[sil] Add a helper SILType::isBoxedNonCopyableType().

I am using this query a lot in SILGen when adding support for escaping
captures. Makes sense to chop it off into a nice little helper on SILType.

Author: gottesmm

include/swift/SIL/SILType.h

@@ -695,7 +695,7 @@ class SILType {
   ///
   /// \p field Return the type of the ith field of the box. Default set to 0
   /// since we only support one field today. This is just future proofing.
-  SILType getSILBoxFieldType(const SILFunction *f, unsigned field = 0);
+  SILType getSILBoxFieldType(const SILFunction *f, unsigned field = 0) const;
 
   /// Returns the hash code for the SILType.
   llvm::hash_code getHashCode() const {
@@ -708,6 +708,17 @@ class SILType {
   SILType getSingletonAggregateFieldType(SILModule &M,
                                          ResilienceExpansion expansion) const;
 
+  /// \returns true if this is a SILBoxType containing a noncopyable type.
+  bool isBoxedNonCopyableType(const SILFunction *fn) const {
+    if (!this->is<SILBoxType>())
+      return false;
+    return getSILBoxFieldType(fn).isMoveOnly();
+  }
+
+  bool isBoxedNonCopyableType(const SILFunction &fn) const {
+    return isBoxedNonCopyableType(&fn);
+  }
+
   //
   // Accessors for types used in SIL instructions:
   //

lib/SIL/IR/SILType.cpp

@@ -861,7 +861,7 @@ bool SILType::isEffectivelyExhaustiveEnumType(SILFunction *f) {
                                        f->getResilienceExpansion());
 }
 
-SILType SILType::getSILBoxFieldType(const SILFunction *f, unsigned field) {
+SILType SILType::getSILBoxFieldType(const SILFunction *f, unsigned field) const {
   auto *boxTy = getASTType()->getAs<SILBoxType>();
   if (!boxTy)
     return SILType();