/// Do a syntactic pattern match to determine whether the call is a call
/// to swap(&base[index1], &base[index2]), which can
/// be replaced with a call to MutableCollection.swapAt(_:_:) on base.
///
/// Returns true if the call can be replaced. Returns the call expression,
/// the base expression, and the two indices as out expressions.
///
/// This method takes an array of all the ApplyInsts for calls to swap()
/// in the function to avoid needing to construct a parent map over the AST
/// to find the CallExpr for the inout accesses.
static bool
canReplaceWithCallToCollectionSwapAt(const BeginAccessInst *Access1,
const BeginAccessInst *Access2,
ArrayRef<ApplyInst *> CallsToSwap,
ASTContext &Ctx,
CallExpr *&FoundCall,
Expr *&Base,
Expr *&Index1,
Expr *&Index2) {
if (CallsToSwap.empty())
return false;
// Inout arguments must be modifications.
if (Access1->getAccessKind() != SILAccessKind::Modify ||
Access2->getAccessKind() != SILAccessKind::Modify) {
return false;
}
SILLocation Loc1 = Access1->getLoc();
SILLocation Loc2 = Access2->getLoc();
if (Loc1.isNull() || Loc2.isNull())
return false;
auto *InOut1 = Loc1.getAsASTNode<InOutExpr>();
auto *InOut2 = Loc2.getAsASTNode<InOutExpr>();
if (!InOut1 || !InOut2)
return false;
FoundCall = nullptr;
// Look through all the calls to swap() recorded in the function to find
// which one we're diagnosing.
for (ApplyInst *AI : CallsToSwap) {
SILLocation CallLoc = AI->getLoc();
if (CallLoc.isNull())
continue;
auto *CE = CallLoc.getAsASTNode<CallExpr>();
if (!CE)
continue;
assert(isCallToStandardLibrarySwap(CE, Ctx));
// swap() takes two arguments.
auto *ArgTuple = cast<TupleExpr>(CE->getArg());
const Expr *Arg1 = ArgTuple->getElement(0);
const Expr *Arg2 = ArgTuple->getElement(1);
if ((Arg1 == InOut1 && Arg2 == InOut2)) {
FoundCall = CE;
break;
}
}
if (!FoundCall)
return false;
// We found a call to swap(&e1, &e2). Now check to see whether it
// matches the form swap(&someCollection[index1], &someCollection[index2]).
auto *SE1 = dyn_cast<SubscriptExpr>(InOut1->getSubExpr());
if (!SE1)
return false;
auto *SE2 = dyn_cast<SubscriptExpr>(InOut2->getSubExpr());
if (!SE2)
return false;
// Do the two subscripts refer to the same subscript declaration?
auto *Decl1 = cast<SubscriptDecl>(SE1->getDecl().getDecl());
auto *Decl2 = cast<SubscriptDecl>(SE2->getDecl().getDecl());
if (Decl1 != Decl2)
return false;
ProtocolDecl *MutableCollectionDecl = Ctx.getMutableCollectionDecl();
// Is the subcript either (1) on MutableCollection itself or (2) a
// a witness for a subscript on MutableCollection?
bool IsSubscriptOnMutableCollection = false;
ProtocolDecl *ProtocolForDecl =
Decl1->getDeclContext()->getAsProtocolOrProtocolExtensionContext();
if (ProtocolForDecl) {
IsSubscriptOnMutableCollection = (ProtocolForDecl == MutableCollectionDecl);
} else {
for (ValueDecl *Req : Decl1->getSatisfiedProtocolRequirements()) {
DeclContext *ReqDC = Req->getDeclContext();
ProtocolDecl *ReqProto = ReqDC->getAsProtocolOrProtocolExtensionContext();
assert(ReqProto && "Protocol requirement not in a protocol?");
if (ReqProto == MutableCollectionDecl) {
IsSubscriptOnMutableCollection = true;
break;
}
}
}
if (!IsSubscriptOnMutableCollection)
return false;
// We're swapping two subscripts on mutable collections -- but are they
// the same collection? Approximate this by checking for textual
// equality on the base expressions. This is just an approximation,
// but is fine for a best-effort Fix-It.
SourceManager &SM = Ctx.SourceMgr;
StringRef Base1Text = extractExprText(SE1->getBase(), SM);
StringRef Base2Text = extractExprText(SE2->getBase(), SM);
if (Base1Text != Base2Text)
return false;
auto *Index1Paren = dyn_cast<ParenExpr>(SE1->getIndex());
if (!Index1Paren)
return false;
auto *Index2Paren = dyn_cast<ParenExpr>(SE2->getIndex());
if (!Index2Paren)
return false;
Base = SE1->getBase();
Index1 = Index1Paren->getSubExpr();
Index2 = Index2Paren->getSubExpr();
return true;
}
