[Async Refactoring] Improve fatalError message to unwrap result arguments in continuation

In the previous `fatalError` message `Expected non-nil result 'result' for nil error`, it wasn’t exactly clear wht the `error` referred to. In some cases, when the error was ignored, there wasn’t even an `error` variable in the refactored code.

The new `Expected non-nil result '...' in the non-error case` is a little more generic and also fits if an error is ignored.

Author: ahoppen

lib/IDE/Refactoring.cpp

@@ -6902,7 +6902,11 @@ class AsyncConverter : private SourceEntityWalker {
         }
         OS << ' ' << tok::kw_else << ' ' << tok::l_brace << '\n';
         OS << "fatalError" << tok::l_paren;
-        OS << "\"Expected non-nil result '" << ArgName << "' for nil error\"";
+        OS << "\"Expected non-nil result ";
+        if (ArgName.str() != "result") {
+          OS << "'" << ArgName << "' ";
+        }
+        OS << "in the non-error case\"";
         OS << tok::r_paren << '\n';
         OS << tok::r_brace << '\n';
       }

test/refactoring/ConvertAsync/convert_to_continuation.swift

@@ -120,7 +120,7 @@ func testThrowingContinuationRelayingErrorAndResult(completionHandler: (Int?, Er
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:         continuation.resume(throwing: error)
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:       } else {
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:         guard let theValue1 = theValue else {
-// THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:           fatalError("Expected non-nil result 'theValue1' for nil error")
+// THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:           fatalError("Expected non-nil result 'theValue1' in the non-error case")
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:         }
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:         continuation.resume(returning: theValue1)
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-RESULT-NEXT:       }
@@ -141,7 +141,7 @@ func testThrowingContinuationRelayingErrorAndComplexResult(completionHandler: (I
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:         continuation.resume(throwing: error)
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:       } else {
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:         guard let result = theValue.map({ $0 + 1 }) else {
-// THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:           fatalError("Expected non-nil result 'result' for nil error")
+// THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:           fatalError("Expected non-nil result in the non-error case")
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:         }
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:         continuation.resume(returning: result)
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-NEXT:       }
@@ -162,10 +162,10 @@ func testThrowingContinuationRelayingErrorAndTwoComplexResults(completionHandler
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:         continuation.resume(throwing: error)
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:       } else {
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:         guard let result0 = theValue.map({ $0 + 1 }) else {
-// THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:           fatalError("Expected non-nil result 'result0' for nil error")
+// THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:           fatalError("Expected non-nil result 'result0' in the non-error case")
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:         }
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:         guard let result1 = theValue.map({ $0 + 2 }) else {
-// THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:           fatalError("Expected non-nil result 'result1' for nil error")
+// THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:           fatalError("Expected non-nil result 'result1' in the non-error case")
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:         }
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:         continuation.resume(returning: (result0, result1))
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-TWO-COMPLEX-RESULTS-NEXT:       }
@@ -186,7 +186,7 @@ func testThrowingContinuationRelayingErrorAndComplexResultWithTrailingClosure(co
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:         continuation.resume(throwing: error)
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:       } else {
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:         guard let result = theValue.map { $0 + 1 }.self else {
-// THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:           fatalError("Expected non-nil result 'result' for nil error")
+// THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:           fatalError("Expected non-nil result in the non-error case")
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:         }
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:         continuation.resume(returning: result)
 // THROWING-CONTINUATION-RELAYING-ERROR-AND-COMPLEX-RESULT-WITH-TRAILING-CLOSURE-NEXT:       }
@@ -461,10 +461,10 @@ func testMultipleReturnValuesAndError(completion: (Int?, String?, Error?) -> Voi
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:         continuation.resume(throwing: error)
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:       } else {
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:         guard let first1 = first else {
-// MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:           fatalError("Expected non-nil result 'first1' for nil error")
+// MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:           fatalError("Expected non-nil result 'first1' in the non-error case")
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:         }
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:         guard let second1 = second else {
-// MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:           fatalError("Expected non-nil result 'second1' for nil error")
+// MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:           fatalError("Expected non-nil result 'second1' in the non-error case")
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:         }
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:         continuation.resume(returning: (first1, second1))
 // MULTIPLE-RETURN-VALUES-AND-ERROR-NEXT:       }
@@ -496,7 +496,7 @@ func testMixedOptionalAnNonOptionaResults(completion: (Int?, String?, Error?) ->
 // MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:   return try await withCheckedThrowingContinuation { continuation in 
 // MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:     withoutAsyncAlternativeThrowing { (theResult, error) in
 // MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:       guard let theResult1 = theResult else {
-// MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:         fatalError("Expected non-nil result 'theResult1' for nil error")
+// MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:         fatalError("Expected non-nil result 'theResult1' in the non-error case")
 // MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:       }
 // MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:       continuation.resume(returning: (theResult1, "hi"))
 // MIXED-OPTIONAL-AND-NON-OPTIONAL-RESULT-NEXT:     }
@@ -514,7 +514,7 @@ func testUseOptionalResultValueAfterCompletionHandlerCall(completion: (Int?, Str
 // USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:   return try await withCheckedThrowingContinuation { continuation in 
 // USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:     withoutAsyncAlternativeThrowing { (theResult, error) in
 // USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:       guard let theResult1 = theResult else {
-// USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:         fatalError("Expected non-nil result 'theResult1' for nil error")
+// USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:         fatalError("Expected non-nil result 'theResult1' in the non-error case")
 // USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:       }
 // USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:       continuation.resume(returning: (theResult1, "hi"))
 // USE-OPTIONAL-RESULT-AFTER-COMPLETION-HANDLER-CALL-NEXT:       print(theResult.map { $0 + 1 } as Any)
@@ -533,10 +533,10 @@ func testPassSameResultTwice(completion: (Int?, Int?, Error?) -> Void) {
 // PASS-SAME-RESULT-TWICE-NEXT:   return try await withCheckedThrowingContinuation { continuation in 
 // PASS-SAME-RESULT-TWICE-NEXT:     withoutAsyncAlternativeThrowing { (theResult, error) in
 // PASS-SAME-RESULT-TWICE-NEXT:       guard let theResult1 = theResult else {
-// PASS-SAME-RESULT-TWICE-NEXT:         fatalError("Expected non-nil result 'theResult1' for nil error")
+// PASS-SAME-RESULT-TWICE-NEXT:         fatalError("Expected non-nil result 'theResult1' in the non-error case")
 // PASS-SAME-RESULT-TWICE-NEXT:       }
 // PASS-SAME-RESULT-TWICE-NEXT:       guard let theResult2 = theResult else {
-// PASS-SAME-RESULT-TWICE-NEXT:         fatalError("Expected non-nil result 'theResult2' for nil error")
+// PASS-SAME-RESULT-TWICE-NEXT:         fatalError("Expected non-nil result 'theResult2' in the non-error case")
 // PASS-SAME-RESULT-TWICE-NEXT:       }
 // PASS-SAME-RESULT-TWICE-NEXT:       continuation.resume(returning: (theResult1, theResult2))
 // PASS-SAME-RESULT-TWICE-NEXT:     }
@@ -558,7 +558,7 @@ func testUseResultAfterAmbiguousCompletionHandlerCall(completion: (Int?, Error?)
 // USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:         continuation.resume(throwing: error)
 // USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:       } else {
 // USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:         guard let theResult1 = theResult else {
-// USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:           fatalError("Expected non-nil result 'theResult1' for nil error")
+// USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:           fatalError("Expected non-nil result 'theResult1' in the non-error case")
 // USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:         }
 // USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:         continuation.resume(returning: theResult1)
 // USE-RESULT-AFTER-AMBIGUOUS-HANLDER-CALL-NEXT:       }
@@ -581,15 +581,15 @@ func testTwoCompletionHandlerCalls(completion: (Int?, Error?) -> Void) {
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         continuation.resume(throwing: error)
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:       } else {
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         guard let theResult1 = theResult else {
-// TWO-COMPLEITON-HANDLER-CALLS-NEXT:           fatalError("Expected non-nil result 'theResult1' for nil error")
+// TWO-COMPLEITON-HANDLER-CALLS-NEXT:           fatalError("Expected non-nil result 'theResult1' in the non-error case")
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         }
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         continuation.resume(returning: theResult1)
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:       }
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:       if let error = error {
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         continuation.resume(throwing: error)
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:       } else {
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         guard let theResult2 = theResult else {
-// TWO-COMPLEITON-HANDLER-CALLS-NEXT:           fatalError("Expected non-nil result 'theResult2' for nil error")
+// TWO-COMPLEITON-HANDLER-CALLS-NEXT:           fatalError("Expected non-nil result 'theResult2' in the non-error case")
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         }
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:         continuation.resume(returning: theResult2)
 // TWO-COMPLEITON-HANDLER-CALLS-NEXT:       }