AST: Add VarDecl::isLazyStorageProperty() and set it

Author: slavapestov

include/swift/AST/Decl.h

@@ -370,7 +370,7 @@ class alignas(1 << DeclAlignInBits) Decl {
     IsStatic : 1
   );
 
-  SWIFT_INLINE_BITFIELD(VarDecl, AbstractStorageDecl, 4+1+1+1+1,
+  SWIFT_INLINE_BITFIELD(VarDecl, AbstractStorageDecl, 4+1+1+1+1+1,
     /// The specifier associated with this variable or parameter.  This
     /// determines the storage semantics of the value e.g. mutability.
     Specifier : 4,
@@ -387,6 +387,8 @@ class alignas(1 << DeclAlignInBits) Decl {
     /// It is up to the debugger to instruct SIL how to access this variable.
     IsDebuggerVar : 1,
 
+    /// Whether this is the backing storage for a lazy property.
+    IsLazyStorageProperty : 1,
 
     /// Whether this is the backing storage for a property wrapper.
     IsPropertyWrapperBackingProperty : 1
@@ -4803,6 +4805,7 @@ class VarDecl : public AbstractStorageDecl {
     Bits.VarDecl.Specifier = static_cast<unsigned>(Sp);
     Bits.VarDecl.IsCaptureList = IsCaptureList;
     Bits.VarDecl.IsDebuggerVar = false;
+    Bits.VarDecl.IsLazyStorageProperty = false;
     Bits.VarDecl.HasNonPatternBindingInit = false;
     Bits.VarDecl.IsPropertyWrapperBackingProperty = false;
   }
@@ -5091,6 +5094,13 @@ class VarDecl : public AbstractStorageDecl {
   void setDebuggerVar(bool IsDebuggerVar) {
     Bits.VarDecl.IsDebuggerVar = IsDebuggerVar;
   }
+
+  /// Is this the synthesized storage for a 'lazy' property?
+  bool isLazyStorageProperty() const {
+    return Bits.VarDecl.IsLazyStorageProperty;
+  }
+  void setLazyStorageProperty(bool IsLazyStorage) {
+    Bits.VarDecl.IsLazyStorageProperty = IsLazyStorage;
   }
 
   /// Retrieve the custom attribute that attaches a property wrapper to this

lib/Sema/CodeSynthesis.cpp

@@ -1625,6 +1625,7 @@ void swift::completeLazyVarImplementation(VarDecl *VD) {
                                         StorageName,
                                         VD->getDeclContext());
   Storage->setInterfaceType(StorageInterfaceTy);
+  Storage->setLazyStorageProperty(true);
   Storage->setUserAccessible(false);
 
   // Mark the backing property as 'final'. There's no sensible way to override.