Sema: Stash the existential archetype in PreparedOverload

Author: slavapestov

include/swift/Sema/ConstraintSystem.h

@@ -3413,7 +3413,8 @@ class ConstraintSystem {
 
   /// Update OpenedExistentials and record a change in the trail.
   void recordOpenedExistentialType(ConstraintLocator *locator,
-                                   ExistentialArchetypeType *opened);
+                                   ExistentialArchetypeType *opened,
+                                   PreparedOverload *preparedOverload = nullptr);
 
   /// Retrieve the generic environment for the opened element of a given pack
   /// expansion, or \c nullptr if no environment was recorded yet.

include/swift/Sema/PreparedOverload.h

@@ -17,6 +17,7 @@
 
 namespace swift {
 
+class ExistentialArchetypeType;
 class GenericTypeParamType;
 class TypeVariableType;
 
@@ -33,6 +34,7 @@ struct PreparedOverload {
   SmallVector<TypeVariableType *, 2> TypeVariables;
   SmallVector<Constraint *, 2> Constraints;
   SmallVector<OpenedType, 2> Replacements;
+  ExistentialArchetypeType *OpenedExistential = nullptr;
 
   void discharge(ConstraintSystem &cs, ConstraintLocatorBuilder locator) const;
 };

lib/Sema/ConstraintSystem.cpp

@@ -38,6 +38,7 @@
 #include "swift/Sema/CSFix.h"
 #include "swift/Sema/ConstraintGraph.h"
 #include "swift/Sema/IDETypeChecking.h"
+#include "swift/Sema/PreparedOverload.h"
 #include "swift/Sema/SolutionResult.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallSet.h"
@@ -899,7 +900,15 @@ ConstraintSystem::openAnyExistentialType(Type type,
 }
 
 void ConstraintSystem::recordOpenedExistentialType(
-    ConstraintLocator *locator, ExistentialArchetypeType *opened) {
+    ConstraintLocator *locator,
+    ExistentialArchetypeType *opened,
+    PreparedOverload *preparedOverload) {
+  if (preparedOverload) {
+    ASSERT(!preparedOverload->OpenedExistential);
+    preparedOverload->OpenedExistential = opened;
+    return;
+  }
+
   bool inserted = OpenedExistentialTypes.insert({locator, opened}).second;
   ASSERT(inserted);
 

lib/Sema/TypeOfReference.cpp

@@ -1753,7 +1753,8 @@ DeclReferenceType ConstraintSystem::getTypeOfMemberReference(
   } else if (baseObjTy->isExistentialType()) {
     auto openedArchetype =
         ExistentialArchetypeType::get(baseObjTy->getCanonicalType());
-    recordOpenedExistentialType(getConstraintLocator(locator), openedArchetype);
+    recordOpenedExistentialType(getConstraintLocator(locator), openedArchetype,
+                                preparedOverload);
     baseOpenedTy = openedArchetype;
   }
 
@@ -2471,6 +2472,10 @@ void PreparedOverload::discharge(ConstraintSystem &cs,
     cs.activateConstraint(c);
   }
   cs.recordOpenedTypes(locator, Replacements);
+  if (OpenedExistential) {
+    cs.recordOpenedExistentialType(cs.getConstraintLocator(locator),
+                                   OpenedExistential);
+  }
 }
 
 void ConstraintSystem::resolveOverload(ConstraintLocator *locator,