Document diagnostic span

Author: josevalim

lib/elixir/lib/code.ex

@@ -199,7 +199,8 @@ defmodule Code do
 
   If there is a file and position, then the diagnostic is precise
   and you can use the given file and position for generating snippets,
-  IDEs annotations, and so on.
+  IDEs annotations, and so on. An optional span is available with
+  the line and column the diagnostic ends.
 
   Otherwise, a stacktrace may be given, which you can place your own
   heuristics to provide better reporting.
@@ -210,7 +211,7 @@ defmodule Code do
           required(:message) => String.t(),
           required(:position) => position(),
           required(:stacktrace) => Exception.stacktrace(),
-          required(:span) => {non_neg_integer(), non_neg_integer()} | nil,
+          required(:span) => {line :: pos_integer(), column :: pos_integer()} | nil,
           optional(:exception) => Exception.t() | nil,
           optional(any()) => any()
         }

lib/mix/lib/mix/task.compiler.ex

@@ -34,7 +34,8 @@ defmodule Mix.Task.Compiler do
 
     If there is a file and position, then the diagnostic is precise
     and you can use the given file and position for generating snippets,
-    IDEs annotations, and so on.
+    IDEs annotations, and so on. An optional span is available with
+    the line and column the diagnostic ends.
 
     Otherwise, a stacktrace may be given, which you can place your own
     heuristics to provide better reporting.
@@ -48,7 +49,7 @@ defmodule Mix.Task.Compiler do
             compiler_name: String.t(),
             details: Exception.t() | any,
             stacktrace: Exception.stacktrace(),
-            span: {non_neg_integer, non_neg_integer} | nil
+            span: {line :: pos_integer(), column :: pos_integer()} | nil
           }
 
     @typedoc """