From 784f845e2d1ec66b9505339b4b0e43d55c2d49a9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Magnus=20L=C3=A5ng?= <margnus1@telia.com>
Date: Mon, 4 Jul 2016 14:12:07 +0200
Subject: dialyzer: Suppress warns on generated case stmts
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Warnings about clauses that cannot match and are also compiler generated
are suppressed unless none of the clauses return.

This feature is useful for non-Erlang BEAM languages (such as Elixir)
that compile to Erlang and expand certain language constructs into case
statements. In that case, as long as the language construct can succeed,
these warnings are undesired and appear spurious to users that do not
check the Erlang code that their program expands into.

Thanks to José Valim for the test (slightly modified).
---
 lib/dialyzer/test/abstract_SUITE.erl | 102 +++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 lib/dialyzer/test/abstract_SUITE.erl

(limited to 'lib/dialyzer/test/abstract_SUITE.erl')

diff --git a/lib/dialyzer/test/abstract_SUITE.erl b/lib/dialyzer/test/abstract_SUITE.erl
new file mode 100644
index 0000000000..269db3e836
--- /dev/null
+++ b/lib/dialyzer/test/abstract_SUITE.erl
@@ -0,0 +1,102 @@
+%% This suite contains cases that cannot be written
+%% in Erlang itself and must be done via the abstract
+%% format.
+
+-module(abstract_SUITE).
+
+-include_lib("common_test/include/ct.hrl").
+-include("dialyzer_test_constants.hrl").
+
+-export([suite/0, all/0, init_per_suite/0, init_per_suite/1]).
+-export([generated_case/1]).
+
+suite() ->
+    [{timetrap, {minutes, 1}}].
+all() ->
+    [generated_case].
+
+init_per_suite() ->
+  [{timetrap, ?plt_timeout}].
+init_per_suite(Config) ->
+  OutDir = ?config(priv_dir, Config),
+  case dialyzer_common:check_plt(OutDir) of
+    fail -> {skip, "Plt creation/check failed."};
+    ok -> [{dialyzer_options, []}|Config]
+  end.
+
+generated_case(Config) when is_list(Config) ->
+    %% Equivalent to:
+    %%
+    %% -module(foo).
+    %% -export(bar).
+    %% bar() ->
+    %%     Arg = sample,
+    %%     case Arg of
+    %%         #{} -> map;
+    %%         _ -> Arg:fn()
+    %%     end.
+    %%
+    %% Except the case statement and its clauses are marked as autogenerated.
+    [] =
+	test([{attribute,1,module,foo},
+	      {attribute,2,export,[{bar,0}]},
+	      {function,3,bar,0,
+	       [{clause,3,[],[],
+		 [{match,4,{var,4,'Arg'},{atom,4,sample}},
+		  {'case',[{location,5},{generated,true}],{var,5,'Arg'},
+		   [{clause,[{location,6},{generated,true}],[{map,6,[]}],[],
+		     [{atom,6,map}]},
+		    {clause,[{location,7},{generated,true}],[{var,7,'_'}],[],
+		     [{call,7,{remote,7,{var,7,'Arg'},{atom,7,fn}},[]}]}]}]}]}],
+	     Config, [], []),
+    %% With the first clause not auto-generated
+    [{warn_matching,{_,6},_}] =
+	test([{attribute,1,module,foo},
+	      {attribute,2,export,[{bar,0}]},
+	      {function,3,bar,0,
+	       [{clause,3,[],[],
+		 [{match,4,{var,4,'Arg'},{atom,4,sample}},
+		  {'case',[{location,5},{generated,true}],{var,5,'Arg'},
+		   [{clause,6,[{map,6,[]}],[],
+		     [{atom,6,map}]},
+		    {clause,[{location,7},{generated,true}],[{var,7,'_'}],[],
+		     [{call,7,{remote,7,{var,7,'Arg'},{atom,7,fn}},[]}]}]}]}]}],
+	     Config, [], []),
+    %% With Arg set to [] so neither clause matches
+    [{warn_return_no_exit,{_,3},_},
+     {warn_matching,{_,6},_},
+     {warn_failing_call,{_,7},_}] =
+	test([{attribute,1,module,foo},
+	      {attribute,2,export,[{bar,0}]},
+	      {function,3,bar,0,
+	       [{clause,3,[],[],
+		 [{match,4,{var,4,'Arg'},{nil,4}},
+		  {'case',[{location,5},{generated,true}],{var,5,'Arg'},
+		   [{clause,[{location,6},{generated,true}],[{map,6,[]}],[],
+		     [{atom,6,map}]},
+		    {clause,[{location,7},{generated,true}],[{var,7,'_'}],[],
+		     [{call,7,{remote,7,{var,7,'Arg'},{atom,7,fn}},[]}]}]}]}]}],
+	     Config, [], []),
+    ok.
+
+test(Prog, Config, COpts, DOpts) ->
+    {ok, BeamFile} = compile(Config, Prog, COpts),
+    run_dialyzer(Config, succ_typings, [BeamFile], DOpts).
+
+compile(Config, Prog, CompileOpts) ->
+    OutDir = ?config(priv_dir, Config),
+    Opts = [{outdir, OutDir}, debug_info, return_errors | CompileOpts],
+    {ok, Module, Source} = compile:forms(Prog, Opts),
+    BeamFile = filename:join([OutDir, lists:concat([Module, ".beam"])]),
+    ok = file:write_file(BeamFile, Source),
+    {ok, BeamFile}.
+
+run_dialyzer(Config, Analysis, Files, Opts) ->
+    OutDir = ?config(priv_dir, Config),
+    PltFilename = dialyzer_common:plt_file(OutDir),
+    dialyzer:run([{analysis_type, Analysis},
+		  {files, Files},
+		  {init_plt, PltFilename},
+		  {check_plt, false},
+		  {from, byte_code} |
+		  Opts]).
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