[dev.regabi] cmd/compile: cleanup import/export code

Now that we have concrete AST node types and better constructor APIs,
we can more cleanup a lot of the import code and some export code too.

Passes toolstash -cmp.

Change-Id: Ie3425d9dac11ac4245e5da675dd298984a926df4
Reviewed-on: https://go-review.googlesource.com/c/go/+/279954
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 6 insertions, 21 deletions

diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index 4ddee01b5a..95a100e6a5 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -1155,7 +1155,7 @@ func (w *exportWriter) stmt(n ir.Node) {
 		w.pos(n.Pos())
 		w.stmtList(n.Init())
 		w.exprsOrNil(nil, nil) // TODO(rsc): Delete (and fix importer).
-		w.caseList(n)
+		w.caseList(n.Cases, false)
 
 	case ir.OSWITCH:
 		n := n.(*ir.SwitchStmt)
@@ -1163,7 +1163,7 @@ func (w *exportWriter) stmt(n ir.Node) {
 		w.pos(n.Pos())
 		w.stmtList(n.Init())
 		w.exprsOrNil(n.Tag, nil)
-		w.caseList(n)
+		w.caseList(n.Cases, isNamedTypeSwitch(n.Tag))
 
 	// case OCASE:
 	//	handled by caseList
@@ -1187,27 +1187,12 @@ func (w *exportWriter) stmt(n ir.Node) {
 	}
 }
 
-func isNamedTypeSwitch(n ir.Node) bool {
-	if n.Op() != ir.OSWITCH {
-		return false
-	}
-	sw := n.(*ir.SwitchStmt)
-	if sw.Tag == nil || sw.Tag.Op() != ir.OTYPESW {
-		return false
-	}
-	guard := sw.Tag.(*ir.TypeSwitchGuard)
-	return guard.Tag != nil
+func isNamedTypeSwitch(x ir.Node) bool {
+	guard, ok := x.(*ir.TypeSwitchGuard)
+	return ok && guard.Tag != nil
 }
 
-func (w *exportWriter) caseList(sw ir.Node) {
-	namedTypeSwitch := isNamedTypeSwitch(sw)
-
-	var cases []ir.Node
-	if sw.Op() == ir.OSWITCH {
-		cases = sw.(*ir.SwitchStmt).Cases
-	} else {
-		cases = sw.(*ir.SelectStmt).Cases
-	}
+func (w *exportWriter) caseList(cases []ir.Node, namedTypeSwitch bool) {
 	w.uint64(uint64(len(cases)))
 	for _, cas := range cases {
 		cas := cas.(*ir.CaseStmt)