diff --git a/src/cmd/compile/internal/gc/const.go b/src/cmd/compile/internal/gc/const.go
index 4d52d091b0..1d67e5fd10 100644
--- a/src/cmd/compile/internal/gc/const.go
+++ b/src/cmd/compile/internal/gc/const.go
@@ -12,7 +12,7 @@ import (
 )
 
 // Ctype describes the constant kind of an "ideal" (untyped) constant.
-type Ctype int8
+type Ctype uint8
 
 const (
 	CTxxx Ctype = iota
@@ -297,7 +297,7 @@ func convlit1(n *Node, t *types.Type, explicit bool, reuse canReuseNode) *Node {
 
 	ct := consttype(n)
 	var et types.EType
-	if ct < 0 {
+	if ct == 0 {
 		goto bad
 	}
 
@@ -591,7 +591,7 @@ func tostr(v Val) Val {
 
 func consttype(n *Node) Ctype {
 	if n == nil || n.Op != OLITERAL {
-		return -1
+		return 0
 	}
 	return n.Val().Ctype()
 }
@@ -693,7 +693,7 @@ func evconst(n *Node) {
 	if nl == nil || nl.Type == nil {
 		return
 	}
-	if consttype(nl) < 0 {
+	if consttype(nl) == 0 {
 		return
 	}
 	wl := nl.Type.Etype
@@ -840,7 +840,7 @@ func evconst(n *Node) {
 	if nr.Type == nil {
 		return
 	}
-	if consttype(nr) < 0 {
+	if consttype(nr) == 0 {
 		return
 	}
 	wr = nr.Type.Etype
diff --git a/src/cmd/compile/internal/gc/order.go b/src/cmd/compile/internal/gc/order.go
index c555a5eabc..fdee8b89a5 100644
--- a/src/cmd/compile/internal/gc/order.go
+++ b/src/cmd/compile/internal/gc/order.go
@@ -187,7 +187,7 @@ func isaddrokay(n *Node) bool {
 // The result of orderaddrtemp MUST be assigned back to n, e.g.
 // 	n.Left = orderaddrtemp(n.Left, order)
 func orderaddrtemp(n *Node, order *Order) *Node {
-	if consttype(n) >= 0 {
+	if consttype(n) > 0 {
 		// TODO: expand this to all static composite literal nodes?
 		n = defaultlit(n, nil)
 		dowidth(n.Type)
diff --git a/src/cmd/compile/internal/gc/swt.go b/src/cmd/compile/internal/gc/swt.go
index b97e68f60c..31d018b152 100644
--- a/src/cmd/compile/internal/gc/swt.go
+++ b/src/cmd/compile/internal/gc/swt.go
@@ -257,7 +257,7 @@ func (s *exprSwitch) walk(sw *Node) {
 	var cas []*Node
 	if s.kind == switchKindTrue || s.kind == switchKindFalse {
 		s.exprname = nodbool(s.kind == switchKindTrue)
-	} else if consttype(cond) >= 0 {
+	} else if consttype(cond) > 0 {
 		// leave constants to enable dead code elimination (issue 9608)
 		s.exprname = cond
 	} else {
@@ -607,12 +607,7 @@ func checkDupExprCases(exprname *Node, clauses []*Node) {
 				//       case GOARCH == "arm" && GOARM == "5":
 				//       case GOARCH == "arm":
 				//     which would both evaluate to false for non-ARM compiles.
-				if ct := consttype(n); ct < 0 || ct == CTBOOL {
-					continue
-				}
-				// If the value has no type, we have
-				// already printed an error about it.
-				if n.Type == nil {
+				if ct := consttype(n); ct == 0 || ct == CTBOOL {
 					continue
 				}
 
@@ -637,12 +632,7 @@ func checkDupExprCases(exprname *Node, clauses []*Node) {
 	seen := make(map[typeVal]*Node)
 	for _, ncase := range clauses {
 		for _, n := range ncase.List.Slice() {
-			if ct := consttype(n); ct < 0 || ct == CTBOOL {
-				continue
-			}
-			// If the value has no type, we have
-			// already printed an error about it.
-			if n.Type == nil {
+			if ct := consttype(n); ct == 0 || ct == CTBOOL {
 				continue
 			}
 			tv := typeVal{