Summary:
Check that all variable names are valid when loading manifest files.
This ensures that getdeps.py will error out if someone makes a typo in a
variable name, rather than treating it as never equal to anything.
Reviewed By: pkaush
Differential Revision: D16477397
fbshipit-source-id: 030e0642ff4a08db8eb74a0a0223e03d53e4880f
Summary:
As part of folding getdeps into fbcode_builder, this
expression parser is needed to allow constrained and deterministic
conditionals in the manifest file format.
For example, the watchman manifest will use this cargo-inspired syntax
for system dependent sections:
```
[dependencies]
folly
[dependencies.not(os=windows)]
thrift
```
Reviewed By: sinancepel
Differential Revision: D14691014
fbshipit-source-id: 080bcdb20579da40d225799f5f22debe65708b03
