Internal error on 0.7.0-alpha.0: compiler

[awllee]

Here is a snippet that works in 0.6 but not 0.7.0-alpha.0. I certainly do not understand what is going on; to construct this MWE I focused on the fact that the conditional in M! appears to be essential. Also, julia does not crash; one can still call bar successfully after the internal error is reported.

mutable struct Float64Data
  x::Float64
  Float64Data() = new()
end

@inline function M!(data::Float64Data, i::Int64)
  if i == 1
    data.x = 0.0
  else
    data.x = data.x
  end
end

function foo()
  data = Float64Data()
  M!(data, 1)
end

function bar(i::Int64)
  data = Float64Data()
  M!(data, i)
end

foo() # no problem
bar(1) # Internal error: encountered unexpected error in runtime```

The error output is

`Internal error: encountered unexpected error in runtime:
BoundsError(a=Array{Any, (1,)}[Main.Float64Data], i=(2,))
rec_backtrace at /buildworker/worker/package_linux64/build/src/stackwalk.c:94
record_backtrace at /buildworker/worker/package_linux64/build/src/task.c:246
jl_throw at /buildworker/worker/package_linux64/build/src/task.c:577
jl_bounds_error_ints at /buildworker/worker/package_linux64/build/src/rtutils.c:187
getindex at ./array.jl:707
jfptr_getindex_234.clone_1 at /home/al17824/julia-latest/lib/julia/sys.so (unknown line)
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2140
val_for_def_expr at ./compiler/ssair/passes.jl:65
compute_value_for_use at ./compiler/ssair/passes.jl:102
getfield_elim_pass! at ./compiler/ssair/passes.jl:716
run_passes at ./compiler/ssair/driver.jl:173
optimize at ./compiler/optimize.jl:183
typeinf at ./compiler/typeinfer.jl:436
typeinf_frame at ./compiler/typeinfer.jl:96 [inlined]
typeinf_code at ./compiler/typeinfer.jl:191
typeinf_ext at ./compiler/typeinfer.jl:233
jfptr_typeinf_ext_12.clone_1 at /home/al17824/julia-latest/lib/julia/sys.so (unknown line)
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2140
jl_apply at /buildworker/worker/package_linux64/build/src/julia.h:1540 [inlined]
jl_apply_with_saved_exception_state at /buildworker/worker/package_linux64/build/src/rtutils.c:257
jl_type_infer at /buildworker/worker/package_linux64/build/src/gf.c:274
jl_compile_method_internal at /buildworker/worker/package_linux64/build/src/gf.c:1778 [inlined]
jl_fptr_trampoline at /buildworker/worker/package_linux64/build/src/gf.c:1822
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2140
do_call at /buildworker/worker/package_linux64/build/src/interpreter.c:324
eval_value at /buildworker/worker/package_linux64/build/src/interpreter.c:416
eval_body at /buildworker/worker/package_linux64/build/src/interpreter.c:559
jl_interpret_toplevel_thunk_callback at /buildworker/worker/package_linux64/build/src/interpreter.c:798
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7f251ade974f)
unknown function (ip: 0xffffffffffffffff)
jl_interpret_toplevel_thunk at /buildworker/worker/package_linux64/build/src/interpreter.c:807
jl_toplevel_eval_flex at /buildworker/worker/package_linux64/build/src/toplevel.c:856
jl_parse_eval_all at /buildworker/worker/package_linux64/build/src/ast.c:852
jl_load at /buildworker/worker/package_linux64/build/src/toplevel.c:894
include at ./boot.jl:314 [inlined]
include_relative at ./loading.jl:1071
include at ./sysimg.jl:29
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2140
exec_options at ./client.jl:267
_start at ./client.jl:427
jl_apply_generic at /buildworker/worker/package_linux64/build/src/gf.c:2140
unknown function (ip: 0x401af8)
unknown function (ip: 0x401523)
__libc_start_main at /build/glibc-Cl5G7W/glibc-2.23/csu/../csu/libc-start.c:291
unknown function (ip: 0x4015c4)
`

[awllee]

This is probably related:

mutable struct Float64Data
  x::Float64
  Float64Data() = new()
end

function baz()
  data = Float64Data()
  return data.x
end

fd = Float64Data(); println(fd.x) # no problem

baz() # internal error

Although in this case one could argue that the code is requiring undefined memory to be accessed.