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Sep 26, 2018
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update mima url #1157

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4 changes: 2 additions & 2 deletions _overviews/core/binary-compatibility-of-scala-releases.md
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Expand Up @@ -9,7 +9,7 @@ permalink: /overviews/core/:title.html

When two versions of Scala are binary compatible, it is safe to compile your project on one Scala version and link against another Scala version at run time. Safe run-time linkage (only!) means that the JVM does not throw a (subclass of) [`LinkageError`](http://docs.oracle.com/javase/7/docs/api/java/lang/LinkageError.html) when executing your program in the mixed scenario, assuming that none arise when compiling and running on the same version of Scala. Concretely, this means you may have external dependencies on your run-time classpath that use a different version of Scala than the one you're compiling with, as long as they're binary compatible. In other words, separate compilation on different binary compatible versions does not introduce problems compared to compiling and running everything on the same version of Scala.

We check binary compatibility automatically with [MiMa](https://github.com/typesafehub/migration-manager). We strive to maintain a similar invariant for the `behavior` (as opposed to just linkage) of the standard library, but this is not checked mechanically (Scala is not a proof assistant so this is out of reach for its type system).
We check binary compatibility automatically with [MiMa](https://github.com/lightbend/migration-manager). We strive to maintain a similar invariant for the `behavior` (as opposed to just linkage) of the standard library, but this is not checked mechanically (Scala is not a proof assistant so this is out of reach for its type system).

#### Forwards and Back
We distinguish forwards and backwards compatibility (think of these as properties of a sequence of versions, not of an individual version). Maintaining backwards compatibility means code compiled on an older version will link with code compiled with newer ones. Forwards compatibility allows you to compile on new versions and run on older ones.
Expand All @@ -22,7 +22,7 @@ These are strict constraints, but they have worked well for us since Scala 2.10.
Note that so far we've only talked about the jars generated by scalac for the standard library and reflection.
Our policies do not extend to the meta-issue: ensuring binary compatibility for bytecode generated from identical sources, by different version of scalac? (The same problem exists for compiling on different JDKs.) While we strive to achieve this, it's not something we can test in general. Notable examples where we know meta-binary compatibility is hard to achieve: specialisation and the optimizer.

In short, we recommend that library authors use to [MiMa](https://github.com/typesafehub/migration-manager) to verify compatibility of minor versions before releasing.
In short, we recommend that library authors use to [MiMa](https://github.com/lightbend/migration-manager) to verify compatibility of minor versions before releasing.
Compiling identical sources with different versions of the scala compiler (or on different JVM versions!) could result in binary incompatible bytecode. This is rare, and we try to avoid it, but we can't guarantee it will never happen.

#### Concretely
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