Odd error for self referencing struct on Julia v0.7

[randy3k]

julia> versioninfo()
Julia Version 0.7.0-DEV.844
Commit e90f29db30 (2017-07-07 06:10 UTC)
Platform Info:
  OS: macOS (x86_64-apple-darwin13.4.0)
  CPU: Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, skylake)

struct Foo
    x::Ptr{Foo}
end

f(x::Int) = f(Foo, x) 
f(::Type{Foo}, x) = bar("x")
f(x) = x
bar(x) = f(x)

bar(1)

is_derived_type at ./inference.jl:933
jlcall_is_derived_type_1588 at /opt/local/julia-dev/lib/julia/sys.dylib (unknown line)
is_derived_type at ./inference.jl:944
jlcall_is_derived_type_1588 at /opt/local/julia-dev/lib/julia/sys.dylib (unknown line)
is_derived_type at ./inference.jl:933
jlcall_is_derived_type_1588 at /opt/local/julia-dev/lib/julia/sys.dylib (unknown line)
is_derived_type at ./inference.jl:944
jlcall_is_derived_type_1588 at /opt/local/julia-dev/lib/julia/sys.dylib (unknown line)
is_derived_type at ./inference.jl:933
jlcall_is_derived_type_1588 at /opt/local/julia-dev/lib/julia/sys.dylib (unknown line)
is_derived_type at ./inference.jl:944
jlcall_is_derived_type_1588 at /opt/local/julia-dev/lib/julia/sys.dylib (unknown line)

• it yields the expected result on Julia v0.6.
• On v0.7, it also yields the expected result if the last line is f(1)
• more strangely, it yields the correct result if f(1) is executed before bar(1).

[randy3k]

may be related to #21933