3 files changed, 35 insertions, 20 deletions
diff --git a/lib/compiler/src/beam_ssa_dead.erl b/lib/compiler/src/beam_ssa_dead.erl
index e220a89ded..64b9b3e222 100644
--- a/lib/compiler/src/beam_ssa_dead.erl
+++ b/lib/compiler/src/beam_ssa_dead.erl
@@ -436,8 +436,22 @@ get_phi_arg([{Val,From}|_], From) -> Val;
 get_phi_arg([_|As], From) -> get_phi_arg(As, From).
 
 eval_terminator(#b_br{bool=#b_var{}=Bool}=Br, Bs, _St) ->
-    Val = get_value(Bool, Bs),
-    beam_ssa:normalize(Br#b_br{bool=Val});
+    case get_value(Bool, Bs) of
+        #b_literal{val=Val}=Lit ->
+            case is_boolean(Val) of
+                true ->
+                    beam_ssa:normalize(Br#b_br{bool=Lit});
+                false ->
+                    %% Non-boolean literal. This means that this `br`
+                    %% terminator will never actually be reached with
+                    %% these bindings. (There must be a previous two-way
+                    %% branch that branches the other way when Bool
+                    %% is bound to a non-boolean literal.)
+                    none
+            end;
+        #b_var{}=Var ->
+            beam_ssa:normalize(Br#b_br{bool=Var})
+    end;
 eval_terminator(#b_br{bool=#b_literal{}}=Br, _Bs, _St) ->
     beam_ssa:normalize(Br);
 eval_terminator(#b_switch{arg=Arg,fail=Fail,list=List}=Sw, Bs, St) ->
diff --git a/lib/compiler/src/beam_ssa_type.erl b/lib/compiler/src/beam_ssa_type.erl
index 417addf921..68920e7dd3 100644
--- a/lib/compiler/src/beam_ssa_type.erl
+++ b/lib/compiler/src/beam_ssa_type.erl
@@ -840,15 +840,8 @@ type({bif,Bif}, Args, Ts, _Ds) ->
         Type ->
             Type
     end;
-type(bs_init, [#b_literal{val=Type}|Args], _Ts, _Ds) ->
-    case {Type,Args} of
-        {new,[_,#b_literal{val=Unit}]} ->
-            {binary,Unit};
-        {append,[_,_,#b_literal{val=Unit}]} ->
-            {binary,Unit};
-        {private_append,[_,_,#b_literal{val=Unit}]} ->
-            {binary,Unit}
-    end;
+type(bs_init, _Args, _Ts, _Ds) ->
+    {binary, 1};
 type(bs_extract, [Ctx], Ts, _Ds) ->
     #t_bs_match{type=Type} = get_type(Ctx, Ts),
     Type;
@@ -896,11 +889,15 @@ type(call, [#b_remote{mod=#b_literal{val=Mod},
                 {_,_} ->
                     #t_tuple{}
             end;
-        {erlang,'++',[List1,List2]} ->
-            case get_type(List1, Ts) =:= cons orelse
-                get_type(List2, Ts) =:= cons of
-                true -> cons;
-                false -> list
+        {erlang,'++',[LHS,RHS]} ->
+            LType = get_type(LHS, Ts),
+            RType = get_type(RHS, Ts),
+            case LType =:= cons orelse RType =:= cons of
+                true ->
+                    cons;
+                false ->
+                    %% `[] ++ RHS` yields RHS, even if RHS is not a list.
+                    join(list, RType)
             end;
         {erlang,'--',[_,_]} ->
             list;
diff --git a/lib/compiler/src/beam_validator.erl b/lib/compiler/src/beam_validator.erl
index 09a5a6c104..ebe9631e09 100644
--- a/lib/compiler/src/beam_validator.erl
+++ b/lib/compiler/src/beam_validator.erl
@@ -2844,10 +2844,14 @@ call_return_type_1(erlang, setelement, 3, Vst) ->
             setelement(3, TupleType, #{})
     end;
 call_return_type_1(erlang, '++', 2, Vst) ->
-    case get_term_type({x,0}, Vst) =:= cons orelse
-        get_term_type({x,1}, Vst) =:= cons of
-        true -> cons;
-        false -> list
+    LType = get_term_type({x,0}, Vst),
+    RType = get_term_type({x,1}, Vst),
+    case LType =:= cons orelse RType =:= cons of
+        true ->
+            cons;
+        false ->
+            %% `[] ++ RHS` yields RHS, even if RHS is not a list
+            join(list, RType)
     end;
 call_return_type_1(erlang, '--', 2, _Vst) ->
     list;