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Merged
merged 6 commits into from
Nov 2, 2020
Merged

Avoid complex diagnostics in snippets which contain newlines #75020

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c269525
Avoid complex diagnostics in snippets which contain newlines
JohnTitor Aug 1, 2020
ad978e5
Separate complex multispan into some notes
JohnTitor Oct 10, 2020
66226ca
Address some code reviews
JohnTitor Oct 10, 2020
2da86a1
Add "this has type `{}` which {}" note
JohnTitor Oct 22, 2020
54d9ffc
Only separate notes if span is multiline
JohnTitor Nov 2, 2020
8d65101
Fix format
JohnTitor Nov 2, 2020
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152 changes: 123 additions & 29 deletions compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1570,36 +1570,130 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
format!("does not implement `{}`", trait_ref.print_only_trait_path())
};

let mut explain_yield = |interior_span: Span,
yield_span: Span,
scope_span: Option<Span>| {
let mut span = MultiSpan::from_span(yield_span);
if let Ok(snippet) = source_map.span_to_snippet(interior_span) {
span.push_span_label(
yield_span,
format!("{} occurs here, with `{}` maybe used later", await_or_yield, snippet),
);
// If available, use the scope span to annotate the drop location.
if let Some(scope_span) = scope_span {
span.push_span_label(
source_map.end_point(scope_span),
format!("`{}` is later dropped here", snippet),
);
let mut explain_yield =
|interior_span: Span, yield_span: Span, scope_span: Option<Span>| {
let mut span = MultiSpan::from_span(yield_span);
if let Ok(snippet) = source_map.span_to_snippet(interior_span) {
// #70935: If snippet contains newlines, display "the value" instead
// so that we do not emit complex diagnostics.
let snippet = &format!("`{}`", snippet);
let snippet = if snippet.contains('\n') { "the value" } else { snippet };
// The multispan can be complex here, like:
// note: future is not `Send` as this value is used across an await
// --> $DIR/issue-70935-complex-spans.rs:13:9
// |
// LL | baz(|| async{
// | __________^___-
// | | _________|
// | ||
// LL | || foo(tx.clone());
// LL | || }).await;
// | || - ^- value is later dropped here
// | ||_________|______|
// | |__________| await occurs here, with value maybe used later
// | has type `closure` which is not `Send`
//
// So, detect it and separate into some notes, like:
//
// note: future is not `Send` as this value is used across an await
// --> $DIR/issue-70935-complex-spans.rs:13:9
// |
// LL | / baz(|| async{
// LL | | foo(tx.clone());
// LL | | }).await;
// | |________________^ first, await occurs here, with the value maybe used later...
// note: the value is later dropped here
// --> $DIR/issue-70935-complex-spans.rs:15:17
// |
// LL | }).await;
// | ^
//
// If available, use the scope span to annotate the drop location.
if let Some(scope_span) = scope_span {
let scope_span = source_map.end_point(scope_span);
let is_overlapped =
yield_span.overlaps(scope_span) || yield_span.overlaps(interior_span);
if is_overlapped {
span.push_span_label(
yield_span,
format!(
"first, {} occurs here, with {} maybe used later...",
await_or_yield, snippet
),
);
err.span_note(
span,
&format!(
"{} {} as this value is used across {}",
future_or_generator, trait_explanation, an_await_or_yield
),
);
if source_map.is_multiline(interior_span) {
err.span_note(
scope_span,
&format!("{} is later dropped here", snippet),
);
err.span_note(
interior_span,
&format!(
"this has type `{}` which {}",
target_ty, trait_explanation
),
);
} else {
let mut span = MultiSpan::from_span(scope_span);
span.push_span_label(
interior_span,
format!("has type `{}` which {}", target_ty, trait_explanation),
);
err.span_note(span, &format!("{} is later dropped here", snippet));
}
} else {
span.push_span_label(
yield_span,
format!(
"{} occurs here, with {} maybe used later",
await_or_yield, snippet
),
);
span.push_span_label(
scope_span,
format!("{} is later dropped here", snippet),
);
span.push_span_label(
interior_span,
format!("has type `{}` which {}", target_ty, trait_explanation),
);
err.span_note(
span,
&format!(
"{} {} as this value is used across {}",
future_or_generator, trait_explanation, an_await_or_yield
),
);
}
} else {
span.push_span_label(
yield_span,
format!(
"{} occurs here, with {} maybe used later",
await_or_yield, snippet
),
);
span.push_span_label(
interior_span,
format!("has type `{}` which {}", target_ty, trait_explanation),
);
err.span_note(
span,
&format!(
"{} {} as this value is used across {}",
future_or_generator, trait_explanation, an_await_or_yield
),
);
}
}
}
span.push_span_label(
interior_span,
format!("has type `{}` which {}", target_ty, trait_explanation),
);

err.span_note(
span,
&format!(
"{} {} as this value is used across {}",
future_or_generator, trait_explanation, an_await_or_yield
),
);
};
};
match interior_or_upvar_span {
GeneratorInteriorOrUpvar::Interior(interior_span) => {
if let Some((scope_span, yield_span, expr, from_awaited_ty)) = interior_extra_info {
Expand Down
25 changes: 25 additions & 0 deletions src/test/ui/async-await/issue-70935-complex-spans.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
// edition:2018
// #70935: Check if we do not emit snippet
// with newlines which lead complex diagnostics.

use std::future::Future;

async fn baz<T>(_c: impl FnMut() -> T) where T: Future<Output=()> {
}

fn foo(tx: std::sync::mpsc::Sender<i32>) -> impl Future + Send {
//~^ ERROR: future cannot be sent between threads safely
async move {
baz(|| async{
foo(tx.clone());
}).await;
}
}

fn bar(_s: impl Future + Send) {
}

fn main() {
let (tx, _rx) = std::sync::mpsc::channel();
bar(foo(tx));
}
30 changes: 30 additions & 0 deletions src/test/ui/async-await/issue-70935-complex-spans.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
error: future cannot be sent between threads safely
--> $DIR/issue-70935-complex-spans.rs:10:45
|
LL | fn foo(tx: std::sync::mpsc::Sender<i32>) -> impl Future + Send {
| ^^^^^^^^^^^^^^^^^^ future created by async block is not `Send`
|
= help: the trait `Sync` is not implemented for `Sender<i32>`
note: future is not `Send` as this value is used across an await
--> $DIR/issue-70935-complex-spans.rs:13:9
|
LL | / baz(|| async{
LL | | foo(tx.clone());
LL | | }).await;
| |________________^ first, await occurs here, with the value maybe used later...
note: the value is later dropped here
--> $DIR/issue-70935-complex-spans.rs:15:17
|
LL | }).await;
| ^
note: this has type `[closure@$DIR/issue-70935-complex-spans.rs:13:13: 15:10]` which is not `Send`
--> $DIR/issue-70935-complex-spans.rs:13:13
|
LL | baz(|| async{
| _____________^
LL | | foo(tx.clone());
LL | | }).await;
| |_________^
Comment on lines +20 to +27
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Added this note separately, since this span has some lines and loses readability when we do as @estebank suggested (#75020 (comment)). I feel it's redundant a bit.

@tmandry Does this make sense for you?

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@JohnTitor something I've done in other errors i check whether Spans are exactly the same, if one encloses the other, or if one of them is multiline to provide different output depending on what looks best. In this case just checking whether the "inner" span is multiline to decide between span_labels and span_notes should be easy to do and reasonable as a solution. What do you two think?

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r=me with or without the proposed changes.

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Sounds good! Addressed via 54d9ffc.


error: aborting due to previous error

12 changes: 8 additions & 4 deletions src/test/ui/async-await/issues/issue-65436-raw-ptr-not-send.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -12,10 +12,14 @@ note: future is not `Send` as this value is used across an await
--> $DIR/issue-65436-raw-ptr-not-send.rs:14:9
|
LL | bar(Foo(std::ptr::null())).await;
| ^^^^^^^^----------------^^^^^^^^- `std::ptr::null()` is later dropped here
| | |
| | has type `*const u8` which is not `Send`
| await occurs here, with `std::ptr::null()` maybe used later
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ first, await occurs here, with `std::ptr::null()` maybe used later...
note: `std::ptr::null()` is later dropped here
--> $DIR/issue-65436-raw-ptr-not-send.rs:14:41
|
LL | bar(Foo(std::ptr::null())).await;
| ---------------- ^
| |
| has type `*const u8` which is not `Send`
help: consider moving this into a `let` binding to create a shorter lived borrow
--> $DIR/issue-65436-raw-ptr-not-send.rs:14:13
|
Expand Down