type inference in row/col start/stop (#377)

* minor improvements in type inference in row/col start/stop

* Remove function barrier

* allow infinite row/col start/stop

Author: jishnub

src/Operators/general/algebra.jl

@@ -397,7 +397,7 @@ for OP in (:rowstart, :rowstop)
             return $defOP(P, k)
         end
         for j = eachindex(P.ops)
-            k = $OP(P.ops[j], k)
+            k = $OP(P.ops[j], k)::Union{Int, InfiniteCardinal{0}}
         end
         k
     end
@@ -410,7 +410,7 @@ for OP in (:colstart, :colstop)
             return $defOP(P, k)
         end
         for j = reverse(eachindex(P.ops))
-            k = $OP(P.ops[j], k)
+            k = $OP(P.ops[j], k)::Union{Int, InfiniteCardinal{0}}
         end
         k
     end

src/PDE/KroneckerOperator.jl

@@ -96,7 +96,7 @@ function rowstop(A::KroneckerOperator,k::Integer)
     K=block(rangespace(A),k)
     ds = domainspace(A)
     K2 = Int(K)+blockbandwidth(A,2)
-    K2 ≥ blocksize(ds) && return size(A,2)
+    K2 ≥ blocksize(ds)[1] && return size(A,2)
     st=blockstop(ds,K2)
     # zero indicates above dimension
     st==0 ? size(A,2) : min(size(A,2),st)