cmd/compile/internal/typecheck: refactor and simplify DeclFunc
This CL refactors typecheck.DeclFunc to require the caller to have
already constructed the ir.Func and signature type using ir.NewFunc
and types.NewSignature, and simplifies typecheck.DeclFunc to simply
return the slices of param and results ONAMEs.
typecheck.DeclFunc was the last reason that ir.Field still exists, so
this CL also gets rid of that.
Change-Id: Ib398420bac2fd135a235810b8af1635fa754965c
Reviewed-on: https://go-review.googlesource.com/c/go/+/520977
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>