Convert keyword argument to required positional hash argument for Class#new, Method#call, UnboundMethod#bind_call

Also add keyword argument separation warnings for Class#new and Method#call.

To allow for keyword argument to required positional hash converstion in
cfuncs, add a vm frame flag indicating the cfunc was called with an empty
keyword hash (which was removed before calling the cfunc).  The cfunc can
check this frame flag and add back an empty hash if it is passing its
arguments to another Ruby method.  Add rb_empty_keyword_given_p function
for checking if called with an empty keyword hash, and
rb_add_empty_keyword for adding back an empty hash to argv.

All of this empty keyword argument support is only for 2.7.  It will be
removed in 3.0 as Ruby 3 will not convert empty keyword arguments to
required positional hash arguments.  Comment all of the relevent code
to make it obvious this is expected to be removed.

Add rb_funcallv_kw as an public C-API function, just like rb_funcallv
but with a keyword flag.  This is used by rb_obj_call_init (internals
of Class#new).  This also required expected call_type enum with
CALL_FCALL_KW, similar to the recent addition of CALL_PUBLIC_KW.

Add rb_vm_call_kw as a internal function, used by call_method_data
(internals of Method#call and UnboundMethod#bind_call). Add tests
for UnboundMethod#bind_call keyword handling.

1 files changed, 22 insertions, 1 deletions

diff --git a/vm_eval.c b/vm_eval.c
index b0249391bf..4a3b9e325f 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -33,6 +33,7 @@ typedef enum call_type {
     CALL_FCALL,
     CALL_VCALL,
     CALL_PUBLIC_KW,
+    CALL_FCALL_KW,
     CALL_TYPE_MAX
 } call_type;
 
@@ -210,6 +211,12 @@ rb_vm_call(rb_execution_context_t *ec, VALUE recv, VALUE id, int argc, const VAL
     return rb_vm_call0(ec, recv, id, argc, argv, me, VM_NO_KEYWORDS);
 }
 
+VALUE
+rb_vm_call_kw(rb_execution_context_t *ec, VALUE recv, VALUE id, int argc, const VALUE *argv, const rb_callable_method_entry_t *me, int kw_splat)
+{
+    return rb_vm_call0(ec, recv, id, argc, argv, me, kw_splat);
+}
+
 static inline VALUE
 vm_call_super(rb_execution_context_t *ec, int argc, const VALUE *argv)
 {
@@ -298,9 +305,17 @@ rb_call0(rb_execution_context_t *ec,
     call_type scope = call_scope;
     int kw_splat = VM_NO_KEYWORDS;
 
-    if (scope == CALL_PUBLIC_KW) {
+    switch(scope) {
+      case(CALL_PUBLIC_KW):
         scope = CALL_PUBLIC;
         kw_splat = 1;
+        break;
+      case(CALL_FCALL_KW):
+        scope = CALL_FCALL;
+        kw_splat = 1;
+        break;
+      default:
+        break;
     }
 
     if (scope == CALL_PUBLIC) {
@@ -861,6 +876,12 @@ rb_funcallv(VALUE recv, ID mid, int argc, const VALUE *argv)
     return rb_call(recv, mid, argc, argv, CALL_FCALL);
 }
 
+VALUE
+rb_funcallv_kw(VALUE recv, ID mid, int argc, const VALUE *argv, int kw_splat)
+{
+    return rb_call(recv, mid, argc, argv, kw_splat ? CALL_FCALL_KW : CALL_FCALL);
+}
+
 /*!
  * Calls a method.
  *