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| author | Björn Gustavsson <bjorn@erlang.org> | 2023-05-05 09:29:07 +0200 |
|---|---|---|
| committer | Björn Gustavsson <bjorn@erlang.org> | 2023-05-05 09:42:43 +0200 |
| commit | 3d158fba7e3a1d5c7dc7d78cb8a45b0eeb2c90da (patch) | |
| tree | aaa58a993b9e76e2ade46d3e86f695f022f74a07 | |
| parent | c6a68a171a299f39a3bd577b085a38f65c7569ae (diff) | |
| download | erlang-3d158fba7e3a1d5c7dc7d78cb8a45b0eeb2c90da.tar.gz | |
Add uppcoming incompatibility note about unbound type variables
| -rw-r--r-- | system/doc/general_info/upcoming_incompatibilities.xml | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/system/doc/general_info/upcoming_incompatibilities.xml b/system/doc/general_info/upcoming_incompatibilities.xml index 4d31784f8d..8538067b57 100644 --- a/system/doc/general_info/upcoming_incompatibilities.xml +++ b/system/doc/general_info/upcoming_incompatibilities.xml @@ -155,6 +155,30 @@ <p>We plan to introduce the same warning in OTP 26.1, but by default it will be disabled.</p> </section> + + <section> + <marker id="singleton_typevars"/> + <title>Singleton type variables will become a compile-time error</title> + + <p>Before Erlang/OTP 26, the compiler would silenty accept the + following spec:</p> + + <pre> +-spec f(Opts) -> term() when + Opts :: {ok, Unknown} | {error, Unknown}. +f(_) -> error.</pre> + + <p>In OTP 26, the compiler emits a warning pointing out that the type variable + <c>Unknown</c> is unbound:</p> + + <pre> +t.erl:6:18: Warning: type variable 'Unknown' is only used once (is unbound) +% 6| Opts :: {ok, Unknown} | {error, Unknown}. +% | ^</pre> + + <p>In OTP 27, that warning will become an error.</p> + </section> + </section> <section> |