StackOverflowError in jl_has_concrete_subtype

[rdeits]

I can reliably generate a stack overflow in jl_has_concrete_subtype with the following code:

julia> struct Bar
           x::NTuple{N, Bar} where N
       end

julia> b = Bar(());
Internal error: encountered unexpected error in runtime:
StackOverflowError()
jl_has_concrete_subtype at /buildworker/worker/package_linux64/build/src/gf.c:2573
jl_has_concrete_subtype at /buildworker/worker/package_linux64/build/src/gf.c:2590
jl_has_concrete_subtype at /buildworker/worker/package_linux64/build/src/gf.c:2590
jl_has_concrete_subtype at /buildworker/worker/package_linux64/build/src/gf.c:2590
.... (truncated)

FWIW I don't see the error in Julia v0.6, but I get it in v0.7-1.1.

julia> versioninfo()
Julia Version 1.1.0
Commit 80516ca202 (2019-01-21 21:24 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, skylake)