Merge pull request #60076 from DougGregor/existential-var-opening

Author: DougGregor

lib/Sema/CSApply.cpp

@@ -5935,7 +5935,8 @@ ArgumentList *ExprRewriter::coerceCallArguments(
 
     // If the argument is an existential type that has been opened, perform
     // the open operation.
-    if (argType->getInOutObjectType()->isAnyExistentialType() &&
+    if (argType->getRValueType()->getInOutObjectType()
+            ->isAnyExistentialType() &&
         paramType->hasOpenedExistential()) {
       // FIXME: Look for an opened existential and use it. We need to
       // know how far out we need to go to close the existentials. Huh.

lib/Sema/CSSimplify.cpp

@@ -1468,6 +1468,7 @@ namespace {
   enum class OpenedExistentialAdjustmentFlags {
     /// The argument should be made inout after opening.
     InOut = 0x01,
+    LValue = 0x02,
   };
 
   using OpenedExistentialAdjustments =
@@ -1541,6 +1542,12 @@ shouldOpenExistentialCallArgument(
 
   OpenedExistentialAdjustments adjustments;
 
+  // The argument may be a "var" instead of a "let".
+  if (auto lv = argTy->getAs<LValueType>()) {
+    argTy = lv->getObjectType();
+    adjustments |= OpenedExistentialAdjustmentFlags::LValue;
+  }
+
   // If the argument is inout, strip it off and we can add it back.
   if (auto inOutArg = argTy->getAs<InOutType>()) {
     argTy = inOutArg->getObjectType();
@@ -1944,6 +1951,9 @@ static ConstraintSystem::TypeMatchResult matchCallArguments(
         std::tie(argTy, opened) = cs.openExistentialType(
             existentialType, cs.getConstraintLocator(loc));
 
+        if (adjustments.contains(OpenedExistentialAdjustmentFlags::LValue))
+          argTy = LValueType::get(argTy);
+
         if (adjustments.contains(OpenedExistentialAdjustmentFlags::InOut))
           argTy = InOutType::get(argTy);
 

test/Constraints/opened_existentials.swift

@@ -25,6 +25,10 @@ func testSimpleExistentialOpening(p: any P, pq: any P & Q, c: any Collection) {
   let pa = acceptGeneric(p)
   let _: Int = pa // expected-error{{cannot convert value of type '(any Q)?' to specified type 'Int'}}
 
+  var vp = p
+  let vpa = acceptGeneric(vp)
+  let _: Int = vpa // expected-error{{cannot convert value of type '(any Q)?' to specified type 'Int'}}
+
   let pqa = acceptGeneric(pq)
   let _: Int = pqa  // expected-error{{cannot convert value of type '(any Q)?' to specified type 'Int'}}