1.9 Type checking examples not working in iex

[sross]

Elixir and Erlang/OTP versions

Erlang/OTP 28 [erts-16.0] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]

Elixir 1.19.0-rc.0 (2a9a4f2) (compiled with Erlang/OTP 28)

Installed via mise

Operating system

Linux - Ubuntu 25.04

Current behavior

Running an example type checking samples from the 1.9 Changelog in a new iex session provides no type checking information.

iex(1)> defmodule Example do
def my_code(first..last//step = range) do
"hello #{range}"
end
end
warning: variable "first" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ iex:2: Example.my_code/1

warning: variable "last" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ iex:2: Example.my_code/1

warning: variable "step" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ iex:2: Example.my_code/1

{ :module, Example, ....}
iex(2)>

Expected behavior

Type checking information is emitted as per the documentation.

Note: Invoking Mix.install [] prior to the examples fixes the issue.

iex(1)> Mix.install []
:ok
iex(2)> defmodule Example do
def my_code(first..last//step = range) do
"hello #{range}"
end
end
warning: variable "first" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ iex:3: Example.my_code/1

warning: variable "last" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ iex:3: Example.my_code/1

warning: variable "step" is unused (if the variable is not meant to be used, prefix it with an underscore)
└─ iex:3: Example.my_code/1

warning: incompatible value given to string interpolation:

range

it has type:

dynamic(%Range{})

but expected a type that implements the String.Chars protocol, it must be one of:

dynamic(
  %Date{} or %DateTime{} or %Hex.Solver.Assignment{} or %Hex.Solver.Constraints.Range{} or
    %Hex.Solver.Constraints.Union{} or %Hex.Solver.Incompatibility{} or %Hex.Solver.PackageRange{} or
    %Hex.Solver.Term{} or %NaiveDateTime{} or %Time{} or %URI{} or %Version{} or
    %Version.Requirement{}
) or %Hex.Solver.Constraints.Empty{} or atom() or binary() or empty_list() or float() or integer() or
  non_empty_list(term(), term())

where "range" was given the type:

# type: dynamic(%Range{})
# from: iex:3
first..last//step = range

hint: string interpolation uses the String.Chars protocol to convert a data structure into a string. Either convert the data type into a string upfront or implement the protocol accordingly

└─ iex:4: Example.my_code/1

{:module, Example, ...}

[josevalim]

Anything related to protocols will require protocol consolidation, and therefore won't work in IEx, it requires a proper compilation. I will add a note to the changelog, thanks!