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Suggest removing .unwrap() or .expect() if followed by a failed `…
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…?` operator
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trevyn committed Jul 8, 2024
1 parent 28cc0b6 commit 7d8d246
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Showing 4 changed files with 102 additions and 0 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -1576,6 +1576,45 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
false
}

/// When a failed try operator follows an `unwrap()` or `expect()`, suggest removing it
fn suggest_remove_unwrap(
&self,
obligation: &PredicateObligation<'tcx>,
err: &mut Diag<'_>,
) -> bool {
if !matches!(obligation.cause.code(), ObligationCauseCode::QuestionMark) {
return false;
}

let Some(body) = self.tcx.hir().maybe_body_owned_by(obligation.cause.body_id) else {
return false;
};

let mut expr_finder = super::FindExprBySpan::new(obligation.cause.span, self.tcx);
expr_finder.visit_expr(body.value);

if let Some(expr) = expr_finder.result
&& let Some(node) = self.tcx.hir().parent_iter(expr.hir_id).nth(2)
&& let hir::Node::Expr(expr) = node.1
&& let hir::ExprKind::Match(expr, _, _) = expr.kind
&& let hir::ExprKind::Call(_, args) = expr.kind
&& let Some(expr) = args.get(0)
&& let hir::ExprKind::MethodCall(pathsegment, receiver, _, span) = expr.kind
&& (pathsegment.ident.name == sym::unwrap || pathsegment.ident.name == sym::expect)
{
err.span_suggestion_verbose(
receiver.span.shrink_to_hi().to(span),
format!("remove the `.{}()`", pathsegment.ident.name),
"",
Applicability::MaybeIncorrect,
);

return true;
}

false
}

fn suggest_remove_await(&self, obligation: &PredicateObligation<'tcx>, err: &mut Diag<'_>) {
let hir = self.tcx.hir();
if let ObligationCauseCode::AwaitableExpr(hir_id) = obligation.cause.code().peel_derives()
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Original file line number Diff line number Diff line change
Expand Up @@ -680,6 +680,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {

self.suggest_floating_point_literal(&obligation, &mut err, leaf_trait_ref);
self.suggest_dereferencing_index(&obligation, &mut err, leaf_trait_predicate);
suggested |= self.suggest_remove_unwrap(&obligation, &mut err);
suggested |= self.suggest_dereferences(&obligation, &mut err, leaf_trait_predicate);
suggested |= self.suggest_fn_call(&obligation, &mut err, leaf_trait_predicate);
let impl_candidates = self.find_similar_impl_candidates(leaf_trait_predicate);
Expand Down
20 changes: 20 additions & 0 deletions tests/ui/try-trait/try-after-unwrap-issue-127345.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,20 @@
fn foo() -> Option<usize> {
let x = Some(42).expect("moop")?;
//~^ ERROR the `?` operator can only be applied to values that implement `Try`
//~| HELP the trait `Try` is not implemented for `{integer}`
//~| HELP remove the `.expect()`
let x = Some(42).unwrap()?;
//~^ ERROR the `?` operator can only be applied to values that implement `Try`
//~| HELP the trait `Try` is not implemented for `{integer}`
//~| HELP remove the `.unwrap()`
x
}

fn bar() -> Option<usize> {
foo().or(Some(43)).unwrap()?
//~^ ERROR the `?` operator can only be applied to values that implement `Try`
//~| HELP the trait `Try` is not implemented for `usize`
//~| HELP remove the `.unwrap()`
}

fn main() {}
42 changes: 42 additions & 0 deletions tests/ui/try-trait/try-after-unwrap-issue-127345.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/try-after-unwrap-issue-127345.rs:2:13
|
LL | let x = Some(42).expect("moop")?;
| ^^^^^^^^^^^^^^^^^^^^^^^^ the `?` operator cannot be applied to type `{integer}`
|
= help: the trait `Try` is not implemented for `{integer}`
help: remove the `.expect()`
|
LL - let x = Some(42).expect("moop")?;
LL + let x = Some(42)?;
|

error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/try-after-unwrap-issue-127345.rs:6:13
|
LL | let x = Some(42).unwrap()?;
| ^^^^^^^^^^^^^^^^^^ the `?` operator cannot be applied to type `{integer}`
|
= help: the trait `Try` is not implemented for `{integer}`
help: remove the `.unwrap()`
|
LL - let x = Some(42).unwrap()?;
LL + let x = Some(42)?;
|

error[E0277]: the `?` operator can only be applied to values that implement `Try`
--> $DIR/try-after-unwrap-issue-127345.rs:14:5
|
LL | foo().or(Some(43)).unwrap()?
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the `?` operator cannot be applied to type `usize`
|
= help: the trait `Try` is not implemented for `usize`
help: remove the `.unwrap()`
|
LL - foo().or(Some(43)).unwrap()?
LL + foo().or(Some(43))?
|

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0277`.

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