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Provide structured suggestion for binding needing type on E0594 #107646

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Merged
merged 2 commits into from
Feb 5, 2023
Merged

Provide structured suggestion for binding needing type on E0594 #107646

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Provide structured suggestion for binding needing type on E0594
estebank Feb 3, 2023
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estebank Feb 3, 2023
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60 changes: 54 additions & 6 deletions compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -606,12 +606,60 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
}
}
Some((false, err_label_span, message)) => {
err.span_label(
err_label_span,
&format!(
"consider changing this binding's type to be: `{message}`"
),
);
struct V {
span: Span,
hir_id: Option<hir::HirId>,
}

impl<'tcx> Visitor<'tcx> for V {
fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
if let hir::StmtKind::Local(local) = s.kind {
if local.pat.span == self.span {
self.hir_id = Some(local.hir_id);
}
}
hir::intravisit::walk_stmt(self, s);
}
}
let hir_map = self.infcx.tcx.hir();
let pat = loop {
// Poor man's try block
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@compiler-errors compiler-errors Feb 3, 2023

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Can we just use a try block here? This is the compiler after all. Or a closure (|| {})() is typically what I see being used instead.

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@compiler-errors compiler-errors Feb 3, 2023

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#![feature(try_blocks)] is already enabled in rustc_borrowck too 😃

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@estebank estebank Feb 3, 2023

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Ended up doing let chains instead :)

let def_id = self.body.source.def_id();
let hir_id =
hir_map.local_def_id_to_hir_id(def_id.as_local().unwrap());
let node = hir_map.find(hir_id);
let Some(hir::Node::Item(item)) = node else { break None; };
let hir::ItemKind::Fn(.., body_id) = item.kind else { break None; };
let body = self.infcx.tcx.hir().body(body_id);
let mut v = V { span: err_label_span, hir_id: None };
v.visit_body(body);
break v.hir_id;
};
if let Some(hir_id) = pat
&& let Some(hir::Node::Local(local)) = hir_map.find(hir_id)
{
let (changing, span, sugg) = match local.ty {
Some(ty) => ("changing", ty.span, message),
None => (
"specifying",
local.pat.span.shrink_to_hi(),
format!(": {message}"),
),
};
err.span_suggestion_verbose(
span,
&format!("consider {changing} this binding's type"),
sugg,
Applicability::HasPlaceholders,
);
} else {
err.span_label(
err_label_span,
&format!(
"consider changing this binding's type to be: `{message}`"
),
);
}
}
None => {}
}
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8 changes: 5 additions & 3 deletions tests/ui/borrowck/borrowck-borrow-mut-base-ptr-in-aliasable-loc.stderr
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Original file line number Diff line number Diff line change
@@ -1,11 +1,13 @@
error[E0594]: cannot assign to `**t1`, which is behind a `&` reference
--> $DIR/borrowck-borrow-mut-base-ptr-in-aliasable-loc.rs:9:5
|
LL | let t1 = t0;
| -- consider changing this binding's type to be: `&mut &mut isize`
LL | let p: &isize = &**t0;
LL | **t1 = 22;
| ^^^^^^^^^ `t1` is a `&` reference, so the data it refers to cannot be written
|
help: consider specifying this binding's type
|
LL | let t1: &mut &mut isize = t0;
| +++++++++++++++++

error[E0502]: cannot borrow `**t0` as immutable because it is also borrowed as mutable
--> $DIR/borrowck-borrow-mut-base-ptr-in-aliasable-loc.rs:14:21
Expand Down
6 changes: 3 additions & 3 deletions tests/ui/borrowck/issue-85765.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
fn main() {
let mut test = Vec::new();
let rofl: &Vec<Vec<i32>> = &mut test;
//~^ NOTE consider changing this binding's type to be
//~^ HELP consider changing this binding's type
rofl.push(Vec::new());
//~^ ERROR cannot borrow `*rofl` as mutable, as it is behind a `&` reference
//~| NOTE `rofl` is a `&` reference, so the data it refers to cannot be borrowed as mutable
Expand All @@ -15,14 +15,14 @@ fn main() {

#[rustfmt::skip]
let x: &usize = &mut{0};
//~^ NOTE consider changing this binding's type to be
//~^ HELP consider changing this binding's type
*x = 1;
//~^ ERROR cannot assign to `*x`, which is behind a `&` reference
//~| NOTE `x` is a `&` reference, so the data it refers to cannot be written

#[rustfmt::skip]
let y: &usize = &mut(0);
//~^ NOTE consider changing this binding's type to be
//~^ HELP consider changing this binding's type
*y = 1;
//~^ ERROR cannot assign to `*y`, which is behind a `&` reference
//~| NOTE `y` is a `&` reference, so the data it refers to cannot be written
Expand Down
24 changes: 15 additions & 9 deletions tests/ui/borrowck/issue-85765.stderr
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Original file line number Diff line number Diff line change
@@ -1,11 +1,13 @@
error[E0596]: cannot borrow `*rofl` as mutable, as it is behind a `&` reference
--> $DIR/issue-85765.rs:5:5
|
LL | let rofl: &Vec<Vec<i32>> = &mut test;
| ---- consider changing this binding's type to be: `&mut Vec<Vec<i32>>`
LL |
LL | rofl.push(Vec::new());
| ^^^^^^^^^^^^^^^^^^^^^ `rofl` is a `&` reference, so the data it refers to cannot be borrowed as mutable
|
help: consider changing this binding's type
|
LL | let rofl: &mut Vec<Vec<i32>> = &mut test;
| ~~~~~~~~~~~~~~~~~~

error[E0594]: cannot assign to `*r`, which is behind a `&` reference
--> $DIR/issue-85765.rs:12:5
Expand All @@ -21,20 +23,24 @@ LL | let r = &mut mutvar;
error[E0594]: cannot assign to `*x`, which is behind a `&` reference
--> $DIR/issue-85765.rs:19:5
|
LL | let x: &usize = &mut{0};
| - consider changing this binding's type to be: `&mut usize`
LL |
LL | *x = 1;
| ^^^^^^ `x` is a `&` reference, so the data it refers to cannot be written
|
help: consider changing this binding's type
|
LL | let x: &mut usize = &mut{0};
| ~~~~~~~~~~

error[E0594]: cannot assign to `*y`, which is behind a `&` reference
--> $DIR/issue-85765.rs:26:5
|
LL | let y: &usize = &mut(0);
| - consider changing this binding's type to be: `&mut usize`
LL |
LL | *y = 1;
| ^^^^^^ `y` is a `&` reference, so the data it refers to cannot be written
|
help: consider changing this binding's type
|
LL | let y: &mut usize = &mut(0);
| ~~~~~~~~~~

error: aborting due to 4 previous errors

Expand Down
2 changes: 1 addition & 1 deletion tests/ui/borrowck/issue-91206.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ impl TestClient {
fn main() {
let client = TestClient;
let inner = client.get_inner_ref();
//~^ NOTE consider changing this binding's type to be
//~^ HELP consider specifying this binding's type
inner.clear();
//~^ ERROR cannot borrow `*inner` as mutable, as it is behind a `&` reference [E0596]
//~| NOTE `inner` is a `&` reference, so the data it refers to cannot be borrowed as mutable
Expand Down
8 changes: 5 additions & 3 deletions tests/ui/borrowck/issue-91206.stderr
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Original file line number Diff line number Diff line change
@@ -1,11 +1,13 @@
error[E0596]: cannot borrow `*inner` as mutable, as it is behind a `&` reference
--> $DIR/issue-91206.rs:13:5
|
LL | let inner = client.get_inner_ref();
| ----- consider changing this binding's type to be: `&mut Vec<usize>`
LL |
LL | inner.clear();
| ^^^^^^^^^^^^^ `inner` is a `&` reference, so the data it refers to cannot be borrowed as mutable
|
help: consider specifying this binding's type
|
LL | let inner: &mut Vec<usize> = client.get_inner_ref();
| +++++++++++++++++

error: aborting due to previous error

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7 changes: 5 additions & 2 deletions tests/ui/borrowck/issue-92015.stderr
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Original file line number Diff line number Diff line change
@@ -1,10 +1,13 @@
error[E0594]: cannot assign to `*foo`, which is behind a `&` reference
--> $DIR/issue-92015.rs:6:5
|
LL | let foo = Some(&0).unwrap();
| --- consider changing this binding's type to be: `&mut i32`
LL | *foo = 1;
| ^^^^^^^^ `foo` is a `&` reference, so the data it refers to cannot be written
|
help: consider specifying this binding's type
|
LL | let foo: &mut i32 = Some(&0).unwrap();
| ++++++++++

error: aborting due to previous error

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1 change: 1 addition & 0 deletions tests/ui/issues/issue-51515.rs
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Expand Up @@ -5,6 +5,7 @@ fn main() {
*foo = 32;
//~^ ERROR cannot assign to `*foo`, which is behind a `&` reference
let bar = foo;
//~^ HELP consider specifying this binding's type
*bar = 64;
//~^ ERROR cannot assign to `*bar`, which is behind a `&` reference
}
9 changes: 6 additions & 3 deletions tests/ui/issues/issue-51515.stderr
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Expand Up @@ -10,12 +10,15 @@ LL | let foo = &mut 16;
| ~~~~~~~

error[E0594]: cannot assign to `*bar`, which is behind a `&` reference
--> $DIR/issue-51515.rs:8:5
--> $DIR/issue-51515.rs:9:5
|
LL | let bar = foo;
| --- consider changing this binding's type to be: `&mut i32`
LL | *bar = 64;
| ^^^^^^^^^ `bar` is a `&` reference, so the data it refers to cannot be written
|
help: consider specifying this binding's type
|
LL | let bar: &mut i32 = foo;
| ++++++++++

error: aborting due to 2 previous errors

Expand Down