Add Either type

tests/tests.nim

@@ -4,6 +4,12 @@ import unittest
 import op
 
 suite "Basic tests":
+  proc divide(a, b: int): OP[float] =
+    if b == 0:
+      return fail "Cannot divide by zero!"
+    else:
+      return ok a / b
+
   test "Check OK":
     let test = ok 1
     check test.isOk == true
@@ -16,9 +22,9 @@ suite "Basic tests":
     proc createValue: OP[string] =
       let myString = "This is test code!"
       ok myString
-    let data = createValue()
-    check data.isOk
-    check data.val == "This is test code!"
+    let r = createValue()
+    check r.isOk
+    check r.val == "This is test code!"
 
   test "Check failing result proc":
     proc someProc(): OP[int] =
@@ -54,38 +60,53 @@ suite "Basic tests":
     check data.isOk == false
     check data.error == "data got corrupted"
 
-  test "Check divider proc":
-    proc divide(a, b: int): OP[float] =
-      if b == 0:
-        return fail(float, "Cannot divide by zero!")
-      else:
-        return ok a / b
-
-    let
-      a = 42
-      b = 0
-    let r = divide(a, b)
-    check r.isOk == false
-    check r.error == "Cannot divide by zero!"
+  test "Check divider OK":
+      let r = divide(12, 6)
+      check r.isOk == true
+      check r.val == 2
 
   test "Check implicit fail type":
-    proc divide(a, b: int): OP[float] =
-      if b == 0:
-        return fail "Cannot divide by zero!"
-      else:
-        return ok a / b
-
     let r = divide(1, 0)
     check r.isOk == false
     check r.error == "Cannot divide by zero!"
 
-  test "Check type of impolicit fail":
-      proc divide(a, b: int): OP[float] =
-        if b == 0:
-          return fail "Cannot divide by zero!"
-        else:
-          return ok a / b
+  test "Check case":
+    let r = divide(1, 2)
+    case r.isOK:
+    of true:
+      check r.val == 0.5
+    of false:
+      echo r.error
 
-      let r = divide(1, 0)
-      check r.isOk == false
-      check r.error == "Cannot divide by zero!"
+  test "Check hiding of Either":
+    let r = divide(1, 2)
+    case r.isOK:
+    of true:
+      check r.val == 0.5
+    of false:
+      echo r.error
+
+  test "Expect invalid field":
+    let r = divide(1, 2)
+    expect FieldError:
+      echo r.error
+
+  test "Expect in case":
+    let r = divide(1, 2)
+    case r.isOK:
+    of true:
+      expect FieldError:
+        echo r.error
+    of false:
+      echo r.error
+
+  # These will not work. How could this be done?
+  # test "Expect access before check":
+  #     let r = divide(1, 2)
+  #     expect FieldError:
+  #       echo r.val
+
+  # test "Expect invalid field after check":
+  #     let r = divide(1, 2)
+  #     if r.isOK:
+  #       echo r.error