Frontend: make takeSILModule out-of-line

The use of `std::move` forces the complete definition of the `SILModule` type.
Move the definition out-of-line to allow a forward declaration of `SILModule`
instead.

Author: compnerd

include/swift/Frontend/Frontend.h

@@ -444,9 +444,7 @@ class CompilerInstance {
     return TheSILModule.get();
   }
 
-  std::unique_ptr<SILModule> takeSILModule() {
-    return std::move(TheSILModule);
-  }
+  std::unique_ptr<SILModule> takeSILModule();
 
   bool hasSILModule() {
     return static_cast<bool>(TheSILModule);

lib/Frontend/Frontend.cpp

@@ -430,6 +430,10 @@ CompilerInstance::openModuleDoc(const InputFile &input) {
   return None;
 }
 
+std::unique_ptr<SILModule> CompilerInstance::takeSILModule() {
+  return std::move(TheSILModule);
+}
+
 ModuleDecl *CompilerInstance::getMainModule() {
   if (!MainModule) {
     Identifier ID = Context->getIdentifier(Invocation.getModuleName());