Updated to Crystal 0.17.4

src/db.cr

@@ -76,7 +76,7 @@ module DB
   alias Any = Nil | String | Int32 | Int64 | Float32 | Float64 | Slice(UInt8)
 
   # Result of a `#exec` statement.
-  record ExecResult, rows_affected, last_insert_id
+  record ExecResult, rows_affected : Int32, last_insert_id : Int64
 
   # :nodoc:
   def self.driver_class(driver_name) : Driver.class

src/db/database.cr

@@ -13,8 +13,10 @@ module DB
     # Returns the uri with the connection settings to the database
     getter uri
 
+    @connection : Connection?
+
     # :nodoc:
-    def initialize(@driver, @uri)
+    def initialize(@driver : Driver, @uri : URI)
       @in_pool = true
       @connection = @driver.build_connection(self)
     end

src/db/statement.cr

@@ -15,7 +15,7 @@ module DB
     # :nodoc:
     getter connection
 
-    def initialize(@connection)
+    def initialize(@connection : Connection)
     end
 
     protected def do_close