From ca118fac3a97a6cd6b9342d301b3b06c515ad5f1 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Tue, 15 Jun 2021 07:58:43 -0700
Subject: expander: bug: atoms in quasiliteral.

Via macros, atoms can sneak into a quasiliteral which then
blow up because they get treated as strings without being
converted.

Example:

  (defmacro two () 2)

  `@(two)xyz` -> ;; error

The expansion produces the invalid form, in which the 2
is subsequently treated as a string.

  (sys:quasi 2 "xyz")

On the other hand, symbol macros don't have this problem:

  (defsymacro two 2)

  `@{two}xyz` -> "2xyz"

The reason is that the (sys:var two) syntax will expand to
(sys:var 2), and not 2.

The straightforward, consistent fix is to ensure that the
first case will also go to (sys:var 2).

* eval.c (expand_quasi): If the expanded form is an atom which
is not a bindable symbol, wrap it in a sys:var.

* tests/012/quasi.tl: Test cases added.
Also adding a compilation test for this file, cribbed from
patmatch.tl.
---
 eval.c             |  3 +++
 tests/012/quasi.tl | 15 +++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/eval.c b/eval.c
index 50d20fad..bdbec0be 100644
--- a/eval.c
+++ b/eval.c
@@ -3823,6 +3823,9 @@ val expand_quasi(val quasi_forms, val menv)
         if (comp_184)
           form_ex = expand(form, menv);
       }
+
+      if (atom(form_ex) && !bindable(form_ex))
+        form_ex = list(var_s, form_ex, nao);
     }
 
     {
diff --git a/tests/012/quasi.tl b/tests/012/quasi.tl
index 276d5395..1cb24578 100644
--- a/tests/012/quasi.tl
+++ b/tests/012/quasi.tl
@@ -36,3 +36,18 @@
     (let ((s))
       (mapcar (ret `<@{(push (inc @1) s) d}>`) (range 0 2))))
   ("<1>" "<2-1>" "<3-2-1>"))
+
+(test
+  (symacrolet ((two 2))
+    `@{two}abc`)
+  "2abc")
+
+(test
+  (macrolet ((two () 2))
+    `@(two)abc`)
+  "2abc")
+
+(compile-only
+  (eval-only
+    (compile-file (base-name *load-path*) "temp.tlo")
+    (remove-path "temp.tlo")))
-- 
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