Add initial support for _resultDependsOnSelf

This is used to establish lifetime dependence between self and the result.

Add under NonEscapableTypes experimental feature

Author: meg-gupta

include/swift/AST/Attr.def

@@ -527,6 +527,9 @@ DECL_ATTR(storageRestrictions, StorageRestrictions,
 CONTEXTUAL_SIMPLE_DECL_ATTR(actor, Actor,
   DeclModifier | OnClass | ConcurrencyOnly | ABIBreakingToAdd | ABIBreakingToRemove | APIBreakingToAdd | APIBreakingToRemove,
   102)
+CONTEXTUAL_SIMPLE_DECL_ATTR(_resultDependsOnSelf, ResultDependsOnSelf,
+  OnFunc | DeclModifier | UserInaccessible | ABIBreakingToAdd | ABIStableToRemove | APIBreakingToAdd | APIStableToRemove,
+  150)
 
 #undef TYPE_ATTR
 #undef DECL_ATTR_ALIAS

include/swift/AST/Decl.h

@@ -241,7 +241,8 @@ enum class SelfAccessKind : uint8_t {
   LegacyConsuming,
   Consuming,
   Borrowing,
-  LastSelfAccessKind = Borrowing,
+  ResultDependsOnSelf,
+  LastSelfAccessKind = ResultDependsOnSelf,
 };
 enum : unsigned {
   NumSelfAccessKindBits =

include/swift/AST/DiagnosticsParse.def

@@ -2166,5 +2166,10 @@ ERROR(duplicate_storage_restrictions_attr_label,none,
 ERROR(storage_restrictions_attr_expected_name,none,
       "expected property name in @storageRestrictions list", ())
 
+ERROR(requires_non_escapable_types, none,
+      "'%0' %select{attribute|parameter specifier}1 is only valid when experimental "
+      "NonEscapableTypes is enabled",
+      (StringRef, bool))
+
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

include/swift/AST/DiagnosticsSema.def

@@ -7701,5 +7701,12 @@ ERROR(referencebindings_binding_must_have_initial_value,none,
 ERROR(referencebindings_binding_must_be_to_lvalue,none,
       "%0 bindings must be bound to an lvalue", (StringRef))
 
+//------------------------------------------------------------------------------
+// MARK: resultDependsOn Errors
+//------------------------------------------------------------------------------
+
+ERROR(result_depends_on_no_result,none,
+      "Incorrect use of %0 with no result", (StringRef))
+
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

lib/APIDigester/ModuleAnalyzerNodes.cpp

@@ -1559,6 +1559,9 @@ SDKNodeInitInfo::SDKNodeInitInfo(SDKContext &Ctx, ValueDecl *VD)
     case SelfAccessKind::Borrowing:
       FuncSelfKind = "Borrowing";
       break;
+    case SelfAccessKind::ResultDependsOnSelf:
+      FuncSelfKind = "ResultDependsOnSelf";
+      break;
     }
   }
 

lib/AST/ASTContext.cpp

@@ -3455,6 +3455,8 @@ AnyFunctionType::Param swift::computeSelfParam(AbstractFunctionDecl *AFD,
   case SelfAccessKind::NonMutating:
     // The default flagless state.
     break;
+  case SelfAccessKind::ResultDependsOnSelf:
+    break;
   }
 
   return AnyFunctionType::Param(selfTy, Identifier(), flags);

lib/AST/ASTPrinter.cpp

@@ -2119,6 +2119,10 @@ void PrintAST::printSelfAccessKindModifiersIfNeeded(const FuncDecl *FD) {
     if (!Options.excludeAttrKind(DAK_Borrowing))
       Printer.printKeyword("borrowing", Options, " ");
     break;
+  case SelfAccessKind::ResultDependsOnSelf:
+    if (!Options.excludeAttrKind(DAK_ResultDependsOnSelf))
+      Printer.printKeyword("_resultDependsOnSelf", Options, " ");
+    break;
   }
 }
 
@@ -3516,8 +3520,15 @@ static bool usesFeatureStructLetDestructuring(Decl *decl) {
 }
 
 static bool usesFeatureNonEscapableTypes(Decl *decl) {
-  return decl->getAttrs().hasAttribute<NonEscapableAttr>()
-    || decl->getAttrs().hasAttribute<UnsafeNonEscapableResultAttr>();
+  if (decl->getAttrs().hasAttribute<NonEscapableAttr>() ||
+      decl->getAttrs().hasAttribute<UnsafeNonEscapableResultAttr>()) {
+    return true;
+  }
+  auto *fd = dyn_cast<FuncDecl>(decl);
+  if (fd && fd->getAttrs().getAttribute(DAK_ResultDependsOnSelf)) {
+    return true;
+  }
+  return false;
 }
 
 static bool hasParameterPacks(Decl *decl) {

lib/AST/Decl.cpp

@@ -604,6 +604,8 @@ llvm::raw_ostream &swift::operator<<(llvm::raw_ostream &OS,
   case SelfAccessKind::LegacyConsuming: return OS << "'__consuming'";
   case SelfAccessKind::Consuming: return OS << "'consuming'";
   case SelfAccessKind::Borrowing: return OS << "'borrowing'";
+  case SelfAccessKind::ResultDependsOnSelf:
+    return OS << "'resultDependsOnSelf'";
   }
   llvm_unreachable("Unknown SelfAccessKind");
 }

lib/ASTGen/Sources/ASTGen/SourceFile.swift

@@ -34,6 +34,7 @@ extension Parser.ExperimentalFeatures {
     mapFeature(.ThenStatements, to: .thenStatements)
     mapFeature(.TypedThrows, to: .typedThrows)
     mapFeature(.DoExpressions, to: .doExpressions)
+    mapFeature(.NonEscapableTypes, to: .nonEscapableTypes)
   }
 }
 

lib/ASTGen/Sources/ASTGen/Types.swift

@@ -217,7 +217,7 @@ extension ASTGenVisitor {
   }
 }
 
-// MARK: - SpecifierTypeRepr/AttrubutedTypeRepr
+// MARK: - SpecifierTypeRepr/AttributedTypeRepr
 
 extension BridgedAttributedTypeSpecifier {
   fileprivate init?(from tokenKind: TokenKind) {