# Fatal: error thrown and no exception handler available for a \* method

**URL:** <https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275>\
**Category:** General Usage\
**Tags:** question\
**Created:** [August 28, 2023, 7:41am UTC](https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275 "2023-08-28T07:41:06Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [August 28, 2023, 7:41am UTC](https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275/1 "2023-08-28T07:41:06Z")

</div>

This is an MWE simplified from some code that tries to implement `*` for a type and `AbstractString`s. In this MWE, the intention is to return a `Foo` whenever _any_ argument is a `Foo`.

Is this a bug, or user error? I think that the `*` method should be more specific than the ` *(s1::Union{AbstractChar, AbstractString}, ss::Union{AbstractChar, AbstractString}...)` in `Base`, so I am not sure why it is causing a problem.

```julia
julia> VERSION
v"1.9.3-DEV.0"

julia> struct Foo end

julia> Base.:(*)(::Foo, ::AbstractString...) = Foo()

julia> Base.:(*)(::AbstractString, ::Union{AbstractString,Foo}...) = Foo()

fatal: error thrown and no exception handler available.
MethodError(f=Base.:(*), args=("", "", "", "", "", ""), world=0x00000000000082c3)
jl_method_error_bare at /home/tamas/src/julia-1.9/src/gf.c:2076
jl_method_error at /home/tamas/src/julia-1.9/src/gf.c:2094
jl_lookup_generic_ at /home/tamas/src/julia-1.9/src/gf.c:2921 [inlined]
ijl_apply_generic at /home/tamas/src/julia-1.9/src/gf.c:2936
#with_output_color#962 at ./util.jl:87
with_output_color at ./util.jl:71 [inlined]
#printstyled#963 at ./util.jl:130 [inlined]
printstyled at ./util.jl:130
unknown function (ip: 0x7fb17932841d)
display_error at ./client.jl:110
unknown function (ip: 0x7fb179327b56)
display_error at ./client.jl:114
unknown function (ip: 0x7fb179327922)
jl_apply at /home/tamas/src/julia-1.9/src/julia.h:1879 [inlined]
jl_f__call_latest at /home/tamas/src/julia-1.9/src/builtins.c:774
#invokelatest#2 at ./essentials.jl:816 [inlined]
invokelatest at ./essentials.jl:813 [inlined]
_start at ./client.jl:524
jfptr__start_43091 at /home/tamas/src/julia-1.9/usr/lib/julia/sys.so (unknown line)
jl_apply at /home/tamas/src/julia-1.9/src/julia.h:1879 [inlined]
true_main at /home/tamas/src/julia-1.9/src/jlapi.c:573
jl_repl_entrypoint at /home/tamas/src/julia-1.9/src/jlapi.c:717
main at julia (unknown line)
unknown function (ip: 0x7fb1936daa8f)
__libc_start_main at /lib/x86_64-linux-gnu/libc.so.6 (unknown line)
_start at julia (unknown line)

```

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<div class="post-metadata">

**Author:** ![oheil](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oheil/32/220745_2.png) [@oheil](https://discourse.julialang.org/u/oheil)\
**Post date:** [August 28, 2023, 8:09am UTC](https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275/2 "2023-08-28T08:09:52Z")

</div>

> [@Please read: make it easier to help you](https://discourse.julialang.org/t/please-read-make-it-easier-to-help-you/14757):
>
> Welcome to the Julia Discourse! We are enthusiastic about helping Julia programmers, both beginner and experienced. This public service announcement (PSA) outlines best practices when asking for help. Following these points makes it easier for us to help you and more likely you’ll get a prompt, useful answer. Keywords are highlighted to make it easier to refer to specific points. Choose a descriptive title that captures the key part of your question, eg “plots with multiple axes” instead of …

🤣 😂  
😘

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**Author:** ![Benny](https://avatars.discourse-cdn.com/v4/letter/b/49beb7/32.png) [@Benny](https://discourse.julialang.org/u/Benny)\
**Post date:** [August 28, 2023, 8:21am UTC](https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275/3 "2023-08-28T08:21:03Z")

</div>

> [@Tamas\_Papp](#):
>
> I think that the `*` method should be more specific than the ` *(s1::Union{AbstractChar, AbstractString}, ss::Union{AbstractChar, AbstractString}...)` in `Base`

It’s actually ambiguous for `*(::String, ::String)`, you can see the `MethodError` by making a new function with the argument signatures. But throwing the `MethodError` required a `*(::String, ::String)` call, so if that fails due to type piracy, we’re stuck.

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<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [August 28, 2023, 8:22am UTC](https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275/4 "2023-08-28T08:22:57Z")

</div>

> [@Benny](#):
>
> you can see the `MethodError` by making a new function with the argument signatures

That seems to work for me.

```julia
julia> struct Foo end

julia> f(::Foo, ::AbstractString...) = Foo()
f (generic function with 1 method)

julia> f(::AbstractString, ::Union{AbstractString,Foo}...) = Foo()
f (generic function with 2 methods)

julia> f(a::AbstractString, b::AbstractString...) = string(a, b...)
f (generic function with 3 methods)

julia> 

julia> f(Foo(), "a")
Foo()

julia> f("a", Foo(), "a")
Foo()

julia> f("a", "b", "a")
"aba"

```

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<div class="post-metadata">

**Author:** ![Benny](https://avatars.discourse-cdn.com/v4/letter/b/49beb7/32.png) [@Benny](https://discourse.julialang.org/u/Benny)\
**Post date:** [August 28, 2023, 8:27am UTC](https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275/5 "2023-08-28T08:27:30Z")

</div>

Like you said, `Base` doesn’t have a `*(::AbstractString, ::AbstractString...)` method. Replace that 3rd method and you find:

```julia
julia> f(s1::Union{AbstractChar, AbstractString}, ss::Union{AbstractChar, AbstractString}...) = 0
f (generic function with 3 methods)

julia> f("h", "i")
ERROR: MethodError: f(::String, ::String) is ambiguous. Candidates:

```

Dispatch issues are expected from the type piracy the 2nd method does.

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<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [August 28, 2023, 8:34am UTC](https://discourse.julialang.org/t/fatal-error-thrown-and-no-exception-handler-available-for-a-method/103275/6 "2023-08-28T08:34:05Z")

</div>

Thanks! I overlooked that.