quasi-quoting a block expression doesn't work

[nrc]

quote_expr!(self.cx, { $result_name = Some($expr); break $loop_label; }) failed with error: expected one of.,;,}, or an operator, found'__hoare_2``(__hoare_2is the expected value of`$loop_label`). This failed in expansion so I couldn't get an expanded AST to find out what was going on.

The work around:

                let stmts = vec![quote_stmt!(self.cx, $result_name = Some($expr);).unwrap(),
                                 quote_stmt!(self.cx, break $loop_label;).unwrap()];
                self.cx.expr_block(self.cx.block(stmts[0].span, stmts, None))

worked fine

[nrc]

I think this has something to do with the ident loop_label, quasi-quoting is not pasting it into the break label position correctly. I previously had similar problems when I forgot to start the label name with a ', but that is not the problem here.

Note that the 'correct' version above compiles without an error, but generates incorrect code - no label to break to. If I build that part of the AST by hand, then it works fine.

[brson]

@nrc do you still care about this issue. Seems like an internal defect that doesn't much matter.

[nrc]

It's not entirely internal since syntax extensions can use quasi-quoting. I suppose this will get 'fixed' when we change to token based quasi-quoting, but until then I think this is relevant

[steveklabnik]

Triage: being removed in #51285