Weird REPL crash

[chethega]

I get a weird REPL crash when pasting the following into a fresh session:

julia> struct Test{A,B} end
julia> Base.show(io::IO, ::Type{Test{A,B}}) where {A,B} = print(io, "fooTest{", A, ",", B, "}")
julia> Test{A,Int} where A

which crashes julia, with output:

Error showing value of type UnionAll:
ERROR: UndefVarError: A not defined
Stacktrace:
 [1] show(::IOContext{REPL.Terminals.TTYTerminal}, ::Type{SYSTEM: show(lasterr) caused an error
UndefVarError(:A)

Stacktrace:
 [1] show(::IOContext{REPL.Terminals.TTYTerminal}, ::Type{ERROR: UndefVarError: A not defined
Stacktrace:
 [1] show(::IOContext{REPL.Terminals.TTYTerminal}, ::Type{fatal: error thrown and no exception handler available.
UndefVarError(var=:A)
unknown function (ip: 0x7fc55f0bf438)
unknown function (ip: 0x7fc55f0903e3)
jl_throw at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_undefined_var_error at /usr/bin/../lib/libjulia.so.1 (unknown line)
show at ./REPL[2]:1
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
show_datatype at ./show.jl:526
show at ./show.jl:436
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
print at ./strings/io.jl:31
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
print at ./strings/io.jl:42
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
show_tuple_as_call at ./show.jl:1490
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
show_spec_linfo at ./stacktraces.jl:261
#show#9 at ./stacktraces.jl:272
unknown function (ip: 0x7fc541b1b753)
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
#show at ./none:0 [inlined]
#show_trace_entry#630 at ./errorshow.jl:471
unknown function (ip: 0x7fc541b1b08c)
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
#show_trace_entry at ./none:0
unknown function (ip: 0x7fc541b1adc8)
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
show_backtrace at ./errorshow.jl:574
#showerror#612 at ./errorshow.jl:79
unknown function (ip: 0x7fc541b182d7)
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
showerror at ./errorshow.jl:74 [inlined]
display_error at ./client.jl:99
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
display_error at ./client.jl:102
jl_fptr_trampoline at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_f__apply at /usr/bin/../lib/libjulia.so.1 (unknown line)
jl_f__apply_latest at /usr/bin/../lib/libjulia.so.1 (unknown line)
unknown function (ip: 0x7fc556752477)
jl_apply_generic at /usr/bin/../lib/libjulia.so.1 (unknown line)
true_main at /home/bruhns/math/persistence/julia/julia7/julia/ui/repl.c:89
 at julia (unknown line)
__libc_start_main at /usr/bin/../lib/libc.so.6 (unknown line)
 at julia (unknown line)

The above trace is on 1.0.1. The reproduction is relatively finnicky; the crash goes away when pasting with a newline in the last command, and appears when the last command is pasted without newline, and I hit enter manually. Regardless of the crash, I don't think dispatching to the new method is correct? Cf also discourse..

I tested on:

julia> versioninfo()
Julia Version 1.0.1
Commit 0d713926f8 (2018-09-29 19:05 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i5-5###U CPU @ 2.00GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.0 (ORCJIT, broadwell)

julia> versioninfo()
Julia Version 1.1.0-DEV.647
Commit c62ff7e8a9 (2018-11-09 15:47 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i5-5###U CPU @ 2.00GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, broadwell)

[JeffBezanson]

Duplicate of #29428, #22363, #28983.