[NFC] Fix @Lifetime SIL parsing: handle AST output

Disable inference diagnostics because the AST output makes implicit initializers
explicit.

Enable parsing the @Lifetime declaration syntax to handle explicit annotations
on declarations.

Author: atrick

lib/AST/LifetimeDependence.cpp

@@ -17,6 +17,7 @@
 #include "swift/AST/DiagnosticsSema.h"
 #include "swift/AST/Module.h"
 #include "swift/AST/ParameterList.h"
+#include "swift/AST/SourceFile.h"
 #include "swift/AST/Type.h"
 #include "swift/AST/TypeRepr.h"
 #include "swift/Basic/Assertions.h"
@@ -538,10 +539,18 @@ LifetimeDependenceInfo::infer(AbstractFunctionDecl *afd) {
                              : afd->getParameters()->size();
 
   auto *cd = dyn_cast<ConstructorDecl>(afd);
-  if (cd && cd->isImplicit()) {
-    if (cd->getParameters()->size() == 0) {
+  if (cd && cd->getParameters()->size() == 0) {
+    if (cd->isImplicit()) {
       return std::nullopt;
     }
+    if (auto *sf = afd->getParentSourceFile()) {
+      // The AST printer makes implicit initializers explicit, but does not
+      // print the @lifetime annotations. Until that is fixed, avoid diagnosing
+      // this as an error.
+      if (sf->Kind == SourceFileKind::SIL) {
+        return std::nullopt;
+      }
+    }
   }
 
   if (!ctx.LangOpts.hasFeature(Feature::LifetimeDependence)) {

lib/Parse/ParseDecl.cpp

@@ -5006,8 +5006,7 @@ ParserResult<LifetimeEntry> Parser::parseLifetimeEntry(SourceLoc loc) {
   auto lParenLoc = consumeAttributeLParen(); // consume the l_paren
 
   std::optional<LifetimeDescriptor> targetDescriptor;
-  if (!isInSILMode() &&
-      Tok.isAny(tok::identifier, tok::integer_literal, tok::kw_self) &&
+  if (Tok.isAny(tok::identifier, tok::integer_literal, tok::kw_self) &&
       peekToken().is(tok::colon)) {
     targetDescriptor = parseLifetimeDescriptor(*this);
     if (!targetDescriptor) {