This saves 35% of wall time in a command such as
$ gopackages -mode=syntax golang.org/x/tools/go/packages/gopackages fmt
that would otherwise typecheck every function in each package that
depends on fmt. It also applies in -mode=types when source was loaded
as a fall back for missing export data due to an error in a lower package.
Also, remove Config.TypeChecker field now that not a single of its
subfields is passed through go/packages to the type checker.
(The Sizes function is logically a result, not an input, of loading,
though we have yet to implement it properly.)
Change-Id: I472d21b34fc5e2832f7353e82992a67a06e4e4cc
Reviewed-on: https://go-review.googlesource.com/129497
Reviewed-by: Ian Cottrell <iancottrell@google.com>
9de1900191