[analyzer] [NFC] Remove "removeInvalidation" from visitor API

[george.karpenkov]

Summary

removeInvalidation is a very problematic API, as it makes suppression order-dependent.
Moreover, it was used only once, and could be rewritten in a much cleaner way.

[NoQ]

Can confirm - that was a nightmare to debug.

include/clang/StaticAnalyzer/Core/BugReporter/BugReporter.h

public:
   /// this particular invalidation, where \p Tag represents the visitor
   /// responsible for invalidation, and \p Data represents the reason this
   /// visitor decided to invalidate the bug report.
   ///
   /// \sa removeInvalidation
   void markInvalid(const void *Tag, const void *Data) {
     Invalidations.insert(std::make_pair(Tag, Data));
   }
   
-  /// Reverses the effects of a previous invalidation.
-  ///
-  /// \sa markInvalid
-  void removeInvalidation(const void *Tag, const void *Data) {
-    Invalidations.erase(std::make_pair(Tag, Data));
-  }
-  
   /// Return the canonical declaration, be it a method or class, where
   /// this issue semantically occurred.
   const Decl *getDeclWithIssue() const;
   
   /// Specifically set the Decl where an issue occurred.  This isn't necessary
   /// for BugReports that cover a path as it will be automatically inferred.
   void setDeclWithIssue(const Decl *declWithIssue) {
     DeclWithIssue = declWithIssue;

lib/StaticAnalyzer/Core/BugReporterVisitors.cpp

class ReturnVisitor : public BugReporterVisitorImpl<ReturnVisitor> {
   const StackFrameContext *StackFrame;
   enum {
     Initial,
     MaybeUnsuppress,
     Satisfied
   } Mode = Initial;
 
   bool EnableNullFPSuppression;
+  bool ShouldInvalidate = true;
 
 public:
   ReturnVisitor(const StackFrameContext *Frame, bool Suppressed)
       : StackFrame(Frame), EnableNullFPSuppression(Suppressed) {}
 
   static void *getTag() {
     static int Tag = 0;
     return static_cast<void *>(&Tag);
for (unsigned I = 0, E = Call->getNumArgs(); I != E; ++I) {
         continue;
 
       // Is it possible for this argument to be non-null?
       if (!State->isNull(*ArgV).isConstrainedTrue())
         continue;
 
       if (bugreporter::trackNullOrUndefValue(N, ArgE, BR, /*IsArg=*/true,
                                              EnableNullFPSuppression))
-        BR.removeInvalidation(ReturnVisitor::getTag(), StackFrame);
+        ShouldInvalidate = false;
 
       // If we /can't/ track the null pointer, we should err on the side of
       // false negatives, and continue towards marking this report invalid.
       // (We will still look at the other arguments, though.)
     }
 
     return nullptr;
   }
case Satisfied:
       return nullptr;
     }
 
     llvm_unreachable("Invalid visit mode!");
   }
 
   void finalizeVisitor(BugReporterContext &BRC, const ExplodedNode *N,
                        BugReport &BR) override {
-    if (EnableNullFPSuppression)
+    if (EnableNullFPSuppression && ShouldInvalidate)
       BR.markInvalid(ReturnVisitor::getTag(), StackFrame);
   }
 };
 
 } // namespace
 
 void FindLastStoreBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
   static int tag = 0;