cmd/compile: add typChan

Passes toolstash -cmp.

Change-Id: I2c71882f957c44047c7ac83c78236dcc3dfa15a1
Reviewed-on: https://go-review.googlesource.com/21304Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/parser.go

@@ -3050,9 +3050,7 @@ func (p *parser) hidden_type_misc() *Type {
 		default:
 			// LCHAN hidden_type_non_recv_chan
 			s2 := p.hidden_type_non_recv_chan()
-			ss := typ(TCHAN)
-			ss.Type = s2
-			ss.Chan = Cboth
+			ss := typeChan(s2, Cboth)
 			return ss
 
 		case '(':
@@ -3060,18 +3058,14 @@ func (p *parser) hidden_type_misc() *Type {
 			p.next()
 			s3 := p.hidden_type_recv_chan()
 			p.want(')')
-			ss := typ(TCHAN)
-			ss.Type = s3
-			ss.Chan = Cboth
+			ss := typeChan(s3, Cboth)
 			return ss
 
 		case LCOMM:
 			// LCHAN hidden_type
 			p.next()
 			s3 := p.hidden_type()
-			ss := typ(TCHAN)
-			ss.Type = s3
-			ss.Chan = Csend
+			ss := typeChan(s3, Csend)
 			return ss
 		}
 
@@ -3090,9 +3084,7 @@ func (p *parser) hidden_type_recv_chan() *Type {
 	p.want(LCHAN)
 	s3 := p.hidden_type()
 
-	ss := typ(TCHAN)
-	ss.Type = s3
-	ss.Chan = Crecv
+	ss := typeChan(s3, Crecv)
 	return ss
 }
 

src/cmd/compile/internal/gc/type.go

@@ -259,6 +259,14 @@ func typeDDDArray(elem *Type) *Type {
 	return t
 }
 
+// typeChan returns a new chan Type with direction dir.
+func typeChan(elem *Type, dir uint8) *Type {
+	t := typ(TCHAN)
+	t.Type = elem
+	t.Chan = dir
+	return t
+}
+
 func newField() *Field {
 	return &Field{
 		Offset: BADWIDTH,

src/cmd/compile/internal/gc/typecheck.go

@@ -413,10 +413,7 @@ OpSwitch:
 			n.Type = nil
 			return n
 		}
-		t := typ(TCHAN)
-		t.Type = l.Type
-		// TODO(marvin): Fix Node.EType type union.
-		t.Chan = uint8(n.Etype)
+		t := typeChan(l.Type, uint8(n.Etype)) // TODO(marvin): Fix Node.EType type union.
 		n.Op = OTYPE
 		n.Type = t
 		n.Left = nil