result: `and` can deal with heterogenous values

stew/result.nim

@@ -266,7 +266,7 @@ func mapCast*[T0, E0](
   if self.isOk: result.ok(cast[T1](self.v))
   else: result.err(self.e)
 
-template `and`*[T, E](self, other: Result[T, E]): Result[T, E] =
+template `and`*[T0, E, T1](self: Result[T0, E], other: Result[T1, E]): Result[T1, E] =
   ## Evaluate `other` iff self.isOk, else return error
   ## fail-fast - will not evaluate other if a is an error
   ##

tests/test_result.nim

@@ -32,6 +32,9 @@ doAssert (rErr and rOk).isErr
 doAssert (rOk or rErr).isOk
 doAssert (rErr or rOk).isOk
 
+# `and` heterogenous types
+doAssert (rOk and rOk.map(proc(x: auto): auto = $x))[] == $(rOk[])
+
 # Exception on access
 let va = try: discard rOk.error; false except: true
 doAssert va, "not an error, should raise"