StackOverflowError for `isapprox(::Variable, ::Variable)`

[kbarros]

using DynamicPolynomials
@polyvar x

# Passes
@assert 1.2x ≈ 1.2x

# StackOverflowError
x ≈ x

The infinite recursion seems to be triggered by:

promote(x, x) == (x, x)