hy.contrib.walk: Add (macroexpand-all)

This function will recursively perform all possible macroexpansions in
the supplied form. Unfortunately, it also traverses into quasiquoted
parts, where it shouldn't, but it is a useful estimation of macro
expansion anyway.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

hy/contrib/walk.hy

@@ -45,3 +45,11 @@
   "Performs depth-first, pre-order traversal of form. Calls f on each
   sub-form, uses f's return value in place of the original."
   (walk (partial prewalk f) identity (f form)))
+
+(defn macroexpand-all [form]
+  "Recursively performs all possible macroexpansions in form."
+  (prewalk (fn [x]
+             (if (instance? HyExpression x)
+               (macroexpand x)
+               x))
+           form))

tests/native_tests/contrib/walk.hy

@@ -22,3 +22,7 @@
     (assert (= (walk identity (partial collector acc) walk-form)
                nil))
     (assert (= acc [walk-form]))))
+
+(defn test-macroexpand-all []
+  (assert (= (macroexpand-all '(with [a b c] (for [d c] foo)))
+             '(with* [a] (with* [b] (with* [c] (do (for* [d c] foo))))))))