Suppress some warnings about generation of non-returning funs

No warnings are emitted for funs that are non-returning when the
function that generates them has a contract that specifies that
it will return such a non-returning fun.

The actual bug, reported by Tuncer Ayaz and simplified by Maria
Christakis is included in Dialyzer's tests.

4 files changed, 317 insertions, 1 deletions

diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index df411342cb..659297f993 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -2952,7 +2952,7 @@ state__get_warnings(#state{tree_map = TreeMap, fun_tab = FunTab,
 		%% Check if the function has a contract that allows this.
 		Warn =
 		  case Contract of
-		    none -> true;
+		    none -> not parent_allows_this(FunLbl, State);
 		    {value, C} ->
 		      GenRet = dialyzer_contracts:get_contract_return(C),
 		      not t_is_unit(GenRet)
@@ -3440,6 +3440,33 @@ map_pats(Pats) ->
 	end,
   cerl_trees:map(Fun, Pats).
 
+parent_allows_this(FunLbl, #state{callgraph = Callgraph, plt = Plt} =State) ->
+  case state__is_escaping(FunLbl, State) of
+    false -> false; % if it isn't escaping it can't be a return value
+    true ->
+      case state__lookup_name(FunLbl, State) of
+	{_M, _F, _A} -> false; % if it has a name it is not a fun
+	_ ->
+	  case dialyzer_callgraph:in_neighbours(FunLbl, Callgraph) of
+	    [Parent] ->
+	      case state__lookup_name(Parent, State) of
+		{_M, _F, _A} = PMFA ->
+		  case dialyzer_plt:lookup_contract(Plt, PMFA) of
+		    none -> false;
+		    {value, C} ->
+		      GenRet = dialyzer_contracts:get_contract_return(C),
+		      case erl_types:t_is_fun(GenRet) of
+			false -> false; % element of structure? far-fetched...
+			true -> t_is_unit(t_fun_range(GenRet))
+		      end
+		  end;
+		_ -> false % parent should have a name to have a contract
+	      end;
+	    _ -> false % called in other funs? far-fetched...
+	  end
+      end
+  end.
+
 classify_returns(Tree) ->
   case find_terminals(cerl:fun_body(Tree)) of
     {false, false} -> no_match;
diff --git a/lib/dialyzer/test/small_SUITE_data/results/failing_funs b/lib/dialyzer/test/small_SUITE_data/results/failing_funs
new file mode 100644
index 0000000000..a1fb22cbc6
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/results/failing_funs
@@ -0,0 +1,20 @@
+
+failing_funs.erl:101: The created fun has no local return
+failing_funs.erl:104: The created fun has no local return
+failing_funs.erl:127: The created fun has no local return
+failing_funs.erl:135: The created fun has no local return
+failing_funs.erl:138: The created fun has no local return
+failing_funs.erl:13: Function foo3/0 has no local return
+failing_funs.erl:13: The pattern 'b' can never match the type 'a'
+failing_funs.erl:161: The created fun has no local return
+failing_funs.erl:169: The created fun has no local return
+failing_funs.erl:172: The created fun has no local return
+failing_funs.erl:17: The pattern 'b' can never match the type 'a'
+failing_funs.erl:195: The created fun has no local return
+failing_funs.erl:203: The created fun has no local return
+failing_funs.erl:206: The created fun has no local return
+failing_funs.erl:229: The created fun has no local return
+failing_funs.erl:55: The created fun has no local return
+failing_funs.erl:62: The created fun has no local return
+failing_funs.erl:69: The created fun has no local return
+failing_funs.erl:76: The created fun has no local return
diff --git a/lib/dialyzer/test/small_SUITE_data/src/failing_funs.erl b/lib/dialyzer/test/small_SUITE_data/src/failing_funs.erl
new file mode 100644
index 0000000000..1784c4a494
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/failing_funs.erl
@@ -0,0 +1,250 @@
+-module(failing_funs).
+
+-compile(export_all).
+
+% Crashes with system call. No spec.
+foo1() -> halt().
+
+% Crashes with system call. With spec.
+-spec foo2() -> no_return().
+foo2() -> halt().
+
+% Crashes on its own. No spec.
+foo3() -> case a of b -> ok end.
+
+% Crashes on its own. With spec.
+-spec foo4() -> no_return().
+foo4() -> case a of b -> ok end.
+
+% Creates fun that crashes with system call. No spec.
+foo5() -> fun() -> halt() end.
+
+% Creates fun that crashes with system call. With spec.
+-spec foo6() -> fun(() -> no_return()).
+foo6() -> fun() -> halt() end.
+
+% Creates fun from named fun that will crash. Neither have spec.
+foo7() -> fun foo1/0.
+
+% Creates fun from named fun that will crash. Has spec.
+-spec foo8() -> fun(() -> no_return()).
+foo8() -> fun foo1/0.
+
+% Creates fun from named fun that will crash. Named has spec.
+foo9() -> fun foo2/0.
+
+% Creates fun from named fun that will crash. Both have specs.
+-spec foo10() -> fun(() -> no_return()).
+foo10() -> fun foo2/0.
+
+% Creates fun from named fun that will crash. Neither have spec.
+foo11() -> fun foo3/0.
+
+% Creates fun from named fun that will crash. Has spec.
+-spec foo12() -> fun(() -> no_return()).
+foo12() -> fun foo3/0.
+
+% Creates fun from named fun that will crash. Named has spec.
+foo13() -> fun foo4/0.
+
+% Creates fun from named fun that will crash. Both have specs.
+-spec foo14() -> fun(() -> no_return()).
+foo14() -> fun foo4/0.
+
+% Creates fun calling a named fun that will crash. Neither have spec.
+foo15() -> fun() -> foo1() end.
+
+% Creates fun calling a named fun that will crash. Has spec.
+-spec foo16() -> fun(() -> no_return()).
+foo16() -> fun() -> foo1() end.
+
+% Creates fun calling a named fun that will crash. Named has spec.
+foo17() -> fun() -> foo2() end.
+
+% Creates fun calling a named fun that will crash. Both have specs.
+-spec foo18() -> fun(() -> no_return()).
+foo18() -> fun() -> foo2() end.
+
+% Creates fun calling a named fun that will crash. Neither have spec.
+foo19() -> fun() -> foo3() end.
+
+% Creates fun calling a named fun that will crash. Has spec.
+-spec foo20() -> fun(() -> no_return()).
+foo20() -> fun() -> foo3() end.
+
+% Creates fun calling a named fun that will crash. Named has spec.
+foo21() -> fun() -> foo4() end.
+
+% Creates fun calling a named fun that will crash. Both have specs.
+-spec foo22() -> fun(() -> no_return()).
+foo22() -> fun() -> foo4() end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo23() ->
+    Bomb = fun() -> halt() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> halt() end
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo24() -> fun(() -> no_return()).
+foo24() ->
+    Bomb = fun() -> halt() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> halt() end
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo25() ->
+    Bomb = fun() -> foo1() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo1() end
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo26() -> fun(() -> no_return()).
+foo26() ->
+    Bomb = fun foo1/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo1/0
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo27() ->
+    Bomb = fun foo1/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo1/0
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo28() -> fun(() -> no_return()).
+foo28() ->
+    Bomb = fun() -> foo1() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo1() end
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo29() ->
+    Bomb = fun() -> foo2() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo2() end
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo30() -> fun(() -> no_return()).
+foo30() ->
+    Bomb = fun foo2/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo2/0
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo31() ->
+    Bomb = fun foo2/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo2/0
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo32() -> fun(() -> no_return()).
+foo32() ->
+    Bomb = fun() -> foo2() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo2() end
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo33() ->
+    Bomb = fun() -> foo3() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo3() end
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo34() -> fun(() -> no_return()).
+foo34() ->
+    Bomb = fun foo3/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo3/0
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo35() ->
+    Bomb = fun foo3/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo3/0
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo36() -> fun(() -> no_return()).
+foo36() ->
+    Bomb = fun() -> foo3() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo3() end
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo37() ->
+    Bomb = fun() -> foo4() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo4() end
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo38() -> fun(() -> no_return()).
+foo38() ->
+    Bomb = fun foo4/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo4/0
+    end.
+
+% Creates two funs with no local return and will return one or die. No spec.
+foo39() ->
+    Bomb = fun foo4/0,
+    case get(42) of
+	a -> Bomb();
+	b -> fun foo4/0
+    end.
+
+% Creates two funs with no local return and will return one or die. With spec.
+-spec foo40() -> fun(() -> no_return()).
+foo40() ->
+    Bomb = fun() -> foo4() end,
+    case get(42) of
+	a -> Bomb();
+	b -> fun() -> foo4() end
+    end.
+
+% Obtains two funs with no local return and will return one or die. No spec.
+foo41() ->
+    Bomb = foo5(),
+    case get(42) of
+	a -> Bomb();
+	b -> foo5()
+    end.
+
+% Obtains two funs with no local return and will return one or die. With spec.
+-spec foo42() -> fun(() -> no_return()).
+foo42() ->
+    Bomb = foo5(),
+    case get(42) of
+	a -> Bomb();
+	b -> foo5()
+    end.
diff --git a/lib/dialyzer/test/small_SUITE_data/src/rebar_no_return.erl b/lib/dialyzer/test/small_SUITE_data/src/rebar_no_return.erl
new file mode 100644
index 0000000000..d3b504ae04
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/rebar_no_return.erl
@@ -0,0 +1,19 @@
+-module(rebar_no_return).
+
+-export([t/0]).
+
+-spec t() -> no_return().
+t() ->
+  F = log_and_halt("baz"),
+  F("foo", 123).
+
+-spec log_and_halt(string()) -> fun((string(),integer()) -> no_return()).
+log_and_halt(Msg) ->
+  fun(_, _) ->
+      abort(Msg)
+  end.
+
+-spec abort(string()) -> no_return().
+abort(Msg) ->
+  io:format("~s~n", [Msg]),
+  halt(1).