output GPIO on DE2

Here is what I have been using. There is an error with the if statement and I have no idea what it is

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;
	
entity DE2_top is
Port(
--////////////////////////	Clock Input	 	////////////////////////
	CLOCK_27 	:in		std_logic;						-- 27 MHz
	CLOCK_50	:in		std_logic;						-- 50 MHz
	EXT_CLOCK	:in		std_logic;						-- External Clock
	
-- ////////////////////////	Push Button		////////////////////////
	KEY			:in		std_logic_vector( 3 downto 0);	--Pushbutton
	
--////////////////////////	DPDT Switch		////////////////////////
	SW			:in		std_logic_vector( 17 downto 0 ); --Toggle Switch
	
--////////////////////////	7-SEG Dispaly	////////////////////////
	HEX0		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 0
	HEX1		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 1
	HEX2		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 2
	HEX3		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 3
	HEX4		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 4
	HEX5		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 5
	HEX6		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 6
	HEX7		:out	std_logic_vector( 6 downto 0);	--Seven Segment Digit 7
--////////////////////////////	LED		////////////////////////////
	LEDG		:out	std_logic_vector( 8 downto 0);	 --LED Green
	LEDR		:out	std_logic_vector( 17 downto 0);	 --LED Red
--////////////////////////////	LED		////////////////////////////
	GPIO_0		:inout std_logic_vector(35 downto 0);
	GPIO_1		:inout std_logic_vector(35 downto 0)
	
	);
	
	end DE2_top;
	
architecture struct of DE2_top is
begin
	    -- GPIO (expansion headers)
	    
	if sw(1) /= '0'then
		gpio_0 <= (others => 'Z');
		gpio_1(0) <= '1';
		gpio_1(1) <= '1';
		gpio_1(2) <= '1';
		gpio_1(3) <= '1';
	else 
		gpio_1(0) <= '0';
		gpio_1(1) <= '0';
		gpio_1(2) <= '0';
		gpio_1(3) <= '0';
	end if;
    
end;