[move-only] Allow for nominal non-class move only types to have destructors.

In the process of doing this I also moved the logic of checking if a type can
have a destructor to the type checker from the parser.

Author: gottesmm

include/swift/Parse/Parser.h

@@ -976,13 +976,12 @@ class Parser {
     PD_AllowTopLevel        = 1 << 1,
     PD_HasContainerType     = 1 << 2,
     PD_DisallowInit         = 1 << 3,
-    PD_AllowDestructor      = 1 << 4,
-    PD_AllowEnumElement     = 1 << 5,
-    PD_InProtocol           = 1 << 6,
-    PD_InClass              = 1 << 7,
-    PD_InExtension          = 1 << 8,
-    PD_InStruct             = 1 << 9,
-    PD_InEnum               = 1 << 10,
+    PD_AllowEnumElement     = 1 << 4,
+    PD_InProtocol           = 1 << 5,
+    PD_InClass              = 1 << 6,
+    PD_InExtension          = 1 << 7,
+    PD_InStruct             = 1 << 8,
+    PD_InEnum               = 1 << 9,
   };
 
   /// Options that control the parsing of declarations.

lib/AST/ASTVerifier.cpp

@@ -3142,8 +3142,9 @@ class Verifier : public ASTWalker {
       PrettyStackTraceDecl debugStack("verifying DestructorDecl", DD);
 
       auto *ND = DD->getDeclContext()->getSelfNominalTypeDecl();
-      if (!isa<ClassDecl>(ND) && !DD->isInvalid()) {
-        Out << "DestructorDecls outside classes should be marked invalid";
+      if (!isa<ClassDecl>(ND) && !ND->isMoveOnly() && !DD->isInvalid()) {
+        Out << "DestructorDecls outside classes/move only types should be "
+               "marked invalid\n";
         abort();
       }
       verifyCheckedBase(DD);

lib/Parse/ParseDecl.cpp

@@ -14,35 +14,36 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "swift/Parse/Parser.h"
-#include "swift/Parse/CodeCompletionCallbacks.h"
-#include "swift/Parse/ParsedSyntaxRecorder.h"
-#include "swift/Parse/ParseSILSupport.h"
-#include "swift/Parse/SyntaxParsingContext.h"
-#include "swift/Syntax/SyntaxKind.h"
-#include "swift/Subsystems.h"
-#include "swift/Strings.h"
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/Attr.h"
-#include "swift/AST/GenericParamList.h"
-#include "swift/AST/LazyResolver.h"
 #include "swift/AST/DebuggerClient.h"
+#include "swift/AST/Decl.h"
 #include "swift/AST/DiagnosticsParse.h"
+#include "swift/AST/GenericParamList.h"
 #include "swift/AST/Initializer.h"
+#include "swift/AST/LazyResolver.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/ParameterList.h"
 #include "swift/AST/ParseRequests.h"
 #include "swift/AST/SourceFile.h"
 #include "swift/Basic/Defer.h"
 #include "swift/Basic/Statistic.h"
 #include "swift/Basic/StringExtras.h"
+#include "swift/Parse/CodeCompletionCallbacks.h"
+#include "swift/Parse/ParseSILSupport.h"
+#include "swift/Parse/ParsedSyntaxRecorder.h"
+#include "swift/Parse/Parser.h"
+#include "swift/Parse/SyntaxParsingContext.h"
+#include "swift/Strings.h"
+#include "swift/Subsystems.h"
+#include "swift/Syntax/SyntaxKind.h"
+#include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/Twine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SaveAndRestore.h"
-#include "llvm/ADT/PointerUnion.h"
-#include "llvm/ADT/StringSwitch.h"
-#include "llvm/ADT/Twine.h"
 #include <algorithm>
 
 using namespace swift;
@@ -5111,9 +5112,7 @@ static Parser::ParseDeclOptions getMemberParseDeclOptions(
         Parser::PD_InProtocol);
 
   case DeclKind::Class:
-    return ParseDeclOptions(
-        Parser::PD_HasContainerType | Parser::PD_AllowDestructor |
-        Parser::PD_InClass);
+    return ParseDeclOptions(Parser::PD_HasContainerType | Parser::PD_InClass);
 
   case DeclKind::Struct:
     return ParseDeclOptions(Parser::PD_HasContainerType | Parser::PD_InStruct);
@@ -8748,8 +8747,13 @@ parseDeclDeinit(ParseDeclOptions Flags, DeclAttributes &Attributes) {
 
   DD->getAttrs() = Attributes;
 
-  // Reject 'destructor' functions outside of classes
-  if (!(Flags & PD_AllowDestructor)) {
+  // Reject 'destructor' functions outside of structs, enums, and classes.
+  //
+  // Later in the type checker, we validate that structs/enums only do this if
+  // they are move only.
+  auto *nom = dyn_cast<NominalTypeDecl>(CurDeclContext);
+  if (!nom ||
+      (!isa<StructDecl>(nom) && !isa<EnumDecl>(nom) && !isa<ClassDecl>(nom))) {
     diagnose(DestructorLoc, diag::destructor_decl_outside_class);
 
     // Tell the type checker not to touch this destructor.

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -31,6 +31,8 @@
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/AccessNotes.h"
 #include "swift/AST/AccessScope.h"
+#include "swift/AST/Decl.h"
+#include "swift/AST/DeclContext.h"
 #include "swift/AST/ExistentialLayout.h"
 #include "swift/AST/Expr.h"
 #include "swift/AST/ForeignErrorConvention.h"
@@ -3349,6 +3351,15 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
   }
 
   void visitDestructorDecl(DestructorDecl *DD) {
+    // Only check again for destructor decl outside of a class if our dstructor
+    // is not marked as invalid.
+    if (!DD->isInvalid()) {
+      auto *nom = dyn_cast<NominalTypeDecl>(DD->getDeclContext());
+      if (!nom || (!isa<ClassDecl>(nom) && !nom->isMoveOnly())) {
+        DD->diagnose(diag::destructor_decl_outside_class);
+      }
+    }
+
     TypeChecker::checkDeclAttributes(DD);
 
     if (DD->getDeclContext()->isLocalContext()) {