As discussed, I have pushed the changes which allow block syntactic
sugar in expressions. I think the best way to describe the rules is as
follows:
- In Rust, a statement is either a declaration or an expression followed
by a semicolon. The result of evaluating the expression is ignored.
- For certain expressions, however, the semicolon may be omitted. In
that case, the result type of the expression must be unit. These
expressions are (a) C-like special forms that begin with `if`, `while`,
`do`, or `alt`; (b) standalone blocks `{...}`; (c) sugared calls with
block arguments `expr {|| ...)`.
- The value of a block expression `{a; b; c}` is the value of the final
expression in the block (`c`, in this case). If a block consists of
only statements (e.g., `{a; b;}`) then the value of the block is unit.
When phrased this way, I think the rules seem simple enough (but then I
would, wouldn't I?). So yes, let's see how it goes: if it seems to trip
people up or feels too complex, I'm happy to reverse the changes and
give up.
Niko
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