txr: bugfix: give @(call) same semantics as direct call.

The @(call) directive is buggy in the following ways, which
cause an indirect call to behave differently from a direct call.

It creates a new context, and so if the opening of a data
source is deferred into the indirectly called function, that
data source is lost when the indirect call terminates.

Furthermore, if a data source is already established, there
is no progress through the data: two consecutive @(call ...)
directives operate on the same data.

It also fails to implement vertical to horizontal fallback; if
a function is not vertically defined, the directive fails.

* match.c (v_call): Rewrite the core logic in the following
way: we rewrite the indirect @(call) syntax into direct call
syntax, substitute that into c->spec, and then just
call v_fun.

* tests/008/call-2.expected: New file.

* tests/008/call-2.txr: New file. Test fails before this commit
because both calls are matching against the same "A" element
of the list.

3 files changed, 9 insertions, 10 deletions

diff --git a/match.c b/match.c
index ef2daf9d..2b1a6f7c 100644
--- a/match.c
+++ b/match.c
@@ -4506,18 +4506,11 @@ static val v_call(match_files_ctx *c)
   val funval = tleval_144(specline, funexpr, c->bindings);
   val argexprs = cdr(exprs);
   val call = cons(funval, argexprs);
-  val spec = cons(cons(call, nil), nil);
-  match_files_ctx ctx = mf_spec_bindings(*c, spec, c->bindings);
-  val ret = v_fun(&ctx);
-
-  if (ret == nil)
-    return nil;
+  val spec = cons(cons(call, nil), cdr(c->spec));
 
-  if (ret == decline_k)
-    sem_error(nil, lit("call: function ~s not found"), funval, nao);
+  c->spec = spec;
 
-  c->bindings = ctx.bindings;
-  return ret;
+  return v_fun(c);
 }
 
 static val h_do(match_line_ctx *c)
diff --git a/tests/008/call-2.expected b/tests/008/call-2.expected
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/tests/008/call-2.expected
diff --git a/tests/008/call-2.txr b/tests/008/call-2.txr
new file mode 100644
index 00000000..10257f62
--- /dev/null
+++ b/tests/008/call-2.txr
@@ -0,0 +1,6 @@
+@(define foo (var))
+@var
+@(end)
+@(next :list '("A" "B"))
+@(call (quote foo) "A")
+@(call (quote foo) "B")