erl_lint: Consistently reject local calls from guards

If a guard test (such as is_list/1) has a local definition in a
module (or is imported), erl_lint will reject a call to it from
a guard if the call is not at the top-level:

foo(L) when is_list(L) =:= true ->   %% Will be rejected.
   ok.

is_list(_) -> ok.

But if the call is at the top-level, it will be accepted (and
cause a crash in a later compiler pass):

foo(L) when is_list(L) ->   %% Will be accepted by erl_lint
   ok.

is_list(_) -> ok.

This inconsistency was an oversight introduced when it became
possible to override BIFs with local definitions.

2 files changed, 28 insertions, 4 deletions

diff --git a/lib/stdlib/src/erl_lint.erl b/lib/stdlib/src/erl_lint.erl
index e5adb84932..2f29954dc9 100644
--- a/lib/stdlib/src/erl_lint.erl
+++ b/lib/stdlib/src/erl_lint.erl
@@ -1804,12 +1804,19 @@ guard_test(G, Vt, St0) ->
 %% Specially handle record type test here.
 guard_test2({call,Line,{atom,Lr,record},[E,A]}, Vt, St0) ->
     gexpr({call,Line,{atom,Lr,is_record},[E,A]}, Vt, St0);
-guard_test2({call,_Line,{atom,_La,F},As}=G, Vt, St0) ->
+guard_test2({call,Line,{atom,_La,F},As}=G, Vt, St0) ->
     {Asvt,St1} = gexpr_list(As, Vt, St0),       %Always check this.
     A = length(As),
     case erl_internal:type_test(F, A) of
-        true when F =/= is_record -> {Asvt,St1};
-        _ -> gexpr(G, Vt, St0)
+        true when F =/= is_record ->
+	    case no_guard_bif_clash(St1, {F,A}) of
+		false ->
+		    {Asvt,add_error(Line, {illegal_guard_local_call,{F,A}}, St1)};
+		true ->
+		    {Asvt,St1}
+	    end;
+	_ ->
+	    gexpr(G, Vt, St0)
     end;
 guard_test2(G, Vt, St) ->
     %% Everything else is a guard expression.
diff --git a/lib/stdlib/test/erl_lint_SUITE.erl b/lib/stdlib/test/erl_lint_SUITE.erl
index 9041adbe5c..e4c7fd5b02 100644
--- a/lib/stdlib/test/erl_lint_SUITE.erl
+++ b/lib/stdlib/test/erl_lint_SUITE.erl
@@ -2631,7 +2631,24 @@ bif_clash(Config) when is_list(Config) ->
                  binary_part(A,B,C).
              ">>,
 	   [warn_unused_import],
-	   {warnings,[{2,erl_lint,{redefine_bif_import,{binary_part,3}}}]}}
+	   {warnings,[{2,erl_lint,{redefine_bif_import,{binary_part,3}}}]}},
+	  %% Don't accept call to a guard BIF if there is a local definition
+	  %% or an import with the same name.
+	  {clash21,
+           <<"-export([is_list/1]).
+              -import(x, [is_tuple/1]).
+              x(T) when is_tuple(T) -> ok;
+              x(T) when is_list(T) -> ok.
+              y(T) when is_tuple(T) =:= true -> ok;
+              y(T) when is_list(T) =:= true -> ok.
+              is_list(_) ->
+                ok.
+             ">>,
+	   [{no_auto_import,[{is_tuple,1}]}],
+	   {errors,[{3,erl_lint,{illegal_guard_local_call,{is_tuple,1}}},
+		    {4,erl_lint,{illegal_guard_local_call,{is_list,1}}},
+		    {5,erl_lint,{illegal_guard_local_call,{is_tuple,1}}},
+		    {6,erl_lint,{illegal_guard_local_call,{is_list,1}}}],[]}}
 	 ],
 
     ?line [] = run(Config, Ts),