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[CSApply] NFC: Clean up some duplicated logic for propagating async from contextual types to closure types. #37282

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merged 1 commit into from
May 12, 2021
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[CSApply] NFC: Clean up some duplicated logic for propagating async from contextual types to closure types. #37282

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44 changes: 15 additions & 29 deletions lib/Sema/CSApply.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6120,13 +6120,14 @@ static bool isClosureLiteralExpr(Expr *expr) {
return (isa<CaptureListExpr>(expr) || isa<ClosureExpr>(expr));
}

/// Whether we should propagate async down to a closure.
static bool shouldPropagateAsyncToClosure(Expr *expr) {
/// Whether the given expression is a closure that should inherit
/// the actor context from where it was formed.
static bool closureInheritsActorContext(Expr *expr) {
if (auto IE = dyn_cast<IdentityExpr>(expr))
return shouldPropagateAsyncToClosure(IE->getSubExpr());
return closureInheritsActorContext(IE->getSubExpr());

if (auto CLE = dyn_cast<CaptureListExpr>(expr))
return shouldPropagateAsyncToClosure(CLE->getClosureBody());
return closureInheritsActorContext(CLE->getClosureBody());

if (auto CE = dyn_cast<ClosureExpr>(expr))
return CE->inheritsActorContext();
Expand Down Expand Up @@ -7012,22 +7013,6 @@ Expr *ExprRewriter::coerceToType(Expr *expr, Type toType,
}
}

// If we have a ClosureExpr, then we can safely propagate the 'async'
// bit to the closure without invalidating prior analysis.
fromEI = fromFunc->getExtInfo();
if (toEI.isAsync() && !fromEI.isAsync() &&
shouldPropagateAsyncToClosure(expr)) {
auto newFromFuncType = fromFunc->withExtInfo(fromEI.withAsync());
if (applyTypeToClosureExpr(cs, expr, newFromFuncType)) {
fromFunc = newFromFuncType->castTo<FunctionType>();

// Propagating the 'concurrent' bit might have satisfied the entire
// conversion. If so, we're done, otherwise keep converting.
if (fromFunc->isEqual(toType))
return expr;
}
}

// If we have a ClosureExpr, then we can safely propagate a global actor
// to the closure without invalidating prior analysis.
fromEI = fromFunc->getExtInfo();
Expand All @@ -7044,27 +7029,28 @@ Expr *ExprRewriter::coerceToType(Expr *expr, Type toType,
}
}

/// Whether the given effect should be propagated to a closure expression.
auto shouldApplyEffect = [&](EffectKind kind) -> bool {
/// Whether the given effect is polymorphic at this location.
auto isEffectPolymorphic = [&](EffectKind kind) -> bool {
auto last = locator.last();
if (!(last && last->is<LocatorPathElt::ApplyArgToParam>()))
return true;
return false;

// The effect should not be applied if the closure is an argument
// to a function where that effect is polymorphic.
if (auto *call = getAsExpr<ApplyExpr>(locator.getAnchor())) {
if (auto *declRef = dyn_cast<DeclRefExpr>(call->getFn())) {
if (auto *fn = dyn_cast<AbstractFunctionDecl>(declRef->getDecl()))
return !fn->hasPolymorphicEffect(kind);
return fn->hasPolymorphicEffect(kind);
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IHMO naming of this method could be improved it's clear what polymorphism has to do with this and there is no comment at the declaration site. @hborla told me that this is about interaction between reasync/rethrows and async/throws attributes.

}
}

return true;
return false;
};

// If we have a ClosureExpr, we can safely propagate 'async' to the closure.
// If we have a ClosureExpr, and we can safely propagate 'async' to the
// closure, do that here.
fromEI = fromFunc->getExtInfo();
if (toEI.isAsync() && !fromEI.isAsync() && shouldApplyEffect(EffectKind::Async)) {
bool shouldPropagateAsync =
!isEffectPolymorphic(EffectKind::Async) || closureInheritsActorContext(expr);
if (toEI.isAsync() && !fromEI.isAsync() && shouldPropagateAsync) {
auto newFromFuncType = fromFunc->withExtInfo(fromEI.withAsync());
if (applyTypeToClosureExpr(cs, expr, newFromFuncType)) {
fromFunc = newFromFuncType->castTo<FunctionType>();
Expand Down