[dev.typeparams] Don't check typecheck(3) on transform, so no need to export/import it

We have a value typecheck(3) that indicates that a node in a generic
function still needs transformation (via the functions in transform.go).
But it is not very desirable to export/import the value of typecheck(3).
So, I changed the stenciling code to just try to transform all relevant
node types during node copy. Almost all tranform functions were already
idempotent. I only had to add an extra if check before calling
transformAssign() in the OAS case. We still use the typecheck(3) in
noder to determine when higher-nodes have to delay transformation
because one or more of their args are delaying transformation.

Added new test mapsimp.go that required these tranformations after import.

As an additional change, export/import of OINDEX requires exporting the
type using w.exoticType() rather than w.typ(), in order to handle
generic functions. Since generic functions can have pre-transform
operations, the index operation can have a tuple type (multiple return
from a map lookup).

Added printing of imported function bodies in -W=3 debug mode.

Change-Id: I220e2428dc5f2741e91db146f075eb5b6045f451
Reviewed-on: https://go-review.googlesource.com/c/go/+/322191
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/typecheck/iimport.go b/src/cmd/compile/internal/typecheck/iimport.go
index 966e865630..d5b549483d 100644
--- a/src/cmd/compile/internal/typecheck/iimport.go
+++ b/src/cmd/compile/internal/typecheck/iimport.go
@@ -1025,6 +1025,10 @@ func (r *importReader) funcBody(fn *ir.Func) {
 	fn.Inl.Body = body
 
 	r.curfn = outerfn
+	if base.Flag.W >= 3 {
+		fmt.Printf("Imported for %v", fn)
+		ir.DumpList("", fn.Inl.Body)
+	}
 }
 
 func (r *importReader) readNames(fn *ir.Func) []*ir.Name {
@@ -1349,7 +1353,7 @@ func (r *importReader) node() ir.Node {
 		n := ir.NewIndexExpr(r.pos(), r.expr(), r.expr())
 		if go117ExportTypes {
 			n.SetOp(op)
-			n.SetType(r.typ())
+			n.SetType(r.exoticType())
 			if op == ir.OINDEXMAP {
 				n.Assigned = r.bool()
 			}