21/07/28 23:25:02.98 SAGnL8kO.net
The syntax for a block is {, then any inner attributes, then any number of statements, then an optional expression, called the final operand, and finally a }.
The type of a block is the type of the final operand, or () if the final operand is omitted.
URLﾘﾝｸ(doc.rust-lang.org)
let foo = { fn_call(); }; // final operandがないのでブロックの型は()
let bar = { fn_call() }; // final operandがあるのブロックの型はfn_call()の型
式文が()を返すわけじゃない