Use Optional for fingerprint

Author: David Ungar

include/swift/AST/DeclContext.h

@@ -802,9 +802,9 @@ class IterableDeclContext {
   // Some Decls are IterableDeclContexts, but not all.
   static bool classof(const Decl *D);
 
-  /// Return a hash of all tokens in the body for dependency analysis.
-  /// Empty string means no hash available.
-  StringRef getBodyFingerprint() const;
+  /// Return a hash of all tokens in the body for dependency analysis, if
+  /// available.
+  Optional<std::string> getBodyFingerprint() const;
 
   bool areDependenciesUsingTokenHashesForTypeBodies() const;
 

include/swift/AST/ParseRequests.h

@@ -28,8 +28,8 @@ void reportEvaluatedRequest(UnifiedStatsReporter &stats,
                             const Request &request);
 
 struct FingerprintAndMembers {
-  std::string fingerprint;
-  ArrayRef<Decl *> members;
+  Optional<std::string> fingerprint = None;
+  ArrayRef<Decl *> members = {};
   bool operator==(const FingerprintAndMembers &x) const {
     return fingerprint == x.fingerprint && members == x.members;
   }

include/swift/Parse/Parser.h

@@ -927,7 +927,7 @@ class Parser {
                                bool IsAtStartOfLineOrPreviousHadSemi,
                                llvm::function_ref<void(Decl*)> Handler);
 
-  std::pair<std::vector<Decl *>, llvm::SmallString<32>>
+  std::pair<std::vector<Decl *>, Optional<std::string>>
   parseDeclListDelayed(IterableDeclContext *IDC);
 
   bool parseMemberDeclList(SourceLoc LBLoc, SourceLoc &RBLoc,
@@ -1066,7 +1066,7 @@ class Parser {
   ParserStatus parseDeclItem(bool &PreviousHadSemi,
                              Parser::ParseDeclOptions Options,
                              llvm::function_ref<void(Decl*)> handler);
-  std::pair<std::vector<Decl *>, llvm::SmallString<32>>
+  std::pair<std::vector<Decl *>, Optional<std::string>>
   parseDeclList(SourceLoc LBLoc, SourceLoc &RBLoc, Diag<> ErrorDiag,
                 ParseDeclOptions Options, IterableDeclContext *IDC,
                 bool &hadError);

lib/AST/DeclContext.cpp

@@ -901,10 +901,10 @@ IterableDeclContext::castDeclToIterableDeclContext(const Decl *D) {
   }
 }
 
-StringRef IterableDeclContext::getBodyFingerprint() const {
+Optional<std::string> IterableDeclContext::getBodyFingerprint() const {
   // Only makes sense for contexts in a source file
   if (!getDecl()->getDeclContext()->getParentSourceFile())
-    return "";
+    return None;
   auto mutableThis = const_cast<IterableDeclContext *>(this);
   return evaluateOrDefault(getASTContext().evaluator,
                            ParseMembersRequest{mutableThis},

lib/AST/FineGrainedDependenciesSourceFileDepGraphConstructor.cpp

@@ -669,11 +669,8 @@ class SourceFileDepGraphConstructor {
     return None;
   }
   static Optional<std::string> getFingerprintIfAny(const Decl *d) {
-    if (const auto *idc = dyn_cast<IterableDeclContext>(d)) {
-      StringRef fp = idc->getBodyFingerprint();
-      if (!fp.empty())
-        return fp.str();
-    }
+    if (const auto *idc = dyn_cast<IterableDeclContext>(d))
+      return idc->getBodyFingerprint();
     return None;
   }
 

lib/Parse/ParseDecl.cpp

@@ -3912,7 +3912,7 @@ static ScopeKind getMemberParseScopeKind(IterableDeclContext *idc) {
   }
 }
 
-std::pair<std::vector<Decl *>, llvm::SmallString<32>>
+std::pair<std::vector<Decl *>, Optional<std::string>>
 Parser::parseDeclListDelayed(IterableDeclContext *IDC) {
   Decl *D = const_cast<Decl*>(IDC->getDecl());
   DeclContext *DC = cast<DeclContext>(D);
@@ -3926,7 +3926,7 @@ Parser::parseDeclListDelayed(IterableDeclContext *IDC) {
 
   if (BodyRange.isInvalid()) {
     assert(D->isImplicit());
-    return {std::vector<Decl *>(), llvm::SmallString<32>()};
+    return {std::vector<Decl *>(), None};
   }
 
   auto BeginParserPosition = getParserPosition({BodyRange.Start, SourceLoc()});
@@ -3952,7 +3952,7 @@ Parser::parseDeclListDelayed(IterableDeclContext *IDC) {
   // If there is no left brace, then return an empty list of declarations;
   // we will have already diagnosed this.
   if (!Tok.is(tok::l_brace))
-    return {std::vector<Decl *>(), llvm::SmallString<32>()};
+    return {std::vector<Decl *>(), None};
 
   // Re-enter the lexical scope. The top-level scope is needed because
   // delayed parsing of members happens with a fresh parser, where there is
@@ -4337,7 +4337,7 @@ bool Parser::parseMemberDeclList(SourceLoc LBLoc, SourceLoc &RBLoc,
     Context.evaluator.cacheOutput(
         ParseMembersRequest{IDC},
         FingerprintAndMembers{
-            membersAndHash.second.str().str(),
+            membersAndHash.second,
             Context.AllocateCopy(llvm::makeArrayRef(membersAndHash.first))});
 
     if (hadError)
@@ -4352,7 +4352,7 @@ bool Parser::parseMemberDeclList(SourceLoc LBLoc, SourceLoc &RBLoc,
 /// \verbatim
 ///    decl* '}'
 /// \endverbatim
-std::pair<std::vector<Decl *>, llvm::SmallString<32>>
+std::pair<std::vector<Decl *>, Optional<std::string>>
 Parser::parseDeclList(SourceLoc LBLoc, SourceLoc &RBLoc, Diag<> ErrorDiag,
                       ParseDeclOptions Options, IterableDeclContext *IDC,
                       bool &hadError) {
@@ -4397,15 +4397,14 @@ Parser::parseDeclList(SourceLoc LBLoc, SourceLoc &RBLoc, Diag<> ErrorDiag,
   if (RBLoc.isInvalid())
     hadError = true;
 
-  llvm::SmallString<32> tokenHashString;
-  // Must return an empty string if there is really no fingerprint
-  if (Context.LangOpts.EnableTypeFingerprints) {
-    llvm::MD5::MD5Result result;
-    tokenHashForThisDeclList.final(result);
-    llvm::MD5::stringifyResult(result, tokenHashString);
-  }
+  if (!Context.LangOpts.EnableTypeFingerprints)
+    return std::make_pair(decls, None);
 
-  return std::make_pair(decls, tokenHashString);
+  llvm::MD5::MD5Result result;
+  tokenHashForThisDeclList.final(result);
+  llvm::SmallString<32> tokenHashString;
+  llvm::MD5::stringifyResult(result, tokenHashString);
+  return std::make_pair(decls, tokenHashString.str().str());
 }
 
 bool Parser::canDelayMemberDeclParsing(bool &HasOperatorDeclarations,

lib/Parse/ParseRequests.cpp

@@ -35,7 +35,10 @@ namespace swift {
 
 void swift::simple_display(llvm::raw_ostream &out,
                            const FingerprintAndMembers &value) {
-  simple_display(out, value.fingerprint);
+  if (value.fingerprint)
+    simple_display(out, value.fingerprint.getValue());
+  else
+    out << "<no fingerprint>";
   out << ", ";
   simple_display(out, value.members);
 }
@@ -53,8 +56,8 @@ ParseMembersRequest::evaluate(Evaluator &evaluator,
   parser.SyntaxContext->disable();
   ASTContext &ctx = idc->getDecl()->getASTContext();
   auto declsAndHash = parser.parseDeclListDelayed(idc);
-  FingerprintAndMembers fingerprintAndMembers = {
-      declsAndHash.second.str().str(), declsAndHash.first};
+  FingerprintAndMembers fingerprintAndMembers = {declsAndHash.second,
+                                                 declsAndHash.first};
   return FingerprintAndMembers{
       fingerprintAndMembers.fingerprint,
       ctx.AllocateCopy(llvm::makeArrayRef(fingerprintAndMembers.members))};