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Account for existing bindings when suggesting pinning

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When we encounter a situation where we'd suggest `pin!()`, we now account for that expression exising as part of an assignment and provide an appropriate suggestion:

```
error[E0599]: no method named `poll` found for type parameter `F` in the current scope
  --> $DIR/pin-needed-to-poll-3.rs:19:28
   |
LL | impl<F> Future for FutureWrapper<F>
   |      - method `poll` not found for this type parameter
...
LL |         let res = self.fut.poll(cx);
   |                            ^^^^ method not found in `F`
   |
help: consider pinning the expression
   |
LL ~         let mut pinned = std::pin::pin!(self.fut);
LL ~         let res = pinned.as_mut().poll(cx);
   |
```

Fix #125661.
This commit is contained in:
Esteban Küber 2024-05-28 20:48:35 +00:00
parent 1a840e7732
commit 5585f3133c
2 changed files with 62 additions and 10 deletions
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68
compiler/rustc_hir_typeck/src/method/suggest.rs
View File

@ -3326,14 +3326,66 @@ fn suggest_traits_to_import(
.source_map()
.indentation_before(rcvr.span)
.unwrap_or_else(|| " ".to_string());
err.multipart_suggestion(
"consider pinning the expression",
vec![
(rcvr.span.shrink_to_lo(), format!("let mut pinned = std::pin::pin!(")),
(rcvr.span.shrink_to_hi(), format!(");\n{indent}pinned.{pin_call}()")),
],
Applicability::MaybeIncorrect,
);
let mut expr = rcvr;
while let Node::Expr(call_expr) = self.tcx.parent_hir_node(expr.hir_id)
&& let hir::ExprKind::MethodCall(hir::PathSegment { .. }, ..) =
call_expr.kind
{
expr = call_expr;
}
match self.tcx.parent_hir_node(expr.hir_id) {
Node::LetStmt(stmt)
if let Some(init) = stmt.init
&& let Ok(code) =
self.tcx.sess.source_map().span_to_snippet(rcvr.span) =>
{
// We need to take care to account for the existing binding when we
// suggest the code.
err.multipart_suggestion(
"consider pinning the expression",
vec![
(
stmt.span.shrink_to_lo(),
format!(
"let mut pinned = std::pin::pin!({code});\n{indent}"
),
),
(
init.span.until(rcvr.span.shrink_to_hi()),
format!("pinned.{pin_call}()"),
),
],
Applicability::MaybeIncorrect,
);
}
Node::Block(_) | Node::Stmt(_) => {
// There's no binding, so we can provide a slightly nicer looking
// suggestion.
err.multipart_suggestion(
"consider pinning the expression",
vec![
(
rcvr.span.shrink_to_lo(),
format!("let mut pinned = std::pin::pin!("),
),
(
rcvr.span.shrink_to_hi(),
format!(");\n{indent}pinned.{pin_call}()"),
),
],
Applicability::MaybeIncorrect,
);
}
_ => {
// We don't quite know what the users' code looks like, so we don't
// provide a pinning suggestion.
err.span_help(
rcvr.span,
"consider pinning the expression with `std::pin::pin!()` and \
assigning that to a new binding",
);
}
}
// We don't care about the other suggestions.
alt_rcvr_sugg = true;
}

4
tests/ui/async-await/pin-needed-to-poll-3.stderr
View File

@ -9,8 +9,8 @@ LL | let res = self.fut.poll(cx);
|
help: consider pinning the expression
|
LL ~ let res = let mut pinned = std::pin::pin!(self.fut);
LL ~ pinned.as_mut().poll(cx);
LL ~ let mut pinned = std::pin::pin!(self.fut);
LL ~ let res = pinned.as_mut().poll(cx);
|
error: aborting due to 1 previous error