Scope of classic @rule matcher

[Audrius-St]

Same issue as reported in SymbolicUtils.jl: reversing the order of two differential operators

# test_simple_rewrite.jl

using Symbolics, Metatheory.Rewriters

begin
    @variables x, t, f(x, t)
    Dx = Differential(x)
    Dt = Differential(t)
    rule = @rule Dt(Dx(~g)) => Dx(Dt(~g))
    rewriter = Chain([rule])
    func = Symbolics.unwrap(Dt(Dx(f)))
    rewriter(func)
end

returns the correct reorder Differential(x)(Differential(t)(f(x, t)))

However, inserting the above code into a function

# test_simple_rewrite_main.jl

using Symbolics, Metatheory.Rewriters

function main()
    @variables x, t, f(x, t)
    Dx = Differential(x)
    Dt = Differential(t)
    rule = @rule Dt(Dx(~g)) => Dx(Dt(~g))
    rewriter = Chain([rule])
    func = Symbolics.unwrap(Dt(Dx(f)))
    rewriter(func)

end

begin
    main()
end

returns the incorrect Differential(t)(Differential(x)(f(x, t))). The differential operators Dt and Dx are not reordered.

As noted by bowenszhu, placing the construction of the differential operators outside of the function

# test_simple_rewrite_main.jl

using Symbolics, Metatheory.Rewriters

@variables x, t, f(x, t)
Dx = Differential(x)
Dt = Differential(t)

function main()
    rule = @rule Dt(Dx(~g)) => Dx(Dt(~g))
    rewriter = Chain([rule])
    func = Symbolics.unwrap(Dt(Dx(f)))
    rewriter(func)

end

begin
    main()

end

again returns the correct reorder Differential(x)(Differential(t)(f(x, t)))

Julia 1.8.0 Symbolics.jl 4.10.4 Metatheory.jl 1.3.4