NLL Diagnostic Review 3: Unions not reinitialized after assignment into field #55657
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This commit makes two changes: First, it updates the dataflow builder to add an init for the place containing a union if there is an assignment into the field of that union. Second, it stops a "use of uninitialized" error occuring when there is an assignment into the field of an uninitialized union that was previously initialized. Making this assignment would re-initialize the union, as tested in `src/test/ui/borrowck/borrowck-union-move-assign.nll.stderr`. The check for previous initialization ensures that we do not start supporting partial initialization yet (cc rust-lang#21232, rust-lang#54499, rust-lang#54986).
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This commit adds a run-pass test for the subset of `src/test/ui/borrowck/borrowck-union-move-assign.rs` that is intended to pass as the union is reinitialized.
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It is necessary to detect whether we are making the first assignment into a union. This is checked by looking at the moves and checking if there are any from locations earlier in the control flow graph. This commit improves the detection of this by switching from a naive method that compared only the statement and basic block indices with a more robust method that looks at the predecessors of a location.
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@bors r+ |
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📌 Commit 1672c27 has been approved by |
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I accidentally beta-nominated this. But for the record, It does not need to be backported, for two reasons:
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⌛ Testing commit 1672c27 with merge 35ae96dfcdb098b84e81ced2dcdce441b1f42295... |
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💔 Test failed - status-appveyor |
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NLL Diagnostic Review 3: Unions not reinitialized after assignment into field Fixes #55651, #55652. This PR makes two changes: First, it updates the dataflow builder to add an init for the place containing a union if there is an assignment into the field of that union. Second, it stops a "use of uninitialized" error occuring when there is an assignment into the field of an uninitialized union that was previously initialized. Making this assignment would re-initialize the union, as tested in `src/test/ui/borrowck/borrowck-union-move-assign.nll.stderr`. The check for previous initialization ensures that we do not start supporting partial initialization yet (cc #21232, #54499, #54986). This PR also fixes #55652 which was marked as requiring investigation as the changes in this PR add an error that was previously missing (and mentioned in the review comments) and confirms that the error that was present is correct and a result of earlier partial initialization changes in NLL. r? @pnkfelix (due to earlier work with partial initialization) cc @nikomatsakis
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☀️ Test successful - status-appveyor, status-travis |
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Fixes #55651, #55652.
This PR makes two changes:
First, it updates the dataflow builder to add an init for the place
containing a union if there is an assignment into the field of
that union.
Second, it stops a "use of uninitialized" error occuring when there is an
assignment into the field of an uninitialized union that was previously
initialized. Making this assignment would re-initialize the union, as
tested in
src/test/ui/borrowck/borrowck-union-move-assign.nll.stderr.The check for previous initialization ensures that we do not start
supporting partial initialization yet (cc #21232, #54499, #54986).
This PR also fixes #55652 which was marked as requiring investigation
as the changes in this PR add an error that was previously missing
(and mentioned in the review comments) and confirms that the error
that was present is correct and a result of earlier partial
initialization changes in NLL.
r? @pnkfelix (due to earlier work with partial initialization)
cc @nikomatsakis