[dev.typeparams] cmd/compile: fix getDictionarySym for methods references, write out sub-dictionaries
For method references (only), selectorExpr() now computes n.Selection,
which is the generic method that is selected. This allows us to compute
as needed the proper sub-dictionary for method reference. Also cleans up
some code for distinguishing method references from references to a
field that has a function value (especially in the presence of embedded
fields).
Change-Id: I9c5b789c15537ff48c70ca7a6444aa0420178a3a
Reviewed-on: https://go-review.googlesource.com/c/go/+/332095
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>