diff --git a/RELEASES.md b/RELEASES.md
index 744d0da021c9..71d5409966c5 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -20,6 +20,9 @@
 - Removed reflective access when loading the OpenCV library
   ([#1727](https://github.com/enso-org/enso/pull/1727)). Illegal reflective
   access operations were deprecated and will be denied in future JVM releases.
+- Overhauled the types we use for errors throughout the standard library
+  ([#1734](https://github.com/enso-org/enso/pull/1734)). They are now much more
+  informative, and should provide more clarity when things go wrong.
 
 ## Miscellaneous
 
diff --git a/distribution/std-lib/Standard/src/Base/Data/Json.enso b/distribution/std-lib/Standard/src/Base/Data/Json.enso
index aec3b98ca73b..fbb744673f32 100644
--- a/distribution/std-lib/Standard/src/Base/Data/Json.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/Json.enso
@@ -153,7 +153,8 @@ type Parse_Error message
 
    Converts the error to a display representation.
 Parse_Error.to_display_text : Text
-Parse_Error.to_display_text = "Parse error in parsing JSON: " + this.message.to_text + "."
+Parse_Error.to_display_text =
+    "Parse error in parsing JSON: " + this.message.to_text + "."
 
 ## Gets the value associated with the given key in this object.
 
@@ -169,8 +170,22 @@ Parse_Error.to_display_text = "Parse error in parsing JSON: " + this.message.to_
          import Standard.Examples
 
          example_get = Examples.json_object.get "title"
-Object.get : Text -> Json ! Nothing
-Object.get field = this.fields.get field
+Object.get : Text -> Json ! No_Such_Field_Error
+Object.get field = this.fields.get field . map_error case _ of
+    Map.No_Value_For_Key_Error _ -> No_Such_Field_Error field
+    x -> x
+
+## UNSTABLE
+
+   An error indicating that there is no such field in the JSON object.
+type No_Such_Field_Error field_name
+
+## UNSTABLE
+
+   Pretty prints the no such field error.
+No_Such_Field_Error.to_display_text : Text
+No_Such_Field_Error.to_display_text =
+    "The field " + this.field_name.to_text + " is not present in this object."
 
 ## UNSTABLE
 
@@ -267,3 +282,4 @@ Base.Boolean.to_json = Boolean this
          Nothing.to_json
 Nothing.to_json : Null
 Nothing.to_json = Null
+
diff --git a/distribution/std-lib/Standard/src/Base/Data/List.enso b/distribution/std-lib/Standard/src/Base/Data/List.enso
index 426e59e6573c..6a8f20c1cea5 100644
--- a/distribution/std-lib/Standard/src/Base/Data/List.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/List.enso
@@ -265,10 +265,10 @@ type List
              import Standard.Examples
 
              example_head = Examples.list.head
-    head : Any ! Nothing
+    head : Any ! Empty_Error
     head = case this of
         Cons a _ -> a
-        Nil -> Error.throw Nothing
+        Nil -> Error.throw Empty_Error
 
     ## Get all elements from the list except the first.
 
@@ -278,10 +278,10 @@ type List
              import Standard.Examples
 
              example_tail = Examples.list.tail
-    tail : List ! Nothing
+    tail : List ! Empty_Error
     tail = case this of
         Cons _ b -> b
-        Nil -> Error.throw Nothing
+        Nil -> Error.throw Empty_Error
 
     ## Get all elements from the list except the last.
 
@@ -291,14 +291,14 @@ type List
              import Standard.Examples
 
              example_init = Examples.list.init
-    init : List ! Nothing
+    init : List ! Empty_Error
     init =
         init' x y = case y of
             Nil -> Nil
             Cons a b -> Cons x (init' a b)
         case this of
             Cons a b -> init' a b
-            Nil -> Error.throw Nothing
+            Nil -> Error.throw Empty_Error
 
     ## Get the last element of the list.
 
@@ -308,9 +308,9 @@ type List
              import Standard.Examples
 
              example_last = Examples.list.last
-    last : Any | Nothing
+    last : Any ! Empty_Error
     last = case this.fold Nothing (_ -> r -> r) of
-        Nothing -> Error.throw Nothing
+        Nothing -> Error.throw Empty_Error
         a -> a
 
     ## Get the first element from the list.
@@ -321,7 +321,7 @@ type List
              import Standard.Examples
 
              example_first = Examples.list.first
-    first : Any ! Nothing
+    first : Any ! Empty_Error
     first = this.head
 
     ## Get all elements from the list except the first.
@@ -332,9 +332,20 @@ type List
              import Standard.Examples
 
              example_rest = Examples.list.rest
-    rest : List ! Nothing
+    rest : List ! Empty_Error
     rest = this.tail
 
+## UNSTABLE
+
+   An error representing that the list is empty.
+type Empty_Error
+
+## UNSTABLE
+
+   Pretty prints the empty error.
+Empty_Error.to_display_text : Text
+Empty_Error.to_display_text = "The List is empty."
+
 ## PRIVATE
    A helper for the `map` function.
 
@@ -346,6 +357,7 @@ type List
    Uses unsafe field mutation under the hood, to rewrite `map` in
    a tail-recursive manner. The mutation is purely internal and does not leak
    to the user-facing API.
+map_helper : List -> Any -> (Any -> Any) -> Nothing
 map_helper list cons f = case list of
     Cons h t ->
         res = Cons (f h) Nil
diff --git a/distribution/std-lib/Standard/src/Base/Data/Map.enso b/distribution/std-lib/Standard/src/Base/Data/Map.enso
index 7d72d97b5755..4314408983f6 100644
--- a/distribution/std-lib/Standard/src/Base/Data/Map.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/Map.enso
@@ -39,7 +39,7 @@ singleton key value = Bin 1 key value Tip Tip
          import Standard.Base.Data.Map.Internal
 
          example_from_vector = Map.from_vector [[1, 2], [3, 4]]
-from_vector : Vector.Vector -> Map
+from_vector : Vector.Vector Any -> Map
 from_vector vec = vec.fold Map.empty (m -> el -> m.insert (el.at 0) (el.at 1))
 
 ## A key-value store. This type assumes all keys are pairwise comparable,
@@ -114,7 +114,7 @@ type Map
              import Standard.Examples
 
              example_to_vector = Examples.map.to_vector
-    to_vector : Vector.Vector
+    to_vector : Vector.Vector Any
     to_vector =
         builder = Vector.new_builder
         to_vector_with_builder m = case m of
@@ -177,8 +177,8 @@ type Map
     insert : Any -> Any -> Map
     insert key value = Internal.insert this key value
 
-    ## Gets the value associated with `key` in this map, or throws a `Nothing`,
-       if `key` is not present.
+    ## Gets the value associated with `key` in this map, or throws a
+       `No_Value_For_Key_Error` if `key` is not present.
 
        Arguments:
        - key: The key to look up in the map.
@@ -190,10 +190,10 @@ type Map
              import Standard.Examples
 
              example_get = Examples.map.get 1
-    get : Any -> Any ! Nothing
+    get : Any -> Any ! No_Value_For_Key_Error
     get key =
         go map = case map of
-            Tip -> Error.throw Nothing
+            Tip -> Error.throw (No_Value_For_Key_Error key)
             Bin _ k v l r ->
                 if k == key then v else
                     if k > key then @Tail_Call go l else @Tail_Call go r
@@ -446,5 +446,12 @@ type Map
 
    Arguments:
    - key: The key that was asked for.
-type No_Value_For_Key key
+type No_Value_For_Key_Error key
+
+## UNSTABLE
+
+   Converts the error into a human-readable representation.
+No_Value_For_Key_Error.to_display_text : Text
+No_Value_For_Key_Error.to_display_text =
+    "The map contained no value for the key " + this.key.to_text + "."
 
diff --git a/distribution/std-lib/Standard/src/Base/Data/Number/Extensions.enso b/distribution/std-lib/Standard/src/Base/Data/Number/Extensions.enso
index ccb5717c314a..63834435460b 100644
--- a/distribution/std-lib/Standard/src/Base/Data/Number/Extensions.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/Number/Extensions.enso
@@ -1,4 +1,4 @@
-from Standard.Base import all
+from Standard.Base import all hiding Parse_Error
 
 polyglot java import java.lang.Double
 polyglot java import java.lang.Math
@@ -231,7 +231,7 @@ Number.to_json : Json.Number
 Number.to_json = Json.Number this
 
 ## Parses a textual representation of a decimal into a decimal number, returning
-   `Nothing` if the text does not represent a valid decimal.
+   a `Parse_Error` if the text does not represent a valid decimal.
 
    Arguments:
    - text: The text to parse into a decimal.
@@ -240,7 +240,20 @@ Number.to_json = Json.Number this
      Parse the text "7.6" into a decimal number.
 
          Decimal.parse 7.6
-Decimal.parse : Text -> Decimal ! Nothing
+Decimal.parse : Text -> Decimal ! Parse_Error
 Decimal.parse text =
-    Panic.recover (Double.parseDouble text) . catch (_ -> Error.throw Nothing)
+    Panic.recover (Double.parseDouble text) . catch _->
+        Error.throw (Parse_Error text)
+
+## UNSTABLE
+
+   A syntax error when parsing a double.
+type Parse_Error text
+
+## UNSTABLE
+
+   Pretty print the syntax error.
+Parse_Error.to_display_text : Text
+Parse_Error.to_display_text =
+    "Could not parse " + this.text.to_text + " as a double."
 
diff --git a/distribution/std-lib/Standard/src/Base/Data/Time.enso b/distribution/std-lib/Standard/src/Base/Data/Time.enso
index e1d46619aa53..88c961dcdd6c 100644
--- a/distribution/std-lib/Standard/src/Base/Data/Time.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/Time.enso
@@ -442,7 +442,8 @@ type Time
              example_format =
                 Time.parse "2020-10-08T16:41:13+03:00[Europe/Moscow]" . format "EEE MMM d (HH:mm)"
     format : Text -> Text
-    format pattern = DateTimeFormatter.ofPattern pattern . format this.internal_zoned_date_time
+    format pattern =
+        DateTimeFormatter.ofPattern pattern . format this.internal_zoned_date_time
 
 type Time_Error
 
diff --git a/distribution/std-lib/Standard/src/Base/Data/Time/Duration.enso b/distribution/std-lib/Standard/src/Base/Data/Time/Duration.enso
index 3e0e080b0360..e9fd8cade267 100644
--- a/distribution/std-lib/Standard/src/Base/Data/Time/Duration.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/Time/Duration.enso
@@ -20,7 +20,11 @@ polyglot java import java.time.Period as Java_Period
          example_between = Duration.between Time.now (Time.new 2010 10 20)
 between : Time -> Time -> Duration
 between start_inclusive end_exclusive =
-   Duration (Java_Period.ofDays 0 . normalized) (Java_Duration.between start_inclusive.internal_zoned_date_time end_exclusive.internal_zoned_date_time)
+    period = Java_Period.ofDays 0 . normalized
+    start = start_inclusive.internal_zoned_date_time
+    end = end_exclusive.internal_zoned_date_time
+    duration = Java_Duration.between start end
+    Duration period duration
 
 type Duration
 
@@ -52,7 +56,10 @@ type Duration
 
              example_add = 1.month + 12.hours
     + : Duration -> Duration
-    + that = Duration (this.internal_period . plus that.internal_period . normalized) (this.internal_duration . plus that.internal_duration)
+    + that =
+        period = this.internal_period . plus that.internal_period . normalized
+        duration = this.internal_duration . plus that.internal_duration
+        Duration period duration
 
     ## Subtract the specified amount of time from this duration.
 
@@ -73,7 +80,10 @@ type Duration
 
              example_subtract = 7.months - 30.minutes
     - : Duration -> Duration
-    - that = Duration (this.internal_period . minus that.internal_period . normalized) (this.internal_duration . minus that.internal_duration)
+    - that =
+        period = this.internal_period . minus that.internal_period . normalized
+        duration = this.internal_duration . minus that.internal_duration
+        Duration period duration
 
     ## Get the portion of the duration expressed in nanoseconds.
 
@@ -167,13 +177,16 @@ type Duration
        seconds and nanosecnods.
 
        > Example
-         Convert duration of a year and a hour to a vector returning `[1, 0, 0, 1, 0, 0, 0]`.
+         Convert duration of a year and a hour to a vector returning
+         `[1, 0, 0, 1, 0, 0, 0]`.
+
              import Standard.Base.Data.Time.Duration
 
              example_to_vec = (1.year + 1.hour).to_vector
 
        > Example
-         Convert duration of 800 nanoseconds to a vector returning `[0, 0, 0, 0, 0, 0, 800]`
+         Convert duration of 800 nanoseconds to a vector returning
+         `[0, 0, 0, 0, 0, 0, 800]`
 
              import Standard.Base.Data.Time.Duration
 
diff --git a/distribution/std-lib/Standard/src/Base/Data/Time/Time_Of_Day.enso b/distribution/std-lib/Standard/src/Base/Data/Time/Time_Of_Day.enso
index c8f9d4f6f31b..e83ecccdaf3f 100644
--- a/distribution/std-lib/Standard/src/Base/Data/Time/Time_Of_Day.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/Time/Time_Of_Day.enso
@@ -113,7 +113,7 @@ new (hour = 0) (minute = 0) (second = 0) (nanosecond = 0) =
          import Standard.Base.Data.Time.Time_Of_Day
 
          example_parse = Time_Of_Day.parse "4:30AM" "h:mma"
-parse : Text -> Text ! Nothing -> Locale -> Time_Of_Day ! Time.Time_Error
+parse : Text -> Text | Nothing -> Locale -> Time_Of_Day ! Time.Time_Error
 parse text pattern=Nothing locale=Locale.default =
     result = Panic.recover <| case pattern of
         Nothing -> LocalTime.parse text
diff --git a/distribution/std-lib/Standard/src/Base/Data/Vector.enso b/distribution/std-lib/Standard/src/Base/Data/Vector.enso
index 0ad124928aa3..263746134635 100644
--- a/distribution/std-lib/Standard/src/Base/Data/Vector.enso
+++ b/distribution/std-lib/Standard/src/Base/Data/Vector.enso
@@ -20,7 +20,7 @@ from Builtins import Array
      Create a copy of the given vector (`my_vec`).
 
          Vector.new my_vec.length (ix -> my_vec.at ix)
-new : Number -> (Number -> Any) -> Vector
+new : Number -> (Number -> Any) -> Vector Any
 new length constructor =
     arr = Array.new length
     0.up_to length . each ix-> arr.set_at ix (constructor ix)
@@ -40,7 +40,7 @@ new length constructor =
      Create a vector containing 50 elements, each being the number `42`.
 
          Vector.fill length=50 item=42
-fill : Number -> Any -> Vector
+fill : Number -> Any -> Vector Any
 fill length ~item =
     arr = Array.new length
     0.up_to length . each ix-> arr.set_at ix item
@@ -87,7 +87,7 @@ new_builder = Builder.new
 
      If this didn't happen then it would be possible for the underlying array to
      be mutated under the hood, and sneak mutability into our immutable data.
-from_array : Any -> Vector.Vector
+from_array : Any -> Vector.Vector Any
 from_array arr = here.new (Polyglot.get_array_size arr) (arr.at _)
 
 ## The basic, immutable, vector type.
@@ -161,17 +161,17 @@ type Vector
        Arguments:
        - function: A binary operation that takes two items and combines them.
 
-       If the vector is empty, it throws Nothing.
+       If the vector is empty, it throws an `Empty_Error`.
 
        > Example
          Compute the sum of all the elements in a vector.
 
              [0, 1, 2] . reduce (+)
-    reduce : (Any -> Any -> Any) -> Any ! Nothing
+    reduce : (Any -> Any -> Any) -> Any ! Empty_Error
     reduce function =
         case this.not_empty of
             True -> this.tail.fold this.head function
-            False -> Error.throw Nothing
+            False -> Error.throw Empty_Error
 
     ## Computes the sum of the values in the vector.
 
@@ -182,12 +182,12 @@ type Vector
          Compute the sum of all fo the elements in a vector.
 
              [0, 1, 2].sum
-    sum : (Any ! Nothing)
+    sum : Any ! (Empty_Error | No_Such_Method_Error)
     sum =
         result = Panic.recover <| this.reduce (+)
         result.map_error x->case x of
-            No_Such_Method_Error _ _ -> Nothing
-            Nothing -> Nothing
+            No_Such_Method_Error _ _ -> x
+            Empty_Error -> x
             _ -> Panic.throw x
 
     ## Checks whether a predicate holds for at least one element of this vector.
@@ -299,7 +299,7 @@ type Vector
          Selecting all elements that are greater than 3.
 
              [1, 2, 3, 4, 5].filter (> 3)
-    filter : (Any -> Boolean) -> Vector
+    filter : (Any -> Boolean) -> Vector Any
     filter predicate =
         check acc ix = if predicate ix then acc + [ix] else acc
         this.fold [] check
@@ -315,7 +315,7 @@ type Vector
          Add 1 to each element of the vector.
 
              [1, 2, 3] . map +1
-    map : (Any -> Any) -> Vector
+    map : (Any -> Any) -> Vector Any
     map function =
         here.new this.length i-> function (this.at i)
 
@@ -330,7 +330,7 @@ type Vector
          Replace each number `n` in the vector with itself repeated n times.
 
             [0, 1, 2] . flat_map (n -> Vector.fill n n)
-    flat_map : (Any -> Vector) -> Vector
+    flat_map : (Any -> Vector Any) -> Vector Any
     flat_map function =
         mapped = this.map function
         length = mapped.fold 0 acc-> elem-> acc + elem.length
@@ -354,7 +354,7 @@ type Vector
          Sum numbers with their indices in a vector.
 
              [1, 2, 3].map_with_index (+)
-    map_with_index : (Integer -> Any -> Any) -> Vector
+    map_with_index : (Integer -> Any -> Any) -> Vector Any
     map_with_index function = here.new this.length i-> function i (this.at i)
 
     ## Applies a function to each element of the vector.
@@ -381,7 +381,7 @@ type Vector
          Reverse a two-element vector.
 
              [1, 2].reverse
-    reverse : Vector
+    reverse : Vector Any
     reverse = here.new this.length (i -> this.at (this.length - (1 + i)))
 
     ## Generates a human-readable text representation of the vector.
@@ -425,7 +425,7 @@ type Vector
          Concatenate two single-element vectors.
 
              [1] + [2]
-    + : Vector -> Vector
+    + : Vector Any -> Vector Any
     + that =
         this_len = this.length
         arr = Array.new (this_len + that.length)
@@ -444,7 +444,7 @@ type Vector
          Add 1 to the start of the vector.
 
              [2, 3].prepend 1
-    prepend : Any -> Vector
+    prepend : Any -> Vector Any
     prepend element = [element] + this
 
     ## Add `element` to the end of `this` vector.
@@ -456,7 +456,7 @@ type Vector
          Add 3 to the end of the vector.
 
              [1, 2].append 3
-    append : Any -> Vector
+    append : Any -> Vector Any
     append element = this + [element]
 
     ## When `this` is a vector of text values, concatenates all the values by
@@ -484,7 +484,7 @@ type Vector
          Remove the first element from the start of the vector.
 
              [1, 2, 3, 4, 5].drop_start 1
-    drop_start : Integer -> Vector
+    drop_start : Integer -> Vector Any
     drop_start count = if count >= this.length then here.new 0 (x -> x) else
         here.new (this.length - count) (i -> this.at i+count)
 
@@ -497,7 +497,7 @@ type Vector
          Remove the last two elements from the end of the vector.
 
              [1, 2, 3, 4, 5].drop_end 2
-    drop_end : Integer -> Vector
+    drop_end : Integer -> Vector Any
     drop_end count = if count >= this.length then here.new 0 (x -> x) else
         this.take_start (this.length - count)
 
@@ -511,7 +511,7 @@ type Vector
          Create a new vector from the first two elements of the vector.
 
              [1, 2, 3, 4, 5].take_start 2
-    take_start : Integer -> Vector
+    take_start : Integer -> Vector Any
     take_start count = if count >= this.length then this else
         here.new count this.at
 
@@ -525,7 +525,7 @@ type Vector
          Create a new vector from the last two elements of the vector.
 
              [1, 2, 3, 4, 5].take_end 3
-    take_end : Integer -> Vector
+    take_end : Integer -> Vector Any
     take_end count = if count >= this.length then this else
         this.drop_start (this.length - count)
 
@@ -550,7 +550,7 @@ type Vector
          of both elements.
 
              [1, 2, 3].zip [4, 5, 6] == [[1, 4], [2, 5], [3, 6]]
-    zip : Vector -> (Any -> Any -> Any) -> Vector
+    zip : Vector Any -> (Any -> Any -> Any) -> Vector Any
     zip that function=[_,_] =
         len = Math.min this.length that.length
         here.new len i-> function (this.at i) (that.at i)
@@ -574,7 +574,7 @@ type Vector
          Extending vector to the length of 5 returns `[1, 2, 3, 4, 5]`
 
              [1, 2, 3, 4, 5].pad 5 0
-    pad : Integer -> Any -> Vector
+    pad : Integer -> Any -> Vector Any
     pad n elem =
         if this.length >= n then this else
             this + (here.fill n-this.length elem)
@@ -588,15 +588,15 @@ type Vector
     to_json : Json.Array
     to_json = Json.Array (this.map .to_json)
 
-    ## Get the first element from the vector, or an error `Nothing` if the
-       vector is empty.
+    ## Get the first element from the vector, or an `Empty_Error` if the vector
+       is empty.
 
        > Example
          The following code returns 1.
 
              [1, 2, 3, 4].head
-    head : Any ! Nothing
-    head = if this.length >= 1 then this.at 0 else Error.throw Nothing
+    head : Any ! Empty_Error
+    head = if this.length >= 1 then this.at 0 else Error.throw Empty_Error
 
     ## Get all elements in the vector except the first.
 
@@ -604,8 +604,9 @@ type Vector
          The following code returns [2, 3, 4].
 
              [1, 2, 3, 4].tail
-    tail : Vector ! Nothing
-    tail = if this.length >= 1 then this.drop_start 1 else Error.throw Nothing
+    tail : Vector ! Empty_Error
+    tail = if this.length >= 1 then this.drop_start 1 else
+        Error.throw Empty_Error
 
     ## Get the all elements in the vector except the last.
 
@@ -613,30 +614,31 @@ type Vector
          The following code returns [1, 2, 3].
 
              [1, 2, 3, 4].init
-    init : Vector ! Nothing
-    init = if this.length >= 1 then this.drop_end 1 else Error.throw Nothing
+    init : Vector ! Empty_Error
+    init = if this.length >= 1 then this.drop_end 1 else Error.throw Empty_Error
 
-    ## Get the last element of the vector, or an error `Nothing` if the vector
-       is empty.
+    ## Get the last element of the vector, or an `Empty_Error` if the vector is
+       empty.
 
        > Example
          The following code returns 4.
 
              [1, 2, 3, 4].last
-    last : Vector ! Nothing
-    last = if this.length >= 1 then (this.take_end 1).at 0 else Error.throw Nothing
+    last : Vector ! Empty_Error
+    last = if this.length >= 1 then (this.take_end 1).at 0 else
+        Error.throw Empty_Error
 
-    ## Get the first element from the vector, or an error `Nothing` if the
-       vector is empty.
+    ## Get the first element from the vector, or an `Empty_Error` if the vector
+       is empty.
 
        > Example
          The following code returns 1.
 
              [1, 2, 3, 4].first
-    first : Vector ! Nothing
+    first : Vector ! Empty_Error
     first = this.head
 
-    ## Get the second element from the vector, or an error `Nothing` if the
+    ## Get the second element from the vector, or a `Singleton_Error` if the
        vector doesn't have a second element.
 
        Useful when tuples are implemented as vectors.
@@ -645,20 +647,16 @@ type Vector
          The following code returns 2.
 
              [1, 2, 3, 4].second
-    second : Vector ! Nothing
-    second = if this.length >= 2 then this.at 1 else Error.throw Nothing
+    second : Vector ! Singleton_Error
+    second = if this.length >= 2 then this.at 1 else
+        Error.throw (Singleton_Error this)
 
     ## Get all elements in the vector except the first.
 
        > Example
          The following code returns [2, 3, 4].
              [1, 2, 3, 4].rest
-
-       > Example
-         Empty vectors return `Nothing`.
-
-             [].rest == Nothing
-    rest : Vector ! Nothing
+    rest : Vector ! Empty_Error
     rest = this.tail
 
     ## Sort the Vector.
@@ -702,7 +700,7 @@ type Vector
          Sorting a vector of `Pair`s on the first element, descending.
 
              [Pair 1 2, Pair -1 8].sort (_.first) (order = Sort_Order.Descending)
-    sort : (Any -> Any) -> (Any -> Any -> Ordering) -> Sort_Order -> Vector
+    sort : (Any -> Any) -> (Any -> Any -> Ordering) -> Sort_Order -> Vector Any
     sort (on = x -> x) (by = (_.compare_to _)) (order = Sort_Order.Ascending) =
         ## Prepare the destination array that will underlie the vector. We do
            not want to sort in place on the original vector, as `sort` is not
@@ -715,7 +713,8 @@ type Vector
            does both.
         comp_ascending l r  = by (on l) (on r)
         comp_descending l r = by (on r) (on l)
-        compare = if order == Sort_Order.Ascending then comp_ascending else comp_descending
+        compare = if order == Sort_Order.Ascending then comp_ascending else
+            comp_descending
 
         new_vec_arr.sort compare
 
@@ -731,6 +730,7 @@ type Vector
         json.to_text
 
 type Builder
+
     ## PRIVATE
 
        A builder type for Enso vectors.
@@ -814,7 +814,7 @@ type Builder
                 bldr.append 10
                 bldr.append 100
                 bldr.to_vector
-    to_vector : Vector
+    to_vector : Vector Any
     to_vector =
         old_array = this.to_array
         new_array = Array.new this.length
@@ -839,3 +839,29 @@ Index_Out_Of_Bounds_Error.to_display_text : Text
 Index_Out_Of_Bounds_Error.to_display_text =
     "The index " + this.index.to_text + " is out of bounds in a vector with length " + this.length.to_text + "."
 
+## UNSTABLE
+
+   An error that indicates that the vector is empty.
+type Empty_Error
+
+## UNSTABLE
+
+   Pretty prints the empty error.
+Empty_Error.to_display_text : Text
+Empty_Error.to_display_text = "The vector is empty."
+
+## UNSTABLE
+
+   An error that indicates that the vector only has one element.
+
+   Arguments:
+   - vec: The vector that only has one element.
+type Singleton_Error vec
+
+## UNSTABLE
+
+   Pretty prints the singleton error.
+Singleton_Error.to_display_text : Text
+Singleton_Error.to_display_text =
+    "The vector " + this.vec.to_text  + " has only one element."
+
diff --git a/distribution/std-lib/Standard/src/Base/System/File.enso b/distribution/std-lib/Standard/src/Base/System/File.enso
index f40cd7004c03..6efe3a213467 100644
--- a/distribution/std-lib/Standard/src/Base/System/File.enso
+++ b/distribution/std-lib/Standard/src/Base/System/File.enso
@@ -12,7 +12,8 @@ polyglot java import java.nio.file.NoSuchFileException
 ## Creates a new file object, pointing to the given path.
 
    Arguments:
-   - path: The path to the file that you want to create.
+   - path: The path to the file that you want to create, or a file itself. The
+     latter is a no-op.
 
    > Example
      Create a new file pointing to the `data.csv` file in the project directory.
@@ -21,8 +22,10 @@ polyglot java import java.nio.file.NoSuchFileException
          import Standard.Examples
 
          example_new = File.new Examples.csv_path
-new : Text -> File
-new path = File (Prim_Io.get_file path)
+new : (Text | File) -> File
+new path = case path of
+    Text -> File (Prim_Io.get_file path)
+    _ -> path
 
 ## Open and read the file at the provided `path`.
 
diff --git a/distribution/std-lib/Standard/src/Table.enso b/distribution/std-lib/Standard/src/Table.enso
index 36145c0b3cfd..619d3bee3270 100644
--- a/distribution/std-lib/Standard/src/Table.enso
+++ b/distribution/std-lib/Standard/src/Table.enso
@@ -34,8 +34,7 @@ from Standard.Table.Data.Order_Rule export Order_Rule
      - Nested properties are not supported and not included in the resulting
        dataframe.
 
-   > Example
-     Converts a JSON array containing key-value pairs into a table for the
+   > Example Converts a JSON array containing key-value pairs into a table for the
      provided headers.
 
          import Standard.Examples
@@ -86,9 +85,9 @@ Json.Array.to_table fields = case this of
          example_to_table =
              json = Examples.geo_json
              json.to_table
-Json.Object.to_table : Vector -> Table ! Nothing
+Json.Object.to_table : Vector -> Table ! Invalid_Format_Error
 Json.Object.to_table fields=Nothing =
-    if this.get_type != Geo_Json.Feature_Collection.to_text then Error.throw Nothing else
+    if this.get_type != Geo_Json.Feature_Collection.to_text then Error.throw (Invalid_Format_Error this "not being a feature collection") else
         case this.get "features" of
             Json.Array items ->
                 feature_rows = items.map .get_feature_row
@@ -105,5 +104,17 @@ Json.Object.to_table fields=Nothing =
                     [n, rows.map (_.at i)]
                 Table.new cols
 
-            _ -> Error.throw Nothing
+            _ -> Error.throw (Invalid_Format_Error this "not having the 'features' key.")
+
+## UNSTABLE
+
+   An error representing an invalid format for conversion.
+type Invalid_Format_Error input message
+
+## UNSTABLE
+
+   Provides a human-readable representation of the Invalid_Format_Error.
+Invalid_Format_Error.to_display_text : Text
+Invalid_Format_Error.to_display_text =
+    "The input " + this.input.to_text + " had an invalid format due to: " + this.message.to_text + "."
 
diff --git a/distribution/std-lib/Standard/src/Table/Data/Column.enso b/distribution/std-lib/Standard/src/Table/Data/Column.enso
index 0f020199f2c2..df6d0022391c 100644
--- a/distribution/std-lib/Standard/src/Table/Data/Column.enso
+++ b/distribution/std-lib/Standard/src/Table/Data/Column.enso
@@ -956,7 +956,7 @@ type Column
        Returns the first element in the column, if it exists.
 
        If the column is empty, this method will return a dataflow error
-       containing `Nothing`.
+       containing an `Empty_Error`.
 
        > Example
          Get the first element of a column.
@@ -964,15 +964,15 @@ type Column
              import Standard.Examples
 
              example_first = Examples.integer_column.first
-    first : Any ! Nothing
-    first = this.at 0 . catch (_ -> Error.throw Nothing)
+    first : Any ! Empty_Error
+    first = this.at 0 . catch (_ -> Error.throw Empty_Error)
 
     ## UNSTABLE
 
        Returns the first element in the column, if it exists.
 
        If the column is empty, this method will return a dataflow error
-       containing `Nothing`.
+       containing an `Empty_Error`.
 
        > Example
          Get the first element of a column.
@@ -980,7 +980,7 @@ type Column
              import Standard.Examples
 
              example_head = Examples.integer_column.head
-    head : Any ! Nothing
+    head : Any ! Empty_Error
     head = this.first
 
     ## UNSTABLE
@@ -988,7 +988,7 @@ type Column
        Returns the last element in the column, if it exists.
 
        If the column is empty, this method will return a dataflow error
-       containing `Nothing`.
+       containing an `Empty_Error`.
 
        > Example
          Get the last element of a column.
@@ -996,8 +996,8 @@ type Column
              import Standard.Examples
 
              example_last = Examples.integer_column.last
-    last : Any ! Nothing
-    last = this.at (this.length - 1) . catch (_ -> Error.throw Nothing)
+    last : Any ! Empty_Error
+    last = this.at (this.length - 1) . catch (_ -> Error.throw Empty_Error)
 
     ## UNSTABLE
 
@@ -1187,6 +1187,17 @@ Index_Out_Of_Bounds_Error.to_display_text =
     len_text = this.length.to_text
     "The index " + ix_text + " is out of bounds in a column of length " + len_text + "."
 
+## UNSTABLE
+
+   An error for when the column contains no elements.
+type Empty_Error
+
+## UNSTABLE
+
+   Pretty prints the error.
+Empty_Error.to_display_text : Text
+Empty_Error.to_display_text = "The column is empty."
+
 ## PRIVATE
 
    Executes a vectorized binary operation over the provided column.
diff --git a/distribution/std-lib/Standard/src/Table/Data/Table.enso b/distribution/std-lib/Standard/src/Table/Data/Table.enso
index 3c4c78e1680b..6f43c438d734 100644
--- a/distribution/std-lib/Standard/src/Table/Data/Table.enso
+++ b/distribution/std-lib/Standard/src/Table/Data/Table.enso
@@ -623,7 +623,7 @@ type Table
        Returns the first row in the table, if it exists.
 
        If the table is empty, this method will return a dataflow error
-       containing `Nothing`.
+       containing an `Empty_Error`.
 
        > Example
          Get the first row from the table.
@@ -631,17 +631,17 @@ type Table
              import Standard.Examples
 
              example_first = Examples.inventory_table.first
-    first : Table ! Nothing
+    first : Table ! Empty_Error
     first =
         table = this.take_start 1
-        if table.row_count != 1 then Error.throw Nothing else table
+        if table.row_count != 1 then Error.throw Empty_Error else table
 
     ## UNSTABLE
 
        Returns the first row in the table, if it exists.
 
        If the table is empty, this method will return a dataflow error
-       containing `Nothing`.
+       containing an `Empty_Error`.
 
        > Example
          Get the first row from the table.
@@ -649,7 +649,7 @@ type Table
              import Standard.Examples
 
              example_head = Examples.inventory_table.head
-    head : Table ! Nothing
+    head : Table ! Empty_Error
     head = this.first
 
     ## UNSTABLE
@@ -657,7 +657,7 @@ type Table
        Returns the last row in the table, if it exists.
 
        If the table is empty, this method will return a dataflow error
-       containing `Nothing`.
+       containing an `Empty_Error`.
 
        > Example
          Get the last row from the table.
@@ -665,10 +665,10 @@ type Table
              import Standard.Examples
 
              example_last = Examples.inventory_table.last
-    last : Table ! Nothing
+    last : Table ! Empty_Error
     last =
         table = this.take_end 1
-        if table.row_count != 1 then Error.throw Nothing else table
+        if table.row_count != 1 then Error.throw Empty_Error else table
 
     ## UNSTABLE
 
@@ -743,9 +743,9 @@ type Aggregate_Table
              import Standard.Examples
 
              example_at = Examples.aggregate_table.at "transaction_id"
-    at : Text -> Column ! Nothing
+    at : Text -> Column ! No_Such_Column_Error
     at name = case this.java_table.getColumnByName name of
-        Nothing -> Error.throw Nothing
+        Nothing -> Error.throw (No_Such_Column_Error name)
         c -> Column.Aggregate_Column c
 
     ## Prints an ASCII-art table with this data to the standard output.
@@ -788,6 +788,17 @@ type No_Index_Set_Error
 No_Index_Set_Error.to_display_text : Text
 No_Index_Set_Error.to_display_text = "The table does not have an index set."
 
+## UNSTABLE
+
+   An error returned when the table contains no rows.
+type Empty_Error
+
+## UNSTABLE
+
+   Pretty prints the error.
+Empty_Error.to_display_text : Text
+Empty_Error.to_display_text = "The table is empty."
+
 ## PRIVATE
 from_columns cols = Table (Java_Table.new cols.to_array)
 
diff --git a/distribution/std-lib/Standard/src/Visualization/Scatter_Plot.enso b/distribution/std-lib/Standard/src/Visualization/Scatter_Plot.enso
index 113161599ba2..f62d994ef8b7 100644
--- a/distribution/std-lib/Standard/src/Visualization/Scatter_Plot.enso
+++ b/distribution/std-lib/Standard/src/Visualization/Scatter_Plot.enso
@@ -67,7 +67,7 @@ type PointData
     name = this.to_text.to_lower_case
 
     ## PRIVATE
-    fallback_column : Table -> Column ! Nothing
+    fallback_column : Table -> Column ! No_Fallback_Column
     fallback_column table = case this of
         X -> table.index.catch_ <| this.iota table.row_count
         Y ->
@@ -77,7 +77,7 @@ type PointData
             is_good c = is_good_enough c && (this.is_recognized c).not
 
             candidates.find is_good . catch_ <| candidates.find is_good_enough
-        _ -> Error.throw Nothing
+        _ -> Error.throw No_Fallback_Column
 
     ## PRIVATE
 
@@ -93,6 +93,14 @@ type PointData
         named = table.lookup_ignore_case this.name
         named.catch_ <| this.fallback_column table
 
+## PRIVATE
+type No_Fallback_Column
+
+## PRIVATE
+No_Fallback_Column.to_display_text : Text
+No_Fallback_Column.to_display_text =
+    "No fallback column found for the scatter plot."
+
 ## PRIVATE
 
    Generates JSON that describes points data.
diff --git a/test/Table_Tests/src/Column_Spec.enso b/test/Table_Tests/src/Column_Spec.enso
index 174d6743a708..99b720538ab1 100644
--- a/test/Table_Tests/src/Column_Spec.enso
+++ b/test/Table_Tests/src/Column_Spec.enso
@@ -34,12 +34,12 @@ spec = Test.group "Columns" <|
     Test.specify "should be able to get the first / head element" <|
         test_column.first . should_equal 1
         test_column.head . should_equal 1
-        empty_column.first.should_fail_with Nothing
-        empty_column.head.should_fail_with Nothing
+        empty_column.first.should_fail_with Column.Empty_Error
+        empty_column.head.should_fail_with Column.Empty_Error
 
     Test.specify "should be able to get the last element" <|
         test_column.last . should_equal 6
-        empty_column.last.should_fail_with Nothing
+        empty_column.last.should_fail_with Column.Empty_Error
 
     Test.specify "should be able to be reversed" <|
         expected_1 = Column.from_vector "Test" [6, 4, 2, 5, 3, 1]
diff --git a/test/Table_Tests/src/Table_Spec.enso b/test/Table_Tests/src/Table_Spec.enso
index 8baf3fd28f82..aced2c4fa69b 100644
--- a/test/Table_Tests/src/Table_Spec.enso
+++ b/test/Table_Tests/src/Table_Spec.enso
@@ -1,6 +1,8 @@
 from Standard.Base import all
 from Standard.Table import all
 
+from Standard.Table.Data.Table as Table_Internal import Empty_Error
+
 import Standard.Table.Data.Storage
 import Standard.Test
 
@@ -16,6 +18,7 @@ My.frobnicate = case this of
     My x1 y1 -> My y1 x1
 
 spec =
+
     Test.group "JSON serialization" <|
         Test.specify "should serialize all column types to correct JSON" <|
             c_1 = [1, 2, 3, Nothing]
@@ -572,7 +575,7 @@ spec =
             empty_col = ['col_1', []]
             empty_table = Table.new [empty_ix, empty_col] . set_index 'ix'
 
-            empty_table.first.should_fail_with Nothing
+            empty_table.first.should_fail_with Empty_Error
 
         Test.specify "should allow getting the last row" <|
             i_1 = ['ix', [1, 2, 3]]
@@ -597,7 +600,7 @@ spec =
             empty_col = ['col_1', []]
             empty_table = Table.new [empty_ix, empty_col] . set_index 'ix'
 
-            empty_table.last.should_fail_with Nothing
+            empty_table.last.should_fail_with Empty_Error
 
         Test.specify "should allow reversing the table" <|
             i_1 = ['ix', [1, 2, 3]]
diff --git a/test/Tests/src/Data/Json_Spec.enso b/test/Tests/src/Data/Json_Spec.enso
index 1fca1a4dbb15..b0f995ef59d1 100644
--- a/test/Tests/src/Data/Json_Spec.enso
+++ b/test/Tests/src/Data/Json_Spec.enso
@@ -28,6 +28,7 @@ Text.should_render_itself =
 
 spec =
     Test.group "JSON Deserialization" <|
+
         Test.specify "should parse JSON structures" <|
             "0    ".should_parse_as 0
             " 123    ".should_parse_as 123
@@ -54,6 +55,7 @@ spec =
             object_json.should_parse_as <|
                 y_v = Json.from_pairs [["z", Nothing], ["w", Nothing]]
                 Json.from_pairs [["foo", "bar"], ["baz", ["foo", "x", False]], ["y", y_v]]
+
         Test.specify "should report meaningful parsing errors" <|
             "foo".should_fail_parsing_with "Expected a false"
             "[,]".should_fail_parsing_with "Expected a start of a JSON value"
@@ -64,6 +66,7 @@ spec =
                   "y": {"z": null, "w": null} }
             deep_err.should_fail_parsing_with "Expected a comma"
             "123 4".should_fail_parsing_with "Expected end of input"
+
         Test.specify "should parse and convert JSON into domain model" <|
             book_1 = Book "Lord of the Rings" <|
                 Author "J. R. R. Tolkien" 1892
@@ -77,7 +80,9 @@ spec =
             parsed = Json.parse json_string
             domain = parsed.into (Vector.Vector (Book title=Text (Author name=Text year_of_birth=Number)))
             domain.should_equal books
+
     Test.group "JSON Serialization" <|
+
         Test.specify "should print JSON structures to valid json" <|
             "0".should_render_itself
             "123".should_render_itself
@@ -93,6 +98,7 @@ spec =
             '["foo","foo\\n",null,true]'.should_render_itself
             object_json = '{"baz":["foo","x",false],"foo":"bar","y":{"w":null,"z":null}}'
             object_json.should_render_itself
+
         Test.specify "should convert arbitrary types to JSON" <|
             1.to_json.should_equal (Json.Number 1)
             1.54.to_json.should_equal (Json.Number 1.54)
@@ -104,3 +110,15 @@ spec =
                 t = Json.String "Author"
                 fields = Map.empty . insert "type" t . insert "name" n . insert "year_of_birth" y
                 Json.Object fields
+
+    Test.group "JSON" <|
+
+        Test.specify "should allow getting object fields" <|
+            object = Json.parse '''
+                { "foo": "bar",
+                  "baz": ["foo", "x", false],
+                  "y": {"z": null, "w": null} }
+
+            object.get "foo" . should_equal (Json.String "bar")
+            object.get "bar" . should_fail_with Json.No_Such_Field_Error
+
diff --git a/test/Tests/src/Data/List_Spec.enso b/test/Tests/src/Data/List_Spec.enso
index 04a51aed58dc..82bbf9167986 100644
--- a/test/Tests/src/Data/List_Spec.enso
+++ b/test/Tests/src/Data/List_Spec.enso
@@ -1,5 +1,7 @@
 from Standard.Base import all
 
+import Standard.Base.Data.List
+
 import Standard.Test
 
 spec = Test.group "List" <|
@@ -60,20 +62,20 @@ spec = Test.group "List" <|
         empty.take_start 2 . should_equal Nil
     Test.specify "should allow getting the head of the list with `.head`" <|
         l.head . should_equal 1
-        empty.head.catch . should_equal Nothing
+        empty.head.should_fail_with List.Empty_Error
     Test.specify "should allow getting the tail of the list with `.tail`" <|
         l.tail . should_equal (Cons 2 (Cons 3 Nil))
-        empty.tail.catch . should_equal Nothing
+        empty.tail.should_fail_with List.Empty_Error
     Test.specify "should allow getting the init of the list with `.init`" <|
         l.init . should_equal (Cons 1 (Cons 2 Nil))
-        empty.init.catch . should_equal Nothing
+        empty.init.should_fail_with List.Empty_Error
     Test.specify "should allow getting the last element of the list with `.last`" <|
         l.last . should_equal 3
-        empty.last.catch . should_equal Nothing
+        empty.last.should_fail_with List.Empty_Error
     Test.specify "should allow getting the head of the list with `.first`" <|
         l.first . should_equal 1
-        empty.first.catch . should_equal Nothing
+        empty.first.should_fail_with List.Empty_Error
     Test.specify "should allow getting the tail of the list with `.rest`" <|
         l.rest . should_equal (Cons 2 (Cons 3 Nil))
-        empty.rest.catch . should_equal Nothing
+        empty.rest.should_fail_with List.Empty_Error
 
diff --git a/test/Tests/src/Data/Map_Spec.enso b/test/Tests/src/Data/Map_Spec.enso
index 5ded8df4b01d..702ffa30a365 100644
--- a/test/Tests/src/Data/Map_Spec.enso
+++ b/test/Tests/src/Data/Map_Spec.enso
@@ -1,5 +1,7 @@
 from Standard.Base import all
 
+from Standard.Base.Data.Map import No_Value_For_Key_Error
+
 import Standard.Test
 
 spec = Test.group "Maps" <|
@@ -43,7 +45,7 @@ spec = Test.group "Maps" <|
         m.get "foo" . should_equal 134
         m.get "bar" . should_equal 654
         m.get "baz" . should_equal "spam"
-        (m.get "nope").should_fail_with Nothing
+        (m.get "nope").should_fail_with No_Value_For_Key_Error
     Test.specify "should support get_or_else" <|
         m = Map.empty . insert 2 3
         m.get_or_else 2 0 . should_equal 3
diff --git a/test/Tests/src/Data/Numbers_Spec.enso b/test/Tests/src/Data/Numbers_Spec.enso
index c78216b08895..3ae25b10d9cc 100644
--- a/test/Tests/src/Data/Numbers_Spec.enso
+++ b/test/Tests/src/Data/Numbers_Spec.enso
@@ -1,8 +1,11 @@
 from Standard.Base import all
 
+from Standard.Base.Data.Number.Extensions import Parse_Error
+
 import Standard.Test
 
 Integer.is_even = this % 2 == 0
+
 Decimal.get_fun_factor = "Wow, " + this.to_text + " is such a fun number!"
 
 spec =
@@ -12,43 +15,59 @@ spec =
     almost_max_long_times_three_plus_1 = 27670116110564327419
     almost_max_long_times_three_decimal = 27670116110564327418.8
     hundred_factorial = 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000
+
     Test.group "Integers" <|
+
         Test.specify "should be of unbound size when multiplied" <|
             1.up_to 101 . fold 1 (*) . should_equal hundred_factorial
+
         Test.specify "should be of unbound size when added" <|
             (almost_max_long + almost_max_long + almost_max_long).should_equal almost_max_long_times_three
-        Test.specify "should be of unbound size when subtracted" <| (0 - almost_max_long - almost_max_long - almost_max_long).should_equal almost_max_long_times_three.negate
+
+        Test.specify "should be of unbound size when subtracted" <|
+            (0 - almost_max_long - almost_max_long - almost_max_long).should_equal almost_max_long_times_three.negate
+
         Test.specify "should be of unbound size when dividing" <|
             expected = 3372816184472482867110284450043137767873196479305249187406461598235841786750685581361224832688174410089430537516012695688121622150430744676
             ((1.up_to 101 . fold 1 (*)).div  3*almost_max_long).should_equal expected
+
         Test.specify "should be of unbound size when taking remainder" <|
             expected = 3191479909175673432
             ((1.up_to 101 . fold 1 (*)) % 3*almost_max_long).should_equal expected
+
         Test.specify "should allow defining extension methods through the Integer type for any number size" <|
             876543.is_even.should_be_false
             (1.up_to 101 . fold 1 (*)).is_even.should_be_true
+
         Test.specify "should handle the negation edge cases" <|
             x = 9223372036854775808
             y = -x
             z = -9223372036854775808
             y.should_equal z
+
         Test.specify "should handle equality between small and big integers" <|
             (1 == hundred_factorial).should_be_false
             (hundred_factorial == 1).should_be_false
+
         Test.specify "should properly handle going to big numbers and back" <|
             ((almost_max_long * 3) / 3) . should_equal almost_max_long
+
         Test.specify "should use floating point arithmetic for division" <|
             (3 / 4) . should_equal 0.75 epsilon=eps
             (almost_max_long * 2 / almost_max_long_times_three) . should_equal 0.6666666 epsilon=eps
+
         Test.specify "should support integer division" <|
             (10.div 3) . should_equal 3
             (10.div 0).should_fail_with Arithmetic_Error
+
         Test.specify "should support integral binary literals" <|
             lit = 2_01101101
             lit . should_equal 109
+
         Test.specify "should support integral hexadecimal literals" <|
             lit = 16_6D
             lit . should_equal 109
+
         Test.specify "should support bitwise and" <|
             left  = 2_01101101
             right = 2_11000100
@@ -58,6 +77,7 @@ spec =
             left.bit_and big_right . should_equal 2_01101100
             big_left.bit_and right . should_equal 2_11000000
             big_left.bit_and big_right . should_equal 16_17ffffffffffffff8
+
         Test.specify "should support bitwise or" <|
             left  = 2_01101101
             right = 2_11000100
@@ -67,6 +87,7 @@ spec =
             left.bit_or big_right . should_equal 16_17ffffffffffffffd
             big_left.bit_or right . should_equal 16_17ffffffffffffffe
             big_left.bit_or right . should_equal 16_17ffffffffffffffe
+
         Test.specify "should support bitwise exclusive or" <|
             left  = 2_01101101
             right = 2_11000100
@@ -76,6 +97,7 @@ spec =
             left.bit_xor big_right . should_equal 16_17fffffffffffff91
             big_left.bit_xor right . should_equal 16_17fffffffffffff3e
             big_left.bit_xor big_right . should_equal 2_00000110
+
         Test.specify "should support bitwise negation" <|
             bits  = 2_01101101
             big_bits = 16_17ffffffffffffffa
@@ -83,6 +105,7 @@ spec =
             bits.bit_not.bit_not . should_equal bits
             big_bits.bit_not . should_equal -16_17ffffffffffffffb
             big_bits.bit_not.bit_not . should_equal big_bits
+
         Test.specify "should support left bit shifts" <|
             positive_bits = 2_01101101
             negative_bits = -2_01101101
@@ -93,28 +116,28 @@ spec =
             positive_bits.bit_shift_l 64 . should_equal 16_6d0000000000000000
             positive_bits.bit_shift_l -2 . should_equal 2_011011
             positive_bits.bit_shift_l -64 . should_equal 0
-            (positive_bits.bit_shift_l positive_big_bits).should_error_with Arithmetic_Error
+            (positive_bits.bit_shift_l positive_big_bits).should_fail_with Arithmetic_Error
             positive_bits.bit_shift_l negative_big_bits . should_equal 0
 
             negative_bits.bit_shift_l 2 . should_equal -436
             negative_bits.bit_shift_l 64 . should_equal -2010695104034341126144
             negative_bits.bit_shift_l -2 . should_equal -28
             negative_bits.bit_shift_l -64 . should_equal -1
-            (negative_bits.bit_shift_l positive_big_bits).should_error_with Arithmetic_Error
+            (negative_bits.bit_shift_l positive_big_bits).should_fail_with Arithmetic_Error
             negative_bits.bit_shift_l negative_big_bits . should_equal -1
 
             positive_big_bits.bit_shift_l 2 . should_equal 110680464442257309672
             positive_big_bits.bit_shift_l 64 . should_equal 510423550381407695084381446705395007488
             positive_big_bits.bit_shift_l -2 . should_equal 6917529027641081854
             positive_big_bits.bit_shift_l -100 . should_equal 0
-            (positive_big_bits.bit_shift_l positive_big_bits).should_error_with Arithmetic_Error
+            (positive_big_bits.bit_shift_l positive_big_bits).should_fail_with Arithmetic_Error
             positive_big_bits.bit_shift_l negative_big_bits . should_equal 0
 
             negative_big_bits.bit_shift_l 2 . should_equal -110680464442257309672
             negative_big_bits.bit_shift_l 64 . should_equal -510423550381407695084381446705395007488
             negative_big_bits.bit_shift_l -2 . should_equal -6917529027641081855
             negative_big_bits.bit_shift_l -100 . should_equal -1
-            (negative_big_bits.bit_shift_l positive_big_bits).should_error_with Arithmetic_Error
+            (negative_big_bits.bit_shift_l positive_big_bits).should_fail_with Arithmetic_Error
             negative_big_bits.bit_shift_l negative_big_bits . should_equal -1
         Test.specify "should support right bit shifts, preserving sign" <|
             positive_bits = 2_01101101
@@ -126,39 +149,50 @@ spec =
             positive_bits.bit_shift_r 64 . should_equal (positive_bits.bit_shift_l -64)
             positive_bits.bit_shift_r -2 . should_equal (positive_bits.bit_shift_l 2)
             positive_bits.bit_shift_r -64 . should_equal (positive_bits.bit_shift_l 64)
-            (positive_bits.bit_shift_r negative_big_bits).should_error_with Arithmetic_Error
+            (positive_bits.bit_shift_r negative_big_bits).should_fail_with Arithmetic_Error
             positive_bits.bit_shift_r positive_big_bits . should_equal 0
 
             negative_bits.bit_shift_r 2 . should_equal (negative_bits.bit_shift_l -2)
             negative_bits.bit_shift_r 64 . should_equal (negative_bits.bit_shift_l -64)
             negative_bits.bit_shift_r -2 . should_equal (negative_bits.bit_shift_l 2)
             negative_bits.bit_shift_r -64 . should_equal (negative_bits.bit_shift_l 64)
-            (negative_bits.bit_shift_r negative_big_bits).should_error_with Arithmetic_Error
+            (negative_bits.bit_shift_r negative_big_bits).should_fail_with Arithmetic_Error
             negative_bits.bit_shift_r positive_big_bits . should_equal -1
 
             positive_big_bits.bit_shift_r 2 . should_equal (positive_big_bits.bit_shift_l -2)
             positive_big_bits.bit_shift_r 64 . should_equal (positive_big_bits.bit_shift_l -64)
             positive_big_bits.bit_shift_r -2 . should_equal (positive_big_bits.bit_shift_l 2)
             positive_big_bits.bit_shift_r -100 . should_equal (positive_big_bits.bit_shift_l 100)
-            (positive_big_bits.bit_shift_r negative_big_bits).should_error_with Arithmetic_Error
+            (positive_big_bits.bit_shift_r negative_big_bits).should_fail_with Arithmetic_Error
             positive_big_bits.bit_shift_r positive_big_bits . should_equal 0
 
             negative_big_bits.bit_shift_r 2 . should_equal (negative_big_bits.bit_shift_l -2)
             negative_big_bits.bit_shift_r 64 . should_equal (negative_big_bits.bit_shift_l -64)
             negative_big_bits.bit_shift_r -2 . should_equal (negative_big_bits.bit_shift_l 2)
             negative_big_bits.bit_shift_r -100 . should_equal (negative_big_bits.bit_shift_l 100)
-            (negative_big_bits.bit_shift_r negative_big_bits).should_error_with Arithmetic_Error
+            (negative_big_bits.bit_shift_r negative_big_bits).should_fail_with Arithmetic_Error
             negative_big_bits.bit_shift_r positive_big_bits . should_equal -1
+
     Test.group "Decimals" <|
+
         Test.specify "should exist and expose basic arithmetic operations" <|
             ((1.5 + 1.5)*1.3 / 2 - 3) . should_equal -1.05 epsilon=eps
+
         Test.specify "should allow defining extension methods through the Decimal type" <|
             32.5.get_fun_factor.should_equal "Wow, 32.5 is such a fun number!"
+
+        Test.specify "should be able to be parsed" <|
+            Decimal.parse "32.5" . should_equal 32.5
+            Decimal.parse "aaaa" . should_fail_with Parse_Error
+
     Test.group "Numbers" <|
+
         Test.specify "should define addition" <|
             2+3 . should_equal 5
+
         Test.specify "should define multiplication" <|
             2*3 . should_equal 6
+
         Test.specify "should expose comparison operators" <|
             (3 < hundred_factorial).should_be_true
             (hundred_factorial < 3).should_be_false
@@ -166,6 +200,7 @@ spec =
             (3.0 <= 3.4).should_be_true
             (3.0 >= 2).should_be_true
             (-hundred_factorial > 0).should_be_false
+
         Test.specify "should expose exponentiation operations" <|
             (3.14 ^ 2.71).should_equal 22.216689546 epsilon=eps
             (3.14 ^ 14).should_equal 9057640.36635 epsilon=eps
@@ -174,17 +209,20 @@ spec =
             (2 ^ 10).should_equal 1024
             (2 ^ 0.5).should_equal 1.41421356237 epsilon=eps
             (a^2)^0.5 . should_equal a epsilon=eps
+
         Test.specify "should expose more involved mathematical functions" <|
             Math.Pi.sin.should_equal 0 epsilon=eps
             (Math.Pi / 4).sin.should_equal (2 ^ 0.5)/2 epsilon=eps
             (Math.Pi / 6).cos.should_equal (3.sqrt / 2) epsilon=eps
             (17 ^ 0.13).log base=17 . should_equal 0.13 epsilon=eps
             0.exp.should_equal 1
+
         Test.specify "should allow calculating the floor value" <|
             1.2314.floor . should_equal 1
             1.floor . should_equal 1
             almost_max_long_times_three_decimal.floor.to_decimal . should_equal almost_max_long_times_three.to_decimal
             almost_max_long_times_three.floor . should_equal almost_max_long_times_three
+
         Test.specify "should allow calculating the ceil value" <|
             1.2314.ceil . should_equal 2
             1.ceil . should_equal 1
diff --git a/test/Tests/src/Data/Vector_Spec.enso b/test/Tests/src/Data/Vector_Spec.enso
index f0f2df623022..d1dca94ee0c4 100644
--- a/test/Tests/src/Data/Vector_Spec.enso
+++ b/test/Tests/src/Data/Vector_Spec.enso
@@ -36,12 +36,12 @@ spec = Test.group "Vectors" <|
 
     Test.specify "should allow to reduce elements if it is non-empty" <|
         [1,2,3].reduce (+) . should_equal 6
-        [].reduce (+) . should_fail_with Nothing
+        [].reduce (+) . should_fail_with Vector.Empty_Error
 
     Test.specify "should allow summing elements if they define +" <|
         [1,2,3].sum . should_equal 6
-        [].sum . should_fail_with Nothing
-        [T 1 2, T 3 4].sum . should_fail_with Nothing
+        [].sum . should_fail_with Vector.Empty_Error
+        [T 1 2, T 3 4].sum . should_fail_with No_Such_Method_Error
 
     Test.specify "should check exists" <|
         vec = [1, 2, 3, 4, 5]
@@ -130,7 +130,7 @@ spec = Test.group "Vectors" <|
         empty_vec = []
         non_empty_vec.head . should_equal 1
         singleton_vec.head . should_equal 1
-        empty_vec.head . should_fail_with Nothing
+        empty_vec.head . should_fail_with Vector.Empty_Error
 
     Test.specify "should allow getting the tail of the vector" <|
         non_empty_vec = [1, 2, 3, 4, 5]
@@ -138,7 +138,7 @@ spec = Test.group "Vectors" <|
         empty_vec = []
         non_empty_vec.tail . should_equal [2, 3, 4, 5]
         singleton_vec.tail . should_equal []
-        empty_vec.tail . should_fail_with Nothing
+        empty_vec.tail . should_fail_with Vector.Empty_Error
 
     Test.specify "should allow getting the init of the vector" <|
         non_empty_vec = [1, 2, 3, 4, 5]
@@ -146,7 +146,7 @@ spec = Test.group "Vectors" <|
         empty_vec = []
         non_empty_vec.init . should_equal [1, 2, 3, 4]
         singleton_vec.init . should_equal []
-        empty_vec.init . should_fail_with Nothing
+        empty_vec.init . should_fail_with Vector.Empty_Error
 
     Test.specify "should allow getting the last element of the vector" <|
         non_empty_vec = [1, 2, 3, 4, 5]
@@ -154,7 +154,7 @@ spec = Test.group "Vectors" <|
         empty_vec = []
         non_empty_vec.last . should_equal 5
         singleton_vec.last . should_equal 1
-        empty_vec.last . should_fail_with Nothing
+        empty_vec.last . should_fail_with Vector.Empty_Error
 
     Test.specify "should allow getting the first element" <|
         non_empty_vec = [1, 2, 3, 4, 5]
@@ -162,7 +162,7 @@ spec = Test.group "Vectors" <|
         empty_vec = []
         non_empty_vec.first . should_equal 1
         singleton_vec.first . should_equal 1
-        empty_vec.first . should_fail_with Nothing
+        empty_vec.first . should_fail_with Vector.Empty_Error
 
     Test.specify "should allow getting the rest of the vector" <|
         non_empty_vec = [1, 2, 3, 4, 5]
@@ -170,7 +170,7 @@ spec = Test.group "Vectors" <|
         empty_vec = []
         non_empty_vec.rest . should_equal [2, 3, 4, 5]
         singleton_vec.rest . should_equal []
-        empty_vec.rest . should_fail_with Nothing
+        empty_vec.rest . should_fail_with Vector.Empty_Error
 
     Test.specify "should be able to be sorted" <|
         empty_vec = []
diff --git a/test/Tests/src/System/File_Spec.enso b/test/Tests/src/System/File_Spec.enso
index 3d9190be7f76..c662c6519d24 100644
--- a/test/Tests/src/System/File_Spec.enso
+++ b/test/Tests/src/System/File_Spec.enso
@@ -6,34 +6,51 @@ spec =
     sample_file = Enso_Project.data / "sample.txt"
     non_existent_file = File.new "does_not_exist.txt"
     Test.group "File Operations" <|
+
+        Test.specify "should allow creating a new file" <|
+            path = sample_file.path
+            File.new path
+
+        Test.specify "should have `new` be a no-op on a file" <|
+            file = File.new sample_file
+            file . should_equal sample_file
+
         Test.specify "should allow reading a file" <|
             contents = sample_file.read
             contents.should .start_with "Cupcake ipsum dolor sit amet."
+
         Test.specify "should allow reading a file to byte vector" <|
             contents = sample_file.read_bytes
             contents.take_start 6 . should_equal [67, 117, 112, 99, 97, 107]
+
         Test.specify "should handle exceptions when reading a non-existent file" <|
             file = File.new "does_not_exist.txt"
             successfully_failed = Panic.recover file.read . catch e-> case e of
                 File.No_Such_File_Error _ -> True
                 _ -> False
             successfully_failed . should_be_true
+
         Test.specify "should check if file exists" <|
             non_existent_file.exists.should_be_false
             sample_file.exists.should_be_true
+
         Test.specify "should check if file is a directory" <|
             sample_file.is_directory.should_be_false
             Enso_Project.root.is_directory.should_be_true
+
         Test.specify "should get file name" <|
             sample_file.name.should_equal "sample.txt"
+
         Test.specify "should convert a file to absolute" <|
             abs = File.new "foo.txt" . absolute
             through_cwd = (File.current_directory / "foo.txt")
             abs.should_equal through_cwd
+
         Test.specify "should normalize file" <|
             f_1 = File.new "foo"
             f_2 = File.new "bar/../baz/../foo"
             f_2.normalize.should_equal f_1
+
         Test.specify "should allow reading a file byte by byte" <|
             f = Enso_Project.data / "short.txt"
             f.delete_if_exists
@@ -46,6 +63,7 @@ spec =
                 stream.read_byte.should_equal -1
             f.delete
             f.exists.should_be_false
+
         Test.specify "should write and append to files" <|
             f = Enso_Project.data / "work.txt"
             f.delete_if_exists
@@ -57,8 +75,12 @@ spec =
             f.read.should_equal 'line 1!\nline 2!'
             f.delete
             f.exists.should_be_false
+
         Test.specify "should open and read the file in one shot" <|
             path_name = sample_file.path
             contents = File.read path_name
             contents.should .start_with "Cupcake ipsum dolor sit amet."
+            file = sample_file
+            contents_2 = File.read file
+            contents_2.should .start_with "Cupcake ipsum dolor sit amet."