Segfault in Julia 1.2.0-rc2.0 on assigning to a static parameter in a while loop

[coroa]

The following MWE leads to a segmentation fault in 1.2-rc2

abstract type A end

abstract type B{F} <: A end

function deunion(::Type{T}) where T <: A
    while T isa UnionAll
        T = T.body
    end
    T
end

deunion(B)

with the stack trace:

➜  ~ julia mwe.jl    

signal (11): Segmentation fault
in expression starting at /home/coroa/mwe.jl:12
_ZL19emit_array_nd_indexR12jl_codectx_tRK10jl_cgval_tP11_jl_value_tlPS2_mS5_.isra.1424 at /home/coroa/.julia/julia-1.2/bin/../lib/libjulia.so.1 (unknown line)
emit_ssaval_assign at /home/coroa/src/juliav1.2/src/codegen.cpp:3737
emit_function at /home/coroa/src/juliav1.2/src/codegen.cpp:3929
jl_compile_linfo at /home/coroa/src/juliav1.2/src/codegen.cpp:1199
jl_compile_method_internal at /home/coroa/src/juliav1.2/src/gf.c:1775
jl_apply_generic at /home/coroa/src/juliav1.2/src/gf.c:2196
do_call at /home/coroa/src/juliav1.2/src/interpreter.c:323
eval_value at /home/coroa/src/juliav1.2/src/interpreter.c:411
eval_stmt_value at /home/coroa/src/juliav1.2/src/interpreter.c:362 [inlined]
eval_body at /home/coroa/src/juliav1.2/src/interpreter.c:758
jl_interpret_toplevel_thunk_callback at /home/coroa/src/juliav1.2/src/interpreter.c:884
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7f9f8b862d8f)
unknown function (ip: 0xffffffffffffffff)
jl_interpret_toplevel_thunk at /home/coroa/src/juliav1.2/src/interpreter.c:893
jl_toplevel_eval_flex at /home/coroa/src/juliav1.2/src/toplevel.c:815
jl_parse_eval_all at /home/coroa/src/juliav1.2/src/ast.c:873
jl_load at /home/coroa/src/juliav1.2/src/toplevel.c:879
include at ./boot.jl:328 [inlined]
include_relative at ./loading.jl:1094
include at ./Base.jl:31
jl_apply_generic at /home/coroa/src/juliav1.2/src/gf.c:2191
exec_options at ./client.jl:295
_start at ./client.jl:464
jl_apply_generic at /home/coroa/src/juliav1.2/src/gf.c:2191
unknown function (ip: 0x5565d46cb6fd)
unknown function (ip: 0x5565d46cb323)
__libc_start_main at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
unknown function (ip: 0x5565d46cb3c9)
Allocations: 199949 (Pool: 199760; Big: 189); GC: 0
[1]    20039 segmentation fault  julia mwe.jl 

Version

julia> versioninfo()
Julia Version 1.2.0-rc2.0
Commit 9248bf7687 (2019-07-08 19:42 UTC)
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: Intel(R) Core(TM) i5-4300U CPU @ 1.90GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, haswell)

Behaviour on 1.1

Julia 1.1 throws a TypeError instead:

➜  ~ julia-1.1
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.1.1 (2019-05-16)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> include("mwe.jl")
ERROR: LoadError: UndefVarError: T not defined
Stacktrace:
 [1] deunion(::Type{B}) at /home/coroa/mwe.jl:6
 [2] top-level scope at none:0
 [3] include at ./boot.jl:326 [inlined]
 [4] include_relative(::Module, ::String) at ./loading.jl:1038
 [5] include(::Module, ::String) at ./sysimg.jl:29
 [6] include(::String) at ./client.jl:403
 [7] top-level scope at none:0
in expression starting at /home/coroa/mwe.jl:12