SI-7548 askTypeAt returns the same type for full/ targeted typecheck (2.10.x)

Re-opened https://github.com/scala/scala/pull/3177 to target 2.10.x

review by @retronym

~~P.S. This commit https://github.com/dotta/scala/commit/652b3b4b9dcbf990e7ace409e050cc4ba4e83b16 will fail the build because the commit is intended to show the issue. I expect this won't be a problem for merging the PR.~~ not true, see comment https://github.com/scala/scala/pull/3208#issuecomment-29605967