func init() {
	// Setting binaryOpPredicates in init avoids declaration cycles.
	binaryOpPredicates = opPredicates{
		token.ADD: allNumericOrString,
		token.SUB: allNumeric,
		token.MUL: allNumeric,
		token.QUO: allNumeric,
		token.REM: allInteger,

		token.AND:     allInteger,
		token.OR:      allInteger,
		token.XOR:     allInteger,
		token.AND_NOT: allInteger,

		token.LAND: allBoolean,

func init() {
	// Setting binaryOpPredicates in init avoids declaration cycles.
	binaryOpPredicates = opPredicates{
		syntax.Add: allNumericOrString,
		syntax.Sub: allNumeric,
		syntax.Mul: allNumeric,
		syntax.Div: allNumeric,
		syntax.Rem: allInteger,

		syntax.And:    allInteger,
		syntax.Or:     allInteger,
		syntax.Xor:    allInteger,
		syntax.AndNot: allInteger,

func allBoolean(t Type) bool         { return allBasic(t, IsBoolean) }
func allInteger(t Type) bool         { return allBasic(t, IsInteger) }
func allUnsigned(t Type) bool        { return allBasic(t, IsUnsigned) }
func allNumeric(t Type) bool         { return allBasic(t, IsNumeric) }
func allString(t Type) bool          { return allBasic(t, IsString) }
func allOrdered(t Type) bool         { return allBasic(t, IsOrdered) }

func allBoolean(t Type) bool         { return allBasic(t, IsBoolean) }
func allInteger(t Type) bool         { return allBasic(t, IsInteger) }
func allUnsigned(t Type) bool        { return allBasic(t, IsUnsigned) }
func allNumeric(t Type) bool         { return allBasic(t, IsNumeric) }
func allString(t Type) bool          { return allBasic(t, IsString) }
func allOrdered(t Type) bool         { return allBasic(t, IsOrdered) }

			check.errorf(inNode(s, s.TokPos), InvalidSyntaxTree, "unknown inc/dec operation %s", s.Tok)
			return
		}

		var x operand
		check.expr(nil, &x, s.X)
		if x.mode == invalid {
			return
		}
		if !allNumeric(x.typ) {
			check.errorf(s.X, NonNumericIncDec, invalidOp+"%s%s (non-numeric type %s)", s.X, s.Tok, x.typ)
			return
		}

		Y := &ast.BasicLit{ValuePos: s.X.Pos(), Kind: token.INT, Value: "1"} // use x's position

		if s.Rhs == nil {
			// x++ or x--
			// (no need to call unpackExpr as s.Lhs must be single-valued)
			var x operand
			check.expr(nil, &x, s.Lhs)
			if x.mode == invalid {
				return
			}
			if !allNumeric(x.typ) {
				check.errorf(s.Lhs, NonNumericIncDec, invalidOp+"%s%s%s (non-numeric type %s)", s.Lhs, s.Op, s.Op, x.typ)
				return
			}
			check.assignVar(s.Lhs, nil, &x, "assignment")
			return
		}