SIGSEGV in a recursion loop in a custom show() method

[fjarri]

The code:

import Base: show

immutable T
    x
end

show(io::IO, t::T) = print(io, "$t.x")

println(T(1))

Results in:

fish: 'julia t.jl' terminated by signal SIGSEGV (Address boundary error)

I discovered it when I forgot to put parentheses around t.x which, I imagine, is not an uncommon mistake. I understand, of course, that this code is bound to fail because it calls for show(::T) from show(::T), and the recursion never ends, so it is not a critical bug. Nevertheless, I would expect it to fail more gracefully, like it does if you remove .x from the print call, which just gives you

ERROR: LoadError: StackOverflowError:
<... long stack trace ...>

as expected. In a longer program it would be much easier to find the mistake from a stack trace like this than just from a SIGSEGV.

versioninfo() output:

Julia Version 0.5.1
Commit 6445c82 (2017-03-05 13:25 UTC)
Platform Info:
OS: macOS (x86_64-apple-darwin13.4.0)
CPU: Intel(R) Core(TM) i7-4771 CPU @ 3.50GHz
WORD_SIZE: 64
BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
LAPACK: libopenblas64_
LIBM: libopenlibm
LLVM: libLLVM-3.7.1 (ORCJIT, haswell)

[yuyichao]

Dup of #17280