Cater for opening var existential followup.

(cherry picked from commit d72b9a4)

Author: johnno1962

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 =
@@ -1541,16 +1542,18 @@ 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();
     adjustments |= OpenedExistentialAdjustmentFlags::InOut;
   }
 
-  // The argument may be a "var" instead of a "let".
-  if (auto lv = dyn_cast<LValueType>(argTy->getCanonicalType()))
-    argTy = lv->getObjectType();
-
   // The argument type needs to be an existential type or metatype thereof.
   if (!argTy->isAnyExistentialType())
     return None;
@@ -1950,6 +1953,9 @@ 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'}}