---

yaml
---
r: 345067
b: refs/heads/master
c: e31046d
h: refs/heads/master
i:
  345065: f713ae9
  345063: 774de99

Author: swift-ci

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: c8e9965725c921369f6812fe66aa8f8fea3f9165
+refs/heads/master: e31046dbba30f9a375191f4a1afba9fa14638781
 refs/heads/master-next: 203b3026584ecad859eb328b2e12490099409cd5
 refs/tags/osx-passed: b6b74147ef8a386f532cf9357a1bde006e552c54
 refs/tags/swift-2.2-SNAPSHOT-2015-12-01-a: 6bb18e013c2284f2b45f5f84f2df2887dc0f7dea

trunk/docs/ByteTree.md

@@ -21,7 +21,7 @@ Arrays are modelled as objects whose fields are all of the same type and whose l
 
 ## Versioning
 
-The ByteTree format is prepended by a 4-byte protocol version number that describes the version of the object tree that was serialized. Its exact semantics are up to each specific application, but it is encouraged to interpret it as a two-comentent number where the first component, consisting of the first three bytes, is incremented for breaking changes and the last byte is incremented for backwards-compatible changes.
+The ByteTree format is prepended by a 4-byte protocol version number that describes the version of the object tree that was serialized. Its exact semantics are up to each specific application, but it is encouraged to interpret it as a two-comentent number where the first component, consisting of the three most significant bytes, is incremented for breaking changes and the last byte is incremented for backwards-compatible changes.
 
 ## Forward compatilibity
 

trunk/include/swift/Syntax/Serialization/SyntaxSerialization.h

@@ -203,6 +203,20 @@ struct NullableTraits<RC<syntax::RawSyntax>> {
 
 namespace byteTree {
 
+/// Increase the major version for every change that is not just adding a new
+/// field at the end of an object. Older swiftSyntax clients will no longer be
+/// able to deserialize the format.
+const uint16_t SYNTAX_TREE_VERSION_MAJOR = 1; // Last change: initial version
+/// Increase the minor version if only new field has been added at the end of
+/// an object. Older swiftSyntax clients will still be able to deserialize the
+/// format.
+const uint8_t SYNTAX_TREE_VERSION_MINOR = 0; // Last change: initial version
+
+// Combine the major and minor version into one. The first three bytes
+// represent the major version, the last byte the minor version.
+const uint32_t SYNTAX_TREE_VERSION =
+    SYNTAX_TREE_VERSION_MAJOR << 8 | SYNTAX_TREE_VERSION_MINOR;
+
 /// The key for a ByteTree serializion user info of type
 /// `std::unordered_set<unsigned> *`. Specifies the IDs of syntax nodes that
 /// shall be omitted when the syntax tree gets serialized.