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On Fn arg mismatch for a fn path, suggest a closure

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When encountering a fn call that has a path to another fn being passed
in, where an `Fn` impl is expected, and the arguments differ, suggest
wrapping the argument with a closure with the appropriate arguments.
This commit is contained in:
Esteban Küber 2023-11-11 04:32:32 +00:00
parent abe34e9ab1
commit dfe32b6a43
15 changed files with 247 additions and 54 deletions
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178
compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
View file

@ -222,6 +222,15 @@ fn report_closure_arg_mismatch(
param_env: ty::ParamEnv<'tcx>,
) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>;
fn note_conflicting_fn_args(
&self,
err: &mut Diagnostic,
cause: &ObligationCauseCode<'tcx>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
);
fn note_conflicting_closure_bounds(
&self,
cause: &ObligationCauseCode<'tcx>,
@ -2005,6 +2014,7 @@ pub(crate) fn build_fn_sig_ty<'tcx>(
let signature_kind = format!("{argument_kind} signature");
err.note_expected_found(&signature_kind, expected_str, &signature_kind, found_str);
self.note_conflicting_fn_args(&mut err, cause, expected, found, param_env);
self.note_conflicting_closure_bounds(cause, &mut err);
if let Some(found_node) = found_node {
@ -2014,6 +2024,152 @@ pub(crate) fn build_fn_sig_ty<'tcx>(
err
}
fn note_conflicting_fn_args(
&self,
err: &mut Diagnostic,
cause: &ObligationCauseCode<'tcx>,
expected: Ty<'tcx>,
found: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) {
let ObligationCauseCode::FunctionArgumentObligation { arg_hir_id, .. } = cause else {
return;
};
let ty::FnPtr(expected) = expected.kind() else {
return;
};
let ty::FnPtr(found) = found.kind() else {
return;
};
let Some(Node::Expr(arg)) = self.tcx.hir().find(*arg_hir_id) else {
return;
};
let hir::ExprKind::Path(path) = arg.kind else {
return;
};
let expected_inputs = self.tcx.erase_late_bound_regions(*expected).inputs();
let found_inputs = self.tcx.erase_late_bound_regions(*found).inputs();
let both_tys = expected_inputs.iter().cloned().zip(found_inputs.iter().cloned());
let arg_expr = |infcx: &InferCtxt<'tcx>, name, expected: Ty<'tcx>, found: Ty<'tcx>| {
let (expected_ty, expected_refs) = get_deref_type_and_refs(expected);
let (found_ty, found_refs) = get_deref_type_and_refs(found);
if infcx.can_eq(param_env, found_ty, expected_ty) {
if found_refs.len() == expected_refs.len()
&& found_refs.iter().zip(expected_refs.iter()).all(|(e, f)| e == f)
{
name
} else if found_refs.len() > expected_refs.len() {
if found_refs[..found_refs.len() - expected_refs.len()]
.iter()
.zip(expected_refs.iter())
.any(|(e, f)| e != f)
{
// The refs have different mutability.
format!(
"{}*{name}",
found_refs[..found_refs.len() - expected_refs.len()]
.iter()
.map(|mutbl| format!("&{}", mutbl.prefix_str()))
.collect::<Vec<_>>()
.join(""),
)
} else {
format!(
"{}{name}",
found_refs[..found_refs.len() - expected_refs.len()]
.iter()
.map(|mutbl| format!("&{}", mutbl.prefix_str()))
.collect::<Vec<_>>()
.join(""),
)
}
} else if expected_refs.len() > found_refs.len() {
format!(
"{}{name}",
(0..(expected_refs.len() - found_refs.len()))
.map(|_| "*")
.collect::<Vec<_>>()
.join(""),
)
} else {
format!(
"{}{name}",
found_refs
.iter()
.map(|mutbl| format!("&{}", mutbl.prefix_str()))
.chain(found_refs.iter().map(|_| "*".to_string()))
.collect::<Vec<_>>()
.join(""),
)
}
} else {
format!("/* {found} */")
}
};
let (closure_names, call_names): (Vec<_>, Vec<_>) =
if both_tys.clone().all(|(expected, found)| {
let (expected_ty, _) = get_deref_type_and_refs(expected);
let (found_ty, _) = get_deref_type_and_refs(found);
self.can_eq(param_env, found_ty, expected_ty)
}) && !expected_inputs.is_empty()
&& expected_inputs.len() == found_inputs.len()
&& let hir::QPath::Resolved(_, path) = path
&& let hir::def::Res::Def(_, fn_def_id) = path.res
&& let Some(node) = self.tcx.hir().get_if_local(fn_def_id)
&& let Some(body_id) = node.body_id()
{
let closure = self
.tcx
.hir()
.body_param_names(body_id)
.map(|name| format!("{name}"))
.collect();
let args = self
.tcx
.hir()
.body_param_names(body_id)
.zip(both_tys)
.map(|(name, (expected, found))| {
arg_expr(self.infcx, format!("{name}"), expected, found)
})
.collect();
(closure, args)
} else {
let closure_args = expected_inputs
.iter()
.enumerate()
.map(|(i, _)| format!("arg{i}"))
.collect::<Vec<_>>();
let call_args = both_tys
.enumerate()
.map(|(i, (expected, found))| {
arg_expr(self.infcx, format!("arg{i}"), expected, found)
})
.collect::<Vec<_>>();
(closure_args, call_args)
};
let closure_names: Vec<_> = closure_names
.into_iter()
.zip(expected_inputs.iter())
.map(|(name, ty)| {
format!(
"{name}{}",
if ty.has_infer_types() { String::new() } else { format!(": {ty}") }
)
})
.collect();
err.multipart_suggestion(
format!("consider wrapping the function in a closure"),
vec![
(arg.span.shrink_to_lo(), format!("|{}| ", closure_names.join(", "))),
(arg.span.shrink_to_hi(), format!("({})", call_names.join(", "))),
],
Applicability::MaybeIncorrect,
);
}
// Add a note if there are two `Fn`-family bounds that have conflicting argument
// requirements, which will always cause a closure to have a type error.
fn note_conflicting_closure_bounds(
@ -4349,17 +4505,6 @@ fn hint_missing_borrow<'tcx>(
let args = fn_decl.inputs.iter();
fn get_deref_type_and_refs(mut ty: Ty<'_>) -> (Ty<'_>, Vec<hir::Mutability>) {
let mut refs = vec![];
while let ty::Ref(_, new_ty, mutbl) = ty.kind() {
ty = *new_ty;
refs.push(*mutbl);
}
(ty, refs)
}
let mut to_borrow = Vec::new();
let mut remove_borrow = Vec::new();
@ -4652,3 +4797,14 @@ pub fn suggest_desugaring_async_fn_to_impl_future_in_trait<'tcx>(
Some(sugg)
}
fn get_deref_type_and_refs(mut ty: Ty<'_>) -> (Ty<'_>, Vec<hir::Mutability>) {
let mut refs = vec![];
while let ty::Ref(_, new_ty, mutbl) = ty.kind() {
ty = *new_ty;
refs.push(*mutbl);
}
(ty, refs)
}

4
tests/ui/generic-associated-types/bugs/issue-88382.stderr
View file

@ -16,6 +16,10 @@ note: required by a bound in `do_something`
|
LL | fn do_something<I: Iterable>(i: I, mut f: impl for<'a> Fn(&mut I::Iterator<'a>)) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `do_something`
help: consider wrapping the function in a closure
|
LL | do_something(SomeImplementation(), |arg0: &mut std::iter::Empty<usize>| test(/* &mut <_ as Iterable>::Iterator<'_> */));
| ++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++
error: aborting due to 1 previous error

4
tests/ui/intrinsics/const-eval-select-bad.stderr
View file

@ -86,6 +86,10 @@ LL | const_eval_select((true,), foo, baz);
found function signature `fn(i32) -> _`
note: required by a bound in `const_eval_select`
--> $SRC_DIR/core/src/intrinsics.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | const_eval_select((true,), |arg0: bool| foo(/* i32 */), baz);
| ++++++++++++ +++++++++++
error: this argument must be a `const fn`
--> $DIR/const-eval-select-bad.rs:42:29

8
tests/ui/mismatched_types/E0631.stderr
View file

@ -48,6 +48,10 @@ note: required by a bound in `foo`
|
LL | fn foo<F: Fn(usize)>(_: F) {}
| ^^^^^^^^^ required by this bound in `foo`
help: consider wrapping the function in a closure
|
LL | foo(|arg0: usize| f(/* u64 */));
| +++++++++++++ +++++++++++
error[E0631]: type mismatch in function arguments
--> $DIR/E0631.rs:10:9
@ -67,6 +71,10 @@ note: required by a bound in `bar`
|
LL | fn bar<F: Fn<(usize,)>>(_: F) {}
| ^^^^^^^^^^^^ required by this bound in `bar`
help: consider wrapping the function in a closure
|
LL | bar(|arg0: usize| f(/* u64 */));
| +++++++++++++ +++++++++++
error: aborting due to 4 previous errors

4
tests/ui/mismatched_types/closure-ref-114180.stderr
View file

@ -12,6 +12,10 @@ LL | v.sort_by(compare);
found closure signature `fn((_,), (_,)) -> _`
note: required by a bound in `slice::<impl [T]>::sort_by`
--> $SRC_DIR/alloc/src/slice.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | v.sort_by(|arg0, arg1| compare(*arg0, *arg1));
| ++++++++++++ ++++++++++++++
help: consider adjusting the signature so it borrows its arguments
|
LL | let compare = |&(a,), &(e,)| todo!();

8
tests/ui/mismatched_types/fn-variance-1.stderr
View file

@ -16,6 +16,10 @@ note: required by a bound in `apply`
|
LL | fn apply<T, F>(t: T, f: F) where F: FnOnce(T) {
| ^^^^^^^^^ required by this bound in `apply`
help: consider wrapping the function in a closure
|
LL | apply(&3, |x| takes_mut(&mut *x));
| +++ +++++++++
error[E0631]: type mismatch in function arguments
--> $DIR/fn-variance-1.rs:15:19
@ -35,6 +39,10 @@ note: required by a bound in `apply`
|
LL | fn apply<T, F>(t: T, f: F) where F: FnOnce(T) {
| ^^^^^^^^^ required by this bound in `apply`
help: consider wrapping the function in a closure
|
LL | apply(&mut 3, |x| takes_imm(&*x));
| +++ +++++
error: aborting due to 2 previous errors

4
tests/ui/mismatched_types/suggest-option-asderef-inference-var.stderr
View file

@ -13,6 +13,10 @@ LL | let _has_inference_vars: Option<i32> = Some(0).map(deref_int);
found function signature `for<'a> fn(&'a i32) -> _`
note: required by a bound in `Option::<T>::map`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | let _has_inference_vars: Option<i32> = Some(0).map(|a| deref_int(&a));
| +++ ++++
help: consider adjusting the signature so it does not borrow its argument
|
LL - fn deref_int(a: &i32) -> i32 {

8
tests/ui/mismatched_types/suggest-option-asderef-unfixable.stderr
View file

@ -13,6 +13,10 @@ LL | let _ = produces_string().and_then(takes_str_but_too_many_refs);
found function signature `for<'a, 'b> fn(&'a &'b str) -> _`
note: required by a bound in `Option::<T>::and_then`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | let _ = produces_string().and_then(|arg0: String| takes_str_but_too_many_refs(/* &&str */));
| ++++++++++++++ +++++++++++++
error[E0277]: expected a `FnOnce(String)` closure, found `for<'a> extern "C" fn(&'a str) -> Option<()> {takes_str_but_wrong_abi}`
--> $DIR/suggest-option-asderef-unfixable.rs:26:40
@ -68,6 +72,10 @@ LL | let _ = Some(TypeWithoutDeref).and_then(takes_str_but_too_many_refs);
found function signature `for<'a, 'b> fn(&'a &'b str) -> _`
note: required by a bound in `Option::<T>::and_then`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | let _ = Some(TypeWithoutDeref).and_then(|arg0: TypeWithoutDeref| takes_str_but_too_many_refs(/* &&str */));
| ++++++++++++++++++++++++ +++++++++++++
error: aborting due to 5 previous errors

39
tests/ui/mismatched_types/suggest-option-asderef.fixed
View file

@ -1,39 +0,0 @@
// run-rustfix
fn produces_string() -> Option<String> {
Some("my cool string".to_owned())
}
fn takes_str(_: &str) -> Option<()> {
Some(())
}
fn takes_str_mut(_: &mut str) -> Option<()> {
Some(())
}
fn generic<T>(_: T) -> Option<()> {
Some(())
}
fn generic_ref<T>(_: T) -> Option<()> {
//~^ HELP consider adjusting the signature so it does not borrow its argument
Some(())
}
fn main() {
let _: Option<()> = produces_string().as_deref().and_then(takes_str);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref()` first
let _: Option<Option<()>> = produces_string().as_deref().map(takes_str);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref()` first
let _: Option<Option<()>> = produces_string().as_deref_mut().map(takes_str_mut);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref_mut()` first
let _ = produces_string().and_then(generic);
let _ = produces_string().as_deref().and_then(generic_ref);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref()` first
}

6
tests/ui/mismatched_types/suggest-option-asderef.rs
View file

@ -1,4 +1,4 @@
// run-rustfix
// this isn't auto-fixable now because we produce two similar suggestions
fn produces_string() -> Option<String> {
Some("my cool string".to_owned())
@ -25,15 +25,19 @@ fn main() {
let _: Option<()> = produces_string().and_then(takes_str);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref()` first
//~| HELP consider wrapping the function in a closure
let _: Option<Option<()>> = produces_string().map(takes_str);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref()` first
//~| HELP consider wrapping the function in a closure
let _: Option<Option<()>> = produces_string().map(takes_str_mut);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref_mut()` first
//~| HELP consider wrapping the function in a closure
let _ = produces_string().and_then(generic);
let _ = produces_string().and_then(generic_ref);
//~^ ERROR type mismatch in function arguments
//~| HELP call `Option::as_deref()` first
//~| HELP consider wrapping the function in a closure
}

22
tests/ui/mismatched_types/suggest-option-asderef.stderr
View file

@ -13,13 +13,17 @@ LL | let _: Option<()> = produces_string().and_then(takes_str);
found function signature `for<'a> fn(&'a str) -> _`
note: required by a bound in `Option::<T>::and_then`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | let _: Option<()> = produces_string().and_then(|arg0: String| takes_str(/* &str */));
| ++++++++++++++ ++++++++++++
help: call `Option::as_deref()` first
|
LL | let _: Option<()> = produces_string().as_deref().and_then(takes_str);
| +++++++++++
error[E0631]: type mismatch in function arguments
--> $DIR/suggest-option-asderef.rs:28:55
--> $DIR/suggest-option-asderef.rs:29:55
|
LL | fn takes_str(_: &str) -> Option<()> {
| ----------------------------------- found signature defined here
@ -33,13 +37,17 @@ LL | let _: Option<Option<()>> = produces_string().map(takes_str);
found function signature `for<'a> fn(&'a str) -> _`
note: required by a bound in `Option::<T>::map`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | let _: Option<Option<()>> = produces_string().map(|arg0: String| takes_str(/* &str */));
| ++++++++++++++ ++++++++++++
help: call `Option::as_deref()` first
|
LL | let _: Option<Option<()>> = produces_string().as_deref().map(takes_str);
| +++++++++++
error[E0631]: type mismatch in function arguments
--> $DIR/suggest-option-asderef.rs:31:55
--> $DIR/suggest-option-asderef.rs:33:55
|
LL | fn takes_str_mut(_: &mut str) -> Option<()> {
| ------------------------------------------- found signature defined here
@ -53,13 +61,17 @@ LL | let _: Option<Option<()>> = produces_string().map(takes_str_mut);
found function signature `for<'a> fn(&'a mut str) -> _`
note: required by a bound in `Option::<T>::map`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | let _: Option<Option<()>> = produces_string().map(|arg0: String| takes_str_mut(/* &mut str */));
| ++++++++++++++ ++++++++++++++++
help: call `Option::as_deref_mut()` first
|
LL | let _: Option<Option<()>> = produces_string().as_deref_mut().map(takes_str_mut);
| +++++++++++++++
error[E0631]: type mismatch in function arguments
--> $DIR/suggest-option-asderef.rs:36:40
--> $DIR/suggest-option-asderef.rs:39:40
|
LL | fn generic_ref<T>(_: &T) -> Option<()> {
| -------------------------------------- found signature defined here
@ -73,6 +85,10 @@ LL | let _ = produces_string().and_then(generic_ref);
found function signature `for<'a> fn(&'a _) -> _`
note: required by a bound in `Option::<T>::and_then`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | let _ = produces_string().and_then(|: String| generic_ref(&));
| ++++++++++ +++
help: consider adjusting the signature so it does not borrow its argument
|
LL - fn generic_ref<T>(_: &T) -> Option<()> {

4
tests/ui/mismatched_types/unboxed-closures-vtable-mismatch.stderr
View file

@ -16,6 +16,10 @@ note: required by a bound in `call_it`
|
LL | fn call_it<F: FnMut(isize, isize) -> isize>(y: isize, mut f: F) -> isize {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `call_it`
help: consider wrapping the function in a closure
|
LL | let z = call_it(3, |arg0: isize, arg1: isize| f(/* usize */, arg1));
| ++++++++++++++++++++++++++ +++++++++++++++++++
error: aborting due to 1 previous error

4
tests/ui/suggestions/enum-variant-arg-mismatch.stderr
View file

@ -16,6 +16,10 @@ note: required by a bound in `map`
|
LL | fn map<'a, F: Fn(String) -> Sexpr<'a>>(f: F) {}
| ^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `map`
help: consider wrapping the function in a closure
|
LL | map(|arg0: String| Sexpr::Ident(/* &str */));
| ++++++++++++++ ++++++++++++
error: aborting due to 1 previous error

4
tests/ui/suggestions/late-bound-in-borrow-closure-sugg.stderr
View file

@ -16,6 +16,10 @@ note: required by a bound in `Trader::<'a>::set_closure`
|
LL | pub fn set_closure(&mut self, function: impl Fn(&mut Trader) + 'a) {
| ^^^^^^^^^^^^^^^ required by this bound in `Trader::<'a>::set_closure`
help: consider wrapping the function in a closure
|
LL | trader.set_closure(|arg0: &mut Trader<'_>| closure(*arg0));
| +++++++++++++++++++++++ +++++++
help: consider adjusting the signature so it borrows its argument
|
LL | let closure = |trader : &mut Trader| {

4
tests/ui/typeck/mismatched-map-under-self.stderr
View file

@ -30,6 +30,10 @@ LL | self.map(Insertable::values).unwrap_or_default()
found function signature `for<'a> fn(&'a _) -> _`
note: required by a bound in `Option::<T>::map`
--> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
|
LL | self.map(|arg0: T| Insertable::values(&arg0)).unwrap_or_default()
| +++++++++ +++++++
error: aborting due to 2 previous errors