Fix and test shape function evaluation for DiscontinuousLagrange (#553)

Author: koehlerson

src/interpolations.jl

@@ -149,7 +149,7 @@ function reference_coordinates(ip::DiscontinuousLagrange{dim,shape,order}) where
     return reference_coordinates(Lagrange{dim,shape,order}())
 end
 function value(ip::DiscontinuousLagrange{dim,shape,order}, i::Int, ξ::Vec{dim}) where {dim,shape,order}
-    return value(Lagrange{dim, ref_type, order}())
+    return value(Lagrange{dim, shape, order}(), i, ξ)
 end
 
 # Excepting the L0 element.

test/test_interpolations.jl

@@ -22,6 +22,11 @@ for interpolation in (
                       DiscontinuousLagrange{3, RefCube, 0}(),
                       DiscontinuousLagrange{2, RefTetrahedron, 0}(),
                       DiscontinuousLagrange{3, RefTetrahedron, 0}(),
+                      DiscontinuousLagrange{1, RefCube, 1}(),
+                      DiscontinuousLagrange{2, RefCube, 1}(),
+                      DiscontinuousLagrange{3, RefCube, 1}(),
+                      DiscontinuousLagrange{2, RefTetrahedron, 1}(),
+                      DiscontinuousLagrange{3, RefTetrahedron, 1}(),
                       #
                       BubbleEnrichedLagrange{2,RefTetrahedron,1}(),
                       #