break
		}
		x = c.Args[0]
	}
	return false
}

// isType reports whether the expression is definitely a type.
// This is conservative--it returns false for an unknown identifier.
func (p *Package) isType(t ast.Expr) bool {
	switch t := t.(type) {
	case *ast.SelectorExpr:
		id, ok := t.X.(*ast.Ident)
		if !ok {
			return false
		}