fix expand for expressions with array indexing

Author: shashi

src/polyform.jl

@@ -160,6 +160,10 @@ function PolyForm(x,
         recurse=false,
         metadata=metadata(x))
 
+    if !(symtype(x) <: Number)
+        return x
+    end
+
     # Polyize and return a PolyForm
     p = polyize(x, pvar2sym, sym2term, vtype, pow, Fs, recurse)
     PolyForm{symtype(x)}(p, pvar2sym, sym2term, metadata)

test/polyform.jl

@@ -32,6 +32,10 @@ end
    #@test expand(Term{Number}(zero, 0)) == 0
    #@test expand(identity(a * b) - b * a) == 0
     @test expand(a * b - b * a) == 0
+
+    @syms A::Vector{Real}
+    # test that the following works
+    expand(Term{Real}(getindex, [A, 3]) - 3)
 end
 
 @testset "simplify_fractions with quick-cancel" begin