cmd/compile: fix constructing expr side-effects when comparing 0-size types
In walkCompare, any ir.OCONVNOP was removed from both operands. So when
constructing assignments for them to preserve any side-effects, using
temporary variables can cause type mismatched with original type.
Instead, using blank assignments will prevent that issue and still make
sure that the operands will be evaluated.
Fixes #52701
Change-Id: I229046acb154890bb36fe441d258563687fdce37
Reviewed-on: https://go-review.googlesource.com/c/go/+/403997
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Robert Griesemer <gri@google.com>