Re: Re: Discussion: making continue and break into an expression

On Mon, Feb 3, 2025, at 19:44, Rob Landers wrote: > On Sun, Feb 2, 2025, at 14:35, Dmitry Derepko wrote: >> >>> On Jan 25, 2024, at 12:16 PM, Robert Landers <landers.robert@gmail.com> wrote: >>> >>> Hello internals, >>> >>> Now that throwing is an expression, it allows for some very concise >>> programming. What are your thoughts on making a break/continue into an >>> expression as well? >> >> Hi! >> I had similar idea to make break, >> continue and return be expressions >> instead of statements to simplify almost the same cases as Robert described above. >> >> Grammar corrections in the PR. >> https://github.com/php/php-src/pull/17647 >> Ilija pointed to memory leaking problems as well. >> >> Thinking about Ilija memory leaking case: >> new Foo + return 1 >> >> I think we may have a workaround here, by allowing all of these constructions only >> available at some specific points: >> - <point> as the statement now >> - $cond ? <point> : <point>; >> - match ($v) { … => <point> } >> >> So it will deny such cases: >> - operand OPERATOR <point> (1 + return; $cond && break; etc) >> >> It may prevent memory leaking problems. Isn’t it? >> >> I’m writing RFC: >> https://wiki.php.net/rfc/return_break_continue_expressions >> I’ll start a new discussion when it will be ready for it. >> >> >> ---------- >> >> Best regards, >> Dmitrii Derepko. >> @xepozz > > Oh, this was a fun one! > > I ended up rewriting the AST during compilation (pass 2) to return/break on the next statement > instead of in the current statement. That let me get around the issue but I guessed nobody would > like it and it probably wouldn’t pass on technical reasons. > > In other words, yes it was an expression on the grammar level, but it was compiled as a > statement. > > — Rob Hello again, I just finished reviewing the diff and didn't notice any tests that show what the value of things actually become. In my diff, I did something like this: $this->x = return $y; // $this->x === $y Which is basically shorthand for: $this->x = $y; return $y; An empty return, break, or continue (well, only one of these has a value) contains the value NULL: $this->x = break; // $this->x === null Shorthand for: $thix->x = null; break; I'm trying to figure out which branch this was on ... but it was likely on my old computer since I originally sent it the email from my gmail address. — Rob