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simplify const params diagnostic on stable #95820

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merged 1 commit into from
Apr 12, 2022
Merged

simplify const params diagnostic on stable #95820

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152 changes: 82 additions & 70 deletions compiler/rustc_typeck/src/check/wfcheck.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -816,16 +816,69 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
hir::GenericParamKind::Const { ty: hir_ty, default: _ } => {
let ty = tcx.type_of(tcx.hir().local_def_id(param.hir_id));

let err_ty_str;
let mut is_ptr = true;
let err = if tcx.features().adt_const_params {
match ty.peel_refs().kind() {
if tcx.features().adt_const_params {
let err = match ty.peel_refs().kind() {
ty::FnPtr(_) => Some("function pointers"),
ty::RawPtr(_) => Some("raw pointers"),
_ => None,
};

if let Some(unsupported_type) = err {
tcx.sess.span_err(
hir_ty.span,
&format!(
"using {} as const generic parameters is forbidden",
unsupported_type
),
);
}

if traits::search_for_structural_match_violation(param.span, tcx, ty).is_some() {
// We use the same error code in both branches, because this is really the same
// issue: we just special-case the message for type parameters to make it
// clearer.
if let ty::Param(_) = ty.peel_refs().kind() {
// Const parameters may not have type parameters as their types,
// because we cannot be sure that the type parameter derives `PartialEq`
// and `Eq` (just implementing them is not enough for `structural_match`).
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"`{}` is not guaranteed to `#[derive(PartialEq, Eq)]`, so may not be \
used as the type of a const parameter",
ty,
)
.span_label(
hir_ty.span,
format!("`{}` may not derive both `PartialEq` and `Eq`", ty),
)
.note(
"it is not currently possible to use a type parameter as the type of a \
const parameter",
)
.emit();
} else {
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"`{}` must be annotated with `#[derive(PartialEq, Eq)]` to be used as \
the type of a const parameter",
ty,
)
.span_label(
hir_ty.span,
format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
)
.emit();
}
}
} else {
match ty.kind() {
let err_ty_str;
let mut is_ptr = true;

let err = match ty.kind() {
ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Error(_) => None,
ty::FnPtr(_) => Some("function pointers"),
ty::RawPtr(_) => Some("raw pointers"),
Expand All @@ -834,74 +887,33 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
err_ty_str = format!("`{}`", ty);
Some(err_ty_str.as_str())
}
}
};
if let Some(unsupported_type) = err {
if is_ptr {
tcx.sess.span_err(
hir_ty.span,
&format!(
"using {} as const generic parameters is forbidden",
unsupported_type
),
);
} else {
let mut err = tcx.sess.struct_span_err(
hir_ty.span,
&format!(
"{} is forbidden as the type of a const generic parameter",
unsupported_type
),
);
err.note("the only supported types are integers, `bool` and `char`");
if tcx.sess.is_nightly_build() {
err.help(
};

if let Some(unsupported_type) = err {
if is_ptr {
tcx.sess.span_err(
hir_ty.span,
&format!(
"using {} as const generic parameters is forbidden",
unsupported_type
),
);
} else {
let mut err = tcx.sess.struct_span_err(
hir_ty.span,
&format!(
"{} is forbidden as the type of a const generic parameter",
unsupported_type
),
);
err.note("the only supported types are integers, `bool` and `char`");
if tcx.sess.is_nightly_build() {
err.help(
"more complex types are supported with `#![feature(adt_const_params)]`",
);
}
err.emit();
}
err.emit();
}
};

if traits::search_for_structural_match_violation(param.span, tcx, ty).is_some() {
// We use the same error code in both branches, because this is really the same
// issue: we just special-case the message for type parameters to make it
// clearer.
if let ty::Param(_) = ty.peel_refs().kind() {
// Const parameters may not have type parameters as their types,
// because we cannot be sure that the type parameter derives `PartialEq`
// and `Eq` (just implementing them is not enough for `structural_match`).
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"`{}` is not guaranteed to `#[derive(PartialEq, Eq)]`, so may not be \
used as the type of a const parameter",
ty,
)
.span_label(
hir_ty.span,
format!("`{}` may not derive both `PartialEq` and `Eq`", ty),
)
.note(
"it is not currently possible to use a type parameter as the type of a \
const parameter",
)
.emit();
} else {
struct_span_err!(
tcx.sess,
hir_ty.span,
E0741,
"`{}` must be annotated with `#[derive(PartialEq, Eq)]` to be used as \
the type of a const parameter",
ty,
)
.span_label(
hir_ty.span,
format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
)
.emit();
}
}
}
Expand Down
9 changes: 1 addition & 8 deletions src/test/ui/const-generics/issues/issue-63322-forbid-dyn.min.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -7,12 +7,5 @@ LL | fn test<const T: &'static dyn A>() {
= note: the only supported types are integers, `bool` and `char`
= help: more complex types are supported with `#![feature(adt_const_params)]`

error[E0741]: `&'static (dyn A + 'static)` must be annotated with `#[derive(PartialEq, Eq)]` to be used as the type of a const parameter
--> $DIR/issue-63322-forbid-dyn.rs:9:18
|
LL | fn test<const T: &'static dyn A>() {
| ^^^^^^^^^^^^^^ `&'static (dyn A + 'static)` doesn't derive both `PartialEq` and `Eq`

error: aborting due to 2 previous errors
error: aborting due to previous error

For more information about this error, try `rustc --explain E0741`.
2 changes: 1 addition & 1 deletion src/test/ui/const-generics/issues/issue-63322-forbid-dyn.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ struct B;
impl A for B {}

fn test<const T: &'static dyn A>() {
//~^ ERROR must be annotated with `#[derive(PartialEq, Eq)]` to be used
//[full]~^ ERROR must be annotated with `#[derive(PartialEq, Eq)]` to be used
//[min]~^^ ERROR `&'static (dyn A + 'static)` is forbidden
unimplemented!()
}
Expand Down
11 changes: 1 addition & 10 deletions src/test/ui/const-generics/nested-type.min.stderr
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Expand Up @@ -14,14 +14,5 @@ LL | | }]>;
= note: the only supported types are integers, `bool` and `char`
= help: more complex types are supported with `#![feature(adt_const_params)]`

error[E0015]: cannot call non-const fn `Foo::{constant#0}::Foo::<17_usize>::value` in constants
--> $DIR/nested-type.rs:15:5
|
LL | Foo::<17>::value()
| ^^^^^^^^^^^^^^^^^^
|
= note: calls in constants are limited to constant functions, tuple structs and tuple variants

error: aborting due to 2 previous errors
error: aborting due to previous error

For more information about this error, try `rustc --explain E0015`.
2 changes: 1 addition & 1 deletion src/test/ui/const-generics/nested-type.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ struct Foo<const N: [u8; { //[min]~ ERROR `[u8; _]` is forbidden
}

Foo::<17>::value()
//~^ ERROR cannot call non-const fn
//[full]~^ ERROR cannot call non-const fn
}]>;

fn main() {}