"Internal error" with reduce on vector of named tuples

[nalimilan]

@jlapeyre spotted this error on master (#26440). Funnily, the result is correct.

julia> reduce(merge,[(a=1,b=2),(c=3,d=4)])
Internal error: encountered unexpected error in runtime:
ErrorException("NamedTuple names and field types must have matching lengths")
rec_backtrace at /home/milan/Dev/julia/src/stackwalk.c:94
record_backtrace at /home/milan/Dev/julia/src/task.c:246
jl_throw at /home/milan/Dev/julia/src/task.c:577
jl_error at /home/milan/Dev/julia/src/rtutils.c:41
inst_datatype_inner at /home/milan/Dev/julia/src/jltypes.c:1232
inst_datatype_env at /home/milan/Dev/julia/src/jltypes.c:1309 [inlined]
inst_datatype_env at /home/milan/Dev/julia/src/jltypes.c:1313 [inlined]
inst_datatype_env at /home/milan/Dev/julia/src/jltypes.c:1313 [inlined]
inst_datatype at /home/milan/Dev/julia/src/jltypes.c:1319 [inlined]
jl_apply_type at /home/milan/Dev/julia/src/jltypes.c:855
intersect at /home/milan/Dev/julia/src/subtype.c:2063
intersect_unionall_ at /home/milan/Dev/julia/src/subtype.c:1559
intersect_unionall at /home/milan/Dev/julia/src/subtype.c:1604
intersect at /home/milan/Dev/julia/src/subtype.c:2006
intersect_unionall_ at /home/milan/Dev/julia/src/subtype.c:1563
intersect_unionall at /home/milan/Dev/julia/src/subtype.c:1604
intersect at /home/milan/Dev/julia/src/subtype.c:1980
intersect_tuple at /home/milan/Dev/julia/src/subtype.c:1706 [inlined]
intersect at /home/milan/Dev/julia/src/subtype.c:2020
intersect_all at /home/milan/Dev/julia/src/subtype.c:2092
jl_type_intersection_env_s at /home/milan/Dev/julia/src/subtype.c:2200
jl_typemap_intersection_node_visitor at /home/milan/Dev/julia/src/typemap.c:480
ml_matches at /home/milan/Dev/julia/src/gf.c:2476
jl_matching_methods at /home/milan/Dev/julia/src/gf.c:1724
abstract_call_gf_by_type at ./reflection.jl:677
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
abstract_call at ./compiler/abstractinterpretation.jl:712
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
abstract_eval_call at ./compiler/abstractinterpretation.jl:741
abstract_eval at ./compiler/abstractinterpretation.jl:813
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
abstract_interpret at ./compiler/abstractinterpretation.jl:931
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
typeinf_work at ./compiler/typeinfer.jl:273
typeinf at ./compiler/typeinfer.jl:407
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 at /home/milan/Dev/julia/usr/lib/julia/sys.so (unknown line)
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
jl_apply at /home/milan/Dev/julia/src/julia.h:1540 [inlined]
jl_apply_with_saved_exception_state at /home/milan/Dev/julia/src/rtutils.c:257
jl_type_infer at /home/milan/Dev/julia/src/gf.c:274
jl_compile_method_internal at /home/milan/Dev/julia/src/gf.c:1778
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1822
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
_mapreduce_dim at ./reducedim.jl:280
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1823
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
#mapreduce#537 at ./reducedim.jl:276
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1823
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
mapreduce at ./reducedim.jl:276
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1823
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
_reduce_dim at ./reducedim.jl:328
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1823
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
#reduce#539 at ./reducedim.jl:325
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1823
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
reduce at ./reducedim.jl:325
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1823
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
do_call at /home/milan/Dev/julia/src/interpreter.c:324
eval_value at /home/milan/Dev/julia/src/interpreter.c:416
eval_body at /home/milan/Dev/julia/src/interpreter.c:559
jl_interpret_toplevel_thunk_callback at /home/milan/Dev/julia/src/interpreter.c:798
unknown function (ip: 0xfffffffffffffffe)
unknown function (ip: 0x7f4e7cac02af)
unknown function (ip: 0x8)
jl_interpret_toplevel_thunk at /home/milan/Dev/julia/src/interpreter.c:807
jl_toplevel_eval_flex at /home/milan/Dev/julia/src/toplevel.c:856
jl_toplevel_eval_in at /home/milan/Dev/julia/src/builtins.c:631
eval at ./boot.jl:317 [inlined]
eval at /home/milan/Dev/julia/usr/share/julia/stdlib/v0.7/REPL/src/REPL.jl:5
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
eval_user_input at /home/milan/Dev/julia/usr/share/julia/stdlib/v0.7/REPL/src/REPL.jl:85
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
macro expansion at /home/milan/Dev/julia/usr/share/julia/stdlib/v0.7/REPL/src/REPL.jl:116 [inlined]
#28 at ./event.jl:92
jl_fptr_trampoline at /home/milan/Dev/julia/src/gf.c:1823
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:2140
jl_apply at /home/milan/Dev/julia/src/julia.h:1540 [inlined]
start_task at /home/milan/Dev/julia/src/task.c:268
unknown function (ip: 0xffffffffffffffff)
(a = 1, b = 2, c = 3, d = 4)

[jlapeyre]

Another data point. This

reduce(merge, [(a=1,b=2), (a=1,b=3,c=4)])

does not trigger the bug.