Fix overridden BIFs

The filters in a list comprehension can be guard expressions or
an ordinary expressions.

If a guard expression is used as a filter, an exception will basically
mean the same as 'false':

  t() ->
    L = [{some_tag,42},an_atom],
    [X || X <- L, element(1, X) =:= some_tag]
    %% Returns [{some_tag,42}]

On the other hand, if an ordinary expression is used as a filter, there
will be an exception:

  my_element(N, T) -> element(N, T).

  t() ->
    L = [{some_tag,42},an_atom],
    [X || X <- L, my_element(1, X) =:= some_tag]
    %% Causes a 'badarg' exception when element(1, an_atom) is evaluated

It has been allowed for several releases to override a BIF with
a local function. Thus, if we define a function called element/2,
it will be called instead of the BIF element/2 within the module.
We must use the "erlang:" prefix to call the BIF.

Therefore, the following code is expected to work the same way as in
our second example above:

-compile({no_auto_import,[element/2]}).

element(N, T) ->
    erlang:element(N, T).

t() ->
    L = [{some_tag,42},an_atom],
    [X || X <- L, element(1, X) =:= some_tag].
    %% Causes a 'badarg' exception when element(1, an_atom) is evaluated

But the compiler refuses to compile the code with the following
diagnostic:

  call to local/imported function element/2 is illegal in guard

1 files changed, 21 insertions, 24 deletions

diff --git a/lib/debugger/src/dbg_iload.erl b/lib/debugger/src/dbg_iload.erl
index 917f213e60..22e2073df8 100644
--- a/lib/debugger/src/dbg_iload.erl
+++ b/lib/debugger/src/dbg_iload.erl
@@ -486,30 +486,10 @@ expr({'try',Anno,Es0,CaseCs0,CatchCs0,As0}, Lc) ->
     CatchCs = icr_clauses(CatchCs0, Lc),
     As = expr_list(As0),
     {'try',ln(Anno),Es,CaseCs,CatchCs,As};
-expr({lc,Anno,E0,Gs0}, _Lc) ->			%R8.
-    Gs = lists:map(fun ({generate,L,P0,Qs}) ->
-			   {generate,L,pattern(P0),expr(Qs, false)};
-		       ({b_generate,L,P0,Qs}) -> %R12.
-			   {b_generate,L,pattern(P0),expr(Qs, false)};
-		       (Expr) ->
-			   case erl_lint:is_guard_test(Expr) of
-			       true -> {guard,guard([[Expr]])};
-			       false -> expr(Expr, false)
-			   end
-		   end, Gs0),
-    {lc,ln(Anno),expr(E0, false),Gs};
-expr({bc,Anno,E0,Gs0}, _Lc) ->			%R12.
-    Gs = lists:map(fun ({generate,L,P0,Qs}) ->
-			   {generate,L,pattern(P0),expr(Qs, false)};
-		       ({b_generate,L,P0,Qs}) -> %R12.
-			   {b_generate,L,pattern(P0),expr(Qs, false)};
-		       (Expr) ->
-			   case erl_lint:is_guard_test(Expr) of
-			       true -> {guard,guard([[Expr]])};
-			       false -> expr(Expr, false)
-			   end
-		   end, Gs0),
-    {bc,ln(Anno),expr(E0, false),Gs};
+expr({lc,_,_,_}=Compr, _Lc) ->
+    expr_lc_bc(Compr);
+expr({bc,_,_,_}=Compr, _Lc) ->
+    expr_lc_bc(Compr);
 expr({match,Anno,P0,E0}, _Lc) ->
     E1 = expr(E0, false),
     P1 = pattern(P0),
@@ -560,6 +540,23 @@ make_bit_type(_Line, Size, Type0) ->            %Integer or 'all'
     {ok,Size,Bt} = erl_bits:set_bit_type(Size, Type0),
     {Size,erl_bits:as_list(Bt)}.
 
+expr_lc_bc({Tag,Anno,E0,Gs0}) ->
+    Gs = lists:map(fun ({generate,L,P0,Qs}) ->
+			   {generate,L,pattern(P0),expr(Qs, false)};
+		       ({b_generate,L,P0,Qs}) -> %R12.
+			   {b_generate,L,pattern(P0),expr(Qs, false)};
+		       (Expr) ->
+			   case is_guard_test(Expr) of
+			       true -> {guard,guard([[Expr]])};
+			       false -> expr(Expr, false)
+			   end
+		   end, Gs0),
+    {Tag,ln(Anno),expr(E0, false),Gs}.
+
+is_guard_test(Expr) ->
+    IsOverridden = fun({_,_}) -> true end,
+    erl_lint:is_guard_test(Expr, [], IsOverridden).
+
 %% The debugger converts both strings "abc" and lists [67, 68, 69]
 %% into {value, Line, [67, 68, 69]}, making it impossible to later
 %% distingish one or the other inside binaries when evaluating. To