Fix erl_eval bug when erlang:'=='/2 is used in guards

Prior to this commit, erl_eval did not properly evaluate
erlang:'=='/2 and friends in guard clauses because it
always flattened it to a local call ==/2. This commit
removes the flattening logic while still normalizing old
guards style.

2 files changed, 24 insertions, 6 deletions

diff --git a/lib/stdlib/src/erl_eval.erl b/lib/stdlib/src/erl_eval.erl
index ca6a4b5c58..970197641f 100644
--- a/lib/stdlib/src/erl_eval.erl
+++ b/lib/stdlib/src/erl_eval.erl
@@ -889,12 +889,16 @@ guard0([], _Bs, _Lf, _Ef) -> true.
 guard_test({call,L,{atom,Ln,F},As0}, Bs0, Lf, Ef) ->
     TT = type_test(F),
     G = {call,L,{atom,Ln,TT},As0},
-    try {value,true,_} = expr(G, Bs0, Lf, Ef, none)
-    catch error:_ -> {value,false,Bs0} end;
-guard_test({call,L,{remote,_Lr,{atom,_Lm,erlang},{atom,_Lf,_F}=T},As0}, 
+    expr_guard_test(G, Bs0, Lf, Ef);
+guard_test({call,L,{remote,Lr,{atom,Lm,erlang},{atom,Lf,F}},As0},
            Bs0, Lf, Ef) ->
-    guard_test({call,L,T,As0}, Bs0, Lf, Ef);
+    TT = type_test(F),
+    G = {call,L,{remote,Lr,{atom,Lm,erlang},{atom,Lf,TT}},As0},
+    expr_guard_test(G, Bs0, Lf, Ef);
 guard_test(G, Bs0, Lf, Ef) ->
+    expr_guard_test(G, Bs0, Lf, Ef).
+
+expr_guard_test(G, Bs0, Lf, Ef) ->
     try {value,true,_} = expr(G, Bs0, Lf, Ef, none)
     catch error:_ -> {value,false,Bs0} end.
     
diff --git a/lib/stdlib/test/erl_eval_SUITE.erl b/lib/stdlib/test/erl_eval_SUITE.erl
index 18ec17a4bf..381a338f71 100644
--- a/lib/stdlib/test/erl_eval_SUITE.erl
+++ b/lib/stdlib/test/erl_eval_SUITE.erl
@@ -26,7 +26,7 @@
 	 match_bin/1,
 	 string_plusplus/1,
 	 pattern_expr/1,
-         guard_3/1, guard_4/1,
+         guard_3/1, guard_4/1, guard_5/1,
          lc/1,
          simple_cases/1,
          unary_plus/1,
@@ -78,7 +78,7 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
 
 all() -> 
     [guard_1, guard_2, match_pattern, string_plusplus,
-     pattern_expr, match_bin, guard_3, guard_4, lc,
+     pattern_expr, match_bin, guard_3, guard_4, guard_5, lc,
      simple_cases, unary_plus, apply_atom, otp_5269,
      otp_6539, otp_6543, otp_6787, otp_6977, otp_7550,
      otp_8133, otp_10622, funs, try_catch, eval_expr_5, zero_width].
@@ -246,6 +246,20 @@ guard_4(Config) when is_list(Config) ->
                 false),
     ok.
 
+guard_5(doc) ->
+    ["Guards with erlang:'=='/2"];
+guard_5(suite) ->
+    [];
+guard_5(Config) when is_list(Config) ->
+    {ok,Tokens ,_} =
+	erl_scan:string("case 1 of A when erlang:'=='(A, 1) -> true end."),
+    {ok, [Expr]} = erl_parse:parse_exprs(Tokens),
+    true = guard_5_compiled(),
+    {value, true, [{'A',1}]} = erl_eval:expr(Expr, []),
+    ok.
+
+guard_5_compiled() ->
+    case 1 of A when erlang:'=='(A, 1) -> true end.
 
 lc(doc) ->
     ["OTP-4518."];