diff --git a/src/cmd/compile/internal/gc/const.go b/src/cmd/compile/internal/gc/const.go
index b3605ab..b24edfc 100644
--- a/src/cmd/compile/internal/gc/const.go
+++ b/src/cmd/compile/internal/gc/const.go
@@ -56,7 +56,6 @@
 	}
 
 	var v Val
-	v.Ctype = CTFLT
 	v.U = oldv
 	overflow(v, t)
 
@@ -136,7 +135,7 @@
 	case OLSH, ORSH:
 		convlit1(&n.Left, t, explicit && isideal(n.Left.Type))
 		t = n.Left.Type
-		if t != nil && t.Etype == TIDEAL && n.Val.Ctype != CTINT {
+		if t != nil && t.Etype == TIDEAL && n.Val.Ctype() != CTINT {
 			n.Val = toint(n.Val)
 		}
 		if t != nil && !Isint[t.Etype] {
@@ -229,7 +228,6 @@
 			if n.Type.Etype == TUNSAFEPTR {
 				n.Val.U = new(Mpint)
 				Mpmovecfix(n.Val.U.(*Mpint), 0)
-				n.Val.Ctype = CTINT
 			} else {
 				goto bad
 			}
@@ -244,7 +242,7 @@
 		if n.Type.Etype == TUNSAFEPTR && t.Etype != TUINTPTR {
 			goto bad
 		}
-		ct := int(n.Val.Ctype)
+		ct := int(n.Val.Ctype())
 		if Isint[et] {
 			switch ct {
 			default:
@@ -307,10 +305,11 @@
 }
 
 func copyval(v Val) Val {
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTINT, CTRUNE:
 		i := new(Mpint)
 		mpmovefixfix(i, v.U.(*Mpint))
+		i.Rune = v.U.(*Mpint).Rune
 		v.U = i
 
 	case CTFLT:
@@ -329,19 +328,17 @@
 }
 
 func tocplx(v Val) Val {
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTINT, CTRUNE:
 		c := new(Mpcplx)
 		Mpmovefixflt(&c.Real, v.U.(*Mpint))
 		Mpmovecflt(&c.Imag, 0.0)
-		v.Ctype = CTCPLX
 		v.U = c
 
 	case CTFLT:
 		c := new(Mpcplx)
 		mpmovefltflt(&c.Real, v.U.(*Mpflt))
 		Mpmovecflt(&c.Imag, 0.0)
-		v.Ctype = CTCPLX
 		v.U = c
 	}
 
@@ -349,11 +346,10 @@
 }
 
 func toflt(v Val) Val {
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTINT, CTRUNE:
 		f := newMpflt()
 		Mpmovefixflt(f, v.U.(*Mpint))
-		v.Ctype = CTFLT
 		v.U = f
 
 	case CTCPLX:
@@ -362,7 +358,6 @@
 		if mpcmpfltc(&v.U.(*Mpcplx).Imag, 0) != 0 {
 			Yyerror("constant %v%vi truncated to real", Fconv(&v.U.(*Mpcplx).Real, obj.FmtSharp), Fconv(&v.U.(*Mpcplx).Imag, obj.FmtSharp|obj.FmtSign))
 		}
-		v.Ctype = CTFLT
 		v.U = f
 	}
 
@@ -370,16 +365,17 @@
 }
 
 func toint(v Val) Val {
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTRUNE:
-		v.Ctype = CTINT
+		i := new(Mpint)
+		mpmovefixfix(i, v.U.(*Mpint))
+		v.U = i
 
 	case CTFLT:
 		i := new(Mpint)
 		if mpmovefltfix(i, v.U.(*Mpflt)) < 0 {
 			Yyerror("constant %v truncated to integer", Fconv(v.U.(*Mpflt), obj.FmtSharp))
 		}
-		v.Ctype = CTINT
 		v.U = i
 
 	case CTCPLX:
@@ -390,7 +386,6 @@
 		if mpcmpfltc(&v.U.(*Mpcplx).Imag, 0) != 0 {
 			Yyerror("constant %v%vi truncated to real", Fconv(&v.U.(*Mpcplx).Real, obj.FmtSharp), Fconv(&v.U.(*Mpcplx).Imag, obj.FmtSharp|obj.FmtSign))
 		}
-		v.Ctype = CTINT
 		v.U = i
 	}
 
@@ -398,7 +393,7 @@
 }
 
 func doesoverflow(v Val, t *Type) bool {
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTINT, CTRUNE:
 		if !Isint[t.Etype] {
 			Fatal("overflow: %v integer constant", t)
@@ -443,7 +438,7 @@
 		return
 	}
 
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTINT, CTRUNE:
 		Yyerror("constant %v overflows %v", v.U.(*Mpint), t)
 
@@ -456,14 +451,13 @@
 }
 
 func tostr(v Val) Val {
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTINT, CTRUNE:
 		if Mpcmpfixfix(v.U.(*Mpint), Minintval[TINT]) < 0 || Mpcmpfixfix(v.U.(*Mpint), Maxintval[TINT]) > 0 {
 			Yyerror("overflow in int -> string")
 		}
 		r := uint(Mpgetfix(v.U.(*Mpint)))
 		v = Val{}
-		v.Ctype = CTSTR
 		v.U = string(r)
 
 	case CTFLT:
@@ -472,7 +466,6 @@
 
 	case CTNIL:
 		v = Val{}
-		v.Ctype = CTSTR
 		v.U = ""
 	}
 
@@ -483,7 +476,7 @@
 	if n == nil || n.Op != OLITERAL {
 		return -1
 	}
-	return int(n.Val.Ctype)
+	return int(n.Val.Ctype())
 }
 
 func Isconst(n *Node, ct int) bool {
@@ -569,7 +562,6 @@
 				nl = Nod(OXXX, nil, nil)
 				*nl = *l1.N
 				nl.Orig = nl
-				nl.Val.Ctype = CTSTR
 				nl.Val.U = strings.Join(strs, "")
 				l1.N = nl
 				l1.Next = l2
@@ -617,7 +609,7 @@
 			v = copyval(v)
 		}
 
-		switch uint32(n.Op)<<16 | uint32(v.Ctype) {
+		switch uint32(n.Op)<<16 | uint32(v.Ctype()) {
 		default:
 			if n.Diag == 0 {
 				Yyerror("illegal constant expression %v %v", Oconv(int(n.Op), 0), nl.Type)
@@ -743,7 +735,7 @@
 		if nr.Type != nil && (Issigned[nr.Type.Etype] || !Isint[nr.Type.Etype]) {
 			goto illegal
 		}
-		if nl.Val.Ctype != CTRUNE {
+		if nl.Val.Ctype() != CTRUNE {
 			nl.Val = toint(nl.Val)
 		}
 		nr.Val = toint(nr.Val)
@@ -760,38 +752,46 @@
 	rv = nr.Val
 
 	// convert to common ideal
-	if v.Ctype == CTCPLX || rv.Ctype == CTCPLX {
+	if v.Ctype() == CTCPLX || rv.Ctype() == CTCPLX {
 		v = tocplx(v)
 		rv = tocplx(rv)
 	}
 
-	if v.Ctype == CTFLT || rv.Ctype == CTFLT {
+	if v.Ctype() == CTFLT || rv.Ctype() == CTFLT {
 		v = toflt(v)
 		rv = toflt(rv)
 	}
 
 	// Rune and int turns into rune.
-	if v.Ctype == CTRUNE && rv.Ctype == CTINT {
-		rv.Ctype = CTRUNE
+	if v.Ctype() == CTRUNE && rv.Ctype() == CTINT {
+		i := new(Mpint)
+		mpmovefixfix(i, rv.U.(*Mpint))
+		i.Rune = true
+		rv.U = i
 	}
-	if v.Ctype == CTINT && rv.Ctype == CTRUNE {
+	if v.Ctype() == CTINT && rv.Ctype() == CTRUNE {
 		if n.Op == OLSH || n.Op == ORSH {
-			rv.Ctype = CTINT
+			i := new(Mpint)
+			mpmovefixfix(i, rv.U.(*Mpint))
+			rv.U = i
 		} else {
-			v.Ctype = CTRUNE
+			i := new(Mpint)
+			mpmovefixfix(i, v.U.(*Mpint))
+			i.Rune = true
+			v.U = i
 		}
 	}
 
-	if v.Ctype != rv.Ctype {
+	if v.Ctype() != rv.Ctype() {
 		// Use of undefined name as constant?
-		if (v.Ctype == 0 || rv.Ctype == 0) && nerrors > 0 {
+		if (v.Ctype() == 0 || rv.Ctype() == 0) && nerrors > 0 {
 			return
 		}
-		Fatal("constant type mismatch %v(%d) %v(%d)", nl.Type, v.Ctype, nr.Type, rv.Ctype)
+		Fatal("constant type mismatch %v(%d) %v(%d)", nl.Type, v.Ctype(), nr.Type, rv.Ctype())
 	}
 
 	// run op
-	switch uint32(n.Op)<<16 | uint32(v.Ctype) {
+	switch uint32(n.Op)<<16 | uint32(v.Ctype()) {
 	default:
 		goto illegal
 
@@ -1075,7 +1075,7 @@
 	lineno = int32(lno)
 
 	// truncate precision for non-ideal float.
-	if v.Ctype == CTFLT && n.Type.Etype != TIDEAL {
+	if v.Ctype() == CTFLT && n.Type.Etype != TIDEAL {
 		n.Val.U = truncfltlit(v.U.(*Mpflt), n.Type)
 	}
 	return
@@ -1104,9 +1104,9 @@
 func nodlit(v Val) *Node {
 	n := Nod(OLITERAL, nil, nil)
 	n.Val = v
-	switch v.Ctype {
+	switch v.Ctype() {
 	default:
-		Fatal("nodlit ctype %d", v.Ctype)
+		Fatal("nodlit ctype %d", v.Ctype())
 
 	case CTSTR:
 		n.Type = idealstring
@@ -1132,10 +1132,9 @@
 	n := Nod(OLITERAL, nil, nil)
 	n.Type = Types[TIDEAL]
 	n.Val.U = c
-	n.Val.Ctype = CTCPLX
 
-	if r.Ctype != CTFLT || i.Ctype != CTFLT {
-		Fatal("nodcplxlit ctype %d/%d", r.Ctype, i.Ctype)
+	if r.Ctype() != CTFLT || i.Ctype() != CTFLT {
+		Fatal("nodcplxlit ctype %d/%d", r.Ctype(), i.Ctype())
 	}
 
 	mpmovefltflt(&c.Real, r.U.(*Mpflt))
@@ -1155,7 +1154,7 @@
 		return CTxxx
 
 	case OLITERAL:
-		return int(n.Val.Ctype)
+		return int(n.Val.Ctype())
 
 		// numeric kinds.
 	case OADD,
@@ -1230,7 +1229,7 @@
 			return
 		}
 
-		if n.Val.Ctype == CTNIL {
+		if n.Val.Ctype() == CTNIL {
 			lineno = int32(lno)
 			if n.Diag == 0 {
 				Yyerror("use of untyped nil")
@@ -1241,7 +1240,7 @@
 			break
 		}
 
-		if n.Val.Ctype == CTSTR {
+		if n.Val.Ctype() == CTSTR {
 			t1 := Types[TSTRING]
 			Convlit(np, t1)
 			break
@@ -1447,12 +1446,11 @@
 	con.Val = n.Val
 
 	if Isint[tt] {
-		con.Val.Ctype = CTINT
 		con.Val.U = new(Mpint)
 		var i int64
-		switch n.Val.Ctype {
+		switch n.Val.Ctype() {
 		default:
-			Fatal("convconst ctype=%d %v", n.Val.Ctype, Tconv(t, obj.FmtLong))
+			Fatal("convconst ctype=%d %v", n.Val.Ctype(), Tconv(t, obj.FmtLong))
 
 		case CTINT, CTRUNE:
 			i = Mpgetfix(n.Val.U.(*Mpint))
@@ -1471,8 +1469,8 @@
 
 	if Isfloat[tt] {
 		con.Val = toflt(con.Val)
-		if con.Val.Ctype != CTFLT {
-			Fatal("convconst ctype=%d %v", con.Val.Ctype, t)
+		if con.Val.Ctype() != CTFLT {
+			Fatal("convconst ctype=%d %v", con.Val.Ctype(), t)
 		}
 		if tt == TFLOAT32 {
 			con.Val.U = truncfltlit(con.Val.U.(*Mpflt), t)
@@ -1636,13 +1634,13 @@
 		}
 
 	case OLITERAL:
-		if n.Val.Ctype != CTNIL {
+		if n.Val.Ctype() != CTNIL {
 			return true
 		}
 
 	case ONAME:
 		l := n.Sym.Def
-		if l != nil && l.Op == OLITERAL && n.Val.Ctype != CTNIL {
+		if l != nil && l.Op == OLITERAL && n.Val.Ctype() != CTNIL {
 			return true
 		}
 
diff --git a/src/cmd/compile/internal/gc/cplx.go b/src/cmd/compile/internal/gc/cplx.go
index 56a4892..7a0c84b 100644
--- a/src/cmd/compile/internal/gc/cplx.go
+++ b/src/cmd/compile/internal/gc/cplx.go
@@ -227,7 +227,6 @@
 	n.Addable = true
 	ullmancalc(n)
 	n.Val.U = fval
-	n.Val.Ctype = CTFLT
 	n.Type = t
 
 	if !Isfloat[t.Etype] {
diff --git a/src/cmd/compile/internal/gc/dcl.go b/src/cmd/compile/internal/gc/dcl.go
index dffb791..fc2f14a 100644
--- a/src/cmd/compile/internal/gc/dcl.go
+++ b/src/cmd/compile/internal/gc/dcl.go
@@ -828,7 +828,7 @@
 		f.Broke = 1
 	}
 
-	switch n.Val.Ctype {
+	switch n.Val.Ctype() {
 	case CTSTR:
 		f.Note = new(string)
 		*f.Note = n.Val.U.(string)
@@ -937,7 +937,7 @@
 		Fatal("interfacefield: oops %v\n", n)
 	}
 
-	if n.Val.Ctype != CTxxx {
+	if n.Val.Ctype() != CTxxx {
 		Yyerror("interface method cannot have annotation")
 	}
 
diff --git a/src/cmd/compile/internal/gc/fmt.go b/src/cmd/compile/internal/gc/fmt.go
index aaf0f95..e3446f2 100644
--- a/src/cmd/compile/internal/gc/fmt.go
+++ b/src/cmd/compile/internal/gc/fmt.go
@@ -299,7 +299,7 @@
 
 // Fmt "%V": Values
 func Vconv(v *Val, flag int) string {
-	switch v.Ctype {
+	switch v.Ctype() {
 	case CTINT:
 		if (flag&obj.FmtSharp != 0) || fmtmode == FExp {
 			return Bconv(v.U.(*Mpint), obj.FmtSharp)
@@ -1109,7 +1109,7 @@
 				return Sconv(n.Sym, 0)
 			}
 		}
-		if n.Val.Ctype == CTNIL && n.Orig != nil && n.Orig != n {
+		if n.Val.Ctype() == CTNIL && n.Orig != nil && n.Orig != n {
 			return exprfmt(n.Orig, prec)
 		}
 		if n.Type != nil && n.Type != Types[n.Type.Etype] && n.Type != idealbool && n.Type != idealstring {
diff --git a/src/cmd/compile/internal/gc/gen.go b/src/cmd/compile/internal/gc/gen.go
index 95049ce..d1b4d44 100644
--- a/src/cmd/compile/internal/gc/gen.go
+++ b/src/cmd/compile/internal/gc/gen.go
@@ -340,14 +340,12 @@
 	case TFLOAT32, TFLOAT64:
 		var zero Mpflt
 		Mpmovecflt(&zero, 0.0)
-		z.Val.Ctype = CTFLT
 		z.Val.U = &zero
 
 	case TPTR32, TPTR64, TCHAN, TMAP:
-		z.Val.Ctype = CTNIL
+		z.Val.U = new(NilVal)
 
 	case TBOOL:
-		z.Val.Ctype = CTBOOL
 		z.Val.U = false
 
 	case TINT8,
@@ -358,7 +356,6 @@
 		TUINT16,
 		TUINT32,
 		TUINT64:
-		z.Val.Ctype = CTINT
 		z.Val.U = new(Mpint)
 		Mpmovecfix(z.Val.U.(*Mpint), 0)
 
diff --git a/src/cmd/compile/internal/gc/go.go b/src/cmd/compile/internal/gc/go.go
index dc33f62..21a8a68 100644
--- a/src/cmd/compile/internal/gc/go.go
+++ b/src/cmd/compile/internal/gc/go.go
@@ -66,8 +66,9 @@
 
 // Mpint represents an integer constant.
 type Mpint struct {
-	Val big.Int
-	Ovf bool // set if Val overflowed compiler limit (sticky)
+	Val  big.Int
+	Ovf  bool // set if Val overflowed compiler limit (sticky)
+	Rune bool // set if syntax indicates default type rune
 }
 
 // Mpflt represents a floating-point constant.
@@ -82,16 +83,40 @@
 }
 
 type Val struct {
-	Ctype int16
 	// U contains one of:
-	// bool     bool when Ctype == CTBOOL
-	// *Mpint   int when Ctype == CTINT, rune when Ctype == CTRUNE
-	// *Mpflt   float when Ctype == CTFLT
-	// *Mpcplx  pair of floats when Ctype == CTCPLX
-	// string   string when Ctype == CTSTR
+	// bool     bool when n.ValCtype() == CTBOOL
+	// *Mpint   int when n.ValCtype() == CTINT, rune when n.ValCtype() == CTRUNE
+	// *Mpflt   float when n.ValCtype() == CTFLT
+	// *Mpcplx  pair of floats when n.ValCtype() == CTCPLX
+	// string   string when n.ValCtype() == CTSTR
+	// *Nilval  when n.ValCtype() == CTNIL
 	U interface{}
 }
 
+type NilVal struct{}
+
+func (v Val) Ctype() int {
+	switch x := v.U.(type) {
+	default:
+		return 0
+	case *NilVal:
+		return CTNIL
+	case bool:
+		return CTBOOL
+	case *Mpint:
+		if x.Rune {
+			return CTRUNE
+		}
+		return CTINT
+	case *Mpflt:
+		return CTFLT
+	case *Mpcplx:
+		return CTCPLX
+	case string:
+		return CTSTR
+	}
+}
+
 type Pkg struct {
 	Name     string // package name
 	Path     string // string literal used in import statement
diff --git a/src/cmd/compile/internal/gc/go.y b/src/cmd/compile/internal/gc/go.y
index 40e273c..b8e9ceb 100644
--- a/src/cmd/compile/internal/gc/go.y
+++ b/src/cmd/compile/internal/gc/go.y
@@ -1996,7 +1996,7 @@
 
 oliteral:
 	{
-		$$.Ctype = CTxxx;
+		$$.U = nil
 	}
 |	LLITERAL
 
@@ -2231,7 +2231,7 @@
 |	'-' LLITERAL
 	{
 		$$ = nodlit($2);
-		switch($$.Val.Ctype){
+		switch($$.Val.Ctype()){
 		case CTINT, CTRUNE:
 			mpnegfix($$.Val.U.(*Mpint));
 			break;
@@ -2258,7 +2258,7 @@
 	hidden_literal
 |	'(' hidden_literal '+' hidden_literal ')'
 	{
-		if $2.Val.Ctype == CTRUNE && $4.Val.Ctype == CTINT {
+		if $2.Val.Ctype() == CTRUNE && $4.Val.Ctype() == CTINT {
 			$$ = $2;
 			mpaddfixfix($2.Val.U.(*Mpint), $4.Val.U.(*Mpint), 0);
 			break;
diff --git a/src/cmd/compile/internal/gc/gsubr.go b/src/cmd/compile/internal/gc/gsubr.go
index 93bd8a2..6dd2bc9 100644
--- a/src/cmd/compile/internal/gc/gsubr.go
+++ b/src/cmd/compile/internal/gc/gsubr.go
@@ -408,7 +408,7 @@
 		if Thearch.Thechar == '8' {
 			a.Width = 0
 		}
-		switch n.Val.Ctype {
+		switch n.Val.Ctype() {
 		default:
 			Fatal("naddr: const %v", Tconv(n.Type, obj.FmtLong))
 
diff --git a/src/cmd/compile/internal/gc/lex.go b/src/cmd/compile/internal/gc/lex.go
index cf41c40..fd64dab 100644
--- a/src/cmd/compile/internal/gc/lex.go
+++ b/src/cmd/compile/internal/gc/lex.go
@@ -639,7 +639,7 @@
 }
 
 func importfile(f *Val, line int) {
-	if f.Ctype != CTSTR {
+	if _, ok := f.U.(string); !ok {
 		Yyerror("import statement not a string")
 		fakeimport()
 		return
@@ -1064,9 +1064,10 @@
 			ungetc(int(v))
 		}
 
-		yylval.val.U = new(Mpint)
-		Mpmovecfix(yylval.val.U.(*Mpint), v)
-		yylval.val.Ctype = CTRUNE
+		x := new(Mpint)
+		yylval.val.U = x
+		Mpmovecfix(x, v)
+		x.Rune = true
 		if Debug['x'] != 0 {
 			fmt.Printf("lex: codepoint literal\n")
 		}
@@ -1410,7 +1411,6 @@
 		Mpmovecfix(yylval.val.U.(*Mpint), 0)
 	}
 
-	yylval.val.Ctype = CTINT
 	if Debug['x'] != 0 {
 		fmt.Printf("lex: integer literal\n")
 	}
@@ -1472,7 +1472,6 @@
 		Mpmovecflt(&yylval.val.U.(*Mpcplx).Real, 0.0)
 	}
 
-	yylval.val.Ctype = CTCPLX
 	if Debug['x'] != 0 {
 		fmt.Printf("lex: imaginary literal\n")
 	}
@@ -1491,7 +1490,6 @@
 		Mpmovecflt(yylval.val.U.(*Mpflt), 0.0)
 	}
 
-	yylval.val.Ctype = CTFLT
 	if Debug['x'] != 0 {
 		fmt.Printf("lex: floating literal\n")
 	}
@@ -1500,7 +1498,6 @@
 
 strlit:
 	yylval.val.U = internString(cp.Bytes())
-	yylval.val.Ctype = CTSTR
 	if Debug['x'] != 0 {
 		fmt.Printf("lex: string literal\n")
 	}
@@ -2235,7 +2232,7 @@
 	Types[TNIL] = typ(TNIL)
 	s = Pkglookup("nil", builtinpkg)
 	var v Val
-	v.Ctype = CTNIL
+	v.U = new(NilVal)
 	s.Def = nodlit(v)
 	s.Def.Sym = s
 }
@@ -2359,7 +2356,7 @@
 	s = Lookup("nil")
 	if s.Def == nil {
 		var v Val
-		v.Ctype = CTNIL
+		v.U = new(NilVal)
 		s.Def = nodlit(v)
 		s.Def.Sym = s
 		s.Origpkg = builtinpkg
diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go
index 690582a..d3849e8 100644
--- a/src/cmd/compile/internal/gc/obj.go
+++ b/src/cmd/compile/internal/gc/obj.go
@@ -383,7 +383,7 @@
 
 func gdata(nam *Node, nr *Node, wid int) {
 	if nr.Op == OLITERAL {
-		switch nr.Val.Ctype {
+		switch nr.Val.Ctype() {
 		case CTCPLX:
 			gdatacomplex(nam, nr.Val.U.(*Mpcplx))
 			return
diff --git a/src/cmd/compile/internal/gc/sinit.go b/src/cmd/compile/internal/gc/sinit.go
index ddcce6a..061711c 100644
--- a/src/cmd/compile/internal/gc/sinit.go
+++ b/src/cmd/compile/internal/gc/sinit.go
@@ -517,7 +517,7 @@
 
 func isliteral(n *Node) bool {
 	if n.Op == OLITERAL {
-		if n.Val.Ctype != CTNIL {
+		if n.Val.Ctype() != CTNIL {
 			return true
 		}
 	}
@@ -1351,7 +1351,7 @@
 func iszero(n *Node) bool {
 	switch n.Op {
 	case OLITERAL:
-		switch n.Val.Ctype {
+		switch n.Val.Ctype() {
 		default:
 			Dump("unexpected literal", n)
 			Fatal("iszero")
diff --git a/src/cmd/compile/internal/gc/subr.go b/src/cmd/compile/internal/gc/subr.go
index 48068fc..4dd8b29 100644
--- a/src/cmd/compile/internal/gc/subr.go
+++ b/src/cmd/compile/internal/gc/subr.go
@@ -667,7 +667,6 @@
 	c.Addable = true
 	c.Val.U = new(Mpint)
 	Mpmovecfix(c.Val.U.(*Mpint), v)
-	c.Val.Ctype = CTINT
 	c.Type = Types[TIDEAL]
 	ullmancalc(c)
 	return c
@@ -678,7 +677,6 @@
 	c.Addable = true
 	c.Val.U = newMpflt()
 	mpmovefltflt(c.Val.U.(*Mpflt), v)
-	c.Val.Ctype = CTFLT
 	c.Type = Types[TIDEAL]
 	ullmancalc(c)
 	return c
@@ -691,7 +689,6 @@
 	ullmancalc(n)
 	n.Val.U = new(Mpint)
 	Mpmovecfix(n.Val.U.(*Mpint), v)
-	n.Val.Ctype = CTINT
 	n.Type = t
 
 	if Isfloat[t.Etype] {
@@ -701,14 +698,13 @@
 
 func nodnil() *Node {
 	c := Nodintconst(0)
-	c.Val.Ctype = CTNIL
+	c.Val.U = new(NilVal)
 	c.Type = Types[TNIL]
 	return c
 }
 
 func Nodbool(b bool) *Node {
 	c := Nodintconst(0)
-	c.Val.Ctype = CTBOOL
 	c.Val.U = b
 	c.Type = idealbool
 	return c
@@ -796,7 +792,7 @@
 	if n.Op != OLITERAL {
 		return false
 	}
-	if n.Val.Ctype != CTNIL {
+	if n.Val.Ctype() != CTNIL {
 		return false
 	}
 	return true
@@ -2431,7 +2427,6 @@
 		var l *NodeList
 
 		var v Val
-		v.Ctype = CTSTR
 		v.U = rcvr.Type.Sym.Pkg.Name // package name
 		l = list(l, nodlit(v))
 		v.U = rcvr.Type.Sym.Name // type name
diff --git a/src/cmd/compile/internal/gc/swt.go b/src/cmd/compile/internal/gc/swt.go
index a3df7e2..6f04328 100644
--- a/src/cmd/compile/internal/gc/swt.go
+++ b/src/cmd/compile/internal/gc/swt.go
@@ -579,7 +579,7 @@
 		switch c.typ {
 		case caseKindTypeNil:
 			var v Val
-			v.Ctype = CTNIL
+			v.U = new(NilVal)
 			a = Nod(OIF, nil, nil)
 			a.Left = Nod(OEQ, s.facename, nodlit(v))
 			typecheck(&a.Left, Erv)
@@ -742,11 +742,11 @@
 	n2 := c2.node.Left
 
 	// sort by type (for switches on interface)
-	ct := int(n1.Val.Ctype)
-	if ct > int(n2.Val.Ctype) {
+	ct := int(n1.Val.Ctype())
+	if ct > int(n2.Val.Ctype()) {
 		return +1
 	}
-	if ct < int(n2.Val.Ctype) {
+	if ct < int(n2.Val.Ctype()) {
 		return -1
 	}
 	if !Eqtype(n1.Type, n2.Type) {
diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index 518a472..36088e7 100644
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -301,7 +301,7 @@
 	case OLITERAL:
 		ok |= Erv
 
-		if n.Type == nil && n.Val.Ctype == CTSTR {
+		if n.Type == nil && n.Val.Ctype() == CTSTR {
 			n.Type = idealstring
 		}
 		break OpSwitch
@@ -756,12 +756,12 @@
 		}
 
 		if et == TINTER {
-			if l.Op == OLITERAL && l.Val.Ctype == CTNIL {
+			if l.Op == OLITERAL && l.Val.Ctype() == CTNIL {
 				// swap for back end
 				n.Left = r
 
 				n.Right = l
-			} else if r.Op == OLITERAL && r.Val.Ctype == CTNIL {
+			} else if r.Op == OLITERAL && r.Val.Ctype() == CTNIL {
 			} else // leave alone for back end
 			if Isinter(r.Type) == Isinter(l.Type) {
 				n.Etype = n.Op
@@ -2833,7 +2833,7 @@
 	}
 
 	var b uint32
-	switch n.Val.Ctype {
+	switch n.Val.Ctype() {
 	default: // unknown, bool, nil
 		b = 23
 
@@ -3486,7 +3486,7 @@
 
 func stringtoarraylit(np **Node) {
 	n := *np
-	if n.Left.Op != OLITERAL || n.Left.Val.Ctype != CTSTR {
+	if n.Left.Op != OLITERAL || n.Left.Val.Ctype() != CTSTR {
 		Fatal("stringtoarraylit %v", n)
 	}
 
@@ -3844,7 +3844,7 @@
 
 func checkmake(t *Type, arg string, n *Node) int {
 	if n.Op == OLITERAL {
-		switch n.Val.Ctype {
+		switch n.Val.Ctype() {
 		case CTINT, CTRUNE, CTFLT, CTCPLX:
 			n.Val = toint(n.Val)
 			if mpcmpfixc(n.Val.U.(*Mpint), 0) < 0 {
diff --git a/src/cmd/compile/internal/gc/unsafe.go b/src/cmd/compile/internal/gc/unsafe.go
index 824ecd0..a41bed8 100644
--- a/src/cmd/compile/internal/gc/unsafe.go
+++ b/src/cmd/compile/internal/gc/unsafe.go
@@ -138,8 +138,6 @@
 	// any side effects disappear; ignore init
 ret:
 	var val Val
-	val.Ctype = CTINT
-
 	val.U = new(Mpint)
 	Mpmovecfix(val.U.(*Mpint), v)
 	n := Nod(OLITERAL, nil, nil)
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 63375fe..07d1309 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -2027,7 +2027,7 @@
 
 		n = l.N
 		if n.Op == OLITERAL {
-			switch n.Val.Ctype {
+			switch n.Val.Ctype() {
 			case CTRUNE:
 				defaultlit(&n, runetype)
 
diff --git a/src/cmd/compile/internal/gc/y.go b/src/cmd/compile/internal/gc/y.go
index c1abdfe..1ee619f 100644
--- a/src/cmd/compile/internal/gc/y.go
+++ b/src/cmd/compile/internal/gc/y.go
@@ -3182,7 +3182,7 @@
 		yyDollar = yyS[yypt-0 : yypt+1]
 		//line go.y:1998
 		{
-			yyVAL.val.Ctype = CTxxx
+			yyVAL.val.U = nil
 		}
 	case 304:
 		yyDollar = yyS[yypt-4 : yypt+1]
@@ -3434,7 +3434,7 @@
 		//line go.y:2232
 		{
 			yyVAL.node = nodlit(yyDollar[2].val)
-			switch yyVAL.node.Val.Ctype {
+			switch yyVAL.node.Val.Ctype() {
 			case CTINT, CTRUNE:
 				mpnegfix(yyVAL.node.Val.U.(*Mpint))
 				break
@@ -3462,7 +3462,7 @@
 		yyDollar = yyS[yypt-5 : yypt+1]
 		//line go.y:2260
 		{
-			if yyDollar[2].node.Val.Ctype == CTRUNE && yyDollar[4].node.Val.Ctype == CTINT {
+			if yyDollar[2].node.Val.Ctype() == CTRUNE && yyDollar[4].node.Val.Ctype() == CTINT {
 				yyVAL.node = yyDollar[2].node
 				mpaddfixfix(yyDollar[2].node.Val.U.(*Mpint), yyDollar[4].node.Val.U.(*Mpint), 0)
 				break