expander: tree-bind: fix incorrect param env.

* eval.c (do_expand): A wrong thing is being done here:
the macro is extended using the original parameter
syntax, that has not been processed by expand_params.
The body is then expanded using that environment.
This subtly breaks support for parameter macros in tree-bind.
They work, but there are spurious warnings about undefined
variables during expansion, and the wrong scope handling
can introduce bugs. The right thing is to derive new_menv
by pulling the parameter symbols from params_ex.

1 files changed, 2 insertions, 2 deletions

diff --git a/eval.c b/eval.c
index dccf3fbd..a3b593ef 100644
--- a/eval.c
+++ b/eval.c
@@ -4673,10 +4673,10 @@ again:
       val params = pop(&args);
       val expr = pop(&args);
       val body = args;
-      val new_menv = make_var_shadowing_env(menv, get_param_syms(params));
-      val ctx_expr_ex = expand(ctx_expr, menv);
       cons_bind (params_ex, body_ex0,
                  expand_params(params, body, menv, t, form));
+      val new_menv = make_var_shadowing_env(menv, get_param_syms(params_ex));
+      val ctx_expr_ex = expand(ctx_expr, menv);
       val body_ex = expand_progn(body_ex0, new_menv);
       val expr_ex = expand(expr, new_menv);