Suggest removal of borrow in index when appropriate #117913
Conversation
rustbot
added
S-waiting-on-review
| self.lookup_indexing(expr, base, base_t, idx, idx_t) | ||
| { | ||
| let (_ty, err) = | ||
| self.demand_coerce_diag(idx, idx_t, index_ty, None, AllowTwoPhase::No); |
There was a problem hiding this comment.
I think you should manually recreate the logic in lookup_indexing, and if you need to process obligations, you should throw them into your own ObligationCtxt.
As for the demand_coerce call, I think it's probably best for us to approximate it with a ObligationCtxt::eq call instead, to again avoid poisoning our own fulfillment context.
Essentially what I want to avoid is that fulfillment_ctxt.select_where_possible. It's not great, and unless you can convince me that there's a good reason that we can't approximate it with less invasive machinery, then I think we should try our best to avoid it.
There was a problem hiding this comment.
What do you think of creating a new fulfillment context for this check instead?
There was a problem hiding this comment.
either works, though I think ObligationCtxt has an easier to use API
rustbot
added
S-waiting-on-author
When encountering
```rust
let a = std::collections::HashMap::<String,String>::new();
let s = "hello";
let _b = &a[&s];
```
suggest `let _b = &a[s];`.
Fix rust-lang#66023.
| let mut autoderef = self.autoderef(base.span, base_t); | ||
| let mut result = None; | ||
| while result.is_none() && autoderef.next().is_some() { | ||
| result = self.try_index_step(expr, base, &autoderef, idx_t, idx); |
There was a problem hiding this comment.
try_index_step still registers things into the fnctxt's fulfullment context :(
I think it's simpler to be creating your own Index trait obligation here -- the only thing that you'd be losing is the [u8; N] -> [u8] deref step, which I guess you could replicate here.
|
☔ The latest upstream changes (presumably #124952) made this pull request unmergeable. Please resolve the merge conflicts. |
|
@estebank any updates on this? thanks |
When encountering
suggest
let _b = &a[s];.Fix #66023.
r? @compiler-errors