The tool should diagnose the change of extension's applicability since
such change can be source-breaking. We need first to support the
requirements in the module dump. Currently, we decorate each
member defined in extension with a field called extension info. The
field will keep track of the generic requirements that need to be satisfied
for this decorated member to be applicable. This patch doesn't implement the checking
of requirements change.
This has three principal advantages:
- It gives some additional type-safety when working
with known accessors.
- It makes it significantly easier to test whether a declaration
is an accessor and encourages the use of a common idiom.
- It saves a small amount of memory in both FuncDecl and its
serialized form.
