swift234

Default-initialize instance variables at the beginning of each constructor.

Perform some trivial (broken) analysis of the constructor so we don't
add obviously redundant initialization. This allows us to actually
write constructors for types whose members cannot be
default-initialized. The test contains some examples of both false
negatives and false positives caused by this lame analysis. We'll want
to replace it with a real dataflow-based guaranteed-initialization
analysis to make this sound.

We should be default-initializing everything. Fixes <rdar://problem/11619148>.



Swift SVN r4984