[scan-build] fix dead store warnings emitted on Clang Sema code base

[apelete]

Summary

This fixes dead store warnings of the type "dead assignment" reported
by Clang Static Analyzer on the following files:

• lib/Sema/SemaDeclCXX.cpp,
• lib/Sema/SemaExpr.cpp,
• lib/Sema/SemaTemplate.cpp.

Signed-off-by: Apelete Seketeli <[e-mail]>

[rtrieu]

lib/Sema/SemaExpr.cpp

9629

Add comment that these variables are only updated when processing MemberExpr's in the while loop.

9635–9637

Remove these lines.

9641

Add "IsDereference = NextIsDereference;" before this line.

[apelete]

[scan-build] fix dead store warnings emitted on clang code base

Changes since last revision:

• lib/Sema/SemaLookup.cpp: remove changes since they were already applied upstream,
• lib/Sema/SemaExpr.cpp: move 'IsDereference' and 'NextIsDereference' variables into the code block where they are used.

lib/Sema/SemaDeclCXX.cpp

if (TemplateParams->size() > 0) {
                                 /*ModulePrivateLoc=*/SourceLocation(),
                                 FriendLoc, TempParamLists.size() - 1,
                                 TempParamLists.data()).get();
     } else {
       // The "template<>" header is extraneous.
       Diag(TemplateParams->getTemplateLoc(), diag::err_template_tag_noparams)
         << TypeWithKeyword::getTagTypeKindName(Kind) << Name;
       isExplicitSpecialization = true;
+      (void) isExplicitSpecialization;
     }
   }
 
   if (Invalid) return nullptr;
 
   bool isAllExplicitSpecializations = true;
   for (unsigned I = TempParamLists.size(); I-- > 0; ) {
     if (TempParamLists[I]->size()) {

lib/Sema/SemaExpr.cpp

static void DiagnoseConstAssignment(Sema &S, const Expr *E,
 
   SourceRange ExprRange = E->getSourceRange();
 
   // Only emit one error on the first const found.  All other consts will emit
   // a note to the error.
   bool DiagnosticEmitted = false;
 
   // Track if the current expression is the result of a derefence, and if the
   // next checked expression is the result of a derefence.
   bool IsDereference = false;
   bool NextIsDereference = false;
 
   // Loop to process MemberExpr chains.
   while (true) {
     IsDereference = NextIsDereference;
     NextIsDereference = false;
+    (void) NextIsDereference;
 
     E = E->IgnoreParenImpCasts();
     if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
       NextIsDereference = ME->isArrow();
       const ValueDecl *VD = ME->getMemberDecl();
       if (const FieldDecl *Field = dyn_cast<FieldDecl>(VD)) {
         // Mutable fields can be modified even if the class is const.
         if (Field->isMutable()) {
           assert(DiagnosticEmitted && "Expected diagnostic not emitted.");
           break;
         }
 

lib/Sema/SemaLookup.cpp

if (TemplateDecl *TD = dyn_cast<TemplateDecl>(D))
     return getDefinitionToImport(TD->getTemplatedDecl());
   return nullptr;
 }
 
 void Sema::diagnoseMissingImport(SourceLocation Loc, NamedDecl *Decl,
                                  bool NeedDefinition, bool Recover) {
   assert(!isVisible(Decl) && "missing import for non-hidden decl?");
 
-  // Suggest importing a module providing the definition of this entity, if
-  // possible.
-  NamedDecl *Def = getDefinitionToImport(Decl);
-  if (!Def)
-    Def = Decl;
-
   // FIXME: Add a Fix-It that imports the corresponding module or includes
   // the header.
   Module *Owner = getOwningModule(Decl);
   assert(Owner && "definition of hidden declaration is not in a module");
 
   llvm::SmallVector<Module*, 8> OwningModules;
   OwningModules.push_back(Owner);
   auto Merged = Context.getModulesWithMergedDefinition(Decl);

lib/Sema/SemaTemplate.cpp

if (TemplateParams && TemplateParams->size() > 0) {
     }
   } else if (TemplateParams) {
     if (TUK == TUK_Friend)
       Diag(KWLoc, diag::err_template_spec_friend)
         << FixItHint::CreateRemoval(
                                 SourceRange(TemplateParams->getTemplateLoc(),
                                             TemplateParams->getRAngleLoc()))
         << SourceRange(LAngleLoc, RAngleLoc);
-    else
-      isExplicitSpecialization = true;
   } else {
     assert(TUK == TUK_Friend && "should have a 'template<>' for this decl");
   }
 
   // Check that the specialization uses the same tag kind as the
   // original template.
   TagTypeKind Kind = TypeWithKeyword::getTagTypeKindForTypeSpec(TagSpec);
   assert(Kind != TTK_Enum && "Invalid enum tag in class template spec!");