Thanks for finding that post! I’m a bit ashamed that I wasn’t able to find it myself 
I thought of that option, and it works quite well if the source language is English (same language as the interpolation key).
In my case, the source language is French (and I am not in a position to change that). So the solution becomes:
<%= gettext("Vous avez déjà un compte ? %{sign_in} pour continuer", sign_in: safe_to_string(link(gettext("Connectez-vous"), to: Routes.session_path(@conn, :new)))) |> raw() %>
It’s less ideal, but works. I’m still not 100% convinced because the two translation strings are not so connected (hard for the translator to make the connection between the two, in the middle of 100s of other strings).
Maybe we can make an exception and use French only for these keys?
<%= gettext("Vous avez déjà un compte ? %{connectez_vous} pour continuer", connectez_vous: safe_to_string(link(gettext("Connectez-vous"), to: Routes.session_path(@conn, :new)))) |> raw() %>
So given all these compromises, I also consider the following solution:
<%= gettext("Vous avez déjà un compte ? %{a_start}Connectez-vous%{a_end} pour continuer", a_start: "<a href='/login'>", a_end: "</a>") |> raw() %>
Unfortunately:
- it’s very brittle
- we can’t use
link/2anymore - if we have multiple links, it starts to be even more brittle (a1_start, a2_start, etc. no good solution)
Compromises 
