[NFC] AST: Add a proxy for getRoot to CanOpenedArchetypeType

Author: AnthonyLatsis

include/swift/AST/Types.h

@@ -5878,6 +5878,9 @@ class OpenedArchetypeType final : public ArchetypeType,
                       LayoutConstraint layout);
 };
 BEGIN_CAN_TYPE_WRAPPER(OpenedArchetypeType, ArchetypeType)
+  CanOpenedArchetypeType getRoot() const {
+    return CanOpenedArchetypeType(getPointer()->getRoot());
+  }
 END_CAN_TYPE_WRAPPER(OpenedArchetypeType, ArchetypeType)
 
 /// An archetype that represents an opaque element of a type sequence in context.

lib/SIL/IR/SILFunctionType.cpp

@@ -2551,7 +2551,7 @@ CanSILFunctionType swift::buildSILFunctionThunkType(
   auto archetypeVisitor = [&](CanType t) {
     if (auto archetypeTy = dyn_cast<ArchetypeType>(t)) {
       if (auto opened = dyn_cast<OpenedArchetypeType>(archetypeTy)) {
-        const auto root = cast<OpenedArchetypeType>(CanType(opened->getRoot()));
+        const auto root = opened.getRoot();
         assert((openedExistential == CanArchetypeType() ||
                 openedExistential == root) &&
                "one too many open existentials");

lib/SIL/IR/SILInstructions.cpp

@@ -56,7 +56,7 @@ static void collectDependentTypeInfo(
     return;
   Ty.visit([&](CanType t) {
     if (const auto opened = dyn_cast<OpenedArchetypeType>(t)) {
-      const auto root = cast<OpenedArchetypeType>(CanType(opened->getRoot()));
+      const auto root = opened.getRoot();
 
       // Add this root opened archetype if it was not seen yet.
       // We don't use a set here, because the number of open archetypes

lib/SIL/Verifier/SILVerifier.cpp

@@ -1469,10 +1469,8 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
               "Operand is of an ArchetypeType that does not exist in the "
               "Caller's generic param list.");
       if (auto OpenedA = getOpenedArchetypeOf(A)) {
-        const auto root =
-            cast<OpenedArchetypeType>(CanType(OpenedA->getRoot()));
         auto *openingInst =
-            F->getModule().getRootOpenedArchetypeDefInst(root, F);
+            F->getModule().getRootOpenedArchetypeDefInst(OpenedA.getRoot(), F);
         require(I == nullptr || openingInst == I ||
                     properlyDominates(openingInst, I),
                 "Use of an opened archetype should be dominated by a "
@@ -1605,7 +1603,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
         require(isArchetypeValidInFunction(A, AI->getFunction()),
                 "Archetype to be substituted must be valid in function.");
 
-        const auto root = cast<OpenedArchetypeType>(CanType(A->getRoot()));
+        const auto root = A.getRoot();
 
         // Collect all root opened archetypes used in the substitutions list.
         FoundRootOpenedArchetypes.insert(root);
@@ -4074,10 +4072,8 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
     Ty.visit([&](CanType t) {
       SILValue Def;
       if (const auto archetypeTy = dyn_cast<OpenedArchetypeType>(t)) {
-        const auto root =
-            cast<OpenedArchetypeType>(CanType(archetypeTy->getRoot()));
-        Def = I->getModule().getRootOpenedArchetypeDefInst(root,
-                                                           I->getFunction());
+        Def = I->getModule().getRootOpenedArchetypeDefInst(
+            archetypeTy.getRoot(), I->getFunction());
         require(Def, "Root opened archetype should be registered in SILModule");
       } else if (t->hasDynamicSelfType()) {
         require(I->getFunction()->hasSelfParam() ||