Autocomplete struct using `%{struct |` syntaxe makes iex crashes

[GuillaumeMilan]

Elixir and Erlang/OTP versions

Elixir: 1.17.3
OTP: 27.1

Operating system

OS X

Current behavior

Let's define in a iex terminal u as

u = %URI{}

then try to autocomplete the following line in iex

iex> %{u |

the terminal crashes as

*** ERROR: Shell process terminated! (^G to start new job) ***

17:07:13.693 [error] Process #PID<0.70.0> raised an exception
** (Protocol.UndefinedError) protocol Enumerable not implemented for %URI{scheme: nil, userinfo: nil, host: nil, port: nil, path: nil, query: nil, fragment: nil} of type URI (a struct). This protocol is implemented for the following type(s): Date.Range, File.Stream, Function, GenEvent.Stream, HashDict, HashSet, Hl7.Repeater, IO.Stream, Jason.OrderedObject, List, Map, MapSet, Range, Stream
    (elixir 1.17.3) lib/enum.ex:1: Enumerable.impl_for!/1
    (elixir 1.17.3) lib/enum.ex:166: Enumerable.reduce/3
    (elixir 1.17.3) lib/enum.ex:4423: Enum.reduce/3
    (iex 1.17.3) lib/iex/autocomplete.ex:366: IEx.Autocomplete.container_context_map_fields/3
    (iex 1.17.3) lib/iex/autocomplete.ex:108: IEx.Autocomplete.expand_code/2
    (kernel 10.1) group.erl:743: :group.get_line1/5
    (kernel 10.1) group.erl:527: :group.get_chars_loop/10
    (kernel 10.1) group.erl:222: :group.io_request/6

Expected behavior

The iex terminal should autocomplete as for any kind of maps

[frerich]

I was able to reproduce this with Elixir 1.18.1 on macOS 15.2, with the exact same symptoms. As soon as pressing <Tab>, the error message shown in the ticket description is printed and IEx seems to become stuck; it no longer reacts to any keyboard input.

[josevalim]

Closed with #14150.