Merge pull request #398 from JuliaSymbolics/s/fix-pow-expansion

fix avoidance of exponentiation in simplify_fractions

Author: shashi

src/polyform.jl

@@ -244,7 +244,7 @@ end
 
 function polyform_factors(d, pvar2sym, sym2term)
     make(xs) = map(xs) do x
-        if x isa Pow && x.base isa Integer && x.exp > 0
+        if x isa Pow && x.exp isa Integer && x.exp > 0
             # here we do want to recurse one level, that's why it's wrong to just
             # use Fs = Union{typeof(+), typeof(*)} here.
             Pow(PolyForm(x.base, pvar2sym, sym2term), x.exp)

test/polyform.jl

@@ -56,6 +56,10 @@ end
     @eqtest simplify_fractions(3x^2/x^3) == 3/x
     @eqtest simplify_fractions(3*(x^2)*(y^3)/(3*(x^3)*(y^2))) == y/x
     @eqtest simplify_fractions(3*(x^x)/x*y) == 3*(x^x)/x*y
+
+    ##404#issuecomment-939404030
+    a = 1 / (x - (2//1)) + ((-5//1) - x) / ((x - (2//1))^2)
+    @test isequal(simplify_fractions(a), -7/(x-2)^2)
 end
 
 @testset "isone iszero" begin