Assertion error during type size limiting

[maleadt]

Reduced MWE:

1@.a*b = 1*c::Tuple{1}

Internal error: encountered unexpected error in runtime:
AssertionError(msg="unhandled TypeVar / Vararg")
_limit_type_size at ./compiler/typelimits.jl:87
__limit_type_size at ./compiler/typelimits.jl:220
_limit_type_size at ./compiler/typelimits.jl:170
__limit_type_size at ./compiler/typelimits.jl:220
_limit_type_size at ./compiler/typelimits.jl:170
__limit_type_size at ./compiler/typelimits.jl:220
_limit_type_size at ./compiler/typelimits.jl:106
__limit_type_size at ./compiler/typelimits.jl:220
_limit_type_size at ./compiler/typelimits.jl:106
limit_type_size at ./compiler/typelimits.jl:21
abstract_call_method at ./compiler/abstractinterpretation.jl:556
abstract_call_gf_by_type at ./compiler/abstractinterpretation.jl:89
abstract_call_known at ./compiler/abstractinterpretation.jl:2056
abstract_call at ./compiler/abstractinterpretation.jl:2138
abstract_call at ./compiler/abstractinterpretation.jl:2131
abstract_call at ./compiler/abstractinterpretation.jl:2287
abstract_eval_call at ./compiler/abstractinterpretation.jl:2302
abstract_eval_statement_expr at ./compiler/abstractinterpretation.jl:2312
abstract_eval_statement at ./compiler/abstractinterpretation.jl:2606
abstract_eval_basic_statement at ./compiler/abstractinterpretation.jl:2902
typeinf_local at ./compiler/abstractinterpretation.jl:3099
typeinf_nocycle at ./compiler/abstractinterpretation.jl:3187
_typeinf at ./compiler/typeinfer.jl:247
typeinf at ./compiler/typeinfer.jl:216

Bisected to #48421.

[vtjnash]

This is also fixed by #51317, since that better validates the introduction of ::Tuple{1} as an element of the lattice before letting it be used as the lattice element. Some other examples of it:

julia> (() -> .*(c::Tuple{1}))()

julia> struct A1
       b::Tuple{1}
       A1() = new()
       end

julia> code_typed(x -> .*(x.b), (A1,))
1-element Vector{Any}:
 CodeInfo(
    @ REPL[10]:1 within `#19`
   ┌ @ Base.jl:37 within `getproperty`
1 ─│ %1 = Base.getfield(x, :b)::Tuple{1}
│  └
│        Base.broadcasted(Main.:*, %1)::Union{}
└──      unreachable
) => Union{}

[vtjnash]

Seems to may need more validation in getfield_tfunc output though:

julia> struct A1
       b::Tuple{1}                                                   
       A1() = new()                                                  
       end          
                                                                     
julia> code_typed(x -> <:(x.b...), (A1,))
ERROR: MethodError: no method matching widenconst(::Int64)

[vtjnash]

also this one

julia> Type{1} <: Int
julia: /home/vtjnash/julia/src/subtype.c:2097: ijl_subtype_env: Assertion `obvious_subtype == 3 || obvious_subtype == subtype || jl_has_free_typevars(x) || jl_has_free_typevars(y)' failed.
obvious_subtype=false
subtype=true

julia> struct A7
       b::Tuple{Type{1}, Type{2}}
       A1() = new()
       end

julia> 

julia> code_typed(x -> +(x.b...), (A7,))
julia: /home/vtjnash/julia1/src/subtype.c:2097: ijl_subtype_env: Assertion `obvious_subtype == 3 || obvious_subtype == subtype || jl_has_free_typevars(x) || jl_has_free_typevars(y)' failed.

[822241] signal (6.-6): Aborted
in expression starting at REPL[2]:1
gsignal at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
abort at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
unknown function (ip: 0x7f898988a728)
__assert_fail at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
ijl_subtype_env at /home/vtjnash/julia1/src/subtype.c:2097
local_forall_exists_subtype at /home/vtjnash/julia1/src/subtype.c:1519
subtype_ccheck at /home/vtjnash/julia1/src/subtype.c:643
var_gt at /home/vtjnash/julia1/src/subtype.c:755
subtype_var at /home/vtjnash/julia1/src/subtype.c:793
subtype at /home/vtjnash/julia1/src/subtype.c:1370
subtype_tuple_tail at /home/vtjnash/julia1/src/subtype.c:1211 [inlined]
subtype_tuple at /home/vtjnash/julia1/src/subtype.c:1290 [inlined]
subtype at /home/vtjnash/julia1/src/subtype.c:1433
subtype_unionall at /home/vtjnash/julia1/src/subtype.c:898
subtype at /home/vtjnash/julia1/src/subtype.c:1396
exists_subtype at /home/vtjnash/julia1/src/subtype.c:1601
_forall_exists_subtype at /home/vtjnash/julia1/src/subtype.c:1632
forall_exists_subtype at /home/vtjnash/julia1/src/subtype.c:1646 [inlined]
ijl_subtype_env at /home/vtjnash/julia1/src/subtype.c:2096
jl_type_intersection_env_s at /home/vtjnash/julia1/src/subtype.c:4186
jl_typemap_intersection_node_visitor at /home/vtjnash/julia1/src/typemap.c:543
jl_typemap_intersection_visitor at /home/vtjnash/julia1/src/typemap.c:807
ml_mtable_visitor at /home/vtjnash/julia1/src/gf.c:3293 [inlined]
ml_matches at /home/vtjnash/julia1/src/gf.c:3666
ml_matches at /home/vtjnash/julia1/src/gf.c:3585 [inlined]
ijl_matching_methods at /home/vtjnash/julia1/src/gf.c:2282