Introduce SILType::mapTypeOutOfContext.

This does the same thing as taking the AST type and running it through mapTypeOutOfContext, but
saves call sites from having to do the unwrap-rewrap dance.

Author: jckarter

include/swift/SIL/SILType.h

@@ -492,6 +492,9 @@ class SILType {
   /// Returns the underlying referent SILType of an @sil_unowned or @sil_weak
   /// Type.
   SILType getReferentType(SILModule &M) const;
+  
+  /// Returns a SILType with any archetypes mapped out of context.
+  SILType mapTypeOutOfContext() const;
 
   /// Given two SIL types which are representations of the same type,
   /// check whether they have an abstraction difference.

lib/IRGen/GenHeap.cpp

@@ -1558,10 +1558,7 @@ class FixedBoxTypeInfoBase : public BoxTypeInfo {
     // Allocate a new object using the layout.
     auto boxedInterfaceType = boxedType;
     if (env) {
-      boxedInterfaceType = SILType::getPrimitiveType(
-        boxedType.getSwiftRValueType()->mapTypeOutOfContext()
-           ->getCanonicalType(),
-         boxedType.getCategory());
+      boxedInterfaceType = boxedType.mapTypeOutOfContext();
     }
 
     auto boxDescriptor = IGF.IGM.getAddrOfBoxDescriptor(

lib/SIL/SILType.cpp

@@ -390,6 +390,12 @@ SILType SILType::getReferentType(SILModule &M) const {
   return M.Types.getLoweredType(Ty->getReferentType()->getCanonicalType());
 }
 
+SILType SILType::mapTypeOutOfContext() const {
+  return SILType::getPrimitiveType(getSwiftRValueType()->mapTypeOutOfContext()
+                                                       ->getCanonicalType(),
+                                   getCategory());
+}
+
 CanType
 SILBoxType::getFieldLoweredType(SILModule &M, unsigned index) const {
   auto fieldTy = getLayout()->getFields()[index].getLoweredType();

lib/SILGen/SILGenExpr.cpp

@@ -3764,10 +3764,7 @@ lowerKeyPathSubscriptIndexTypes(
     auto indexLoweredTy = SGM.Types.getLoweredType(
                                                 AbstractionPattern::getOpaque(),
                                                 indexTy);
-    indexLoweredTy = SILType::getPrimitiveType(
-                     indexLoweredTy.getSwiftRValueType()->mapTypeOutOfContext()
-                                                        ->getCanonicalType(),
-                     indexLoweredTy.getCategory());
+    indexLoweredTy = indexLoweredTy.mapTypeOutOfContext();
     indexPatterns.push_back({indexTy->mapTypeOutOfContext()
                                     ->getCanonicalType(),
                              indexLoweredTy});