swift234

Introduce the notion of structured dependent types, such as a tuple
type with one or more elements of dependent type. Previously, an
expression such as (x, 5) would have the (unstructured) dependent
type, limiting our ability to type-check the subexpression 'x'
early. Now, if 'x' has type 'int' (for example), this expression will
now have the type (int, <<unstructured dependent type>>).

Extend coercion of a tuple to tuple type to handle coercion to
(structured) dependent tuple types, coercing element-by-element. This
code is very lightly tested and may still need to be restructured.




Swift SVN r1294