[Clang][NFC] Simplify initialization of OverloadCandidate objects. (#100318)

Summary:
Initialize some fields of OverloadCandidate in its constructor. The goal
here is try to fix read of uninitialized variable (which I was not able
to reproduce)
#93430 (comment)

We should certainly try to improve the construction of
`OverloadCandidate` further as it can be quite britle.

Test Plan: 

Reviewers: 

Subscribers: 

Tasks: 

Tags: 


Differential Revision: https://phabricator.intern.facebook.com/D60250652

Author: cor3ntin

clang/include/clang/Sema/Overload.h

@@ -998,7 +998,9 @@ class Sema;
   private:
     friend class OverloadCandidateSet;
     OverloadCandidate()
-        : IsSurrogate(false), IsADLCandidate(CallExpr::NotADL), RewriteKind(CRK_None) {}
+        : IsSurrogate(false), IgnoreObjectArgument(false),
+          TookAddressOfOverload(false), IsADLCandidate(CallExpr::NotADL),
+          RewriteKind(CRK_None) {}
   };
 
   /// OverloadCandidateSet - A set of overload candidates, used in C++

clang/lib/Sema/SemaOverload.cpp

@@ -6857,10 +6857,7 @@ void Sema::AddOverloadCandidate(
   Candidate.Viable = true;
   Candidate.RewriteKind =
       CandidateSet.getRewriteInfo().getRewriteKind(Function, PO);
-  Candidate.IsSurrogate = false;
   Candidate.IsADLCandidate = IsADLCandidate;
-  Candidate.IgnoreObjectArgument = false;
-  Candidate.TookAddressOfOverload = false;
   Candidate.ExplicitCallArguments = Args.size();
 
   // Explicit functions are not actually candidates at all if we're not
@@ -7422,8 +7419,6 @@ Sema::AddMethodCandidate(CXXMethodDecl *Method, DeclAccessPair FoundDecl,
   Candidate.Function = Method;
   Candidate.RewriteKind =
       CandidateSet.getRewriteInfo().getRewriteKind(Method, PO);
-  Candidate.IsSurrogate = false;
-  Candidate.IgnoreObjectArgument = false;
   Candidate.TookAddressOfOverload =
       CandidateSet.getKind() == OverloadCandidateSet::CSK_AddressOfOverloadSet;
   Candidate.ExplicitCallArguments = Args.size();
@@ -7617,7 +7612,6 @@ void Sema::AddMethodTemplateCandidate(
     Candidate.IgnoreObjectArgument =
         cast<CXXMethodDecl>(Candidate.Function)->isStatic() ||
         ObjectType.isNull();
-    Candidate.TookAddressOfOverload = false;
     Candidate.ExplicitCallArguments = Args.size();
     if (Result == TemplateDeductionResult::NonDependentConversionFailure)
       Candidate.FailureKind = ovl_fail_bad_conversion;
@@ -7705,7 +7699,6 @@ void Sema::AddTemplateOverloadCandidate(
     Candidate.IgnoreObjectArgument =
         isa<CXXMethodDecl>(Candidate.Function) &&
         !isa<CXXConstructorDecl>(Candidate.Function);
-    Candidate.TookAddressOfOverload = false;
     Candidate.ExplicitCallArguments = Args.size();
     if (Result == TemplateDeductionResult::NonDependentConversionFailure)
       Candidate.FailureKind = ovl_fail_bad_conversion;
@@ -7886,9 +7879,6 @@ void Sema::AddConversionCandidate(
   OverloadCandidate &Candidate = CandidateSet.addCandidate(1);
   Candidate.FoundDecl = FoundDecl;
   Candidate.Function = Conversion;
-  Candidate.IsSurrogate = false;
-  Candidate.IgnoreObjectArgument = false;
-  Candidate.TookAddressOfOverload = false;
   Candidate.FinalConversion.setAsIdentityConversion();
   Candidate.FinalConversion.setFromType(ConvType);
   Candidate.FinalConversion.setAllToTypes(ToType);
@@ -8084,9 +8074,6 @@ void Sema::AddTemplateConversionCandidate(
     Candidate.Function = FunctionTemplate->getTemplatedDecl();
     Candidate.Viable = false;
     Candidate.FailureKind = ovl_fail_bad_deduction;
-    Candidate.IsSurrogate = false;
-    Candidate.IgnoreObjectArgument = false;
-    Candidate.TookAddressOfOverload = false;
     Candidate.ExplicitCallArguments = 1;
     Candidate.DeductionFailure = MakeDeductionFailureInfo(Context, Result,
                                                           Info);
@@ -8119,10 +8106,8 @@ void Sema::AddSurrogateCandidate(CXXConversionDecl *Conversion,
   Candidate.FoundDecl = FoundDecl;
   Candidate.Function = nullptr;
   Candidate.Surrogate = Conversion;
-  Candidate.Viable = true;
   Candidate.IsSurrogate = true;
-  Candidate.IgnoreObjectArgument = false;
-  Candidate.TookAddressOfOverload = false;
+  Candidate.Viable = true;
   Candidate.ExplicitCallArguments = Args.size();
 
   // Determine the implicit conversion sequence for the implicit
@@ -8328,9 +8313,6 @@ void Sema::AddBuiltinCandidate(QualType *ParamTys, ArrayRef<Expr *> Args,
   OverloadCandidate &Candidate = CandidateSet.addCandidate(Args.size());
   Candidate.FoundDecl = DeclAccessPair::make(nullptr, AS_none);
   Candidate.Function = nullptr;
-  Candidate.IsSurrogate = false;
-  Candidate.IgnoreObjectArgument = false;
-  Candidate.TookAddressOfOverload = false;
   std::copy(ParamTys, ParamTys + Args.size(), Candidate.BuiltinParamTypes);
 
   // Determine the implicit conversion sequences for each of the