Reenable io tests and modify write_file function

src/fun/builtins.bend

@@ -323,10 +323,14 @@ def IO/FS/read_line.read_chunks(fd, chunks):
 # Writes a list of bytes to a file given by a path.
 def IO/FS/write_file(path, bytes):
   with IO:
-    f <- IO/done_on_err(IO/FS/open(path, "w"))
-    * <- IO/done_on_err(IO/FS/write(f, bytes))
-    * <- IO/done_on_err(IO/FS/close(f))
-    return wrap(bytes)
+    f <- IO/FS/open(path, "w")
+    match f:
+      case Result/Err:
+        return wrap(Result/Err(f.val))
+      case Result/Ok:
+        * <- IO/done_on_err(IO/FS/write(f.val, bytes))
+        * <- IO/done_on_err(IO/FS/close(f.val))
+        return wrap(Result/Ok(bytes))
 
 ### Standard input and output utilities
 

tests/golden_tests.rs

@@ -427,7 +427,6 @@ fn mutual_recursion() {
 }
 
 #[test]
-#[ignore = "while IO is not implemented for hvm32"]
 fn io() {
   run_golden_test_dir_multiple(
     function_name!(),

tests/snapshots/io__load.bend.snap

@@ -0,0 +1,6 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/io/load.bend
+---
+Strict mode:
+"Contents\n"

tests/snapshots/io__load_fail.bend.snap

@@ -0,0 +1,6 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/io/load_fail.bend
+---
+Strict mode:
+1

tests/snapshots/io__store.bend.snap

@@ -0,0 +1,6 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/io/store.bend
+---
+Strict mode:
+λa (a Result/Ok/tag [40, 77, 97, 105, 110, 41, 32, 61, 32, 48])

tests/snapshots/io__store_fail.bend.snap

@@ -0,0 +1,6 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/io/store_fail.bend
+---
+Strict mode:
+λa (a Result/Err/tag λb (b 2 +2))