Adds failure overload that uses result to determine type

Readme.md

@@ -146,16 +146,16 @@ proc example: ?!int =
   # either return an integer or an error
 ```
 
-Assigning values is done using the `success` and `failure` procs:
+Results can be made using the `success` and `failure` procs:
 
 ```nim
 proc works: ?!seq[int] =
   # always returns a Result holding a sequence
-  @[1, 1, 2, 2, 2].success
+  success @[1, 1, 2, 2, 2]
 
 proc fails: ?!seq[int] =
-  # always returns a Result holding a ValueError
-  seq[int].failure newException(ValueError, "something went wrong")
+  # always returns a Result holding an error
+  failure "something went wrong"
 ```
 
 ### Binding, chaining, fallbacks and operators

questionable/results.nim

@@ -21,6 +21,12 @@ proc failure*(T: type, error: ref CatchableError): ?!T =
 proc failure*(T: type, message: string): ?!T =
   T.failure newException(ResultFailure, message)
 
+template failure*(error: ref CatchableError): auto =
+  err error
+
+template failure*(message: string): auto =
+  failure newException(ResultFailure, message)
+
 proc isSuccess*[T](value: ?!T): bool =
   value.isOk
 

testmodules/result/test.nim

@@ -150,13 +150,20 @@ suite "result":
     check 42.success.option == 42.some
     check int.failure(error).option == int.none
 
+  test "failure can be used without type parameter in procs":
+    proc fails: ?!int =
+      failure "some error"
+
+    check fails().isFailure
+    check fails().error.msg == "some error"
+
   test "examples from readme work":
 
     proc works: ?!seq[int] =
-      @[1, 1, 2, 2, 2].success
+      success @[1, 1, 2, 2, 2]
 
     proc fails: ?!seq[int] =
-      seq[int].failure newException(ValueError, "something went wrong")
+      failure "something went wrong"
 
     # binding:
     if x =? works():