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[Async Refactoring] Add @discardableResult for defaulted completion

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If the completion handler parameter has a default
argument, mark the resulting async function as
`@discardableResult`, as the caller may not care
about the result.

rdar://79190170
This commit is contained in:
Hamish Knight
2021-06-11 11:39:16 +01:00
parent 38c544aa0e
commit e97c781ca1
2 changed files with 35 additions and 0 deletions
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15
lib/IDE/Refactoring.cpp
View File

@@ -4413,6 +4413,14 @@ struct AsyncHandlerParamDesc : public AsyncHandlerDesc {
OS << tok::r_paren;
}
/// Retrieves the parameter decl for the completion handler parameter, or
/// \c nullptr if no valid completion parameter is present.
const ParamDecl *getHandlerParam() const {
if (!isValid())
return nullptr;
return Func->getParameters()->get(Index);
}
bool operator==(const AsyncHandlerParamDesc &Other) const {
return Handler == Other.Handler && Type == Other.Type &&
HasError == Other.HasError && Index == Other.Index;
@@ -6313,6 +6321,13 @@ private:
void addFuncDecl(const FuncDecl *FD) {
auto *Params = FD->getParameters();
auto *HandlerParam = TopHandler.getHandlerParam();
// If the completion handler parameter has a default argument, the async
// version is effectively @discardableResult, as not all the callers care
// about receiving the completion call.
if (HandlerParam && HandlerParam->isDefaultArgument())
OS << tok::at_sign << "discardableResult" << "\n";
// First chunk: start -> the parameter to remove (if any)
SourceLoc LeftEndLoc = Params->getLParenLoc().getAdvancedLoc(1);

20
test/refactoring/ConvertAsync/convert_function.swift
View File

@@ -1,3 +1,5 @@
// RUN: %empty-directory(%t)
enum CustomError : Error {
case Bad
}
@@ -309,3 +311,21 @@ func rdar78693050(_ completion: () -> Void) {
// RDAR78693050-NEXT: }
// RDAR78693050-NEXT: return
// RDAR78693050-NEXT: }
// RUN: %refactor-check-compiles -convert-to-async -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=DISCARDABLE-RESULT %s
func withDefaultedCompletion(arg: String, completion: @escaping (String) -> Void = {_ in}) {
completion(arg)
}
// DISCARDABLE-RESULT: @discardableResult
// DISCARDABLE-RESULT-NEXT: func withDefaultedCompletion(arg: String) async -> String {
// DISCARDABLE-RESULT-NEXT: return arg
// DISCARDABLE-RESULT-NEXT: }
// RUN: %refactor-check-compiles -convert-to-async -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=DEFAULT-ARG %s
func withDefaultArg(x: String = "") {
}
// DEFAULT-ARG: convert_function.swift [[# @LINE-3]]:1 -> [[# @LINE-2]]:2
// DEFAULT-ARG-NOT: @discardableResult
// DEFAULT-ARG-NEXT: {{^}}func withDefaultArg(x: String = "") async