Support fun types as macro arguments

A fun type would not be accepted in a macro argument.

Resolves #10280

Author: bjorng

lib/stdlib/src/epp.erl

@@ -2024,7 +2024,8 @@ macro_arg([{'if',Li}|Toks], E, Arg) ->
 macro_arg([{'case',Lc}|Toks], E, Arg) ->
     macro_arg(Toks, ['end'|E], [{'case',Lc}|Arg]);
 macro_arg([{'fun',Lc}|[{'(',_}|_]=Toks], E, Arg) ->
-    macro_arg(Toks, ['end'|E], [{'fun',Lc}|Arg]);
+    %% This can be either a fun definition or a fun type.
+    macro_arg(Toks, [fun_end|E], [{'fun',Lc}|Arg]);
 macro_arg([{'fun',_}=Fun,{var,_,_}=Name|[{'(',_}|_]=Toks], E, Arg) ->
     macro_arg(Toks, ['end'|E], [Name,Fun|Arg]);
 macro_arg([{'maybe',Lb}|Toks], E, Arg) ->
@@ -2035,6 +2036,23 @@ macro_arg([{'try',Lr}|Toks], E, Arg) ->
     macro_arg(Toks, ['end'|E], [{'try',Lr}|Arg]);
 macro_arg([{'cond',Lr}|Toks], E, Arg) ->
     macro_arg(Toks, ['end'|E], [{'cond',Lr}|Arg]);
+macro_arg([{'when',_}|_]=Toks, [fun_end|E], Arg) ->
+    %% This is the `when` inside a fun definition such as:
+    %%   fun() when true, true -> true end.
+    macro_arg(Toks, ['end'|E], Arg);
+macro_arg([{'->',_}|_]=Toks, [fun_end|E], Arg) ->
+    %% This is the `->` inside a fun definition such as:
+    %%   fun() -> ok end.
+    macro_arg(Toks, ['end'|E], Arg);
+macro_arg([{Rb,_Lrb}=T|Toks], [fun_end|E], Arg) ->
+    case Rb of
+        Eb when Eb =:= ','; Eb =:= ')'  ->
+            %% This is the end of a fun type such as:
+            %%    fun(() -> 'ok').
+            macro_arg([T|Toks], E, Arg);
+        _ ->
+            macro_arg(Toks, [fun_end|E], [T|Arg])
+    end;
 macro_arg([{Rb,Lrb}|Toks], [Rb|E], Arg) ->	%Found matching close
     macro_arg(Toks, E, [{Rb,Lrb}|Arg]);
 macro_arg([T|Toks], E, Arg) ->

lib/stdlib/test/epp_SUITE.erl

@@ -35,7 +35,8 @@
          deterministic_include/1, nondeterministic_include/1,
          gh_8268/1,
          moduledoc_include/1,
-         stringify/1
+         stringify/1,
+         fun_type_arg/1
         ]).
 
 -export([epp_parse_erl_form/2]).
@@ -82,7 +83,8 @@ all() ->
      deterministic_include, nondeterministic_include,
      gh_8268,
      moduledoc_include,
-     stringify].
+     stringify,
+     fun_type_arg].
 
 groups() ->
     [{upcase_mac, [], [upcase_mac_1, upcase_mac_2]},
@@ -2139,6 +2141,49 @@ stringify(Config) ->
     [] = run(Config, Ts),
     ok.
 
+%% GH-10280. A fun type could not be used as a macro argument.
+fun_type_arg(Config) ->
+    Ts = [{fun_type_1,
+           ~"""
+            -define(FOO(X), X).
+            -define(BAR(X, Y), {X,Y}).
+
+            -type foo() :: ?FOO(fun(() -> 'ok')).
+            -type bar() :: ?BAR(fun((integer()) -> integer()), integer()).
+            -type frotz() :: ?FOO(fun((integer()) -> {atom(),integer()})).
+
+            -define(mk_fun_var(Fun, Vars), mk_fun_var(Fun, Vars)).
+
+            t() ->
+                ok = f(fun() -> ok end),
+                42 = g({fun(I) -> 2 * I end, 21}),
+                {ok,7} = h(fun(I) -> {ok,I} end),
+                #{a := 1, b := 2} =
+                    ?mk_fun_var(fun(Map0) ->
+                       Map1 = Map0#{a => 1},
+                       Map1#{b => 2}
+                    end, #{}),
+                42 = ?FOO(fun(((I))) -> I + 1 end)(41),
+                true = (?FOO(fun (_) when true, true -> true end))(0),
+                ok.
+
+            -spec f(foo()) -> 'ok'.
+            f(F) -> F().
+
+            -spec g(bar()) -> integer().
+            g({F,I}) -> F(I).
+
+            -spec h(frotz()) -> {atom(),integer()}.
+            h(H) -> H(7).
+
+            mk_fun_var(Fun, Vars) -> Fun(Vars).
+            """,
+           [],
+           ok}],
+    [] = run(Config, Ts),
+    ok.
+
+
 %% Start location is 1.
 check(Config, Tests) ->
     eval_tests(Config, fun check_test/3, Tests).