Merge branch 'bjorn/compiler/use-lists-types'

* bjorn/compiler/use-lists-types:
  beam_ssa_type: Use types from some 'lists' functions

2 files changed, 127 insertions, 0 deletions

diff --git a/lib/compiler/src/beam_ssa_type.erl b/lib/compiler/src/beam_ssa_type.erl
index c040fb2dde..aa4720d222 100644
--- a/lib/compiler/src/beam_ssa_type.erl
+++ b/lib/compiler/src/beam_ssa_type.erl
@@ -884,6 +884,9 @@ type(call, [#b_remote{mod=#b_literal{val=Mod},
             end;
         {erlang,'--',[_,_]} ->
             list;
+        {lists,F,Args} ->
+            Types = get_types(Args, Ts),
+            lists_function_type(F, Types);
         {math,_,_} ->
             case is_math_bif(Name, length(Args)) of
                 false -> any;
@@ -975,6 +978,70 @@ arith_op_type(Args, Ts) ->
              (_, _) -> none
           end, unknown, Types).
 
+lists_function_type(F, Types) ->
+    case {F,Types} of
+        %% Functions that return booleans.
+        {all,[_,_]} ->
+            t_boolean();
+        {any,[_,_]} ->
+            t_boolean();
+        {keymember,[_,_,_]} ->
+            t_boolean();
+        {member,[_,_]} ->
+            t_boolean();
+        {prefix,[_,_]} ->
+            t_boolean();
+        {suffix,[_,_]} ->
+            t_boolean();
+
+        %% Functions that return lists.
+        {dropwhile,[_,_]} ->
+            list;
+        {duplicate,[_,_]} ->
+            list;
+        {filter,[_,_]} ->
+            list;
+        {flatten,[_]} ->
+            list;
+        {map,[_Fun,List]} ->
+            same_length_type(List);
+        {MapFold,[_Fun,_Acc,List]} when MapFold =:= mapfoldl;
+                                        MapFold =:= mapfoldr ->
+            #t_tuple{size=2,exact=true,
+                     elements=#{1=>same_length_type(List)}};
+        {partition,[_,_]} ->
+            t_two_tuple(list, list);
+        {reverse,[List]} ->
+            same_length_type(List);
+        {sort,[List]} ->
+            same_length_type(List);
+        {splitwith,[_,_]} ->
+            t_two_tuple(list, list);
+        {takewhile,[_,_]} ->
+            list;
+        {unzip,[List]} ->
+            ListType = same_length_type(List),
+            t_two_tuple(ListType, ListType);
+        {usort,[List]} ->
+            same_length_type(List);
+        {zip,[_,_]} ->
+            list;
+        {zipwith,[_,_,_]} ->
+            list;
+        {_,_} ->
+            any
+    end.
+
+%% For a lists function that return a list of the same
+%% length as the input list, return the type of the list.
+same_length_type(cons) -> cons;
+same_length_type(nil) -> nil;
+same_length_type(_) -> list.
+
+t_two_tuple(Type1, Type2) ->
+    #t_tuple{size=2,exact=true,
+             elements=#{1=>Type1,2=>Type2}}.
+
 %% will_succeed(TestOperation, Type) -> yes|no|maybe.
 %%  Test whether TestOperation applied to an argument of type Type
 %%  will succeed.  Return yes, no, or maybe.
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 8ca90870c4..5175be3ad5 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -2502,6 +2502,8 @@ call_return_type_1(erlang, '--', 2, _Vst) ->
     list;
 call_return_type_1(erlang, F, A, _) ->
     erlang_mod_return_type(F, A);
+call_return_type_1(lists, F, A, Vst) ->
+    lists_mod_return_type(F, A, Vst);
 call_return_type_1(math, F, A, _) ->
     math_mod_return_type(F, A);
 call_return_type_1(M, F, A, _) when is_atom(M), is_atom(F), is_integer(A), A >= 0 ->
@@ -2540,6 +2542,64 @@ math_mod_return_type(fmod, 2) -> {float,[]};
 math_mod_return_type(pi, 0) -> {float,[]};
 math_mod_return_type(F, A) when is_atom(F), is_integer(A), A >= 0 -> term.
 
+lists_mod_return_type(dropwhile, 2, _Vst) ->
+    list;
+lists_mod_return_type(duplicate, 2, _Vst) ->
+    list;
+lists_mod_return_type(filter, 2, _Vst) ->
+    list;
+lists_mod_return_type(flatten, 2, _Vst) ->
+    list;
+lists_mod_return_type(map, 2, Vst) ->
+    same_length_type({x,1}, Vst);
+lists_mod_return_type(MF, 3, Vst) when MF =:= mapfoldl; MF =:= mapfoldr ->
+    ListType = same_length_type({x,2}, Vst),
+    {tuple,2,#{1=>ListType}};
+lists_mod_return_type(partition, 2, _Vst) ->
+    two_tuple(list, list);
+lists_mod_return_type(reverse, 1, Vst) ->
+    same_length_type({x,0}, Vst);
+lists_mod_return_type(seq, 2, _Vst) ->
+    list;
+lists_mod_return_type(seq, 3, _Vst) ->
+    list;
+lists_mod_return_type(sort, 1, Vst) ->
+    same_length_type({x,0}, Vst);
+lists_mod_return_type(sort, 2, Vst) ->
+    same_length_type({x,1}, Vst);
+lists_mod_return_type(splitwith, 2, _Vst) ->
+    two_tuple(list, list);
+lists_mod_return_type(takewhile, 2, _Vst) ->
+    list;
+lists_mod_return_type(unzip, 1, Vst) ->
+    ListType = same_length_type({x,0}, Vst),
+    two_tuple(ListType, ListType);
+lists_mod_return_type(usort, 1, Vst) ->
+    same_length_type({x,0}, Vst);
+lists_mod_return_type(usort, 2, Vst) ->
+    same_length_type({x,1}, Vst);
+lists_mod_return_type(zip, 2, _Vst) ->
+    list;
+lists_mod_return_type(zip3, 3, _Vst) ->
+    list;
+lists_mod_return_type(zipwith, 3, _Vst) ->
+    list;
+lists_mod_return_type(zipwith3, 4, _Vst) ->
+    list;
+lists_mod_return_type(_, _, _) ->
+    term.
+
+two_tuple(Type1, Type2) ->
+    {tuple,2,#{1=>Type1,2=>Type2}}.
+
+same_length_type(Reg, Vst) ->
+    case get_term_type(Reg, Vst) of
+        {literal,[_|_]} -> cons;
+        cons -> cons;
+        nil -> nil;
+        _ -> list
+    end.
+
 check_limit({x,X}) when is_integer(X), X < 1023 ->
     %% Note: x(1023) is reserved for use by the BEAM loader.
     ok;