[CodeCompletion] Don't track preferred types if code completion is disabled.

[sammccall]

Summary

Some of this work isn't quite trivial.

(As requested in D96058)

[sammccall]

Omit narrower, now-redundant check

[kadircet]

thanks, lgtm!

clang/include/clang/Parse/Parser.h

944–945

while here s/p/P/

clang/include/clang/Parse/Parser.h

class TentativeParsingAction {
     Parser &P;
     PreferredTypeBuilder PrevPreferredType;
     Token PrevTok;
     size_t PrevTentativelyDeclaredIdentifierCount;
     unsigned short PrevParenCount, PrevBracketCount, PrevBraceCount;
     bool isActive;
 
   public:
-    explicit TentativeParsingAction(Parser& p) : P(p) {
-      PrevPreferredType = P.PreferredType;
+    explicit TentativeParsingAction(Parser &p)
+        : P(p), PrevPreferredType(P.PreferredType) {
       PrevTok = P.Tok;
       PrevTentativelyDeclaredIdentifierCount =
           P.TentativelyDeclaredIdentifiers.size();
       PrevParenCount = P.ParenCount;
       PrevBracketCount = P.BracketCount;
       PrevBraceCount = P.BraceCount;
       P.PP.EnableBacktrackAtThisPos();
       isActive = true;

clang/include/clang/Sema/Sema.h

FileNullability &operator[](FileID file) {
 
     // Pull this entry into the cache.
     Cache.File = file;
     Cache.Nullability = Map[file];
     return Cache.Nullability;
   }
 };
 
-/// Keeps track of expected type during expression parsing. The type is tied to
-/// a particular token, all functions that update or consume the type take a
-/// start location of the token they are looking at as a parameter. This allows
-/// to avoid updating the type on hot paths in the parser.
+/// Tracks expected type during expression parsing, for use in code completion.
+/// The type is tied to a particular token, all functions that update or consume
+/// the type take a start location of the token they are looking at as a
+/// parameter. This avoids updating the type on hot paths in the parser.
 class PreferredTypeBuilder {
 public:
-  PreferredTypeBuilder() = default;
-  explicit PreferredTypeBuilder(QualType Type) : Type(Type) {}
+  PreferredTypeBuilder(bool Enabled) : Enabled(Enabled) {}
 
   void enterCondition(Sema &S, SourceLocation Tok);
   void enterReturn(Sema &S, SourceLocation Tok);
   void enterVariableInit(SourceLocation Tok, Decl *D);
   /// Handles e.g. BaseType{ .D = Tok...
   void enterDesignatedInitializer(SourceLocation Tok, QualType BaseType,
                                   const Designation &D);
   /// Computing a type for the function argument may require running
void enterUnary(Sema &S, SourceLocation Tok, tok::TokenKind OpKind,
                   SourceLocation OpLoc);
   void enterBinary(Sema &S, SourceLocation Tok, Expr *LHS, tok::TokenKind Op);
   void enterMemAccess(Sema &S, SourceLocation Tok, Expr *Base);
   void enterSubscript(Sema &S, SourceLocation Tok, Expr *LHS);
   /// Handles all type casts, including C-style cast, C++ casts, etc.
   void enterTypeCast(SourceLocation Tok, QualType CastType);
 
   QualType get(SourceLocation Tok) const {
-    if (Tok != ExpectedLoc)
+    if (!Enabled || Tok != ExpectedLoc)
       return QualType();
     if (!Type.isNull())
       return Type;
     if (ComputeType)
       return ComputeType();
     return QualType();
   }
 
 private:
+  bool Enabled;
   /// Start position of a token for which we store expected type.
   SourceLocation ExpectedLoc;
   /// Expected type for a token starting at ExpectedLoc.
   QualType Type;
   /// A function to compute expected type at ExpectedLoc. It is only considered
   /// if Type is null.
   llvm::function_ref<QualType()> ComputeType;
 };

clang/lib/Parse/ParseInit.cpp

 ///
 /// NOTE: [OBC] allows '[ objc-receiver objc-message-args ]' as an
 /// initializer (because it is an expression).  We need to consider this case
 /// when parsing array designators.
 ///
 /// \p CodeCompleteCB is called with Designation parsed so far.
 ExprResult Parser::ParseInitializerWithPotentialDesignator(
     DesignatorCompletionInfo DesignatorCompletion) {
-  if (!getPreprocessor().isCodeCompletionEnabled())
-    DesignatorCompletion.PreferredBaseType = QualType(); // skip field lookup
-
   // If this is the old-style GNU extension:
   //   designation ::= identifier ':'
   // Handle it as a field designator.  Otherwise, this must be the start of a
   // normal expression.
   if (Tok.is(tok::identifier)) {
     const IdentifierInfo *FieldName = Tok.getIdentifierInfo();
 
     SmallString<256> NewSyntax;

clang/lib/Parse/Parser.cpp

IdentifierInfo *Parser::getSEHExceptKeyword() {
   // __except is accepted as a (contextual) keyword
   if (!Ident__except && (getLangOpts().MicrosoftExt || getLangOpts().Borland))
     Ident__except = PP.getIdentifierInfo("__except");
 
   return Ident__except;
 }
 
 Parser::Parser(Preprocessor &pp, Sema &actions, bool skipFunctionBodies)
-  : PP(pp), Actions(actions), Diags(PP.getDiagnostics()),
-    GreaterThanIsOperator(true), ColonIsSacred(false),
-    InMessageExpression(false), TemplateParameterDepth(0),
-    ParsingInObjCContainer(false) {
+    : PP(pp), PreferredType(pp.isCodeCompletionEnabled()), Actions(actions),
+      Diags(PP.getDiagnostics()), GreaterThanIsOperator(true),
+      ColonIsSacred(false), InMessageExpression(false),
+      TemplateParameterDepth(0), ParsingInObjCContainer(false) {
   SkipFunctionBodies = pp.isCodeCompletionEnabled() || skipFunctionBodies;
   Tok.startToken();
   Tok.setKind(tok::eof);
   Actions.CurScope = nullptr;
   NumCachedScopes = 0;
   CurParsedObjCImpl = nullptr;
 
   // Add #pragma handlers. These are removed and destroyed in the

clang/lib/Sema/SemaCodeComplete.cpp

public:
   bool IsObjCMessageReceiverOrLambdaCapture(const NamedDecl *ND) const;
   bool IsObjCCollection(const NamedDecl *ND) const;
   bool IsImpossibleToSatisfy(const NamedDecl *ND) const;
   //@}
 };
 } // namespace
 
 void PreferredTypeBuilder::enterReturn(Sema &S, SourceLocation Tok) {
+  if (!Enabled)
+    return;
   if (isa<BlockDecl>(S.CurContext)) {
     if (sema::BlockScopeInfo *BSI = S.getCurBlock()) {
       ComputeType = nullptr;
       Type = BSI->ReturnType;
       ExpectedLoc = Tok;
     }
   } else if (const auto *Function = dyn_cast<FunctionDecl>(S.CurContext)) {
     ComputeType = nullptr;
     Type = Function->getReturnType();
     ExpectedLoc = Tok;
   } else if (const auto *Method = dyn_cast<ObjCMethodDecl>(S.CurContext)) {
     ComputeType = nullptr;
     Type = Method->getReturnType();
     ExpectedLoc = Tok;
   }
 }
 
 void PreferredTypeBuilder::enterVariableInit(SourceLocation Tok, Decl *D) {
+  if (!Enabled)
+    return;
   auto *VD = llvm::dyn_cast_or_null<ValueDecl>(D);
   ComputeType = nullptr;
   Type = VD ? VD->getType() : QualType();
   ExpectedLoc = Tok;
 }
 
 static QualType getDesignatedType(QualType BaseType, const Designation &Desig);
 
 void PreferredTypeBuilder::enterDesignatedInitializer(SourceLocation Tok,
                                                       QualType BaseType,
                                                       const Designation &D) {
+  if (!Enabled)
+    return;
   ComputeType = nullptr;
   Type = getDesignatedType(BaseType, D);
   ExpectedLoc = Tok;
 }
 
 void PreferredTypeBuilder::enterFunctionArgument(
     SourceLocation Tok, llvm::function_ref<QualType()> ComputeType) {
+  if (!Enabled)
+    return;
   this->ComputeType = ComputeType;
   Type = QualType();
   ExpectedLoc = Tok;
 }
 
 void PreferredTypeBuilder::enterParenExpr(SourceLocation Tok,
                                           SourceLocation LParLoc) {
+  if (!Enabled)
+    return;
   // expected type for parenthesized expression does not change.
   if (ExpectedLoc == LParLoc)
     ExpectedLoc = Tok;
 }
 
 static QualType getPreferredTypeOfBinaryRHS(Sema &S, Expr *LHS,
                                             tok::TokenKind Op) {
   if (!LHS)
static QualType getPreferredTypeOfUnaryArg(Sema &S, QualType ContextType,
   default:
     assert(false && "unhandled unary op");
     return QualType();
   }
 }
 
 void PreferredTypeBuilder::enterBinary(Sema &S, SourceLocation Tok, Expr *LHS,
                                        tok::TokenKind Op) {
+  if (!Enabled)
+    return;
   ComputeType = nullptr;
   Type = getPreferredTypeOfBinaryRHS(S, LHS, Op);
   ExpectedLoc = Tok;
 }
 
 void PreferredTypeBuilder::enterMemAccess(Sema &S, SourceLocation Tok,
                                           Expr *Base) {
-  if (!Base)
+  if (!Enabled || !Base)
     return;
   // Do we have expected type for Base?
   if (ExpectedLoc != Base->getBeginLoc())
     return;
   // Keep the expected type, only update the location.
   ExpectedLoc = Tok;
   return;
 }
 
 void PreferredTypeBuilder::enterUnary(Sema &S, SourceLocation Tok,
                                       tok::TokenKind OpKind,
                                       SourceLocation OpLoc) {
+  if (!Enabled)
+    return;
   ComputeType = nullptr;
   Type = getPreferredTypeOfUnaryArg(S, this->get(OpLoc), OpKind);
   ExpectedLoc = Tok;
 }
 
 void PreferredTypeBuilder::enterSubscript(Sema &S, SourceLocation Tok,
                                           Expr *LHS) {
+  if (!Enabled)
+    return;
   ComputeType = nullptr;
   Type = S.getASTContext().IntTy;
   ExpectedLoc = Tok;
 }
 
 void PreferredTypeBuilder::enterTypeCast(SourceLocation Tok,
                                          QualType CastType) {
+  if (!Enabled)
+    return;
   ComputeType = nullptr;
   Type = !CastType.isNull() ? CastType.getCanonicalType() : QualType();
   ExpectedLoc = Tok;
 }
 
 void PreferredTypeBuilder::enterCondition(Sema &S, SourceLocation Tok) {
+  if (!Enabled)
+    return;
   ComputeType = nullptr;
   Type = S.getASTContext().BoolTy;
   ExpectedLoc = Tok;
 }
 
 class ResultBuilder::ShadowMapEntry::iterator {
   llvm::PointerUnion<const NamedDecl *, const DeclIndexPair *> DeclOrIterator;
   unsigned SingleDeclIndex;