Merge pull request #1725 from michalmuskala/fun-literals

Compile external fun expressions to literals

OTP-15003

6 files changed, 20 insertions, 3 deletions

diff --git a/lib/compiler/src/cerl.erl b/lib/compiler/src/cerl.erl
index 6b936a7687..fce23bfd68 100644
--- a/lib/compiler/src/cerl.erl
+++ b/lib/compiler/src/cerl.erl
@@ -433,6 +433,8 @@ is_literal_term(T) when is_tuple(T) ->
 is_literal_term(B) when is_bitstring(B) -> true;
 is_literal_term(M) when is_map(M) ->
     is_literal_term_list(maps:to_list(M));
+is_literal_term(F) when is_function(F) ->
+    erlang:fun_info(F, type) =:= {type,external};
 is_literal_term(_) ->
     false.
 
diff --git a/lib/compiler/src/core_parse.yrl b/lib/compiler/src/core_parse.yrl
index 85444023c6..11c4cd8b50 100644
--- a/lib/compiler/src/core_parse.yrl
+++ b/lib/compiler/src/core_parse.yrl
@@ -36,7 +36,7 @@ other_pattern atomic_pattern tuple_pattern cons_pattern tail_pattern
 binary_pattern segment_patterns segment_pattern
 
 expression single_expression
-literal literals atomic_literal tuple_literal cons_literal tail_literal
+literal literals atomic_literal tuple_literal cons_literal tail_literal fun_literal
 nil tuple cons tail
 binary segments segment
 
@@ -267,6 +267,7 @@ single_expression -> cons : '$1'.
 single_expression -> binary : '$1'.
 single_expression -> variable : '$1'.
 single_expression -> function_name : '$1'.
+single_expression -> fun_literal : '$1'.
 single_expression -> fun_expr : '$1'.
 single_expression -> let_expr : '$1'.
 single_expression -> letrec_expr : '$1'.
@@ -303,6 +304,9 @@ tail_literal -> ']' : #c_literal{val=[]}.
 tail_literal -> '|' literal ']' : '$2'.
 tail_literal -> ',' literal tail_literal : c_cons('$2', '$3').
 
+fun_literal -> 'fun' atom ':' atom '/' integer :
+	#c_literal{val = erlang:make_fun(tok_val('$2'), tok_val('$4'), tok_val('$6'))}.
+
 tuple -> '{' '}' : c_tuple([]).
 tuple -> '{' anno_expressions '}' : c_tuple('$2').
 
diff --git a/lib/compiler/src/core_pp.erl b/lib/compiler/src/core_pp.erl
index 2516a9a1e1..f247722b4c 100644
--- a/lib/compiler/src/core_pp.erl
+++ b/lib/compiler/src/core_pp.erl
@@ -136,6 +136,11 @@ format_1(#c_literal{anno=A,val=M},Ctxt) when is_map(M) ->
 			  key=#c_literal{val=K},
 			  val=#c_literal{val=V}} || {K,V} <- Pairs],
     format_1(#c_map{anno=A,arg=#c_literal{val=#{}},es=Cpairs},Ctxt);
+format_1(#c_literal{val=F},_Ctxt) when is_function(F) ->
+    {module,M} = erlang:fun_info(F, module),
+    {name,N} = erlang:fun_info(F, name),
+    {arity,A} = erlang:fun_info(F, arity),
+    ["fun ",core_atom(M),$:,core_atom(N),$/,integer_to_list(A)];
 format_1(#c_var{name={I,A}}, _) ->
     [core_atom(I),$/,integer_to_list(A)];
 format_1(#c_var{name=V}, _) ->
@@ -541,4 +546,3 @@ segs_from_bitstring(Bitstring) ->
 	      unit=#c_literal{val=1},
 	      type=#c_literal{val=integer},
 	      flags=#c_literal{val=[unsigned,big]}}].
-
diff --git a/lib/compiler/src/erl_bifs.erl b/lib/compiler/src/erl_bifs.erl
index bafa9d75b7..8fab2400f7 100644
--- a/lib/compiler/src/erl_bifs.erl
+++ b/lib/compiler/src/erl_bifs.erl
@@ -109,6 +109,7 @@ is_pure(erlang, list_to_integer, 1) -> true;
 is_pure(erlang, list_to_pid, 1) -> true;
 is_pure(erlang, list_to_tuple, 1) -> true;
 is_pure(erlang, max, 2) -> true;
+is_pure(erlang, make_fun, 3) -> true;
 is_pure(erlang, min, 2) -> true;
 is_pure(erlang, phash, 2) -> false;
 is_pure(erlang, pid_to_list, 1) -> true;
@@ -196,6 +197,7 @@ is_safe(erlang, is_port, 1) -> true;
 is_safe(erlang, is_reference, 1) -> true;
 is_safe(erlang, is_tuple, 1) -> true;
 is_safe(erlang, make_ref, 0) -> true;
+is_safe(erlang, make_fun, 3) -> true;
 is_safe(erlang, max, 2) -> true;
 is_safe(erlang, min, 2) -> true;
 is_safe(erlang, node, 0) -> true;
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 395b6bd677..bb3a9c7628 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -404,7 +404,7 @@ expr(#c_receive{clauses=Cs0,timeout=T0,action=A0}=Recv, Ctxt, Sub) ->
 expr(#c_apply{anno=Anno,op=Op0,args=As0}=App, _, Sub) ->
     Op1 = expr(Op0, value, Sub),
     As1 = expr_list(As0, value, Sub),
-    case cerl:is_data(Op1) of
+    case cerl:is_data(Op1) andalso not is_literal_fun(Op1) of
         false ->
 	    App#c_apply{op=Op1,args=As1};
 	true ->
@@ -499,6 +499,9 @@ bitstr_list(Es, Sub) ->
 bitstr(#c_bitstr{val=Val,size=Size}=BinSeg, Sub) ->
     BinSeg#c_bitstr{val=expr(Val, Sub),size=expr(Size, value, Sub)}.
 
+is_literal_fun(#c_literal{val=F}) -> is_function(F);
+is_literal_fun(_) -> false.
+
 %% is_safe_simple(Expr, Sub) -> true | false.
 %%  A safe simple cannot fail with badarg and is safe to use
 %%  in a guard.
diff --git a/lib/stdlib/src/erl_parse.yrl b/lib/stdlib/src/erl_parse.yrl
index 14ca24362e..0c338b5952 100644
--- a/lib/stdlib/src/erl_parse.yrl
+++ b/lib/stdlib/src/erl_parse.yrl
@@ -1377,6 +1377,8 @@ normalise({map,_,Pairs}=M) ->
 		({map_field_assoc,_,K,V}) -> {normalise(K),normalise(V)};
 		(_) -> erlang:error({badarg,M})
 	    end, Pairs));
+normalise({'fun',_,{function,{atom,_,M},{atom,_,F},{integer,_,A}}}) ->
+    fun M:F/A;
 %% Special case for unary +/-.
 normalise({op,_,'+',{char,_,I}}) -> I;
 normalise({op,_,'+',{integer,_,I}}) -> I;