// arbitrarily large.
func (check *Checker) overflow(x *operand, opPos syntax.Pos) {
	assert(x.mode == constant_)

	if x.val.Kind() == constant.Unknown {
		// TODO(gri) We should report exactly what went wrong. At the
		//           moment we don't have the (go/constant) API for that.
		//           See also TODO in go/constant/value.go.
		check.error(atPos(opPos), InvalidConstVal, "constant result is not representable")
		return
	}

// arbitrarily large.
func (check *Checker) overflow(x *operand, opPos token.Pos) {
	assert(x.mode == constant_)

	if x.val.Kind() == constant.Unknown {
		// TODO(gri) We should report exactly what went wrong. At the
		//           moment we don't have the (go/constant) API for that.
		//           See also TODO in go/constant/value.go.
		check.error(atPos(opPos), InvalidConstVal, "constant result is not representable")
		return
	}

			}
			// x is a constant so xval != nil and it must be of Int kind.
			x.val = constant.Shift(xval, op, uint(s))
			x.expr = e
			opPos := x.Pos()
			if b, _ := e.(*ast.BinaryExpr); b != nil {
				opPos = b.OpPos
			}
			check.overflow(x, opPos)
			return
		}

		// non-constant shift with constant lhs
		if isUntyped(x.typ) {
			// spec: "If the left operand of a non-constant shift

			tok(n.TokPos, len(n.Tok.String())))

	case *ast.BasicLit:
		children = append(children,
			tok(n.ValuePos, len(n.Value)))

	case *ast.BinaryExpr:
		children = append(children, tok(n.OpPos, len(n.Op.String())))

	case *ast.BlockStmt:
		children = append(children,
			tok(n.Lbrace, len("{")),
			tok(n.Rbrace, len("}")))

	case *ast.BranchStmt:
		children = append(children,

			return false
		}
	} else {
		check.errorf(x, InvalidSyntaxTree, "unknown operator %s", op)
		return false
	}
	return true
}

// opPos returns the position of the operator if x is an operation;
// otherwise it returns the start position of x.
func opPos(x syntax.Expr) syntax.Pos {
	switch op := x.(type) {
	case nil:
		return nopos // don't crash
	case *syntax.Operation:
		return op.Pos()
	default:

	for p.tok == token.OR {
		t := new(ast.BinaryExpr)
		t.OpPos = p.pos
		t.Op = token.OR
		p.next()
		t.X = x
		t.Y = p.embeddedTerm()
		x = t
	}
	return x
}

func (p *parser) embeddedTerm() ast.Expr {
	if p.trace {
		defer un(trace(p, "EmbeddedTerm"))
	}
	if p.tok == token.TILDE {
		t := new(ast.UnaryExpr)
		t.OpPos = p.pos
		t.Op = token.TILDE
		p.next()

	// Unary "*" expressions are represented via StarExpr nodes.
	//
	UnaryExpr struct {
		OpPos token.Pos   // position of Op
		Op    token.Token // operator
		X     Expr        // operand
	}

	// A BinaryExpr node represents a binary expression.
	BinaryExpr struct {
		X     Expr        // left operand
		OpPos token.Pos   // position of Op
		Op    token.Token // operator
		Y     Expr        // right operand
	}

		if len(lhs) > 0 {
			if n.Tok == token.DEFINE {
				// Note: we can't exactly match the behavior of object resolution
				// during the parsing pass here, as it uses the position of the RANGE
				// token for the RHS OpPos. That information is not contained within
				// the AST.
				as := &ast.AssignStmt{
					Lhs:    lhs,
					Tok:    token.DEFINE,
					TokPos: n.TokPos,

	p.expr1(x.X, prec, depth+diffPrec(x.X, prec))
	if printBlank {
		p.print(blank)
	}
	xline := p.pos.Line // before the operator (it may be on the next line!)
	yline := p.lineFor(x.Y.Pos())
	p.setPos(x.OpPos)
	p.print(x.Op)
	if xline != yline && xline > 0 && yline > 0 {
		// at least one line break, but respect an extra empty line
		// in the source
		if p.linebreak(yline, 1, ws, true) > 0 {
			ws = ignore

		{"BasicLit", Type, 0},
		{"BasicLit.Kind", Field, 0},
		{"BasicLit.Value", Field, 0},
		{"BasicLit.ValuePos", Field, 0},
		{"BinaryExpr", Type, 0},
		{"BinaryExpr.Op", Field, 0},
		{"BinaryExpr.OpPos", Field, 0},
		{"BinaryExpr.X", Field, 0},
		{"BinaryExpr.Y", Field, 0},
		{"BlockStmt", Type, 0},
		{"BlockStmt.Lbrace", Field, 0},
		{"BlockStmt.List", Field, 0},
		{"BlockStmt.Rbrace", Field, 0},