Multiple dialyzer warnings with OTP 19

[aaronjensen]

Brand new phoenix app created with mix phoenix.new on OTP 19 has these warnings.

Here's a repro app: https://github.com/aaronjensen/dialyzer_repro

Some of these may be plug or ecto, so let me know if you'd like me to open issues in the respective places.

Starting Dialyzer
dialyzer --no_check_plt --plt /Users/aaronjensen/.dialyxir_core_19_1.3.2.plt -Wunmatched_returns -Werror_handling -Wrace_conditions -Wunderspecs /Users/aaronjensen/Source/dialyzer_repro/_build/dev/lib/dialyzer_repro/ebin
  Proceeding with analysis...
endpoint.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((map()) -> map())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()},...], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
endpoint.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any()),...], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'peer':={{_,_,_,_} | {_,_,_,_,_,_,_,_},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
endpoint.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', _=>_}
endpoint.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((map()) -> map())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
repo.ex:2: The inferred type for the 1st argument of insert_or_update/2 (#{'__struct__':='Elixir.Ecto.Changeset', 'data':=#{'__meta__':=#{'state':=_, _=>_}, _=>_}, 'valid?'=>boolean(), _=>_}) is not a supertype of #{'__struct__':='Elixir.Ecto.Changeset', 'action':='delete' | 'insert' | 'nil' | 'replace' | 'update', 'changes':=#{atom()=>_}, 'constraints':=[#{'constraint':=binary(), 'field':=atom(), 'match':='exact' | 'suffix', 'message':={binary(),[{atom(),_}]}, 'type':='unique'}], 'data':='nil' | #{'__struct__':=atom()}, 'errors':=[{atom(),{binary(),[{atom(),_}]}}], 'filters':=#{atom()=>_}, 'params':='nil' | #{binary()=>_}, 'prepare':=[fun((#{'__struct__':='Elixir.Ecto.Changeset', 'action':='delete' | 'insert' | 'nil' | 'replace' | 'update', 'changes':=map(), 'constraints':=[any()], _=>_}) -> #{'__struct__':='Elixir.Ecto.Changeset', 'action':='delete' | 'insert' | 'nil' | 'replace' | 'update', 'changes':=map(), 'constraints':=[any()], _=>_})], 'repo':=atom(), 'required':=[atom()], 'types':='nil' | #{atom()=>atom() | {'array',_} | {'embed',#{'__struct__':='Elixir.Ecto.Embedded', 'cardinality':='many' | 'one', 'field':=atom(), 'on_cast':='nil' | fun(), 'on_replace':='delete' | 'mark_as_invalid' | 'raise', 'owner':=atom(), 'related':=atom()}} | {'in',_} | {'map',_}}, 'valid?':=boolean(), 'validations':=[{atom(),_}]}, which is expected type for this argument in the callback of the 'Elixir.Ecto.Repo' behaviour
repo.ex:2: The inferred type for the 1st argument of 'insert_or_update!'/2 (#{'__struct__':='Elixir.Ecto.Changeset', 'data':=#{'__meta__':=#{'state':=_, _=>_}, _=>_}, 'valid?'=>boolean(), _=>_}) is not a supertype of #{'__struct__':='Elixir.Ecto.Changeset', 'action':='delete' | 'insert' | 'nil' | 'replace' | 'update', 'changes':=#{atom()=>_}, 'constraints':=[#{'constraint':=binary(), 'field':=atom(), 'match':='exact' | 'suffix', 'message':={binary(),[{atom(),_}]}, 'type':='unique'}], 'data':='nil' | #{'__struct__':=atom()}, 'errors':=[{atom(),{binary(),[{atom(),_}]}}], 'filters':=#{atom()=>_}, 'params':='nil' | #{binary()=>_}, 'prepare':=[fun((#{'__struct__':='Elixir.Ecto.Changeset', 'action':='delete' | 'insert' | 'nil' | 'replace' | 'update', 'changes':=map(), 'constraints':=[any()], _=>_}) -> #{'__struct__':='Elixir.Ecto.Changeset', 'action':='delete' | 'insert' | 'nil' | 'replace' | 'update', 'changes':=map(), 'constraints':=[any()], _=>_})], 'repo':=atom(), 'required':=[atom()], 'types':='nil' | #{atom()=>atom() | {'array',_} | {'embed',#{'__struct__':='Elixir.Ecto.Embedded', 'cardinality':='many' | 'one', 'field':=atom(), 'on_cast':='nil' | fun(), 'on_replace':='delete' | 'mark_as_invalid' | 'raise', 'owner':=atom(), 'related':=atom()}} | {'in',_} | {'map',_}}, 'valid?':=boolean(), 'validations':=[{atom(),_}]}, which is expected type for this argument in the callback of the 'Elixir.Ecto.Repo' behaviour
repo.ex:2: Function rollback/1 has no local return
repo.ex:2: The inferred type for the 1st argument of 'update!'/2 (#{'__struct__':='Elixir.Ecto.Changeset', 'action':=_, 'repo':=_, 'valid?':=boolean(), _=>_}) is not a supertype of #{'__struct__':=atom()}, which is expected type for this argument in the callback of the 'Elixir.Ecto.Repo' behaviour
page_controller.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
gettext.ex:1: Function lngettext/6 has no local return
gettext.ex:1: The call 'Elixir.Gettext.Interpolation':interpolate(_@7::any(),_@8::#{'count':=_, _=>_}) breaks the contract (binary(),#{}) -> {'ok',binary()} | {'error',binary()}
gettext.ex:23: Function lngettext/5 has no local return
router.ex:0: The pattern #{'static_url':=_@3} can never match the type atom()
router.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'peer':={{_,_,_,_} | {_,_,_,_,_,_,_,_},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
router.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'peer':={{_,_,_,_} | {_,_,_,_,_,_,_,_},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
router.ex:4: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
router.ex:4: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any()),...], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'peer':={{_,_,_,_} | {_,_,_,_,_,_,_,_},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
router.ex:4: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((map()) -> map())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
router.ex:12: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
index.html.eex:1: The pattern {'safe', _@2} can never match the type binary()
 done in 0m3.37s
done (warnings were emitted)

[josevalim]

Erlang 19 had a regression and it was reporting warnings in cases it should not. It was fixed in OTP's maint branch but it was not released yet: erlang/otp@784f845

It should fix all of the cases for the variable _ and that the pattern can never match type atom. The other warnings should be reported to Ecto (I'm already fixing those) and Gettext. :)

[aaronjensen]

Thanks @josevalim, issues filed. What about:

index.html.eex:1: The pattern {'safe', _@2} can never match the type binary()

[josevalim]

Dialyzer bug as well.

[aaronjensen]

Ah, same one or different one? Is that one filed somewhere? Thanks!

[josevalim]

Same. This is the one: erlang/otp@784f845

[aaronjensen]

@josevalim sorry, another clarification, is router.ex:0: The pattern #{'static_url':=_@3} can never match the type atom() related to the dialyzer bug as well?

It seems like dialyzer is seeing endpoint as a map even though it's meant to be an atom and endpoint.static_url should be a function call, not a map access.

[aaronjensen]

@josevalim @chrismccord would it be possible to reopen this with the idea that we can suppress these warnings in phoenix temporarily? It'd be great if we had a clean dialyzer bill of health out of the gate. As it stands, some things are impossible for user-land to suppress AFAICT since they are in generated modules.

[josevalim]

@aaronjensen we should not suppress warnings because that just leads to the situation we will keep on suppressing warnings while we should fix them. The static_url is also due to the dialyzer bug.

[aaronjensen]

@josevalim I'm not sure I understand that reasoning. Right now it's impossible to get a clean dialyzer run on phoenix w/ erlang 19. That means that we've not been running dialyzer because we haven't set up a hack like https://github.com/basho/riak/blob/develop/Makefile#L161-L162 yet.

Allowing end-users to run dialyzer cleanly seems orthogonal to a project's commitment to fixing warnings that are temporarily suppressed.

An issue could be left open to track the suppressed warnings. In the meantime, we can be encouraging dialyzer usage. I would love to see dialyzer usage be the default, not the exception. Heck maybe one day it can be included in mix new or mix phoenix.new.

[josevalim]

Allowing end-users to run dialyzer cleanly seems orthogonal to a project's commitment to fixing warnings that are temporarily suppressed.

Except that's not what happens in practice. Once we suppress some warnings, we will be giving us an implicit excuse to suppress warnings instead of fixing them in the future. A bit like in the Broken Windows theory. Plus, if we suppress warnings, we will be unable to know further offences since warnings won't be reported. At least I believe Erlang 19.1 will be coming out soon. If you prefer, you can fork the latest stable Phoenix release you are running on and add the annotations directly.

[aaronjensen]

Once we suppress some warnings, we will be giving us an implicit excuse to suppress warnings instead of fixing them in the future.

You'd know better than I. My sense is that this is totally up to the project maintainer(s) to enforce or not, to be diligent or not.

Plus, if we suppress warnings, we will be unable to know further offences since warnings won't be reported.

You can be pretty specific about the suppression:

      @dialyzer({:no_match, phoenix_controller_pipeline: 2})

If you prefer, you can fork the latest stable Phoenix release you are running on and add the annotations directly.

Yeah, this is what I plan on doing for now. I'll post a link here when I'm done in case anyone else wants clean dialyzer for now.

[josevalim]

I'll post a link here when I'm done in case anyone else wants clean dialyzer for now.

❤️ 💚 💙 💛 💜

[aaronjensen]

This was enough (after fixing other dependency issues) to get dialyzer working with OTP 19 and Elixir 1.3.2

https://github.com/aaronjensen/phoenix/tree/suppress-dialyzer-warnings
and
https://github.com/aaronjensen/ecto

Add this to your mix.exs:

     # Based on 1.2.1
     # Should be able to upgrade after Erlang 19.1 and *maybe* Elixir 1.4 too
     # https://github.com/phoenixframework/phoenix/issues/1872
     {:phoenix,
      github: "aaronjensen/phoenix",
      ref: "suppress-dialyzer-warnings",
      override: true},
     # Based on 2.0.5
     # https://github.com/elixir-ecto/ecto/pull/1689
     {:ecto, github: "aaronjensen/ecto", override: true},

Also add these to your repo.ex:

  @dialyzer({:nowarn_function, insert_or_update: 2})
  @dialyzer({:nowarn_function, insert_or_update!: 2})

[josevalim]

@aaronjensen beautiful. We should have a new Ecto release relatively soon too.

[aaronjensen]

@josevalim fyi, an update, these are the errors w/ OTP 19.1, Elixir 1.3.3, phoenix 1.2.1, and ecto 2.1.0-rc.0:

dialyzer --no_check_plt --plt .local.19_1.3.3.plt -Werror_handling -Wrace_conditions -Wno_opaque --fullpath /Users/aaronjensen/Source/the-link/_build/dev/lib/the_link/ebin
  Compiling some key modules to native code... done in 0m0.23s
  Proceeding with analysis...
web/controllers/api/v1/current_user_controller.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/controllers/api/v1/register_user_controller.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/controllers/api/v1/sign_in_controller.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/controllers/api/v1/sign_out_controller.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/controllers/page_controller.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/controllers/styleguide_controller.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/router.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'halted':=_, _=>_}
web/router.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'peer':={{_,_,_,_} | {_,_,_,_,_,_,_,_},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/router.ex:1: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'halted':=_, _=>_}
web/router.ex:4: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/router.ex:4: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any()),...], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'peer':={{_,_,_,_} | {_,_,_,_,_,_,_,_},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/router.ex:4: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((map()) -> map())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/router.ex:12: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/router.ex:12: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'peer':={{_,_,_,_} | {_,_,_,_,_,_,_,_},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
web/router.ex:12: The variable _ can never match since previous clauses completely covered the type #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((map()) -> map())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'path_info':=[binary()], 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | map()] | #{binary()=>binary() | [any()] | map()}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'unset', 'status':='nil' | non_neg_integer()}
 done in 0m2.35s
done (warnings were emitted)

[josevalim]

@aaronjensen given the reports, I am thinking they are all coming from here:

https://github.com/elixir-lang/plug/blob/master/lib/plug/builder.ex#L225-L226

Can you fork plug (or change plug in your deps/plug) to remove that line, then run mix deps.compile plug, and then recompile the source and re-run dialyzer and let us know if they disappear? If they are fixed, we will need to find a way to tell dialyzer to not warn on that clause.

[aaronjensen]

@josevalim that's the line that causes the errors.

I can only think of a few ways to not warn on that clause:

1. Disable that warning on any function that includes the results of Plug.Builder.compile. Seems fragile
2. Remove the clause entirely and maybe replace w/ a try/catch? Seems dirty
3. Extract the match out to its own public function that would return the conn as is or throw if it's not a conn. Then that case doesn't need that clause anymore. It's an extra function call and pattern match for a type checker though...
4. ???

[josevalim]

@aaronjensen let me try something out and I should have a code snippet for you to try out soon. Thank you for the help! ❤️

[josevalim]

@aaronjensen can you please try replacing the whole quote_plug I have linked to above by this one:

  defp quote_plug({plug_type, plug, opts, guards}, acc, env, builder_opts) do
    call = quote_plug_call(plug_type, plug, opts)

    error_message = case plug_type do
      :module   -> "expected #{inspect plug}.call/2 to return a Plug.Conn"
      :function -> "expected #{plug}/2 to return a Plug.Conn"
    end <> ", all plugs must receive a connection (conn) and return a connection"

    {fun, meta, [arg, [do: clauses]]} =
      quote do
        case unquote(compile_guards(call, guards)) do
          %Plug.Conn{halted: true} = conn ->
            unquote(log_halt(plug_type, plug, env, builder_opts))
            conn
          %Plug.Conn{} = conn ->
            unquote(acc)
          _ ->
            raise unquote(error_message)
        end
      end

    clauses =
      Enum.map(clauses, fn {:->, meta, args} ->
        {:->, [generated: true] ++ Keyword.put(meta, :line, -1), args}
      end)

    {fun, meta, [arg, [do: clauses]]}
  end

and then please let me know if it works as expected. :)

[aaronjensen]

@josevalim awesome I knew there was a 4. 😄

That worked, now the only warnings left on https://github.com/aaronjensen/dialyzer_repro are gettext:

Starting Dialyzer
dialyzer --no_check_plt --plt .local.plt -Wunmatched_returns -Werror_handling -Wrace_conditions -Wunderspecs /Users/aaronjensen/Source/dialyzer_repro/_build/dev/lib/dialyzer_repro/ebin
  Proceeding with analysis...
gettext.ex:1: Function lngettext/6 has no local return
gettext.ex:1: The call 'Elixir.Gettext.Interpolation':interpolate(_@7::any(),_@8::#{'count':=_, _=>_}) breaks the contract (binary(),#{}) -> {'ok',binary()} | {'error',binary()}
 done in 0m2.69s
done (warnings were emitted)

[josevalim]

That worked, now the only warnings left on https://github.com/aaronjensen/dialyzer_repro are gettext:

Yay! 🎉

I am closing this issue then because we already have an open one for the gettext warnings: elixir-gettext/gettext#115

❤️ 💚 💙 💛 💜

[novaugust]

So to summarize the solution here, either:

1. use @aaronjensen 's phoenix and ecto forks
   • https://github.com/aaronjensen/phoenix/tree/suppress-dialyzer-warnings
   • https://github.com/aaronjensen/ecto
2. wait for the following version releases
   • erlang 19.1.1
   • ecto 2.1
   • gettext
   • phoenix is good (via erlang fix?)

Correct?

[josevalim]

@novaugust yes. erlang 19.1 is out and ecto 2.1 already has a rc out. gettext is not fixed yet i believe.

[novaugust]

@josevalim I think the fix you linked is in 19.1.1 (tagged 7 days ago), not just 19.1 (15 days ago). I still see the _ can never match errors on ESL's 19.1rev3, which is the latest they're offering.