This change properly transforms literal AST nodes during code-gen.
This includes emitting CloudFormation !Refs where appropriate, for
intra-stack references (capability types).
Right now, the AWS ECS scheduler simply passes through to the underlying
AWS cloud provider. However, now we have the necessary hooks to start
incrementally recognizing stack types and emitting specialized code for
them (e.g., starting with mu/container).
This change mostly replaces explicit if/then/glog.Fatalf calls with
util.Assert calls. In addition, it adds a companion util.Fail family
of methods that does the same thing as a failed assertion, except that
it is unconditional.
This change eliminates the diag.Sink field, Diag, on the Compiland struct.
Instead, we should provide it at backend provider construction time. This
is consistent with how other phases of the compiler work and also ensures
the backends can properly implement the core.Phase interface.
This change includes a few steps towards AWS backend code-generation:
* Add a BoundDependencies property to ast.Stack to remember the *ast.Stack
objects bound during Stack binding.
* Make a few CloudFormation properties optional (cfOutput Export/Condition).
* Rename clouds.ArchMap, clouds.ArchNames, schedulers.ArchMap, and
schedulers.ArchNames to clouds.Values, clouds.Names, schedulers.Values,
and schedulers.Names, respectively. This reads much nicer to my eyes.
* Create a new anonymous ast.Target for deployments if no specific target
was specified; this is to support quick-and-easy "one off" deployments,
as will be common when doing local development.
* Sketch out more of the AWS Cloud implementation. We actually map the
Mu Services into CloudFormation Resources; well, kinda sorta, since we
don't actually have Service-specific logic in here yet, however all of
the structure and scaffolding is now here.
This change adds a Backend Phase to the compiler, implemented by each of the
cloud/scheduler implementations. It also reorganizes some of the modules to
ensure we can do everything we need without cycles, including introducing the
mu/pkg/compiler/backends package, under which the clouds/ and schedulers/
sub-packages now reside. The backends.New(Arch) factory function acts as the
entrypoint into the entire thing so callers can easily create new Backend instances.
