[drop tracking] Use parent expression for scope, not parent node #101217
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Previously we were just using the parent node as the scope for a
temporary value, but it turns out this is too narrow. For example, in
an expression like
Foo {
b: &42,
a: async { 0 }.await,
}
the scope for the &42 was set to the ExprField node for `b: &42`, when
we actually want to use the Foo struct expression.
We fix this by recursively searching through parent nodes until we find
a Node::Expr. It may be that we don't find one, and if so that's okay,
we will just fall back on the enclosing temporary scope which is always
sufficient.
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| let find_parent_expr = |mut hir_id| { | ||
| let hir = self.fcx.tcx.hir(); | ||
| hir_id = hir.find_parent_node(hir_id)?; | ||
| loop { |
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Ah, thanks! I didn't know about that method. I think that's way cleaner, so I rewrote my code to use that. I also added a doc comment to find_parent_node to point people towards parent_iter when more appropriate.
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I don't think so. This is only observable if an await point is in the new wider scope but wasn't in the old narrower scope. In that case, MIR would have found the type and we should have gotten an ICE saying the types didn't match. At any rate, the old behavior was incorrect (as shown by how issue-73137.rs broke with drop tracking), so it seems better to correct that. |
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[drop tracking] Use parent expression for scope, not parent node
Previously we were just using the parent node as the scope for a temporary value, but it turns out this is too narrow. For example, in an expression like
Foo {
b: &42,
a: async { 0 }.await,
}
the scope for the &42 was set to the ExprField node for `b: &42`, when we actually want to use the Foo struct expression.
We fix this by recursively searching through parent nodes until we find a Node::Expr. It may be that we don't find one, and if so that's okay, we will just fall back on the enclosing temporary scope which is always sufficient.
Helps with rust-lang#97331
r? `@jyn514`
Dylan-DPC
added a commit
to Dylan-DPC/rust
that referenced
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Sep 2, 2022
[drop tracking] Use parent expression for scope, not parent node
Previously we were just using the parent node as the scope for a temporary value, but it turns out this is too narrow. For example, in an expression like
Foo {
b: &42,
a: async { 0 }.await,
}
the scope for the &42 was set to the ExprField node for `b: &42`, when we actually want to use the Foo struct expression.
We fix this by recursively searching through parent nodes until we find a Node::Expr. It may be that we don't find one, and if so that's okay, we will just fall back on the enclosing temporary scope which is always sufficient.
Helps with rust-lang#97331
r? `@jyn514`
bors
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Sep 3, 2022
Rollup of 7 pull requests Successful merges: - rust-lang#99736 (Partially stabilize `bound_as_ref` by stabilizing `Bound::as_ref`) - rust-lang#100928 (Migrate rustc_metadata to SessionDiagnostics) - rust-lang#101217 ([drop tracking] Use parent expression for scope, not parent node ) - rust-lang#101325 (Windows RNG: Use `BCRYPT_RNG_ALG_HANDLE` by default) - rust-lang#101330 (Fix `std::collections::HashSet::drain` documentation) - rust-lang#101338 (Fix unsupported syntax in .manifest file) - rust-lang#101348 (Cleanup css theme) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
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Previously we were just using the parent node as the scope for a temporary value, but it turns out this is too narrow. For example, in an expression like
the scope for the &42 was set to the ExprField node for
b: &42, when we actually want to use the Foo struct expression.We fix this by recursively searching through parent nodes until we find a Node::Expr. It may be that we don't find one, and if so that's okay, we will just fall back on the enclosing temporary scope which is always sufficient.
Helps with #97331
r? @jyn514