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Rollup merge of #134945 - compiler-errors:map-mutate-nits, r=estebank

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Some small nits to the borrowck suggestions for mutating a map through index

1. Suggesting users to either use `.insert` or `.get_mut` (which do totally different things) can be a bit of a footgun, so let's make that a bit more nuanced.
2. I find the suggestion of `.get_mut(|val| { *val = whatever; })` to be a bit awkward. I changed this to be an if-let instead.
3. Fix a bug which was suppressing the structured suggestion for some mutations via the index operator on `HashMap`/`BTreeMap`.

r? estebank or reassign
This commit is contained in:
Stuart Cook 2025-01-01 16:35:31 +11:00 • committed by GitHub
commit f91bfd97bf
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6 changed files with 30 additions and 21 deletions
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17
compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
View file

@ -575,7 +575,8 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
// ---------- place
self.err.multipart_suggestions(
format!(
"to modify a `{}`, use `.get_mut()`, `.insert()` or the entry API",
"use `.insert()` to insert a value into a `{}`, `.get_mut()` \
to modify it, or the entry API for more flexibility",
self.ty,
),
vec![
@ -592,16 +593,17 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
(rv.span.shrink_to_hi(), ")".to_string()),
],
vec![
// val.get_mut(index).map(|v| { *v = rv; });
// if let Some(v) = val.get_mut(index) { *v = rv; }
(val.span.shrink_to_lo(), "if let Some(val) = ".to_string()),
(
val.span.shrink_to_hi().with_hi(index.span.lo()),
".get_mut(".to_string(),
),
(
index.span.shrink_to_hi().with_hi(place.span.hi()),
").map(|val| { *val".to_string(),
") { *val".to_string(),
),
(rv.span.shrink_to_hi(), "; })".to_string()),
(rv.span.shrink_to_hi(), "; }".to_string()),
],
vec![
// let x = val.entry(index).or_insert(rv);
@ -622,21 +624,22 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
self.suggested = true;
} else if let hir::ExprKind::MethodCall(_path, receiver, _, sp) = expr.kind
&& let hir::ExprKind::Index(val, index, _) = receiver.kind
&& expr.span == self.assign_span
&& receiver.span == self.assign_span
{
// val[index].path(args..);
self.err.multipart_suggestion(
format!("to modify a `{}` use `.get_mut()`", self.ty),
vec![
(val.span.shrink_to_lo(), "if let Some(val) = ".to_string()),
(
val.span.shrink_to_hi().with_hi(index.span.lo()),
".get_mut(".to_string(),
),
(
index.span.shrink_to_hi().with_hi(receiver.span.hi()),
").map(|val| val".to_string(),
") { val".to_string(),
),
(sp.shrink_to_hi(), ")".to_string()),
(sp.shrink_to_hi(), "; }".to_string()),
],
Applicability::MachineApplicable,
);

11
tests/ui/borrowck/index-mut-help.stderr
View file

@ -5,7 +5,10 @@ LL | map["peter"].clear();
| ^^^^^^^^^^^^ cannot borrow as mutable
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `HashMap<&str, String>`
= help: to modify a `HashMap<&str, String>`, use `.get_mut()`, `.insert()` or the entry API
help: to modify a `HashMap<&str, String>` use `.get_mut()`
|
LL | if let Some(val) = map.get_mut("peter") { val.clear(); };
| ++++++++++++++++++ ~~~~~~~~~ ~~~~~~~ +++
error[E0594]: cannot assign to data in an index of `HashMap<&str, String>`
--> $DIR/index-mut-help.rs:11:5
@ -14,12 +17,12 @@ LL | map["peter"] = "0".to_string();
| ^^^^^^^^^^^^ cannot assign
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `HashMap<&str, String>`
help: to modify a `HashMap<&str, String>`, use `.get_mut()`, `.insert()` or the entry API
help: use `.insert()` to insert a value into a `HashMap<&str, String>`, `.get_mut()` to modify it, or the entry API for more flexibility
|
LL | map.insert("peter", "0".to_string());
| ~~~~~~~~ ~ +
LL | map.get_mut("peter").map(|val| { *val = "0".to_string(); });
| ~~~~~~~~~ ~~~~~~~~~~~~~~~~~~ ++++
LL | if let Some(val) = map.get_mut("peter") { *val = "0".to_string(); };
| ++++++++++++++++++ ~~~~~~~~~ ~~~~~~~~ +++
LL | let val = map.entry("peter").or_insert("0".to_string());
| +++++++++ ~~~~~~~ ~~~~~~~~~~~~ +

6
tests/ui/btreemap/btreemap-index-mut-2.stderr
View file

@ -5,12 +5,12 @@ LL | map[&0] = 1;
| ^^^^^^^^^^^ cannot assign
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `BTreeMap<u32, u32>`
help: to modify a `BTreeMap<u32, u32>`, use `.get_mut()`, `.insert()` or the entry API
help: use `.insert()` to insert a value into a `BTreeMap<u32, u32>`, `.get_mut()` to modify it, or the entry API for more flexibility
|
LL | map.insert(&0, 1);
| ~~~~~~~~ ~ +
LL | map.get_mut(&0).map(|val| { *val = 1; });
| ~~~~~~~~~ ~~~~~~~~~~~~~~~~~~ ++++
LL | if let Some(val) = map.get_mut(&0) { *val = 1; };
| ++++++++++++++++++ ~~~~~~~~~ ~~~~~~~~ +++
LL | let val = map.entry(&0).or_insert(1);
| +++++++++ ~~~~~~~ ~~~~~~~~~~~~ +

6
tests/ui/btreemap/btreemap-index-mut.stderr
View file

@ -5,12 +5,12 @@ LL | map[&0] = 1;
| ^^^^^^^^^^^ cannot assign
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `BTreeMap<u32, u32>`
help: to modify a `BTreeMap<u32, u32>`, use `.get_mut()`, `.insert()` or the entry API
help: use `.insert()` to insert a value into a `BTreeMap<u32, u32>`, `.get_mut()` to modify it, or the entry API for more flexibility
|
LL | map.insert(&0, 1);
| ~~~~~~~~ ~ +
LL | map.get_mut(&0).map(|val| { *val = 1; });
| ~~~~~~~~~ ~~~~~~~~~~~~~~~~~~ ++++
LL | if let Some(val) = map.get_mut(&0) { *val = 1; };
| ++++++++++++++++++ ~~~~~~~~~ ~~~~~~~~ +++
LL | let val = map.entry(&0).or_insert(1);
| +++++++++ ~~~~~~~ ~~~~~~~~~~~~ +

6
tests/ui/hashmap/hashmap-index-mut.stderr
View file

@ -5,12 +5,12 @@ LL | map[&0] = 1;
| ^^^^^^^^^^^ cannot assign
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `HashMap<u32, u32>`
help: to modify a `HashMap<u32, u32>`, use `.get_mut()`, `.insert()` or the entry API
help: use `.insert()` to insert a value into a `HashMap<u32, u32>`, `.get_mut()` to modify it, or the entry API for more flexibility
|
LL | map.insert(&0, 1);
| ~~~~~~~~ ~ +
LL | map.get_mut(&0).map(|val| { *val = 1; });
| ~~~~~~~~~ ~~~~~~~~~~~~~~~~~~ ++++
LL | if let Some(val) = map.get_mut(&0) { *val = 1; };
| ++++++++++++++++++ ~~~~~~~~~ ~~~~~~~~ +++
LL | let val = map.entry(&0).or_insert(1);
| +++++++++ ~~~~~~~ ~~~~~~~~~~~~ +

5
tests/ui/issues/issue-41726.stderr
View file

@ -5,7 +5,10 @@ LL | things[src.as_str()].sort();
| ^^^^^^^^^^^^^^^^^^^^ cannot borrow as mutable
|
= help: trait `IndexMut` is required to modify indexed content, but it is not implemented for `HashMap<String, Vec<String>>`
= help: to modify a `HashMap<String, Vec<String>>`, use `.get_mut()`, `.insert()` or the entry API
help: to modify a `HashMap<String, Vec<String>>` use `.get_mut()`
|
LL | if let Some(val) = things.get_mut(src.as_str()) { val.sort(); };
| ++++++++++++++++++ ~~~~~~~~~ ~~~~~~~ +++
error: aborting due to 1 previous error