cmd/compile: avoid copying Pos from ONAME when creating converts for maps
ONAME nodes are shared, so using their position for anything is almost
always a mistake. There are probably more instances of this mistake
elsewhere. For now, handle the case of map key temporaries, where it's
been a problem.
Fixes #53456.
Change-Id: Id44e845d08d428592ad3ba31986635b6b87b0041
Reviewed-on: https://go-review.googlesource.com/c/go/+/417076
Run-TryBot: David Chase <drchase@google.com> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>