[ConstraintSystem] Remove disjunction number as we're not currently

using it.

It was added to use for selecting the order we visit disjunctions, but
this order turned out to not be great (and I don't think there are
simple variations on the creation order, like reverse order), that
will work well either.

Author: rudkx

lib/Sema/Constraint.cpp

@@ -823,7 +823,6 @@ Constraint *Constraint::createDisjunction(ConstraintSystem &cs,
   auto disjunction =  new (mem) Constraint(ConstraintKind::Disjunction,
                               cs.allocateCopy(constraints), locator, typeVars);
   disjunction->RememberChoice = (bool) rememberChoice;
-  cs.noteNewDisjunction(disjunction);
   return disjunction;
 }
 

lib/Sema/ConstraintSystem.h

@@ -912,10 +912,6 @@ class ConstraintSystem {
   /// \brief The total number of disjunctions created.
   unsigned CountDisjunctions = 0;
 
-  /// \brief Map from disjunction to the number indicating the order it
-  //         was created in.
-  llvm::DenseMap<Constraint *, unsigned> DisjunctionNumber;
-
 private:
 
   /// \brief Allocator used for all of the related constraint systems.
@@ -1895,11 +1891,6 @@ class ConstraintSystem {
                                        bool allowFixes,
                                        ConstraintLocatorBuilder locator);
 
-  void noteNewDisjunction(Constraint *constraint) {
-    assert(constraint->getKind() == ConstraintKind::Disjunction);
-    DisjunctionNumber[constraint] = CountDisjunctions++;
-  }
-
   /// \brief Add a disjunction constraint.
   void addDisjunctionConstraint(ArrayRef<Constraint *> constraints,
                                 ConstraintLocatorBuilder locator,