Change was_lvalue_sub back to X; spell out the only use of it

OK, now I understand what’s happening.

If there is a public macro (PUSHSUB) that contains a call to a pri-
vate function (was_lvalue_sub), that function has to be exported, so
that non-core code can call it.  But if it is marked X, there is no
was_lvalue_sub shorthand macro visible to non-core code, so when the
PUSHSUB macro is expanded in such code, the was_lvalue_sub(...) bit
becomes a call to the function literally named was_lvalue_sub, as
opposed to Perl_lvalue_sub (and is compiled that way on forgiving
platforms).  Making it A makes that macro available to non-core code,
but also implies that it is available for direct use by extensions,
which is not the case with was_lvalue_sub.

So, this commit makes it X again, but spells it out in PUSHSUB, so
there is no need for the function’s macro to be available when
PUSHSUB is expanded.

Hence, there is no need for the was_lvalue_sub macro to exist, so this
commit also removes it.

See also these three commits:

c73b0699db
7b70e81778
777d901444

3 files changed, 2 insertions, 3 deletions

diff --git a/cop.h b/cop.h
index d261edf13b..e6650a2400 100644
--- a/cop.h
+++ b/cop.h
@@ -640,7 +640,7 @@ struct block_format {
 	   (PL_op->op_flags & OPf_WANT)					\
 	       ? OPpENTERSUB_LVAL_MASK					\
 	       : !(PL_op->op_private & OPpENTERSUB_LVAL_MASK)		\
-	           ? 0 : was_lvalue_sub();				\
+	           ? 0 : Perl_was_lvalue_sub(aTHX);			\
 	PUSHSUB_BASE(cx)						\
 	cx->blk_u16 = PL_op->op_private &				\
 	                  (phlags|OPpENTERSUB_DEREF);			\
diff --git a/embed.fnc b/embed.fnc
index e787f10ba5..0f4424a4b0 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -544,7 +544,7 @@ p	|bool	|io_close	|NN IO* io|bool not_implicit
 pR	|OP*	|invert		|NULLOK OP* cmd
 ApR	|I32	|is_lvalue_sub
 : Used in cop.h
-ApR	|I32	|was_lvalue_sub
+XopR	|I32	|was_lvalue_sub
 ApPR	|U32	|to_uni_upper_lc|U32 c
 ApPR	|U32	|to_uni_title_lc|U32 c
 ApPR	|U32	|to_uni_lower_lc|U32 c
diff --git a/embed.h b/embed.h
index 750c0da68d..fa1a2a9045 100644
--- a/embed.h
+++ b/embed.h
@@ -680,7 +680,6 @@
 #ifndef PERL_IMPLICIT_CONTEXT
 #define warner			Perl_warner
 #endif
-#define was_lvalue_sub()	Perl_was_lvalue_sub(aTHX)
 #define whichsig(a)		Perl_whichsig(aTHX_ a)
 #if !(defined(HAS_SIGACTION) && defined(SA_SIGINFO))
 #define csighandler		Perl_csighandler