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Don't open an existential argument that's completely self-conforming. #42011

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Merged
merged 3 commits into from
Mar 24, 2022
Merged

Don't open an existential argument that's completely self-conforming. #42011

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f20a52e
Fix flag name for `-disable-experimental-opened-existential-types`
DougGregor Mar 24, 2022
25e71a3
Don't open an existential argument that's completely self-conforming.
DougGregor Mar 24, 2022
b9f31a8
Remove SwiftOnoneSupport hack for implicit opening of existentials
DougGregor Mar 24, 2022
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2 changes: 1 addition & 1 deletion include/swift/Option/FrontendOptions.td
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Original file line number Diff line number Diff line change
Expand Up @@ -538,7 +538,7 @@ def enable_experimental_opened_existential_types :
HelpText<"Enable experimental support for implicitly opened existentials">;

def disable_experimental_opened_existential_types :
Flag<["-"], "disble-experimental-opened-existential-types">,
Flag<["-"], "disable-experimental-opened-existential-types">,
HelpText<"Disable experimental support for implicitly opened existentials">;

def enable_deserialization_recovery :
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5 changes: 0 additions & 5 deletions lib/Frontend/CompilerInvocation.cpp
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Expand Up @@ -459,11 +459,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
Opts.EnableExperimentalVariadicGenerics |=
Args.hasArg(OPT_enable_experimental_variadic_generics);

// SwiftOnoneSupport produces different symbols when opening existentials,
// so disable it.
if (FrontendOpts.ModuleName == SWIFT_ONONE_SUPPORT)
Opts.EnableOpenedExistentialTypes = false;

Opts.EnableExperimentalDistributed |=
Args.hasArg(OPT_enable_experimental_distributed);

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19 changes: 19 additions & 0 deletions lib/Sema/CSSimplify.cpp
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Expand Up @@ -1501,6 +1501,25 @@ shouldOpenExistentialCallArgument(
if (!argTy->isAnyExistentialType())
return None;

if (argTy->isExistentialType()) {
// If the existential argument type conforms to all of its protocol
// requirements, don't open the existential.
auto layout = argTy->getExistentialLayout();
auto module = cs.DC->getParentModule();
bool containsNonSelfConformance = false;
for (auto proto : layout.getProtocols()) {
auto protoDecl = proto->getDecl();
auto conformance = module->lookupExistentialConformance(argTy, protoDecl);
if (conformance.isInvalid()) {
containsNonSelfConformance = true;
break;
}
}

if (!containsNonSelfConformance)
return None;
}

auto param = getParameterAt(callee, paramIdx);
if (!param)
return None;
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4 changes: 3 additions & 1 deletion test/Constraints/opened_existentials_suppression.swift
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Expand Up @@ -6,6 +6,8 @@ func acceptsBox<T>(_ value: T) { }

// CHECK: passBox
// CHECK-NOT: open_existential_expr
func passBox(p: P) {
func passBox(p: P, obj: AnyObject, err: Error) {
acceptsBox(p as P)
acceptsBox(obj)
acceptsBox(err)
}