Fix operator!= for Dialects.

[fedelebron]

Summary

Currently the global operator!=(bool, bool) is selected due to the implicit bool
conversion operator. Since this is never the desired semantics, we give it a
standard operator!= and make the bool conversion explicit.

Depends On D86809

[rriddle]

mlir/include/mlir/TableGen/Dialect.h

69

nit: I'd just drop this newline.

mlir/include/mlir/TableGen/Dialect.h

public:
   bool hasRegionArgAttrVerify() const;
 
   /// Returns if this dialect has a region result attribute verifier.
   bool hasRegionResultAttrVerify() const;
 
   // Returns whether two dialects are equal by checking the equality of the
   // underlying record.
   bool operator==(const Dialect &other) const;
 
+  bool operator!=(const Dialect &other) const { return !(*this == other); }
+
   // Compares two dialects by comparing the names of the dialects.
   bool operator<(const Dialect &other) const;
 
   // Returns whether the dialect is defined.
-  operator bool() const { return def != nullptr; }
+  explicit operator bool() const { return def != nullptr; }
 
 private:
   const llvm::Record *def;
   std::vector<StringRef> dependentDialects;
 };
 } // end namespace tblgen
 } // end namespace mlir
 
 #endif // MLIR_TABLEGEN_DIALECT_H_