minor symfony#9717 Update BC policy to tell about adding/removing return types (nicolas-grekas)

This PR was merged into the 2.7 branch. Discussion ---------- Update BC policy to tell about adding/removing return types Fixes symfony#8609 Commits ------- c424648 Update BC policy to tell about adding/removing return types

Author: javiereguiluz

contributing/code/bc.rst

@@ -73,6 +73,8 @@ backward compatibility promise:
 +-----------------------------------------------+-----------------------------+
 | Add a default value to an argument | Yes |
 +-----------------------------------------------+-----------------------------+
+| Add a return type to an implemented method | Yes |
++-----------------------------------------------+-----------------------------+
 
 Using our Classes
 ~~~~~~~~~~~~~~~~~
@@ -164,6 +166,8 @@ Remove default value of an argument No
 Add type hint to an argument No
 Remove type hint of an argument No
 Change argument type No
+Add return type No
+Remove return type No [9]_
 Change return type No
 **Constants**
 Add constant Yes
@@ -220,6 +224,8 @@ Remove default value of an argument No
 Add type hint to an argument No [7]_ [8]_
 Remove type hint of an argument No [7]_ [8]_
 Change argument type No [7]_ [8]_
+Add return type No [7]_ [8]_
+Remove return type No [7]_ [8]_ [9]_
 Change return type No [7]_ [8]_
 **Protected Methods**
 Add protected method Yes
@@ -235,6 +241,8 @@ Remove default value of an argument No [7]_
 Add type hint to an argument No [7]_ [8]_
 Remove type hint of an argument No [7]_ [8]_
 Change argument type No [7]_ [8]_
+Add return type No [7]_ [8]_
+Remove return type No [7]_ [8]_ [9]_
 Change return type No [7]_ [8]_
 **Private Methods**
 Add private method Yes
@@ -248,6 +256,8 @@ Remove default value of an argument Yes
 Add type hint to an argument Yes
 Remove type hint of an argument Yes
 Change argument type Yes
+Add return type Yes
+Remove return type Yes
 Change return type Yes
 **Static Methods**
 Turn non static into static No [7]_ [8]_
@@ -291,6 +301,8 @@ Change value of a constant Yes [1]_ [5]_
  Changing an argument type is only possible with a parent type.
  Changing a return type is only possible with a child type.
 
+.. [9] Allowed for the ``void`` return type.
+
 .. _Semantic Versioning: https://semver.org/
 .. _scalar type: https://php.net/manual/en/function.is-scalar.php
 .. _boolean values: https://php.net/manual/en/function.boolval.php