Sets the value of the field from the specified expression.
This generates code that accesses the field from outside.
@param block The code will be generated into this block.
@param uniqueName Identifier that the caller guarantees to be unique in the given block. When the callee needs to produce additional variables, it can do so by adding suffixes to this unique name. For example, if the uniqueName is "abc", then the caller guarantees that any identifier "abc.*" is unused in this block.
@param $var The expression that evaluates to a value of the type {@link FieldOutline#getRawType()}.