test type inference for substitution

Author: rdeits

test/subs.jl

@@ -1,3 +1,5 @@
+import Base.Test: @inferred
+
 facts("Substitution") do
   @polyvar x[1:3]
 
@@ -23,4 +25,7 @@ facts("Substitution") do
   P = [1 2 3; 2 4 5; 3 5 6]
   p = MatPolynomial(P, x)
   @fact p(ones(3), x) --> 31
+
+  p = x[1] + x[2] + 2*x[1]^2 + 3*x[1]*x[2]^2
+  @inferred p([1.0, 2.0], [x[1], x[2]])
 end