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Rollup merge of #126226 - gurry:125325-improve-closure-arg-sugg, r=oli-obk

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Make suggestion to change `Fn` to `FnMut` work with methods as well

Fixes #125325

The issue occurred because the code that emitted the suggestion to change `Fn` to `FnMut` worked only for function calls  and not method calls. This PR makes it work with methods as well.
This commit is contained in:
Guillaume Gomez 2024-06-17 11:28:53 +02:00 committed by GitHub
commit 9f5e2e314c
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GPG Key ID: B5690EEEBB952194
3 changed files with 126 additions and 44 deletions
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113
compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
View File

@ -937,56 +937,81 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
let node = self.infcx.tcx.hir_node(fn_call_id);
let def_id = hir.enclosing_body_owner(fn_call_id);
let mut look_at_return = true;
// If we can detect the expression to be an `fn` call where the closure was an argument,
// we point at the `fn` definition argument...
if let hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Call(func, args), .. }) = node {
let arg_pos = args
// If the HIR node is a function or method call gets the def ID
// of the called function or method and the span and args of the call expr
let get_call_details = || {
let hir::Node::Expr(hir::Expr { hir_id, kind, .. }) = node else {
return None;
};
let typeck_results = self.infcx.tcx.typeck(def_id);
match kind {
hir::ExprKind::Call(expr, args) => {
if let Some(ty::FnDef(def_id, _)) =
typeck_results.node_type_opt(expr.hir_id).as_ref().map(|ty| ty.kind())
{
Some((*def_id, expr.span, *args))
} else {
None
}
}
hir::ExprKind::MethodCall(_, _, args, span) => {
if let Some(def_id) = typeck_results.type_dependent_def_id(*hir_id) {
Some((def_id, *span, *args))
} else {
None
}
}
_ => None,
}
};
// If we can detect the expression to be an function or method call where the closure was an argument,
// we point at the function or method definition argument...
if let Some((callee_def_id, call_span, call_args)) = get_call_details() {
let arg_pos = call_args
.iter()
.enumerate()
.filter(|(_, arg)| arg.hir_id == closure_id)
.map(|(pos, _)| pos)
.next();
let tables = self.infcx.tcx.typeck(def_id);
if let Some(ty::FnDef(def_id, _)) =
tables.node_type_opt(func.hir_id).as_ref().map(|ty| ty.kind())
{
let arg = match hir.get_if_local(*def_id) {
Some(
hir::Node::Item(hir::Item {
ident, kind: hir::ItemKind::Fn(sig, ..), ..
let arg = match hir.get_if_local(callee_def_id) {
Some(
hir::Node::Item(hir::Item { ident, kind: hir::ItemKind::Fn(sig, ..), .. })
| hir::Node::TraitItem(hir::TraitItem {
ident,
kind: hir::TraitItemKind::Fn(sig, _),
..
})
| hir::Node::ImplItem(hir::ImplItem {
ident,
kind: hir::ImplItemKind::Fn(sig, _),
..
}),
) => Some(
arg_pos
.and_then(|pos| {
sig.decl.inputs.get(
pos + if sig.decl.implicit_self.has_implicit_self() {
1
} else {
0
},
)
})
| hir::Node::TraitItem(hir::TraitItem {
ident,
kind: hir::TraitItemKind::Fn(sig, _),
..
})
| hir::Node::ImplItem(hir::ImplItem {
ident,
kind: hir::ImplItemKind::Fn(sig, _),
..
}),
) => Some(
arg_pos
.and_then(|pos| {
sig.decl.inputs.get(
pos + if sig.decl.implicit_self.has_implicit_self() {
1
} else {
0
},
)
})
.map(|arg| arg.span)
.unwrap_or(ident.span),
),
_ => None,
};
if let Some(span) = arg {
err.span_label(span, "change this to accept `FnMut` instead of `Fn`");
err.span_label(func.span, "expects `Fn` instead of `FnMut`");
err.span_label(closure_span, "in this closure");
look_at_return = false;
}
.map(|arg| arg.span)
.unwrap_or(ident.span),
),
_ => None,
};
if let Some(span) = arg {
err.span_label(span, "change this to accept `FnMut` instead of `Fn`");
err.span_label(call_span, "expects `Fn` instead of `FnMut`");
err.span_label(closure_span, "in this closure");
look_at_return = false;
}
}

29
tests/ui/closures/wrong-closure-arg-suggestion-125325.rs Normal file
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@ -0,0 +1,29 @@
// Regression test for #125325
// Tests that we suggest changing an `impl Fn` param
// to `impl FnMut` when the provided closure arg
// is trying to mutate the closure env.
// Ensures that it works that way for both
// functions and methods
struct S;
impl S {
fn assoc_func(&self, _f: impl Fn()) -> usize {
0
}
}
fn func(_f: impl Fn()) -> usize {
0
}
fn test_func(s: &S) -> usize {
let mut x = ();
s.assoc_func(|| x = ());
//~^ cannot assign to `x`, as it is a captured variable in a `Fn` closure
func(|| x = ())
//~^ cannot assign to `x`, as it is a captured variable in a `Fn` closure
}
fn main() {}

28
tests/ui/closures/wrong-closure-arg-suggestion-125325.stderr Normal file
View File

@ -0,0 +1,28 @@
error[E0594]: cannot assign to `x`, as it is a captured variable in a `Fn` closure
--> $DIR/wrong-closure-arg-suggestion-125325.rs:23:21
|
LL | fn assoc_func(&self, _f: impl Fn()) -> usize {
| --------- change this to accept `FnMut` instead of `Fn`
...
LL | s.assoc_func(|| x = ());
| --------------^^^^^^-
| | | |
| | | cannot assign
| | in this closure
| expects `Fn` instead of `FnMut`
error[E0594]: cannot assign to `x`, as it is a captured variable in a `Fn` closure
--> $DIR/wrong-closure-arg-suggestion-125325.rs:25:13
|
LL | fn func(_f: impl Fn()) -> usize {
| --------- change this to accept `FnMut` instead of `Fn`
...
LL | func(|| x = ())
| ---- -- ^^^^^^ cannot assign
| | |
| | in this closure
| expects `Fn` instead of `FnMut`
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0594`.