diff --git a/src/cmd/internal/gc/closure.go b/src/cmd/internal/gc/closure.go
index 56b418985bd..c29674928cc 100644
--- a/src/cmd/internal/gc/closure.go
+++ b/src/cmd/internal/gc/closure.go
@@ -402,7 +402,7 @@ func transformclosure(xfunc *Node) {
 				addr = newname(Lookup(namebuf))
 				addr.Ntype = Nod(OIND, typenod(v.Type), nil)
 				addr.Class = PAUTO
-				addr.Used = 1
+				addr.Used = true
 				addr.Curfn = xfunc
 				xfunc.Dcl = list(xfunc.Dcl, addr)
 				v.Heapaddr = addr
@@ -461,7 +461,7 @@ func walkclosure(func_ *Node, init **NodeList) *Node {
 
 	clos := Nod(OCOMPLIT, nil, Nod(OIND, typ, nil))
 	clos.Esc = func_.Esc
-	clos.Right.Implicit = 1
+	clos.Right.Implicit = true
 	clos.List = concat(list1(Nod(OCFUNC, func_.Closure.Nname, nil)), func_.Enter)
 
 	// Force type conversion from *struct to the func type.
@@ -609,7 +609,7 @@ func makepartialcall(fn *Node, t0 *Type, meth *Node) *Node {
 	ptr.Class = PAUTO
 	ptr.Addable = 1
 	ptr.Ullman = 1
-	ptr.Used = 1
+	ptr.Used = true
 	ptr.Curfn = xfunc
 	xfunc.Dcl = list(xfunc.Dcl, ptr)
 	var body *NodeList
@@ -667,7 +667,7 @@ func walkpartialcall(n *Node, init **NodeList) *Node {
 
 	clos := Nod(OCOMPLIT, nil, Nod(OIND, typ, nil))
 	clos.Esc = n.Esc
-	clos.Right.Implicit = 1
+	clos.Right.Implicit = true
 	clos.List = list1(Nod(OCFUNC, n.Nname.Nname, nil))
 	clos.List = list(clos.List, n.Left)
 
diff --git a/src/cmd/internal/gc/esc.go b/src/cmd/internal/gc/esc.go
index 0714f9c599c..8affbaf5544 100644
--- a/src/cmd/internal/gc/esc.go
+++ b/src/cmd/internal/gc/esc.go
@@ -1095,7 +1095,7 @@ func esccall(e *EscState, n *Node, up *Node) {
 		src.Class = PAUTO
 		src.Curfn = Curfn
 		src.Escloopdepth = e.loopdepth
-		src.Used = 1
+		src.Used = true
 		src.Lineno = n.Lineno
 		n.Escretval = list(n.Escretval, src)
 	}
diff --git a/src/cmd/internal/gc/fmt.go b/src/cmd/internal/gc/fmt.go
index 43ffb80e0d0..66f5d212a37 100644
--- a/src/cmd/internal/gc/fmt.go
+++ b/src/cmd/internal/gc/fmt.go
@@ -273,8 +273,8 @@ func Jconv(n *Node, flag int) string {
 		fp += fmt.Sprintf(" isddd(%d)", n.Isddd)
 	}
 
-	if n.Implicit != 0 {
-		fp += fmt.Sprintf(" implicit(%d)", n.Implicit)
+	if n.Implicit {
+		fp += fmt.Sprintf(" implicit(%v)", n.Implicit)
 	}
 
 	if n.Embedded != 0 {
@@ -289,8 +289,8 @@ func Jconv(n *Node, flag int) string {
 		fp += " assigned"
 	}
 
-	if c == 0 && n.Used != 0 {
-		fp += fmt.Sprintf(" used(%d)", n.Used)
+	if c == 0 && n.Used {
+		fp += fmt.Sprintf(" used(%v)", n.Used)
 	}
 	return fp
 }
@@ -859,7 +859,7 @@ func stmtfmt(n *Node) string {
 		}
 
 	case OASOP:
-		if n.Implicit != 0 {
+		if n.Implicit {
 			if n.Etype == OADD {
 				f += fmt.Sprintf("%v++", Nconv(n.Left, 0))
 			} else {
@@ -1109,7 +1109,7 @@ var opprec = []int{
 }
 
 func exprfmt(n *Node, prec int) string {
-	for n != nil && n.Implicit != 0 && (n.Op == OIND || n.Op == OADDR) {
+	for n != nil && n.Implicit && (n.Op == OIND || n.Op == OADDR) {
 		n = n.Left
 	}
 
@@ -1266,9 +1266,9 @@ func exprfmt(n *Node, prec int) string {
 		return f
 
 	case OCOMPLIT:
-		ptrlit := n.Right != nil && n.Right.Implicit != 0 && n.Right.Type != nil && Isptr[n.Right.Type.Etype]
+		ptrlit := n.Right != nil && n.Right.Implicit && n.Right.Type != nil && Isptr[n.Right.Type.Etype]
 		if fmtmode == FErr {
-			if n.Right != nil && n.Right.Type != nil && n.Implicit == 0 {
+			if n.Right != nil && n.Right.Type != nil && !n.Implicit {
 				if ptrlit {
 					return fmt.Sprintf("&%v literal", Tconv(n.Right.Type.Type, 0))
 				} else {
@@ -1289,7 +1289,7 @@ func exprfmt(n *Node, prec int) string {
 		return f
 
 	case OPTRLIT:
-		if fmtmode == FExp && n.Left.Implicit != 0 {
+		if fmtmode == FExp && n.Left.Implicit {
 			return fmt.Sprintf("%v", Nconv(n.Left, 0))
 		}
 		var f string
@@ -1299,7 +1299,7 @@ func exprfmt(n *Node, prec int) string {
 	case OSTRUCTLIT:
 		if fmtmode == FExp { // requires special handling of field names
 			var f string
-			if n.Implicit != 0 {
+			if n.Implicit {
 				f += "{"
 			} else {
 				f += fmt.Sprintf("(%v{", Tconv(n.Type, 0))
@@ -1314,7 +1314,7 @@ func exprfmt(n *Node, prec int) string {
 				}
 			}
 
-			if n.Implicit == 0 {
+			if !n.Implicit {
 				f += "})"
 				return f
 			}
@@ -1330,7 +1330,7 @@ func exprfmt(n *Node, prec int) string {
 		if fmtmode == FErr {
 			return fmt.Sprintf("%v literal", Tconv(n.Type, 0))
 		}
-		if fmtmode == FExp && n.Implicit != 0 {
+		if fmtmode == FExp && n.Implicit {
 			return fmt.Sprintf("{ %v }", Hconv(n.List, obj.FmtComma))
 		}
 		var f string
diff --git a/src/cmd/internal/gc/gen.go b/src/cmd/internal/gc/gen.go
index 7089b9cec49..70c218e667c 100644
--- a/src/cmd/internal/gc/gen.go
+++ b/src/cmd/internal/gc/gen.go
@@ -613,7 +613,7 @@ func Tempname(nn *Node, t *Type) {
 func temp(t *Type) *Node {
 	n := Nod(OXXX, nil, nil)
 	Tempname(n, t)
-	n.Sym.Def.Used = 1
+	n.Sym.Def.Used = true
 	return n.Orig
 }
 
diff --git a/src/cmd/internal/gc/go.y b/src/cmd/internal/gc/go.y
index 0961da248a2..2e3625da783 100644
--- a/src/cmd/internal/gc/go.y
+++ b/src/cmd/internal/gc/go.y
@@ -418,7 +418,7 @@ simple_stmt:
 		switch($$.Op) {
 		case ONAME, ONONAME, OTYPE, OPACK, OLITERAL:
 			$$ = Nod(OPAREN, $$, nil);
-			$$.Implicit = 1;
+			$$.Implicit = true;
 			break;
 		}
 	}
@@ -460,13 +460,13 @@ simple_stmt:
 |	expr LINC
 	{
 		$$ = Nod(OASOP, $1, Nodintconst(1));
-		$$.Implicit = 1;
+		$$.Implicit = true;
 		$$.Etype = OADD;
 	}
 |	expr LDEC
 	{
 		$$ = Nod(OASOP, $1, Nodintconst(1));
-		$$.Implicit = 1;
+		$$.Implicit = true;
 		$$.Etype = OSUB;
 	}
 
@@ -886,7 +886,7 @@ uexpr:
 			// Special case for &T{...}: turn into (*T){...}.
 			$$ = $2;
 			$$.Right = Nod(OIND, $$.Right, nil);
-			$$.Right.Implicit = 1;
+			$$.Right.Implicit = true;
 		} else {
 			$$ = Nod(OADDR, $2, nil);
 		}
@@ -949,7 +949,7 @@ pexpr_no_paren:
 		if $1.Op == OPACK {
 			var s *Sym
 			s = restrictlookup($3.Name, $1.Pkg);
-			$1.Used = 1;
+			$1.Used = true;
 			$$ = oldname(s);
 			break;
 		}
@@ -1034,7 +1034,7 @@ bare_complitexpr:
 		switch($$.Op) {
 		case ONAME, ONONAME, OTYPE, OPACK, OLITERAL:
 			$$ = Nod(OPAREN, $$, nil);
-			$$.Implicit = 1;
+			$$.Implicit = true;
 		}
 	}
 |	'{' start_complit braced_keyval_list '}'
@@ -1160,7 +1160,7 @@ name:
 	{
 		$$ = oldname($1);
 		if $$.Pack != nil {
-			$$.Pack.Used = 1;
+			$$.Pack.Used = true;
 		}
 	}
 
@@ -1238,7 +1238,7 @@ dotname:
 		if $1.Op == OPACK {
 			var s *Sym
 			s = restrictlookup($3.Name, $1.Pkg);
-			$1.Used = 1;
+			$1.Used = true;
 			$$ = oldname(s);
 			break;
 		}
@@ -1626,7 +1626,7 @@ packname:
 		$$ = $1;
 		n = oldname($1);
 		if n.Pack != nil {
-			n.Pack.Used = 1;
+			n.Pack.Used = true;
 		}
 	}
 |	LNAME '.' sym
@@ -1637,7 +1637,7 @@ packname:
 			Yyerror("%v is not a package", Sconv($1, 0));
 			pkg = localpkg;
 		} else {
-			$1.Def.Used = 1;
+			$1.Def.Used = true;
 			pkg = $1.Def.Pkg;
 		}
 		$$ = restrictlookup($3.Name, pkg);
diff --git a/src/cmd/internal/gc/gsubr.go b/src/cmd/internal/gc/gsubr.go
index e86d2ab3e4d..44e0d22a870 100644
--- a/src/cmd/internal/gc/gsubr.go
+++ b/src/cmd/internal/gc/gsubr.go
@@ -174,12 +174,12 @@ func fixautoused(p *obj.Prog) {
 		if p == nil {
 			break
 		}
-		if p.As == obj.ATYPE && p.From.Node != nil && p.From.Name == obj.NAME_AUTO && ((p.From.Node).(*Node)).Used == 0 {
+		if p.As == obj.ATYPE && p.From.Node != nil && p.From.Name == obj.NAME_AUTO && !((p.From.Node).(*Node)).Used {
 			*lp = p.Link
 			continue
 		}
 
-		if (p.As == obj.AVARDEF || p.As == obj.AVARKILL) && p.To.Node != nil && ((p.To.Node).(*Node)).Used == 0 {
+		if (p.As == obj.AVARDEF || p.As == obj.AVARKILL) && p.To.Node != nil && !((p.To.Node).(*Node)).Used {
 			// Cannot remove VARDEF instruction, because - unlike TYPE handled above -
 			// VARDEFs are interspersed with other code, and a jump might be using the
 			// VARDEF as a target. Replace with a no-op instead. A later pass will remove
@@ -267,11 +267,11 @@ func markautoused(p *obj.Prog) {
 		}
 
 		if p.From.Node != nil {
-			((p.From.Node).(*Node)).Used = 1
+			((p.From.Node).(*Node)).Used = true
 		}
 
 		if p.To.Node != nil {
-			((p.To.Node).(*Node)).Used = 1
+			((p.To.Node).(*Node)).Used = true
 		}
 	}
 }
diff --git a/src/cmd/internal/gc/inl.go b/src/cmd/internal/gc/inl.go
index c00881ee2f4..6d6c7992b78 100644
--- a/src/cmd/internal/gc/inl.go
+++ b/src/cmd/internal/gc/inl.go
@@ -840,7 +840,7 @@ func inlvar(var_ *Node) *Node {
 	n := newname(var_.Sym)
 	n.Type = var_.Type
 	n.Class = PAUTO
-	n.Used = 1
+	n.Used = true
 	n.Curfn = Curfn // the calling function, not the called one
 	n.Addrtaken = var_.Addrtaken
 
@@ -863,7 +863,7 @@ func retvar(t *Type, i int) *Node {
 	n := newname(Lookup(namebuf))
 	n.Type = t.Type
 	n.Class = PAUTO
-	n.Used = 1
+	n.Used = true
 	n.Curfn = Curfn // the calling function, not the called one
 	Curfn.Dcl = list(Curfn.Dcl, n)
 	return n
@@ -876,7 +876,7 @@ func argvar(t *Type, i int) *Node {
 	n := newname(Lookup(namebuf))
 	n.Type = t.Type
 	n.Class = PAUTO
-	n.Used = 1
+	n.Used = true
 	n.Curfn = Curfn // the calling function, not the called one
 	Curfn.Dcl = list(Curfn.Dcl, n)
 	return n
diff --git a/src/cmd/internal/gc/lex.go b/src/cmd/internal/gc/lex.go
index e712752337a..816e67e89a4 100644
--- a/src/cmd/internal/gc/lex.go
+++ b/src/cmd/internal/gc/lex.go
@@ -3131,7 +3131,7 @@ func mkpackage(pkgname string) {
 				// leave s->block set to cause redeclaration
 				// errors if a conflicting top-level name is
 				// introduced by a different file.
-				if s.Def.Used == 0 && nsyntaxerrors == 0 {
+				if !s.Def.Used && nsyntaxerrors == 0 {
 					pkgnotused(int(s.Def.Lineno), s.Def.Pkg.Path, s.Name)
 				}
 				s.Def = nil
@@ -3141,9 +3141,9 @@ func mkpackage(pkgname string) {
 			if s.Def.Sym != s {
 				// throw away top-level name left over
 				// from previous import . "x"
-				if s.Def.Pack != nil && s.Def.Pack.Used == 0 && nsyntaxerrors == 0 {
+				if s.Def.Pack != nil && !s.Def.Pack.Used && nsyntaxerrors == 0 {
 					pkgnotused(int(s.Def.Pack.Lineno), s.Def.Pack.Pkg.Path, "")
-					s.Def.Pack.Used = 1
+					s.Def.Pack.Used = true
 				}
 
 				s.Def = nil
diff --git a/src/cmd/internal/gc/pgen.go b/src/cmd/internal/gc/pgen.go
index ef6e9c1d8f0..81b02e1e1b0 100644
--- a/src/cmd/internal/gc/pgen.go
+++ b/src/cmd/internal/gc/pgen.go
@@ -197,8 +197,8 @@ func cmpstackvar(a *Node, b *Node) int {
 		return 0
 	}
 
-	if (a.Used == 0) != (b.Used == 0) {
-		return int(b.Used) - int(a.Used)
+	if a.Used != b.Used {
+		return bool2int(b.Used) - bool2int(a.Used)
 	}
 
 	ap := bool2int(haspointers(a.Type))
@@ -235,7 +235,7 @@ func allocauto(ptxt *obj.Prog) {
 	// Mark the PAUTO's unused.
 	for ll := Curfn.Dcl; ll != nil; ll = ll.Next {
 		if ll.N.Class == PAUTO {
-			ll.N.Used = 0
+			ll.N.Used = false
 		}
 	}
 
@@ -247,7 +247,7 @@ func allocauto(ptxt *obj.Prog) {
 	ll := Curfn.Dcl
 
 	n := ll.N
-	if n.Class == PAUTO && n.Op == ONAME && n.Used == 0 {
+	if n.Class == PAUTO && n.Op == ONAME && !n.Used {
 		// No locals used at all
 		Curfn.Dcl = nil
 
@@ -257,7 +257,7 @@ func allocauto(ptxt *obj.Prog) {
 
 	for ll := Curfn.Dcl; ll.Next != nil; ll = ll.Next {
 		n = ll.Next.N
-		if n.Class == PAUTO && n.Op == ONAME && n.Used == 0 {
+		if n.Class == PAUTO && n.Op == ONAME && !n.Used {
 			ll.Next = nil
 			Curfn.Dcl.End = ll
 			break
diff --git a/src/cmd/internal/gc/select.go b/src/cmd/internal/gc/select.go
index 4fbf826dd2f..145d18688ff 100644
--- a/src/cmd/internal/gc/select.go
+++ b/src/cmd/internal/gc/select.go
@@ -45,7 +45,7 @@ func typecheckselect(sel *Node) {
 			// remove implicit conversions; the eventual assignment
 			// will reintroduce them.
 			case OAS:
-				if (n.Right.Op == OCONVNOP || n.Right.Op == OCONVIFACE) && n.Right.Implicit != 0 {
+				if (n.Right.Op == OCONVNOP || n.Right.Op == OCONVIFACE) && n.Right.Implicit {
 					n.Right = n.Right.Left
 				}
 
diff --git a/src/cmd/internal/gc/subr.go b/src/cmd/internal/gc/subr.go
index e678a98bb41..d61f9a4d968 100644
--- a/src/cmd/internal/gc/subr.go
+++ b/src/cmd/internal/gc/subr.go
@@ -1341,7 +1341,7 @@ func assignconv(n *Node, t *Type, context string) *Node {
 			r := Nod(OCONVNOP, n, nil)
 			r.Type = Types[TBOOL]
 			r.Typecheck = 1
-			r.Implicit = 1
+			r.Implicit = true
 			n = r
 		}
 	}
@@ -1360,7 +1360,7 @@ func assignconv(n *Node, t *Type, context string) *Node {
 	r := Nod(op, n, nil)
 	r.Type = t
 	r.Typecheck = 1
-	r.Implicit = 1
+	r.Implicit = true
 	r.Orig = n.Orig
 	return r
 }
@@ -2146,7 +2146,7 @@ func adddot(n *Node) *Node {
 			// rebuild elided dots
 			for c := d - 1; c >= 0; c-- {
 				if n.Left.Type != nil && Isptr[n.Left.Type.Etype] {
-					n.Left.Implicit = 1
+					n.Left.Implicit = true
 				}
 				n.Left = Nod(ODOT, n.Left, newname(dotlist[c].field.Sym))
 			}
diff --git a/src/cmd/internal/gc/syntax.go b/src/cmd/internal/gc/syntax.go
index 3a52130de33..0aca4c04bea 100644
--- a/src/cmd/internal/gc/syntax.go
+++ b/src/cmd/internal/gc/syntax.go
@@ -43,10 +43,10 @@ type Node struct {
 	Local          uint8
 	Dodata         uint8
 	Initorder      uint8
-	Used           uint8
+	Used           bool
 	Isddd          uint8
 	Readonly       bool
-	Implicit       uint8
+	Implicit       bool
 	Addrtaken      bool // address taken, even if not moved to heap
 	Assigned       bool // is the variable ever assigned to
 	Captured       bool // is the variable captured by a closure
diff --git a/src/cmd/internal/gc/typecheck.go b/src/cmd/internal/gc/typecheck.go
index cee081729b0..05311da89ec 100644
--- a/src/cmd/internal/gc/typecheck.go
+++ b/src/cmd/internal/gc/typecheck.go
@@ -336,7 +336,7 @@ OpSwitch:
 				return
 			}
 
-			n.Used = 1
+			n.Used = true
 		}
 
 		if top&Ecall == 0 && isunsafebuiltin(n) {
@@ -667,7 +667,7 @@ OpSwitch:
 
 		if t.Etype != TIDEAL && !Eqtype(l.Type, r.Type) {
 			defaultlit2(&l, &r, 1)
-			if n.Op == OASOP && n.Implicit != 0 {
+			if n.Op == OASOP && n.Implicit {
 				Yyerror("invalid operation: %v (non-numeric type %v)", Nconv(n, 0), Tconv(l.Type, 0))
 				n.Type = nil
 				return
@@ -1146,7 +1146,7 @@ OpSwitch:
 			}
 
 			n.Left = Nod(OADDR, n.Left, nil)
-			n.Left.Implicit = 1
+			n.Left.Implicit = true
 			typecheck(&n.Left, Erv)
 			l = n.Left
 		}
@@ -1210,7 +1210,7 @@ OpSwitch:
 			}
 
 			n.Left = Nod(OADDR, n.Left, nil)
-			n.Left.Implicit = 1
+			n.Left.Implicit = true
 			typecheck(&n.Left, Erv)
 			l = n.Left
 		}
@@ -2343,7 +2343,7 @@ func implicitstar(nn **Node) {
 		return
 	}
 	n = Nod(OIND, n, nil)
-	n.Implicit = 1
+	n.Implicit = true
 	typecheck(&n, Erv)
 	*nn = n
 }
@@ -2506,7 +2506,7 @@ func lookdot(n *Node, t *Type, dostrcmp int) bool {
 		if t.Etype == TINTER {
 			if Isptr[n.Left.Type.Etype] {
 				n.Left = Nod(OIND, n.Left, nil) // implicitstar
-				n.Left.Implicit = 1
+				n.Left.Implicit = true
 				typecheck(&n.Left, Erv)
 			}
 
@@ -2524,11 +2524,11 @@ func lookdot(n *Node, t *Type, dostrcmp int) bool {
 			if int(rcvr.Etype) == Tptr && Eqtype(rcvr.Type, tt) {
 				checklvalue(n.Left, "call pointer method on")
 				n.Left = Nod(OADDR, n.Left, nil)
-				n.Left.Implicit = 1
+				n.Left.Implicit = true
 				typecheck(&n.Left, Etype|Erv)
 			} else if int(tt.Etype) == Tptr && int(rcvr.Etype) != Tptr && Eqtype(tt.Type, rcvr) {
 				n.Left = Nod(OIND, n.Left, nil)
-				n.Left.Implicit = 1
+				n.Left.Implicit = true
 				typecheck(&n.Left, Etype|Erv)
 			} else if int(tt.Etype) == Tptr && int(tt.Type.Etype) == Tptr && Eqtype(derefall(tt), derefall(rcvr)) {
 				Yyerror("calling method %v with receiver %v requires explicit dereference", Nconv(n.Right, 0), Nconv(n.Left, obj.FmtLong))
@@ -2538,7 +2538,7 @@ func lookdot(n *Node, t *Type, dostrcmp int) bool {
 						break
 					}
 					n.Left = Nod(OIND, n.Left, nil)
-					n.Left.Implicit = 1
+					n.Left.Implicit = true
 					typecheck(&n.Left, Etype|Erv)
 					tt = tt.Type
 				}
@@ -2551,7 +2551,7 @@ func lookdot(n *Node, t *Type, dostrcmp int) bool {
 		for ll.Left != nil {
 			ll = ll.Left
 		}
-		if ll.Implicit != 0 {
+		if ll.Implicit {
 			if Isptr[ll.Type.Etype] && ll.Type.Sym != nil && ll.Type.Sym.Def != nil && ll.Type.Sym.Def.Op == OTYPE {
 				// It is invalid to automatically dereference a named pointer type when selecting a method.
 				// Make n->left == ll to clarify error message.
@@ -2946,8 +2946,8 @@ func pushtype(n *Node, t *Type) {
 
 	if n.Right == nil {
 		n.Right = typenod(t)
-		n.Implicit = 1       // don't print
-		n.Right.Implicit = 1 // * is okay
+		n.Implicit = true       // don't print
+		n.Right.Implicit = true // * is okay
 	} else if Debug['s'] != 0 {
 		typecheck(&n.Right, Etype)
 		if n.Right.Type != nil && Eqtype(n.Right.Type, t) {
@@ -2991,7 +2991,7 @@ func typecheckcomplit(np **Node) {
 	if Isptr[t.Etype] {
 		// For better or worse, we don't allow pointers as the composite literal type,
 		// except when using the &T syntax, which sets implicit on the OIND.
-		if n.Right.Implicit == 0 {
+		if !n.Right.Implicit {
 			Yyerror("invalid pointer type %v for composite literal (use &%v instead)", Tconv(t, 0), Tconv(t.Type, 0))
 			n.Type = nil
 			return
diff --git a/src/cmd/internal/gc/walk.go b/src/cmd/internal/gc/walk.go
index 48146886a17..90636977c7c 100644
--- a/src/cmd/internal/gc/walk.go
+++ b/src/cmd/internal/gc/walk.go
@@ -37,22 +37,22 @@ func walk(fn *Node) {
 
 	// Propagate the used flag for typeswitch variables up to the NONAME in it's definition.
 	for l := fn.Dcl; l != nil; l = l.Next {
-		if l.N.Op == ONAME && l.N.Class&^PHEAP == PAUTO && l.N.Defn != nil && l.N.Defn.Op == OTYPESW && l.N.Used != 0 {
-			l.N.Defn.Left.Used++
+		if l.N.Op == ONAME && l.N.Class&^PHEAP == PAUTO && l.N.Defn != nil && l.N.Defn.Op == OTYPESW && l.N.Used {
+			l.N.Defn.Left.Used = true
 		}
 	}
 
 	for l := fn.Dcl; l != nil; l = l.Next {
-		if l.N.Op != ONAME || l.N.Class&^PHEAP != PAUTO || l.N.Sym.Name[0] == '&' || l.N.Used != 0 {
+		if l.N.Op != ONAME || l.N.Class&^PHEAP != PAUTO || l.N.Sym.Name[0] == '&' || l.N.Used {
 			continue
 		}
 		if l.N.Defn != nil && l.N.Defn.Op == OTYPESW {
-			if l.N.Defn.Left.Used != 0 {
+			if l.N.Defn.Left.Used {
 				continue
 			}
 			lineno = l.N.Defn.Left.Lineno
 			Yyerror("%v declared and not used", Sconv(l.N.Sym, 0))
-			l.N.Defn.Left.Used = 1 // suppress repeats
+			l.N.Defn.Left.Used = true // suppress repeats
 		} else {
 			lineno = l.N.Lineno
 			Yyerror("%v declared and not used", Sconv(l.N.Sym, 0))
diff --git a/src/cmd/internal/gc/y.go b/src/cmd/internal/gc/y.go
index e1871ffe32a..2fa6a9b46aa 100644
--- a/src/cmd/internal/gc/y.go
+++ b/src/cmd/internal/gc/y.go
@@ -1430,7 +1430,7 @@ yydefault:
 			switch yyVAL.node.Op {
 			case ONAME, ONONAME, OTYPE, OPACK, OLITERAL:
 				yyVAL.node = Nod(OPAREN, yyVAL.node, nil)
-				yyVAL.node.Implicit = 1
+				yyVAL.node.Implicit = true
 				break
 			}
 		}
@@ -1480,7 +1480,7 @@ yydefault:
 		//line go.y:461
 		{
 			yyVAL.node = Nod(OASOP, yyDollar[1].node, Nodintconst(1))
-			yyVAL.node.Implicit = 1
+			yyVAL.node.Implicit = true
 			yyVAL.node.Etype = OADD
 		}
 	case 54:
@@ -1488,7 +1488,7 @@ yydefault:
 		//line go.y:467
 		{
 			yyVAL.node = Nod(OASOP, yyDollar[1].node, Nodintconst(1))
-			yyVAL.node.Implicit = 1
+			yyVAL.node.Implicit = true
 			yyVAL.node.Etype = OSUB
 		}
 	case 55:
@@ -1991,7 +1991,7 @@ yydefault:
 				// Special case for &T{...}: turn into (*T){...}.
 				yyVAL.node = yyDollar[2].node
 				yyVAL.node.Right = Nod(OIND, yyVAL.node.Right, nil)
-				yyVAL.node.Right.Implicit = 1
+				yyVAL.node.Right.Implicit = true
 			} else {
 				yyVAL.node = Nod(OADDR, yyDollar[2].node, nil)
 			}
@@ -2069,7 +2069,7 @@ yydefault:
 			if yyDollar[1].node.Op == OPACK {
 				var s *Sym
 				s = restrictlookup(yyDollar[3].sym.Name, yyDollar[1].node.Pkg)
-				yyDollar[1].node.Used = 1
+				yyDollar[1].node.Used = true
 				yyVAL.node = oldname(s)
 				break
 			}
@@ -2175,7 +2175,7 @@ yydefault:
 			switch yyVAL.node.Op {
 			case ONAME, ONONAME, OTYPE, OPACK, OLITERAL:
 				yyVAL.node = Nod(OPAREN, yyVAL.node, nil)
-				yyVAL.node.Implicit = 1
+				yyVAL.node.Implicit = true
 			}
 		}
 	case 143:
@@ -2308,7 +2308,7 @@ yydefault:
 		{
 			yyVAL.node = oldname(yyDollar[1].sym)
 			if yyVAL.node.Pack != nil {
-				yyVAL.node.Pack.Used = 1
+				yyVAL.node.Pack.Used = true
 			}
 		}
 	case 163:
@@ -2393,7 +2393,7 @@ yydefault:
 			if yyDollar[1].node.Op == OPACK {
 				var s *Sym
 				s = restrictlookup(yyDollar[3].sym.Name, yyDollar[1].node.Pkg)
-				yyDollar[1].node.Used = 1
+				yyDollar[1].node.Used = true
 				yyVAL.node = oldname(s)
 				break
 			}
@@ -2818,7 +2818,7 @@ yydefault:
 			yyVAL.sym = yyDollar[1].sym
 			n = oldname(yyDollar[1].sym)
 			if n.Pack != nil {
-				n.Pack.Used = 1
+				n.Pack.Used = true
 			}
 		}
 	case 237:
@@ -2831,7 +2831,7 @@ yydefault:
 				Yyerror("%v is not a package", Sconv(yyDollar[1].sym, 0))
 				pkg = localpkg
 			} else {
-				yyDollar[1].sym.Def.Used = 1
+				yyDollar[1].sym.Def.Used = true
 				pkg = yyDollar[1].sym.Def.Pkg
 			}
 			yyVAL.sym = restrictlookup(yyDollar[3].sym.Name, pkg)