("oh no")
   // STRING-TUPLE-RESULT-NEXT: }
 
+  // RUN: %refactor-check-compiles -convert-call-to-async-alternative -dump-text -source-filename %s -pos=%(line+1):3 | %FileCheck -check-prefix=STRING-TUPLE-RESULT %s
+  stringTupleResult { res in
+    switch res {
+    case let .success((x, y)):
+      print(x, y)
+    case .failure:
+      print("oh no")
+    }
+  }
+
   // RUN: %refactor-check-compiles -convert-call-to-async-alternative -dump-text -source-filename %s -pos=%(line+1):3 | %FileCheck -check-prefix=MIXED-TUPLE-RESULT %s
   mixedTupleResult { res in
     if case .failure(let err) = res {