Look like SPM is right here.

Author: Alexander Perechnev

SidebarOverlay.xcodeproj/project.pbxproj

@@ -15,7 +15,8 @@
 		3298C7101E66B58700198719 /* Info.plist in Resources */ = {isa = PBXBuildFile; fileRef = 3298C7091E66B58700198719 /* Info.plist */; };
 		3298C7121E66B74A00198719 /* SidebarOverlay.h in Headers */ = {isa = PBXBuildFile; fileRef = 3298C7041E66B58700198719 /* SidebarOverlay.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		3298C7131E66B84800198719 /* SOContainerViewControllerTestCase.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3298C70A1E66B58700198719 /* SOContainerViewControllerTestCase.swift */; };
-		3298C7171E66B95700198719 /* Package.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3298C7161E66B95700198719 /* Package.swift */; };
+		3298C71A1E66B9BD00198719 /* UIKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 3298C7191E66B9BD00198719 /* UIKit.framework */; };
+		3298C71D1E66BC0F00198719 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 3298C71C1E66BC0F00198719 /* Foundation.framework */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -39,13 +40,17 @@
 		3298C7091E66B58700198719 /* Info.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		3298C70A1E66B58700198719 /* SOContainerViewControllerTestCase.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = SOContainerViewControllerTestCase.swift; sourceTree = "<group>"; };
 		3298C7161E66B95700198719 /* Package.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Package.swift; sourceTree = "<group>"; };
+		3298C7191E66B9BD00198719 /* UIKit.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = UIKit.framework; path = System/Library/Frameworks/UIKit.framework; sourceTree = SDKROOT; };
+		3298C71C1E66BC0F00198719 /* Foundation.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Foundation.framework; path = System/Library/Frameworks/Foundation.framework; sourceTree = SDKROOT; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
 		322EAC0B1C2B3F820077D684 /* Frameworks */ = {
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				3298C71D1E66BC0F00198719 /* Foundation.framework in Frameworks */,
+				3298C71A1E66B9BD00198719 /* UIKit.framework in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -67,6 +72,7 @@
 				3298C7021E66B58700198719 /* Source */,
 				3298C7081E66B58700198719 /* Tests */,
 				322EAC101C2B3F820077D684 /* Products */,
+				3298C7181E66B9BC00198719 /* Frameworks */,
 			);
 			sourceTree = "<group>";
 		};
@@ -100,6 +106,15 @@
 			path = Tests;
 			sourceTree = "<group>";
 		};
+		3298C7181E66B9BC00198719 /* Frameworks */ = {
+			isa = PBXGroup;
+			children = (
+				3298C71C1E66BC0F00198719 /* Foundation.framework */,
+				3298C7191E66B9BD00198719 /* UIKit.framework */,
+			);
+			name = Frameworks;
+			sourceTree = "<group>";
+		};
 /* End PBXGroup section */
 
 /* Begin PBXHeadersBuildPhase section */
@@ -213,7 +228,6 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				3298C7171E66B95700198719 /* Package.swift in Sources */,
 				3298C70E1E66B58700198719 /* SOSide.swift in Sources */,
 				3298C70D1E66B58700198719 /* SOContainerViewController.swift in Sources */,
 				3298C70F1E66B58700198719 /* UIViewController.swift in Sources */,