[Parser] Pass code completion status from attribute parsing to decl parsing

This is needed to be able to perform code completion inside `@freestanding` and `@attached`.

Author: ahoppen

include/swift/Parse/Parser.h

@@ -1019,9 +1019,10 @@ class Parser {
                                       PatternBindingInitializer *initContext);
 
   /// Parse the optional modifiers before a declaration.
-  bool parseDeclModifierList(DeclAttributes &Attributes, SourceLoc &StaticLoc,
-                             StaticSpellingKind &StaticSpelling,
-                             bool isFromClangAttribute = false);
+  ParserStatus parseDeclModifierList(DeclAttributes &Attributes,
+                                     SourceLoc &StaticLoc,
+                                     StaticSpellingKind &StaticSpelling,
+                                     bool isFromClangAttribute = false);
 
   /// Parse an availability attribute of the form
   /// @available(*, introduced: 1.0, deprecated: 3.1).
@@ -1133,9 +1134,9 @@ class Parser {
   ParserResult<CustomAttr> parseCustomAttribute(
       SourceLoc atLoc, PatternBindingInitializer *&initContext);
 
-  bool parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
-                             DeclAttrKind DK,
-                             bool isFromClangAttribute = false);
+  ParserStatus parseNewDeclAttribute(DeclAttributes &Attributes,
+                                     SourceLoc AtLoc, DeclAttrKind DK,
+                                     bool isFromClangAttribute = false);
 
   /// Parse a version tuple of the form x[.y[.z]]. Returns true if there was
   /// an error parsing.

lib/ClangImporter/ImportDecl.cpp

@@ -7658,9 +7658,11 @@ ClangImporter::Implementation::importSwiftAttrAttributes(Decl *MappedDecl) {
       } else {
         SourceLoc staticLoc;
         StaticSpellingKind staticSpelling;
-        hadError = parser.parseDeclModifierList(
-            MappedDecl->getAttrs(), staticLoc, staticSpelling,
-            /*isFromClangAttribute=*/true);
+        hadError = parser
+                       .parseDeclModifierList(MappedDecl->getAttrs(), staticLoc,
+                                              staticSpelling,
+                                              /*isFromClangAttribute=*/true)
+                       .isError();
       }
 
       if (hadError) {