[cxx-interop] Do not require the LifetimeDependence feature in _SwiftifyImport

We use experimental features to let people know that the construct is
subject to change and users should not rely on this unless they are
willing to rewrite the uses of this feature later. However, in compiler
generated code everything should be fair game, we will update the
compiler when these features change. This is a requirement to be able to
turn safe wrapper generation on by default.

Author: Gabor Horvath

include/swift/Basic/SourceManager.h

@@ -550,6 +550,10 @@ class SourceManager {
   /// translated.
   SourceLoc getLocForForeignLoc(SourceLoc otherLoc, SourceManager &otherMgr);
 
+  /// Returns true when the location is in a buffer generated by the
+  /// \p _SwiftifyImport macro.
+  bool isImportMacroGeneratedLoc(SourceLoc loc);
+
 private:
   int getLineOffset(SourceLoc Loc) const {
     if (auto VFile = getVirtualFile(Loc))

lib/AST/LifetimeDependence.cpp

@@ -23,6 +23,7 @@
 #include "swift/Basic/Assertions.h"
 #include "swift/Basic/Defer.h"
 #include "swift/Basic/Range.h"
+#include "swift/Basic/SourceManager.h"
 
 namespace swift {
 
@@ -576,7 +577,8 @@ LifetimeDependenceInfo::infer(AbstractFunctionDecl *afd) {
     }
   }
 
-  if (!ctx.LangOpts.hasFeature(Feature::LifetimeDependence)) {
+  if (!ctx.LangOpts.hasFeature(Feature::LifetimeDependence) &&
+      !ctx.SourceMgr.isImportMacroGeneratedLoc(returnLoc)) {
     diags.diagnose(returnLoc, diag::lifetime_dependence_feature_required);
     return std::nullopt;
   }

lib/Basic/SourceLoc.cpp

@@ -865,3 +865,15 @@ bool SourceManager::encloses(SourceRange enclosing, SourceRange inner) const {
   return containsLoc(enclosing, inner.Start) &&
       isAtOrBefore(inner.End, enclosing.End);
 }
+
+bool SourceManager::isImportMacroGeneratedLoc(SourceLoc loc) {
+  if (loc.isInvalid())
+    return false;
+
+  auto buffer = findBufferContainingLoc(loc);
+  auto genInfo = getGeneratedSourceInfo(buffer);
+  if (genInfo && genInfo->macroName == "_SwiftifyImport")
+    return true;
+
+  return false;
+}

lib/Parse/ParseDecl.cpp

@@ -31,6 +31,7 @@
 #include "swift/AST/SourceFile.h"
 #include "swift/Basic/Assertions.h"
 #include "swift/Basic/Defer.h"
+#include "swift/Basic/SourceManager.h"
 #include "swift/Basic/Statistic.h"
 #include "swift/Basic/StringExtras.h"
 #include "swift/Bridging/ASTGen.h"
@@ -2556,7 +2557,8 @@ parseLifetimeDescriptor(Parser &P,
 ParserResult<LifetimeAttr> Parser::parseLifetimeAttribute(SourceLoc atLoc,
                                                           SourceLoc loc) {
   ParserStatus status;
-  if (!Context.LangOpts.hasFeature(Feature::LifetimeDependence)) {
+  if (!Context.LangOpts.hasFeature(Feature::LifetimeDependence) &&
+      !Context.SourceMgr.isImportMacroGeneratedLoc(atLoc)) {
     diagnose(loc, diag::requires_experimental_feature, "@lifetime", false,
              getFeatureName(Feature::LifetimeDependence));
     status.setIsParseError();

test/Macros/SwiftifyImport/CxxSpan/LifetimeboundSpan.swift

@@ -1,8 +1,7 @@
 
 // REQUIRES: swift_swift_parser
-// REQUIRES: swift_feature_LifetimeDependence
 
-// RUN: %target-swift-frontend %s -enable-experimental-cxx-interop -I %S/Inputs -Xcc -std=c++20 -swift-version 5 -module-name main -disable-availability-checking -typecheck -enable-experimental-feature LifetimeDependence -plugin-path %swift-plugin-dir -dump-macro-expansions -verify -strict-memory-safety 2>&1 | %FileCheck --match-full-lines %s
+// RUN: %target-swift-frontend %s -enable-experimental-cxx-interop -I %S/Inputs -Xcc -std=c++20 -swift-version 5 -module-name main -disable-availability-checking -typecheck -plugin-path %swift-plugin-dir -dump-macro-expansions -verify -strict-memory-safety 2>&1 | %FileCheck --match-full-lines %s
 
 // FIXME swift-ci linux tests do not support std::span
 // UNSUPPORTED: OS=linux-gnu