[Swiftify] fix missing owning module

Implicit decls don't have an owning module, since multiple modules could
instantiate them on demand. Since no implicit functions currently have
any need for safe wrappers we can simply detect this and early exit. For
templated functions, we need to fetch the owning module from the
instantiation.

Author: hnrklssn

lib/ClangImporter/SwiftifyDecl.cpp

@@ -24,6 +24,7 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Attr.h"
 #include "clang/AST/Decl.h"
+#include "clang/AST/DeclObjC.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/AST/Type.h"
@@ -337,9 +338,9 @@ struct UnaliasedInstantiationVisitor
 struct ForwardDeclaredConcreteTypeVisitor
     : clang::RecursiveASTVisitor<ForwardDeclaredConcreteTypeVisitor> {
   bool hasForwardDeclaredConcreteType = false;
-  clang::Module *Owner;
+  const clang::Module *Owner;
 
-  ForwardDeclaredConcreteTypeVisitor(clang::Module *Owner) : Owner(Owner) {};
+  ForwardDeclaredConcreteTypeVisitor(const clang::Module *Owner) : Owner(Owner) { ASSERT(Owner); };
 
   bool VisitRecordType(clang::RecordType *RT) {
     const clang::RecordDecl *RD = RT->getDecl()->getDefinition();
@@ -393,6 +394,13 @@ static size_t getNumParams(const clang::FunctionDecl* D) {
 }
 } // namespace
 
+static const clang::Decl *getTemplateInstantiation(const clang::FunctionDecl *D) {
+  return D->getTemplateInstantiationPattern();
+}
+static const clang::Decl *getTemplateInstantiation(const clang::ObjCMethodDecl *) {
+  return nullptr;
+}
+
 template<typename T>
 static bool swiftifyImpl(ClangImporter::Implementation &Self,
                          SwiftifyInfoFunctionPrinter &printer,
@@ -406,9 +414,20 @@ static bool swiftifyImpl(ClangImporter::Implementation &Self,
       ClangDecl->getAccess() == clang::AS_private)
     return false;
 
+  if (ClangDecl->isImplicit()) {
+    DLOG("implicit functions lack lifetime and bounds info");
+    return false;
+  }
+
   clang::ASTContext &clangASTContext = Self.getClangASTContext();
 
-  ForwardDeclaredConcreteTypeVisitor CheckForwardDecls(ClangDecl->getOwningModule());
+  const clang::Module *OwningModule = nullptr;
+  if (const auto *Instance = getTemplateInstantiation(ClangDecl)) {
+    OwningModule = Instance->getOwningModule();
+  } else {
+    OwningModule = ClangDecl->getOwningModule();
+  }
+  ForwardDeclaredConcreteTypeVisitor CheckForwardDecls(OwningModule);
 
   // We only attach the macro if it will produce an overload. Any __counted_by
   // will produce an overload, since UnsafeBufferPointer is still an improvement