A function with "local variable T conflicts with a static parameter" warning invokes Illegal instruction error

[tkf]

I found that the following (incorrect) function leads to the Illegal instruction error. I can see that it prints warnings so maybe I should not be surprised when it ends up in Illegal instruction? I checked it with 1.0.0 and 1.1.0-DEV.334.

julia> function illegal_instruction(e::T) where {T}
           try
               return string(T)
           catch
               try
                   io = IOBuffer()
                   Base.show_datatype(io, T)
                   T = String(take!(io))
               catch
                   T = "_UNKNOWN_TYPE_"
               end
               return string(T)
           end
       end
WARNING: local variable T conflicts with a static parameter in illegal_instruction at REPL[1]:2.
WARNING: local variable T conflicts with a static parameter in illegal_instruction at REPL[1]:2.
illegal_instruction (generic function with 1 method)

julia> println(illegal_instruction(1))
Unreachable reached at 0x7fce8009d4ee

signal (4): Illegal instruction
in expression starting at no file:0
illegal_instruction at ./REPL[1]:7
unknown function (ip: 0x7fce8009d503)
jl_fptr_trampoline at /home/takafumi/repos/watch/julia/src/gf.c:1843
jl_apply_generic at /home/takafumi/repos/watch/julia/src/gf.c:2198
do_call at /home/takafumi/repos/watch/julia/src/interpreter.c:324
eval_value at /home/takafumi/repos/watch/julia/src/interpreter.c:430
eval_stmt_value at /home/takafumi/repos/watch/julia/src/interpreter.c:363 [inlined]
eval_body at /home/takafumi/repos/watch/julia/src/interpreter.c:678
jl_interpret_toplevel_thunk_callback at /home/takafumi/repos/watch/julia/src/interpreter.c:808
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7fce8a38621f)
unknown function (ip: 0xffffffffffffffff)
jl_interpret_toplevel_thunk at /home/takafumi/repos/watch/julia/src/interpreter.c:817
jl_toplevel_eval_flex at /home/takafumi/repos/watch/julia/src/toplevel.c:818
jl_toplevel_eval_in at /home/takafumi/repos/watch/julia/src/builtins.c:622
eval at ./boot.jl:319
jl_apply_generic at /home/takafumi/repos/watch/julia/src/gf.c:2198
eval_user_input at /home/takafumi/repos/watch/julia/usr/share/julia/stdlib/v1.1/REPL/src/REPL.jl:85
macro expansion at /home/takafumi/.julia/packages/Revise/aU3Za/src/Revise.jl:764 [inlined]
#41 at ./task.jl:259
jl_fptr_trampoline at /home/takafumi/repos/watch/julia/src/gf.c:1843
jl_apply_generic at /home/takafumi/repos/watch/julia/src/gf.c:2198
jl_apply at /home/takafumi/repos/watch/julia/src/julia.h:1559 [inlined]
start_task at /home/takafumi/repos/watch/julia/src/task.c:271
unknown function (ip: 0xffffffffffffffff)
Allocations: 10007756 (Pool: 10005494; Big: 2262); GC: 21

[JeffBezanson]

This warning should probably become an error.

[StefanKarpinski]

Triage dixit: we should make this an error now and then open an issue about allowing it that someone can do if and when they feel like it.