[6.2] Add support for inout lifetime dependencies

include/swift/AST/ASTBridging.h

@@ -1086,8 +1086,9 @@ BridgedInlineAttr BridgedInlineAttr_createParsed(BridgedASTContext cContext,
 
 enum ENUM_EXTENSIBILITY_ATTR(closed) BridgedParsedLifetimeDependenceKind {
   BridgedParsedLifetimeDependenceKindDefault,
-  BridgedParsedLifetimeDependenceKindScope,
+  BridgedParsedLifetimeDependenceKindBorrow,
   BridgedParsedLifetimeDependenceKindInherit,
+  BridgedParsedLifetimeDependenceKindInout
 };
 
 class BridgedLifetimeDescriptor {

include/swift/AST/DiagnosticsSema.def

@@ -8169,8 +8169,11 @@ ERROR(lifetime_dependence_invalid_inherit_escapable_type, none,
       "'@lifetime(borrow %0)' instead",
       (StringRef))
 ERROR(lifetime_dependence_cannot_use_parsed_borrow_consuming, none,
-      "invalid use of borrow dependence with consuming ownership",
-      ())
+      "invalid use of %0 dependence with %1 ownership",
+      (StringRef, StringRef))
+ERROR(lifetime_dependence_cannot_use_default_escapable_consuming, none,
+      "invalid lifetime dependence on an Escapable value with %0 ownership",
+      (StringRef))
 ERROR(lifetime_dependence_cannot_use_parsed_borrow_inout, none,
       "invalid use of borrow dependence on the same inout parameter",
       ())

include/swift/AST/LifetimeDependence.h

@@ -38,8 +38,9 @@ class SILResultInfo;
 
 enum class ParsedLifetimeDependenceKind : uint8_t {
   Default = 0,
-  Scope,
-  Inherit // Only used with deserialized decls
+  Borrow,
+  Inherit, // Only used with deserialized decls
+  Inout
 };
 
 enum class LifetimeDependenceKind : uint8_t { Inherit = 0, Scope };
@@ -182,6 +183,7 @@ class LifetimeEntry final
          ArrayRef<LifetimeDescriptor> sources,
          std::optional<LifetimeDescriptor> targetDescriptor = std::nullopt);
 
+  std::string getString() const;
   SourceLoc getLoc() const { return startLoc; }
   SourceLoc getStartLoc() const { return startLoc; }
   SourceLoc getEndLoc() const { return endLoc; }
@@ -193,35 +195,6 @@ class LifetimeEntry final
   std::optional<LifetimeDescriptor> getTargetDescriptor() const {
     return targetDescriptor;
   }
-
-  std::string getString() const {
-    std::string result = "@lifetime(";
-    if (targetDescriptor.has_value()) {
-      result += targetDescriptor->getString();
-      result += ": ";
-    }
-
-    bool firstElem = true;
-    for (auto source : getSources()) {
-      if (!firstElem) {
-        result += ", ";
-      }
-      switch (source.getParsedLifetimeDependenceKind()) {
-      case ParsedLifetimeDependenceKind::Scope:
-        result += "borrow ";
-        break;
-      case ParsedLifetimeDependenceKind::Inherit:
-        result += "copy ";
-        break;
-      default:
-        break;
-      }
-      result += source.getString();
-      firstElem = false;
-    }
-    result += ")";
-    return result;
-  }
 };
 
 class LifetimeDependenceInfo {
@@ -366,6 +339,9 @@ filterEscapableLifetimeDependencies(GenericSignature sig,
         SmallVectorImpl<LifetimeDependenceInfo> &outputs,
         llvm::function_ref<Type (unsigned targetIndex)> getSubstTargetType);
 
+StringRef
+getNameForParsedLifetimeDependenceKind(ParsedLifetimeDependenceKind kind);
+
 } // namespace swift
 
 #endif

include/swift/Basic/Features.def

@@ -416,6 +416,9 @@ EXPERIMENTAL_FEATURE(StructLetDestructuring, true)
 /// Enable returning non-escapable types from functions.
 EXPERIMENTAL_FEATURE(LifetimeDependence, true)
 
+/// Enable inout lifetime dependence - @lifetime(&arg)
+EXPERIMENTAL_FEATURE(InoutLifetimeDependence, true)
+
 /// Enable the `@_staticExclusiveOnly` attribute.
 EXPERIMENTAL_FEATURE(StaticExclusiveOnly, true)
 

lib/AST/Bridging/DeclAttributeBridging.cpp

@@ -470,10 +470,12 @@ unbridged(BridgedParsedLifetimeDependenceKind kind) {
   switch (kind) {
   case BridgedParsedLifetimeDependenceKindDefault:
     return swift::ParsedLifetimeDependenceKind::Default;
-  case BridgedParsedLifetimeDependenceKindScope:
-    return swift::ParsedLifetimeDependenceKind::Scope;
+  case BridgedParsedLifetimeDependenceKindBorrow:
+    return swift::ParsedLifetimeDependenceKind::Borrow;
   case BridgedParsedLifetimeDependenceKindInherit:
     return swift::ParsedLifetimeDependenceKind::Inherit;
+  case BridgedParsedLifetimeDependenceKindInout:
+    return swift::ParsedLifetimeDependenceKind::Inout;
   }
   llvm_unreachable("unhandled enum value");
 }

lib/AST/FeatureSet.cpp

@@ -271,6 +271,29 @@ static bool usesFeatureLifetimeDependence(Decl *decl) {
   return false;
 }
 
+static bool usesFeatureInoutLifetimeDependence(Decl *decl) {
+  auto hasInoutLifetimeDependence = [](Decl *decl) {
+    for (auto attr : decl->getAttrs().getAttributes<LifetimeAttr>()) {
+      for (auto source : attr->getLifetimeEntry()->getSources()) {
+        if (source.getParsedLifetimeDependenceKind() ==
+            ParsedLifetimeDependenceKind::Inout) {
+          return true;
+        }
+      }
+    }
+    return false;
+  };
+
+  switch (decl->getKind()) {
+  case DeclKind::Var: {
+    auto *var = cast<VarDecl>(decl);
+    return llvm::any_of(var->getAllAccessors(), hasInoutLifetimeDependence);
+  }
+  default:
+    return hasInoutLifetimeDependence(decl);
+  }
+}
+
 UNINTERESTING_FEATURE(DynamicActorIsolation)
 UNINTERESTING_FEATURE(NonfrozenEnumExhaustivity)
 UNINTERESTING_FEATURE(ClosureIsolation)