From dd67d22b9540b3d795cc0c80f60eac4889963afc Mon Sep 17 00:00:00 2001
From: Gustavo Massaccesi <gustavo@oma.org.ar>
Date: Thu, 28 Mar 2019 22:36:01 -0300
Subject: [PATCH] cptypes: reduce (if t <error> x) ==> (begin (if t <error>
 (void)) x)

so the surrounding code can be reduced, for example

(+ 2 (if t <error> 3)) ==> (begin (if t <error> (void)) 5)

original commit: c1993e7c707b3528c6de5e1d4b36005655d22aff
---
 mats/cp0.ms    | 4 ++--
 mats/record.ms | 5 +++--
 s/cptypes.ss   | 9 +++++++--
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/mats/cp0.ms b/mats/cp0.ms
index bade6706b7..36941f4510 100644
--- a/mats/cp0.ms
+++ b/mats/cp0.ms
@@ -2873,7 +2873,7 @@
                (display "1")
                (list q n))))))
     '(lambda (v)
-       (let ([v2 (if (#2%vector? v) v (#2%error))])
+       (let ([v2 (begin (if (#2%vector? v) (#2%void) (#2%error)) v)])
          (let ([q (#2%vector-sort v2)] [n (#3%vector-length v)])
            (#2%display "1")
            (#2%list q n)))))
@@ -2886,7 +2886,7 @@
                (display "1")
                (list q n))))))
     '(lambda (v)
-       (let ([q (#2%vector-sort (if (#2%vector? v) v (#2%error)))]
+       (let ([q (#2%vector-sort (begin (if (#2%vector? v) (#2%void) (#2%error)) v))]
              [n (if v v 72)])
          (#2%display "1")
          (#2%list q n))))
diff --git a/mats/record.ms b/mats/record.ms
index 4d9726dd14..2cb281024e 100644
--- a/mats/record.ms
+++ b/mats/record.ms
@@ -8586,8 +8586,9 @@
              (if b (frob-x x) 72)))))
     `(lambda (b)
        (if b
-          (#3%$record-oops 'frob-x 'x ',record-type-descriptor?)
-           72)))
+           (#3%$record-oops 'frob-x 'x ',record-type-descriptor?)
+           (#2%void))
+       72))
   (equivalent-expansion?
     (parameterize ([optimize-level 3] [enable-cp0 #t] [#%$suppress-primitive-inlining #f])
       (expand/optimize
diff --git a/s/cptypes.ss b/s/cptypes.ss
index 9d42b73fa8..cc46bfd0de 100644
--- a/s/cptypes.ss
+++ b/s/cptypes.ss
@@ -688,10 +688,15 @@ Notes:
                         [(f-types3) (or f-types3 types3)])
             (let ([ir `(if ,e1 ,e2 ,e3)])
               (cond
-                [(predicate-implies? ret2 'bottom) ;check bottom first
+                [(and (predicate-implies? ret2 'bottom)  ;check bottom first
+                      (predicate-implies? ret3 'bottom)) ;check bottom first
                  (values ir ret3 types3 t-types3 f-types3)]
+                [(predicate-implies? ret2 'bottom) ;check bottom first
+                 (values (make-seq ctxt `(if ,e1 ,e2 ,void-rec) e3)
+                         ret3 types3 t-types3 f-types3)]
                 [(predicate-implies? ret3 'bottom) ;check bottom first
-                 (values ir ret2 types2 t-types2 f-types2)]
+                 (values (make-seq ctxt `(if ,e1 ,void-rec ,e3) e2)
+                         ret2 types2 t-types2 f-types2)]
                 [else
                  (let ([new-types (pred-env-union/super-base types2 t-types1
                                                              types3 f-types1