go/types, types2: remove argument "getter" use from Checker.builtins (cleanup)
Check all arguments for validity once, in the beginning.
Conservatively replace arg(x, i) calls with *x = args[i].
Use y (2nd arguments) directly, w/o copying.
Remove unnecessary copies and slice creations in append.
Change-Id: I1e2891cba9658f5b3cdf897e81db2f690a99b16b
Reviewed-on: https://go-review.googlesource.com/c/go/+/495515
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Griesemer <gri@google.com> Reviewed-by: Robert Findley <rfindley@google.com> Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>