cmd/compile: fix printing of OCASE nodes

Switch lowering splits each case expression out
into its own OCASE node.

Change-Id: Ifcb72b99975ed36da8540f6e43343e9aa2058572
Reviewed-on: https://go-review.googlesource.com/26769
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -886,13 +886,20 @@ func stmtfmt(n *Node) string {
 
 		f += fmt.Sprintf(" { %v }", n.List)
 
-	case OCASE, OXCASE:
+	case OXCASE:
 		if n.List.Len() != 0 {
 			f += fmt.Sprintf("case %v: %v", hconv(n.List, FmtComma), n.Nbody)
 		} else {
 			f += fmt.Sprintf("default: %v", n.Nbody)
 		}
 
+	case OCASE:
+		if n.Left != nil {
+			f += fmt.Sprintf("case %v: %v", n.Left, n.Nbody)
+		} else {
+			f += fmt.Sprintf("default: %v", n.Nbody)
+		}
+
 	case OBREAK,
 		OCONTINUE,
 		OGOTO,

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

@@ -425,7 +425,7 @@ const (
 	// statements
 	OBLOCK    // { List } (block of code)
 	OBREAK    // break
-	OCASE     // case List: Nbody (select case after processing; List==nil means default)
+	OCASE     // case Left: Nbody (select case after processing; Left==nil means default)
 	OXCASE    // case List: Nbody (select case before processing; List==nil means default)
 	OCONTINUE // continue
 	ODEFER    // defer Left (Left must be call)