[MLIR][Presburger] Make constructors from PresburgerSpace explicit

[Groverkss]

Summary

This patch makes constructors of IntegerRelation, IntegerPolyhedron,
PresburgerRelation, PresburgerSet from PresburgerSpace explicit. This
prevents bugs like:

void fun(IntegerRelation a, IntegerRelation b) {
  IntegerPolyhedron c = a.intersect(b);
}

Here, a.intersect(b) will return IntegerRelation, which will be implicitly
converted to PresburgerSpace and will use the PresburgerSpace constructor
for IntegerPolyhedron. Leading to loss of any constraints in the intersection
of a and b. After this patch, this will give a compile error.

[arjunp]

LGTM

mlir/include/mlir/Analysis/Presburger/IntegerRelation.h

IntegerRelation(unsigned numReservedInequalities,
       : PresburgerSpace(space),
         equalities(0, getNumIds() + 1, numReservedEqualities, numReservedCols),
         inequalities(0, getNumIds() + 1, numReservedInequalities,
                      numReservedCols) {
     assert(numReservedCols >= getNumIds() + 1);
   }
 
   /// Constructs a relation with the specified number of dimensions and symbols.
-  IntegerRelation(const PresburgerSpace &space)
+  explicit IntegerRelation(const PresburgerSpace &space)
       : IntegerRelation(/*numReservedInequalities=*/0,
                         /*numReservedEqualities=*/0,
                         /*numReservedCols=*/space.getNumIds() + 1, space) {}
 
   /// Return a system with no constraints, i.e., one which is satisfied by all
   /// points.
   static IntegerRelation getUniverse(const PresburgerSpace &space) {
     return IntegerRelation(space);
IntegerPolyhedron(unsigned numReservedInequalities,
       : IntegerRelation(numReservedInequalities, numReservedEqualities,
                         numReservedCols, space) {
     assert(space.getNumDomainIds() == 0 &&
            "Number of domain id's should be zero in Set kind space.");
   }
 
   /// Constructs a relation with the specified number of dimensions and
   /// symbols.
-  IntegerPolyhedron(const PresburgerSpace &space)
+  explicit IntegerPolyhedron(const PresburgerSpace &space)
       : IntegerPolyhedron(/*numReservedInequalities=*/0,
                           /*numReservedEqualities=*/0,
                           /*numReservedCols=*/space.getNumIds() + 1, space) {}
 
   /// Return a system with no constraints, i.e., one which is satisfied by all
   /// points.
   static IntegerPolyhedron getUniverse(const PresburgerSpace &space) {
     return IntegerPolyhedron(space);

mlir/include/mlir/Analysis/Presburger/PresburgerRelation.h

public:
 
   /// Print the set's internal state.
   void print(raw_ostream &os) const;
   void dump() const;
 
 protected:
   /// Construct an empty PresburgerRelation with the specified number of
   /// dimension and symbols.
-  PresburgerRelation(const PresburgerSpace &space) : PresburgerSpace(space) {
+  explicit PresburgerRelation(const PresburgerSpace &space)
+      : PresburgerSpace(space) {
     assert(space.getNumLocalIds() == 0 &&
            "PresburgerRelation cannot have local ids.");
   }
 
   /// The list of disjuncts that this set is the union of.
   SmallVector<IntegerRelation, 2> disjuncts;
 
   friend class SetCoalescer;
public:
   PresburgerSet intersect(const PresburgerRelation &set) const;
   PresburgerSet complement() const;
   PresburgerSet subtract(const PresburgerRelation &set) const;
   PresburgerSet coalesce() const;
 
 protected:
   /// Construct an empty PresburgerRelation with the specified number of
   /// dimension and symbols.
-  PresburgerSet(const PresburgerSpace &space) : PresburgerRelation(space) {
+  explicit PresburgerSet(const PresburgerSpace &space)
+      : PresburgerRelation(space) {
     assert(space.getNumDomainIds() == 0 && "Set type cannot have domain ids.");
     assert(space.getNumLocalIds() == 0 &&
            "PresburgerRelation cannot have local ids.");
   }
 };
 
 } // namespace presburger
 } // namespace mlir
 
 #endif // MLIR_ANALYSIS_PRESBURGER_PRESBURGERRELATION_H