Don't copy funs into guards

Funs must not be created in guards. The instruction for creating
a fun clobbers all X registers, which is a bad thing to do in
a guard.

2 files changed, 20 insertions, 1 deletions

diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 5e1602cb5b..4922953407 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -1130,7 +1130,13 @@ clause_1(#c_clause{guard=G0,body=B0}=Cl, Ps1, Cexpr, Ctxt, Sub1) ->
 		   %%
 		   %%   case A of NewVar when true -> ...
 		   %%
-		   sub_set_var(Var, Cexpr, Sub2);
+		   case cerl:is_c_fname(Cexpr) of
+		       false ->
+			   sub_set_var(Var, Cexpr, Sub2);
+		       true ->
+			   %% We must not copy funs, and especially not into guards.
+			   Sub2
+		   end;
 	       _ ->
 		   Sub2
 	   end,
diff --git a/lib/compiler/test/guard_SUITE.erl b/lib/compiler/test/guard_SUITE.erl
index 6302f82f29..429d6b79e0 100644
--- a/lib/compiler/test/guard_SUITE.erl
+++ b/lib/compiler/test/guard_SUITE.erl
@@ -87,6 +87,7 @@ misc(Config) when is_list(Config) ->
     {ok,buf,<<>>} = get_data({o,true,0}, 42, buf),
     {ok,buf,<<>>} = get_data({o,false,0}, 0, buf),
     error = get_data({o,false,0}, 42, buf),
+
     ok.
     
 
@@ -343,6 +344,11 @@ complex_semicolon(Config) when is_list(Config) ->
     ok = csemi7(#{a=>1}, 3, 3),
     ok = csemi7(#{a=>1, b=>3}, 0, 0),
 
+    %% 8: Make sure that funs cannot be copied into guards.
+    ok = csemi8(true),
+    error = csemi8(false),
+    error = csemi8(42),
+
     ok.
 
 csemi1(Type, Val) when is_list(Val), Type == float;
@@ -457,6 +463,13 @@ csemi6(_, _) -> error.
 csemi7(A, B, C) when A#{a:=B} > #{a=>1}; abs(C) > 2 -> ok;
 csemi7(_, _, _) -> error.
 
+csemi8(Together) ->
+  case fun csemi8/1 of
+      Typically when Together; Typically, Together -> ok;
+      _ -> error
+  end.
+
+
 comma(Config) when is_list(Config) ->
 
     %% ',' combinations of literal true/false.