Convert Dependency Graph Tasks from in_tasks to with_tasks
#40376
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A task function is now given as a `fn` pointer to ensure that it carries no state. Each fn can take two arguments, because that worked out to be convenient -- these two arguments must be of some type that is `DepGraphSafe`, a new trait that is intended to prevent "leaking" information into the task that was derived from tracked state. This intentionally leaves `DepGraph::in_task()`, the more common form, alone. Eventually all uses of `DepGraph::in_task()` should be ported to `with_task()`, but I wanted to start with a smaller subset. Originally I wanted to use closures bound by an auto trait, but that approach has some limitations: - the trait cannot have a `read()` method; since the current method is unused, that may not be a problem. - more importantly, we would want the auto trait to be "undefined" for all types *by default* -- that is, this use case doesn't really fit the typical auto trait scenario. For example, imagine that there is a `u32` loaded out of a `hir::Node` -- we don't really want to be passing that `u32` into the task!
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Can we wait until the next release, so we can use closure to |
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@eddyb That'd be a lot prettier, haha |
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It doesn't seem that different? we'd delete a line or two per case, basically, but we'd still wind up re-indenting and everything. |
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Anyway by the time we land this it'll probably be the next release anyway... |
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☔ The latest upstream changes (presumably #40308) made this pull request unmergeable. Please resolve the merge conflicts. |
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So @cramertj should we close this in favor of the on-demandification approach? |
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@nikomatsakis Sure. |
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r? @nikomatsakis