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42e8472ca6
fixes #10440, fixes #13871, fixes #14665, fixes #19672, fixes #23677 The false positive in #23677 was caused by behavior in `implicitlyDiscardable` where only the last node of `if`/`case`/`try` etc expressions were considered, as in the final node of the final branch (in this case `else`). To fix this we use the same iteration in `implicitlyDiscardable` that we use in `endsInNoReturn`, with the difference that for an `if`/`case`/`try` statement to be implicitly discardable, all of its branches must be implicitly discardable. `noreturn` calls are also considered implicitly discardable for this reason, otherwise stuff like `if true: discardableCall() else: error()` doesn't compile. However `endsInNoReturn` also had bugs, one where `finally` was considered in noreturn checking when it shouldn't, another where only `nkIfStmt` was checked and not `nkIfExpr`, and the node given for the error message was bad. So `endsInNoReturn` now skips over `skipForDiscardable` which no longer contains `nkIfStmt`/`nkCaseStmt`/`nkTryStmt`, stores the first encountered returning node in a var parameter for the error message, and handles `finally` and `nkIfExpr`. Fixing #23677 already broke a line in `syncio` so some package code might be affected.