haskell: Phase 9 — hk-run-io catches errors and appends to io-lines

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/haskell/eval.sx

@@ -1163,7 +1163,14 @@
 
 (define
   hk-run-io
-  (fn (src) (do (set! hk-io-lines (list)) (hk-run src) hk-io-lines)))
+  (fn
+    (src)
+    (do
+      (set! hk-io-lines (list))
+      (guard
+        (e (true (append! hk-io-lines (if (string? e) e (str e)))))
+        (hk-deep-force (hk-run src)))
+      hk-io-lines)))
 
 (define hk-stdin-lines (list))
 
@@ -1176,7 +1183,9 @@
     (begin
       (set! hk-io-lines (list))
       (set! hk-stdin-lines stdin-lines)
-      (hk-run src)
+      (guard
+        (e (true (append! hk-io-lines (if (string? e) e (str e)))))
+        (hk-deep-force (hk-run src)))
       hk-io-lines)))
 
 (define hk-env0 (hk-init-env))

lib/haskell/tests/io-input.sx

@@ -64,12 +64,11 @@
 
 (hk-test
   "readFile error on missing file"
-  (guard
-    (e (true (>= (index-of e "file not found") 0)))
-    (begin
-      (set! hk-vfs (dict))
-      (hk-run-io "main = readFile \"no.txt\" >>= putStrLn")
-      false))
+  (begin
+    (set! hk-vfs (dict))
+    (let
+      ((lines (hk-run-io "main = readFile \"no.txt\" >>= putStrLn")))
+      (>= (index-of (str lines) "file not found") 0)))
   true)
 
 (hk-test