[Sema/SIL] NFC: Get existential layout directly from an existential type

Author: xedin

lib/SIL/IR/SILInstructions.cpp

@@ -2971,8 +2971,7 @@ BoundGenericType *KeyPathInst::getKeyPathType() const {
   auto kpTy = getType();
 
   if (auto existential = kpTy.getAs<ExistentialType>()) {
-    auto containedTy = existential->getConstraintType();
-    return containedTy->getExistentialLayout()
+    return existential->getExistentialLayout()
         .explicitSuperclass->castTo<BoundGenericType>();
   }
 

lib/Sema/CSApply.cpp

@@ -5010,8 +5010,7 @@ namespace {
         leafTy = fnTy->getResult();
         isFunctionType = true;
       } else if (auto *existential = exprType->getAs<ExistentialType>()) {
-        auto constrainedTy = existential->getConstraintType();
-        auto layout = constrainedTy->getExistentialLayout();
+        auto layout = existential->getExistentialLayout();
         auto keyPathTy = layout.explicitSuperclass->castTo<BoundGenericType>();
         baseTy = keyPathTy->getGenericArgs()[0];
         leafTy = keyPathTy->getGenericArgs()[1];