swift234

Check base expr when determining mutability of a member

When in an initializer, we allow setting into immutable properties
provided that the type of base in `base.member` matches that of that
initializer's containing type. This was an approximation for allowing
full access into `self` during initialization but this doesn't work when
passing in a different struct of the same type because that struct
should be still be immutable.

Check whether the base of the member access is the implicit self
parameter of the initializer before allowing mutation.

rdar://problem/19814302

Swift SVN r28634