refactor: expressions are now statements
refactored useless expressions to statements

CompoundExpression -> CompoundStatement
BlockExpression -> BlockStatement
ElseExpression -> ElseStatement
IfExpression -> IfStatement
LoopExpression -> LoopStatement
WhileExpression -> WhileStatement
ForExpression -> ForStatement
SwitchExpression -> SwitchStatement

it seemed like a good idea to eschew statements and make
everything an expression. After some thought, that doesn't fit in
a system level language.