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Rollup merge of rust-lang#115744 - fmease:fix-e0401, r=compiler-errors

Improve diagnostic for generic params from outer items (E0401)

Generalize the wording of E0401 to talk about *outer items* instead of *outer functions* since the current phrasing is outdated. The outer item can be a function, constant, trait, ADT or impl block (see the new UI test for the more exotic examples).

Further, don't suggest introducing generic parameters to constant items unless the feature `generic_const_items` is enabled.

Lastly, make E0401 translatable while we're at it.

Fixes rust-lang#115720.
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rust-timer authored Sep 11, 2023
2 parents 3ebb562 + daf3c45 commit 00b5de4
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6 changes: 3 additions & 3 deletions compiler/rustc_error_codes/src/error_codes/E0401.md
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
Inner items do not inherit type or const parameters from the functions
Inner items do not inherit the generic parameters from the items
they are embedded in.

Erroneous code example:
Expand Down Expand Up @@ -32,8 +32,8 @@ fn foo<T>(x: T) {
}
```

Items inside functions are basically just like top-level items, except
that they can only be used from the function they are in.
Items nested inside other items are basically just like top-level items, except
that they can only be used from the item they are in.

There are a couple of solutions for this.

Expand Down
29 changes: 13 additions & 16 deletions compiler/rustc_resolve/messages.ftl
Original file line number Diff line number Diff line change
Expand Up @@ -68,9 +68,6 @@ resolve_cannot_find_ident_in_this_scope =
resolve_cannot_glob_import_possible_crates =
cannot glob-import all possible crates
resolve_cannot_use_self_type_here =
can't use `Self` here
resolve_change_import_binding =
you can use `as` to change the binding name of the import
Expand All @@ -90,9 +87,6 @@ resolve_const_not_member_of_trait =
const `{$const_}` is not a member of trait `{$trait_}`
.label = not a member of trait `{$trait_}`
resolve_const_param_from_outer_fn =
const parameter from outer function
resolve_const_param_in_enum_discriminant =
const parameters may not be used in enum discriminant values
Expand All @@ -119,10 +113,19 @@ resolve_forward_declared_generic_param =
generic parameters with a default cannot use forward declared identifiers
.label = defaulted generic parameters cannot be forward declared
resolve_generic_params_from_outer_function =
can't use generic parameters from outer function
.label = use of generic parameter from outer function
.suggestion = try using a local generic parameter instead
resolve_generic_params_from_outer_item =
can't use generic parameters from outer item
.label = use of generic parameter from outer item
.refer_to_type_directly = refer to the type directly here instead
.suggestion = try introducing a local generic parameter here
resolve_generic_params_from_outer_item_const_param = const parameter from outer item
resolve_generic_params_from_outer_item_self_ty_alias = `Self` type implicitly declared here, by this `impl`
resolve_generic_params_from_outer_item_self_ty_param = can't use `Self` here
resolve_generic_params_from_outer_item_ty_param = type parameter from outer item
resolve_glob_import_doesnt_reexport =
glob import doesn't reexport anything because no candidate is public enough
Expand Down Expand Up @@ -277,9 +280,6 @@ resolve_type_not_member_of_trait =
type `{$type_}` is not a member of trait `{$trait_}`
.label = not a member of trait `{$trait_}`
resolve_type_param_from_outer_fn =
type parameter from outer function
resolve_type_param_in_enum_discriminant =
type parameters may not be used in enum discriminant values
Expand Down Expand Up @@ -315,9 +315,6 @@ resolve_unreachable_label_suggestion_use_similarly_named =
resolve_unreachable_label_with_similar_name_exists =
a label with a similar name exists but is unreachable
resolve_use_a_type_here_instead =
use a type here instead
resolve_variable_bound_with_different_mode =
variable `{$variable_name}` is bound inconsistently across alternatives separated by `|`
.label = bound in different ways
Expand Down
47 changes: 20 additions & 27 deletions compiler/rustc_resolve/src/diagnostics.rs
Original file line number Diff line number Diff line change
Expand Up @@ -553,53 +553,47 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
resolution_error: ResolutionError<'a>,
) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
match resolution_error {
ResolutionError::GenericParamsFromOuterFunction(outer_res, has_generic_params) => {
let mut err = struct_span_err!(
self.tcx.sess,
ResolutionError::GenericParamsFromOuterItem(outer_res, has_generic_params) => {
use errs::GenericParamsFromOuterItemLabel as Label;
let mut err = errs::GenericParamsFromOuterItem {
span,
E0401,
"can't use generic parameters from outer function",
);
err.span_label(span, "use of generic parameter from outer function");
label: None,
refer_to_type_directly: None,
sugg: None,
};

let sm = self.tcx.sess.source_map();
let def_id = match outer_res {
Res::SelfTyParam { .. } => {
err.span_label(span, "can't use `Self` here");
return err;
err.label = Some(Label::SelfTyParam(span));
return self.tcx.sess.create_err(err);
}
Res::SelfTyAlias { alias_to: def_id, .. } => {
err.span_label(
reduce_impl_span_to_impl_keyword(sm, self.def_span(def_id)),
"`Self` type implicitly declared here, by this `impl`",
);
err.span_label(span, "use a type here instead");
return err;
err.label = Some(Label::SelfTyAlias(reduce_impl_span_to_impl_keyword(
sm,
self.def_span(def_id),
)));
err.refer_to_type_directly = Some(span);
return self.tcx.sess.create_err(err);
}
Res::Def(DefKind::TyParam, def_id) => {
err.span_label(self.def_span(def_id), "type parameter from outer function");
err.label = Some(Label::TyParam(self.def_span(def_id)));
def_id
}
Res::Def(DefKind::ConstParam, def_id) => {
err.span_label(
self.def_span(def_id),
"const parameter from outer function",
);
err.label = Some(Label::ConstParam(self.def_span(def_id)));
def_id
}
_ => {
bug!(
"GenericParamsFromOuterFunction should only be used with \
"GenericParamsFromOuterItem should only be used with \
Res::SelfTyParam, Res::SelfTyAlias, DefKind::TyParam or \
DefKind::ConstParam"
);
}
};

if let HasGenericParams::Yes(span) = has_generic_params {
// Try to retrieve the span of the function signature and generate a new
// message with a local type or const parameter.
let sugg_msg = "try using a local generic parameter instead";
let name = self.tcx.item_name(def_id);
let (span, snippet) = if span.is_empty() {
let snippet = format!("<{name}>");
Expand All @@ -609,11 +603,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
let snippet = format!("{name}, ");
(span, snippet)
};
// Suggest the modification to the user
err.span_suggestion(span, sugg_msg, snippet, Applicability::MaybeIncorrect);
err.sugg = Some(errs::GenericParamsFromOuterItemSugg { span, snippet });
}

err
self.tcx.sess.create_err(err)
}
ResolutionError::NameAlreadyUsedInParameterList(name, first_use_span) => self
.tcx
Expand Down
34 changes: 34 additions & 0 deletions compiler/rustc_resolve/src/errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,40 @@ pub(crate) struct CrateRootNamesMustBeNamedExplicitly(#[primary_span] pub(crate)
#[diag(resolve_crate_root_imports_must_be_named_explicitly)]
pub(crate) struct ResolutionError(#[primary_span] pub(crate) Span);

#[derive(Diagnostic)]
#[diag(resolve_generic_params_from_outer_item, code = "E0401")]
pub(crate) struct GenericParamsFromOuterItem {
#[primary_span]
#[label]
pub(crate) span: Span,
#[subdiagnostic]
pub(crate) label: Option<GenericParamsFromOuterItemLabel>,
#[label(resolve_refer_to_type_directly)]
pub(crate) refer_to_type_directly: Option<Span>,
#[subdiagnostic]
pub(crate) sugg: Option<GenericParamsFromOuterItemSugg>,
}

#[derive(Subdiagnostic)]
pub(crate) enum GenericParamsFromOuterItemLabel {
#[label(resolve_generic_params_from_outer_item_self_ty_param)]
SelfTyParam(#[primary_span] Span),
#[label(resolve_generic_params_from_outer_item_self_ty_alias)]
SelfTyAlias(#[primary_span] Span),
#[label(resolve_generic_params_from_outer_item_ty_param)]
TyParam(#[primary_span] Span),
#[label(resolve_generic_params_from_outer_item_const_param)]
ConstParam(#[primary_span] Span),
}

#[derive(Subdiagnostic)]
#[suggestion(resolve_suggestion, code = "{snippet}", applicability = "maybe-incorrect")]
pub(crate) struct GenericParamsFromOuterItemSugg {
#[primary_span]
pub(crate) span: Span,
pub(crate) snippet: String,
}

#[derive(Diagnostic)]
#[diag(resolve_name_is_already_used_as_generic_parameter, code = "E0403")]
pub(crate) struct NameAlreadyUsedInParameterList {
Expand Down
10 changes: 2 additions & 8 deletions compiler/rustc_resolve/src/ident.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1229,10 +1229,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
if let Some(span) = finalize {
self.report_error(
span,
ResolutionError::GenericParamsFromOuterFunction(
res,
has_generic_params,
),
ResolutionError::GenericParamsFromOuterItem(res, has_generic_params),
);
}
return Res::Err;
Expand Down Expand Up @@ -1296,10 +1293,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
if let Some(span) = finalize {
self.report_error(
span,
ResolutionError::GenericParamsFromOuterFunction(
res,
has_generic_params,
),
ResolutionError::GenericParamsFromOuterItem(res, has_generic_params),
);
}
return Res::Err;
Expand Down
6 changes: 5 additions & 1 deletion compiler/rustc_resolve/src/late.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2450,7 +2450,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
ItemKind::Const(box ast::ConstItem { ref generics, ref ty, ref expr, .. }) => {
self.with_generic_param_rib(
&generics.params,
RibKind::Item(HasGenericParams::Yes(generics.span)),
RibKind::Item(if self.r.tcx.features().generic_const_items {
HasGenericParams::Yes(generics.span)
} else {
HasGenericParams::No
}),
LifetimeRibKind::Generics {
binder: item.id,
kind: LifetimeBinderKind::ConstItem,
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_resolve/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -186,8 +186,8 @@ struct BindingError {

#[derive(Debug)]
enum ResolutionError<'a> {
/// Error E0401: can't use type or const parameters from outer function.
GenericParamsFromOuterFunction(Res, HasGenericParams),
/// Error E0401: can't use type or const parameters from outer item.
GenericParamsFromOuterItem(Res, HasGenericParams),
/// Error E0403: the name is already used for a type or const parameter in this generic
/// parameter list.
NameAlreadyUsedInParameterList(Symbol, Span),
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/const-generics/early/const-param-from-outer-fn.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
fn foo<const X: u32>() {
fn bar() -> u32 {
X //~ ERROR can't use generic parameters from outer function
X //~ ERROR can't use generic parameters from outer item
}
}

Expand Down
Original file line number Diff line number Diff line change
@@ -1,12 +1,12 @@
error[E0401]: can't use generic parameters from outer function
error[E0401]: can't use generic parameters from outer item
--> $DIR/const-param-from-outer-fn.rs:3:9
|
LL | fn foo<const X: u32>() {
| - const parameter from outer function
| - const parameter from outer item
LL | fn bar() -> u32 {
| - help: try using a local generic parameter instead: `<X>`
| - help: try introducing a local generic parameter here: `<X>`
LL | X
| ^ use of generic parameter from outer function
| ^ use of generic parameter from outer item

error: aborting due to previous error

Expand Down
22 changes: 11 additions & 11 deletions tests/ui/error-codes/E0401.stderr
Original file line number Diff line number Diff line change
@@ -1,26 +1,26 @@
error[E0401]: can't use generic parameters from outer function
error[E0401]: can't use generic parameters from outer item
--> $DIR/E0401.rs:4:39
|
LL | fn foo<T>(x: T) {
| - type parameter from outer function
| - type parameter from outer item
LL | fn bfnr<U, V: Baz<U>, W: Fn()>(y: T) {
| - ^ use of generic parameter from outer function
| - ^ use of generic parameter from outer item
| |
| help: try using a local generic parameter instead: `T,`
| help: try introducing a local generic parameter here: `T,`

error[E0401]: can't use generic parameters from outer function
error[E0401]: can't use generic parameters from outer item
--> $DIR/E0401.rs:9:16
|
LL | fn foo<T>(x: T) {
| - type parameter from outer function
| - type parameter from outer item
...
LL | fn baz<U,
| - help: try using a local generic parameter instead: `T,`
| - help: try introducing a local generic parameter here: `T,`
...
LL | (y: T) {
| ^ use of generic parameter from outer function
| ^ use of generic parameter from outer item

error[E0401]: can't use generic parameters from outer function
error[E0401]: can't use generic parameters from outer item
--> $DIR/E0401.rs:24:25
|
LL | impl<T> Iterator for A<T> {
Expand All @@ -29,8 +29,8 @@ LL | impl<T> Iterator for A<T> {
LL | fn helper(sel: &Self) -> u8 {
| ^^^^
| |
| use of generic parameter from outer function
| use a type here instead
| use of generic parameter from outer item
| refer to the type directly here instead

error[E0282]: type annotations needed
--> $DIR/E0401.rs:11:5
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/generics/issue-94432-garbage-ice.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@

fna<e>(){fnp(){e}} //~ ERROR unknown start of token: \u{fffd}
//~^ ERROR unknown start of token: \u{fffd}
//~^^ ERROR can't use generic parameters from outer function [E0401]
//~^^ ERROR can't use generic parameters from outer item [E0401]
//~^^^ WARN type parameter `e` should have an upper camel case name

fn main(){}
2 changes: 1 addition & 1 deletion tests/ui/generics/issue-98432.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ struct Struct<T>(T);

impl<T> Struct<T> {
const CONST: fn() = || {
struct _Obligation where T:; //~ ERROR can't use generic parameters from outer function
struct _Obligation where T:; //~ ERROR can't use generic parameters from outer item
};
}

Expand Down
8 changes: 4 additions & 4 deletions tests/ui/generics/issue-98432.stderr
Original file line number Diff line number Diff line change
@@ -1,13 +1,13 @@
error[E0401]: can't use generic parameters from outer function
error[E0401]: can't use generic parameters from outer item
--> $DIR/issue-98432.rs:5:34
|
LL | impl<T> Struct<T> {
| - type parameter from outer function
| - type parameter from outer item
LL | const CONST: fn() = || {
LL | struct _Obligation where T:;
| - ^ use of generic parameter from outer function
| - ^ use of generic parameter from outer item
| |
| help: try using a local generic parameter instead: `<T>`
| help: try introducing a local generic parameter here: `<T>`

error: aborting due to previous error

Expand Down
2 changes: 1 addition & 1 deletion tests/ui/inner-static-type-parameter.rs
Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ enum Bar<T> { What } //~ ERROR parameter `T` is never used

fn foo<T>() {
static a: Bar<T> = Bar::What;
//~^ ERROR can't use generic parameters from outer function
//~^ ERROR can't use generic parameters from outer item
}

fn main() {
Expand Down
6 changes: 3 additions & 3 deletions tests/ui/inner-static-type-parameter.stderr
Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
error[E0401]: can't use generic parameters from outer function
error[E0401]: can't use generic parameters from outer item
--> $DIR/inner-static-type-parameter.rs:6:19
|
LL | fn foo<T>() {
| - type parameter from outer function
| - type parameter from outer item
LL | static a: Bar<T> = Bar::What;
| ^ use of generic parameter from outer function
| ^ use of generic parameter from outer item

error[E0392]: parameter `T` is never used
--> $DIR/inner-static-type-parameter.rs:3:10
Expand Down
2 changes: 1 addition & 1 deletion tests/ui/issues/issue-3214.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
fn foo<T>() {
struct Foo {
x: T, //~ ERROR can't use generic parameters from outer function
x: T, //~ ERROR can't use generic parameters from outer item
}

impl<T> Drop for Foo<T> {
Expand Down
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