STYLE: Avoid repeating parent aliases in operator classes

Avoid repeating parent aliases in `Common` operator classes whenever
possible.

Use the preferred `using typename Superclass::{TypeAlias}` aliasing
form for the relevant type.

Make the `CoefficientVector` type be public in `itk::NeighborhoodOperator`
so that child classes can have access to it.

Modules/Core/Common/include/itkAnnulusOperator.h

@@ -78,8 +78,8 @@ class ITK_TEMPLATE_EXPORT AnnulusOperator : public NeighborhoodOperator<TPixel,
 
   /** Additional type aliases. */
   using PixelType = TPixel;
-  using SizeType = typename Superclass::SizeType;
-  using OffsetType = typename Superclass::OffsetType;
+  using typename Superclass::SizeType;
+  using typename Superclass::OffsetType;
   using SpacingType = Vector<double, TDimension>;
 
   /** Run-time type information (and related methods). */
@@ -222,9 +222,8 @@ class ITK_TEMPLATE_EXPORT AnnulusOperator : public NeighborhoodOperator<TPixel,
   }
 
 protected:
-  /** Typedef support for coefficient vector type.  Necessary to
-   *  work around compiler bug on VC++. */
-  using CoefficientVector = typename Superclass::CoefficientVector;
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
 
   /** Calculates operator coefficients. */
   CoefficientVector

Modules/Core/Common/include/itkBackwardDifferenceOperator.h

@@ -55,11 +55,12 @@ class ITK_TEMPLATE_EXPORT BackwardDifferenceOperator : public NeighborhoodOperat
   /** Run-time type information (and related methods). */
   itkTypeMacro(BackwardDifferenceOperator, NeighborhoodOperator);
 
-  using PixelType = typename Superclass::PixelType;
+  /** Type alias support for pixel type. */
+  using PixelType = TPixel;
 
 protected:
-  /** Necessary to work around a compiler bug in VC++. */
-  using CoefficientVector = typename Superclass::CoefficientVector;
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
 
   /** Calculates operator coefficients. */
   CoefficientVector

Modules/Core/Common/include/itkDerivativeOperator.h

@@ -76,8 +76,8 @@ class ITK_TEMPLATE_EXPORT DerivativeOperator : public NeighborhoodOperator<TPixe
   /** Run-time type information (and related methods). */
   itkTypeMacro(DerivativeOperator, NeighborhoodOperator);
 
-  using PixelType = TPixel;
-  using PixelRealType = typename Superclass::PixelRealType;
+  /** Type alias support for pixel real type.*/
+  using typename Superclass::PixelRealType;
 
   /** Sets the order of the derivative. */
   void
@@ -102,9 +102,8 @@ class ITK_TEMPLATE_EXPORT DerivativeOperator : public NeighborhoodOperator<TPixe
   }
 
 protected:
-  /** Typedef support for coefficient vector type.  Necessary to
-   * work around compiler bug on VC++. */
-  using CoefficientVector = typename Superclass::CoefficientVector;
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
 
   /** Calculates operator coefficients. */
   CoefficientVector

Modules/Core/Common/include/itkForwardDifferenceOperator.h

@@ -54,11 +54,12 @@ class ITK_TEMPLATE_EXPORT ForwardDifferenceOperator : public NeighborhoodOperato
   /** Run-time type information (and related methods). */
   itkTypeMacro(ForwardDifferenceOperator, NeighborhoodOperator);
 
-  using PixelType = typename Superclass::PixelType;
+  /** Type alias support for pixel type. */
+  using PixelType = TPixel;
 
 protected:
-  /** Necessary to work around VC++ compiler bug. */
-  using CoefficientVector = typename Superclass::CoefficientVector;
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
 
   /** Calculates operator coefficients. */
   CoefficientVector

Modules/Core/Common/include/itkGaussianDerivativeOperator.h

@@ -210,7 +210,8 @@ class ITK_TEMPLATE_EXPORT GaussianDerivativeOperator : public NeighborhoodOperat
   PrintSelf(std::ostream & os, Indent i) const override;
 
 protected:
-  using CoefficientVector = typename Superclass::CoefficientVector;
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
 
   /** Returns the value of the modified Bessel function I0(x) at a point x >= 0.
    */

Modules/Core/Common/include/itkGaussianOperator.h

@@ -141,9 +141,6 @@ class ITK_TEMPLATE_EXPORT GaussianOperator : public NeighborhoodOperator<TPixel,
     Superclass::PrintSelf(os, i.GetNextIndent());
   }
 
-protected:
-  using CoefficientVector = typename Superclass::CoefficientVector;
-
 public:
   /** Returns the value of the modified Bessel function I0(x) at a point x >= 0.
    */
@@ -161,6 +158,9 @@ class ITK_TEMPLATE_EXPORT GaussianOperator : public NeighborhoodOperator<TPixel,
   ModifiedBesselI(int, double);
 
 protected:
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
+
   /** Calculates operator coefficients. */
   CoefficientVector
   GenerateCoefficients() override;

Modules/Core/Common/include/itkImageKernelOperator.h

@@ -54,8 +54,6 @@ class ITK_TEMPLATE_EXPORT ImageKernelOperator : public NeighborhoodOperator<TPix
   using Superclass = NeighborhoodOperator<TPixel, VDimension, TAllocator>;
 
   using ImageType = Image<TPixel, VDimension>;
-  using SizeType = typename Superclass::SizeType;
-  using CoefficientVector = typename Superclass::CoefficientVector;
 
   /** Run-time type information (and related methods). */
   itkTypeMacro(ImageKernelOperator, NeighborhoodOperator);
@@ -79,6 +77,9 @@ class ITK_TEMPLATE_EXPORT ImageKernelOperator : public NeighborhoodOperator<TPix
   }
 
 protected:
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
+
   /** Calculates operator coefficients. */
   CoefficientVector
   GenerateCoefficients() override;

Modules/Core/Common/include/itkLaplacianOperator.h

@@ -74,7 +74,6 @@ class ITK_TEMPLATE_EXPORT LaplacianOperator : public NeighborhoodOperator<TPixel
   /** Run-time type information (and related methods). */
   itkTypeMacro(LaplacianOperator, NeighborhoodOperator);
 
-  using PixelType = TPixel;
   using SizeType = typename Superclass::SizeType;
 
   LaplacianOperator()
@@ -105,9 +104,8 @@ class ITK_TEMPLATE_EXPORT LaplacianOperator : public NeighborhoodOperator<TPixel
   itkGetConstMacro(DerivativeScalings, const double *);
 
 protected:
-  /** Alias support for coefficient vector type. Necessary to
-   * work around compiler bug on VC++. */
-  using CoefficientVector = typename Superclass::CoefficientVector;
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
 
   /** Calculates operator coefficients. */
   CoefficientVector

Modules/Core/Common/include/itkNeighborhoodOperator.h

@@ -87,6 +87,8 @@ class ITK_TEMPLATE_EXPORT NeighborhoodOperator : public Neighborhood<TPixel, VDi
   /** Slice iterator type alias support */
   using SliceIteratorType = SliceIterator<TPixel, Self>;
 
+  using PixelRealType = typename NumericTraits<TPixel>::RealType;
+
   /** Sets the dimensional direction of a directional operator. */
   void
   SetDirection(const unsigned long & direction)
@@ -135,16 +137,14 @@ class ITK_TEMPLATE_EXPORT NeighborhoodOperator : public Neighborhood<TPixel, VDi
     Superclass::PrintSelf(os, i.GetNextIndent());
   }
 
-  using PixelRealType = typename NumericTraits<TPixel>::RealType;
-
   /** Multiplies all of the coefficients of the kernel by a single scalar value.
    */
   void ScaleCoefficients(PixelRealType);
 
 protected:
-  /** Typedef support  for coefficient vector type.  Necessary
+  /** Type alias support for coefficient vector type. Necessary
    * to fix bug in the microsoft VC++ compiler. */
-  using CoefficientVector = std::vector<PixelRealType>;
+  using CoefficientVector = typename std::vector<PixelRealType>;
 
   /** A subclass-specific algorithm that computes the coefficients
    * of the operator. */

Modules/Core/Common/include/itkSobelOperator.h

@@ -132,10 +132,8 @@ class ITK_TEMPLATE_EXPORT SobelOperator : public NeighborhoodOperator<TPixel, VD
   }
 
 protected:
-  /** Alias support for coefficient vector type. Necessary to
-   * work around compiler bug on VC++. */
-  using CoefficientVector = typename Superclass::CoefficientVector;
-  using PixelType = typename Superclass::PixelType;
+  /** Type alias support for coefficient vector type.*/
+  using typename Superclass::CoefficientVector;
 
   /** Calculates operator coefficients. */
   CoefficientVector