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Added help message for impl_trait_in_bindings feature gate #54623

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Merged
merged 1 commit into from
Oct 1, 2018
+88 −56
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Added help message for impl_trait_in_bindings feature gate #54623

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138 changes: 82 additions & 56 deletions src/librustc/hir/lowering.rs
View file
Original file line number Diff line number Diff line change
@@ -54,6 +54,7 @@ use rustc_data_structures::fx::FxHashSet;
use rustc_data_structures::indexed_vec::IndexVec;
use rustc_data_structures::thin_vec::ThinVec;
use session::Session;
use session::config::nightly_options;
use util::common::FN_OUTPUT_NAME;
use util::nodemap::{DefIdMap, NodeMap};

@@ -188,16 +189,28 @@ enum ImplTraitContext<'a> {
Existential(Option<DefId>),

/// `impl Trait` is not accepted in this position.
Disallowed,
Disallowed(ImplTraitPosition),
}

/// Position in which `impl Trait` is disallowed. Used for error reporting.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum ImplTraitPosition {
Binding,
Other,
}

impl<'a> ImplTraitContext<'a> {
#[inline]
fn disallowed() -> Self {
ImplTraitContext::Disallowed(ImplTraitPosition::Other)
}

fn reborrow(&'b mut self) -> ImplTraitContext<'b> {
use self::ImplTraitContext::*;
match self {
Universal(params) => Universal(params),
Existential(did) => Existential(*did),
Disallowed => Disallowed,
Disallowed(pos) => Disallowed(*pos),
}
}
}
@@ -1142,7 +1155,7 @@ impl<'a> LoweringContext<'a> {
generic_params: this.lower_generic_params(
&f.generic_params,
&NodeMap(),
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
),
unsafety: this.lower_unsafety(f.unsafety),
abi: f.abi,
@@ -1255,20 +1268,27 @@ impl<'a> LoweringContext<'a> {
}),
))
}
ImplTraitContext::Disallowed => {
ImplTraitContext::Disallowed(pos) => {
let allowed_in = if self.sess.features_untracked()
.impl_trait_in_bindings {
"bindings or function and inherent method return types"
} else {
"function and inherent method return types"
};
span_err!(
let mut err = struct_span_err!(
self.sess,
t.span,
E0562,
"`impl Trait` not allowed outside of {}",
allowed_in,
);
if pos == ImplTraitPosition::Binding &&
nightly_options::is_nightly_build() {
help!(err,
"add #![feature(impl_trait_in_bindings)] to the crate attributes \
to enable");
}
err.emit();
hir::TyKind::Err
}
}
@@ -1742,7 +1762,7 @@ impl<'a> LoweringContext<'a> {
param_mode,
0,
ParenthesizedGenericArgs::Err,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
)
})
.chain(ident.map(|ident| hir::PathSegment::from_ident(ident)))
@@ -1872,9 +1892,11 @@ impl<'a> LoweringContext<'a> {
self.with_anonymous_lifetime_mode(
AnonymousLifetimeMode::PassThrough,
|this| {
const DISALLOWED: ImplTraitContext<'_> = ImplTraitContext::Disallowed;
let &ParenthesisedArgs { ref inputs, ref output, span } = data;
let inputs = inputs.iter().map(|ty| this.lower_ty_direct(ty, DISALLOWED)).collect();
let inputs = inputs
.iter()
.map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed()))
.collect();
let mk_tup = |this: &mut Self, tys, span| {
let LoweredNodeId { node_id, hir_id } = this.next_id();
hir::Ty { node: hir::TyKind::Tup(tys), id: node_id, hir_id, span }
@@ -1889,7 +1911,7 @@ impl<'a> LoweringContext<'a> {
ident: Ident::from_str(FN_OUTPUT_NAME),
ty: output
.as_ref()
.map(|ty| this.lower_ty(&ty, DISALLOWED))
.map(|ty| this.lower_ty(&ty, ImplTraitContext::disallowed()))
.unwrap_or_else(|| P(mk_tup(this, hir::HirVec::new(), span))),
span: output.as_ref().map_or(span, |ty| ty.span),
}
@@ -1921,7 +1943,7 @@ impl<'a> LoweringContext<'a> {
if self.sess.features_untracked().impl_trait_in_bindings {
ImplTraitContext::Existential(Some(parent_def_id))
} else {
ImplTraitContext::Disallowed
ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
}
)),
pat: self.lower_pat(&l.pat),
@@ -1983,7 +2005,7 @@ impl<'a> LoweringContext<'a> {
if let Some((_, ref mut ibty)) = in_band_ty_params {
self.lower_ty_direct(&arg.ty, ImplTraitContext::Universal(ibty))
} else {
self.lower_ty_direct(&arg.ty, ImplTraitContext::Disallowed)
self.lower_ty_direct(&arg.ty, ImplTraitContext::disallowed())
}
})
.collect::<HirVec<_>>();
@@ -1999,9 +2021,12 @@ impl<'a> LoweringContext<'a> {
match decl.output {
FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
Some((def_id, _)) if impl_trait_return_allow => {
hir::Return(self.lower_ty(ty, ImplTraitContext::Existential(Some(def_id))))
hir::Return(self.lower_ty(ty,
ImplTraitContext::Existential(Some(def_id))))
}
_ => {
hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed()))
}
_ => hir::Return(self.lower_ty(ty, ImplTraitContext::Disallowed)),
},
FunctionRetTy::Default(span) => hir::DefaultReturn(span),
}
@@ -2369,7 +2394,7 @@ impl<'a> LoweringContext<'a> {
span: ident.span,
kind: hir::GenericParamKind::Type {
default: default.as_ref().map(|x| {
self.lower_ty(x, ImplTraitContext::Disallowed)
self.lower_ty(x, ImplTraitContext::disallowed())
}),
synthetic: param.attrs.iter()
.filter(|attr| attr.check_name("rustc_synthetic"))
@@ -2472,9 +2497,9 @@ impl<'a> LoweringContext<'a> {
bound_generic_params: this.lower_generic_params(
bound_generic_params,
&NodeMap(),
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::Disallowed),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
bounds: bounds
.iter()
.filter_map(|bound| match *bound {
@@ -2483,7 +2508,7 @@ impl<'a> LoweringContext<'a> {
GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
_ => Some(this.lower_param_bound(
bound,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
)),
})
.collect(),
@@ -2499,7 +2524,7 @@ impl<'a> LoweringContext<'a> {
}) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
span,
lifetime: self.lower_lifetime(lifetime),
bounds: self.lower_param_bounds(bounds, ImplTraitContext::Disallowed),
bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
}),
WherePredicate::EqPredicate(WhereEqPredicate {
id,
@@ -2508,8 +2533,8 @@ impl<'a> LoweringContext<'a> {
span,
}) => hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
id: self.lower_node_id(id).node_id,
lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::Disallowed),
rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::Disallowed),
lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
span,
}),
}
@@ -2579,7 +2604,7 @@ impl<'a> LoweringContext<'a> {
None => Ident::new(Symbol::intern(&index.to_string()), f.span),
},
vis: self.lower_visibility(&f.vis, None),
ty: self.lower_ty(&f.ty, ImplTraitContext::Disallowed),
ty: self.lower_ty(&f.ty, ImplTraitContext::disallowed()),
attrs: self.lower_attrs(&f.attrs),
}
}
@@ -2686,7 +2711,7 @@ impl<'a> LoweringContext<'a> {
if self.sess.features_untracked().impl_trait_in_bindings {
ImplTraitContext::Existential(None)
} else {
ImplTraitContext::Disallowed
ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
}
),
self.lower_mutability(m),
@@ -2701,7 +2726,7 @@ impl<'a> LoweringContext<'a> {
if self.sess.features_untracked().impl_trait_in_bindings {
ImplTraitContext::Existential(None)
} else {
ImplTraitContext::Disallowed
ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
}
),
value
@@ -2740,12 +2765,12 @@ impl<'a> LoweringContext<'a> {
ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
ItemKind::Ty(ref t, ref generics) => hir::ItemKind::Ty(
self.lower_ty(t, ImplTraitContext::Disallowed),
self.lower_generics(generics, ImplTraitContext::Disallowed),
self.lower_ty(t, ImplTraitContext::disallowed()),
self.lower_generics(generics, ImplTraitContext::disallowed()),
),
ItemKind::Existential(ref b, ref generics) => hir::ItemKind::Existential(hir::ExistTy {
generics: self.lower_generics(generics, ImplTraitContext::Disallowed),
bounds: self.lower_param_bounds(b, ImplTraitContext::Disallowed),
generics: self.lower_generics(generics, ImplTraitContext::disallowed()),
bounds: self.lower_param_bounds(b, ImplTraitContext::disallowed()),
impl_trait_fn: None,
}),
ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
@@ -2756,20 +2781,20 @@ impl<'a> LoweringContext<'a> {
.map(|x| self.lower_variant(x))
.collect(),
},
self.lower_generics(generics, ImplTraitContext::Disallowed),
self.lower_generics(generics, ImplTraitContext::disallowed()),
),
ItemKind::Struct(ref struct_def, ref generics) => {
let struct_def = self.lower_variant_data(struct_def);
hir::ItemKind::Struct(
struct_def,
self.lower_generics(generics, ImplTraitContext::Disallowed),
self.lower_generics(generics, ImplTraitContext::disallowed()),
)
}
ItemKind::Union(ref vdata, ref generics) => {
let vdata = self.lower_variant_data(vdata);
hir::ItemKind::Union(
vdata,
self.lower_generics(generics, ImplTraitContext::Disallowed),
self.lower_generics(generics, ImplTraitContext::disallowed()),
)
}
ItemKind::Impl(
@@ -2802,7 +2827,7 @@ impl<'a> LoweringContext<'a> {
AnonymousLifetimeMode::CreateParameter,
|this, _| {
let trait_ref = trait_ref.as_ref().map(|trait_ref| {
this.lower_trait_ref(trait_ref, ImplTraitContext::Disallowed)
this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
});

if let Some(ref trait_ref) = trait_ref {
@@ -2811,7 +2836,7 @@ impl<'a> LoweringContext<'a> {
}
}

let lowered_ty = this.lower_ty(ty, ImplTraitContext::Disallowed);
let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());

(trait_ref, lowered_ty)
},
@@ -2838,22 +2863,22 @@ impl<'a> LoweringContext<'a> {
)
}
ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
let bounds = self.lower_param_bounds(bounds, ImplTraitContext::Disallowed);
let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
let items = items
.iter()
.map(|item| self.lower_trait_item_ref(item))
.collect();
hir::ItemKind::Trait(
self.lower_is_auto(is_auto),
self.lower_unsafety(unsafety),
self.lower_generics(generics, ImplTraitContext::Disallowed),
self.lower_generics(generics, ImplTraitContext::disallowed()),
bounds,
items,
)
}
ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
self.lower_generics(generics, ImplTraitContext::Disallowed),
self.lower_param_bounds(bounds, ImplTraitContext::Disallowed),
self.lower_generics(generics, ImplTraitContext::disallowed()),
self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
),
ItemKind::MacroDef(..) | ItemKind::Mac(..) => panic!("Shouldn't still be around"),
}
@@ -3043,9 +3068,9 @@ impl<'a> LoweringContext<'a> {

let (generics, node) = match i.node {
TraitItemKind::Const(ref ty, ref default) => (
self.lower_generics(&i.generics, ImplTraitContext::Disallowed),
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::TraitItemKind::Const(
self.lower_ty(ty, ImplTraitContext::Disallowed),
self.lower_ty(ty, ImplTraitContext::disallowed()),
default
.as_ref()
.map(|x| self.lower_body(None, |this| this.lower_expr(x))),
@@ -3077,12 +3102,12 @@ impl<'a> LoweringContext<'a> {
(generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
}
TraitItemKind::Type(ref bounds, ref default) => (
self.lower_generics(&i.generics, ImplTraitContext::Disallowed),
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::TraitItemKind::Type(
self.lower_param_bounds(bounds, ImplTraitContext::Disallowed),
self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
default
.as_ref()
.map(|x| self.lower_ty(x, ImplTraitContext::Disallowed)),
.map(|x| self.lower_ty(x, ImplTraitContext::disallowed())),
),
),
TraitItemKind::Macro(..) => panic!("Shouldn't exist any more"),
@@ -3132,9 +3157,9 @@ impl<'a> LoweringContext<'a> {
ImplItemKind::Const(ref ty, ref expr) => {
let body_id = self.lower_body(None, |this| this.lower_expr(expr));
(
self.lower_generics(&i.generics, ImplTraitContext::Disallowed),
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::ImplItemKind::Const(
self.lower_ty(ty, ImplTraitContext::Disallowed),
self.lower_ty(ty, ImplTraitContext::disallowed()),
body_id,
),
)
@@ -3152,13 +3177,13 @@ impl<'a> LoweringContext<'a> {
(generics, hir::ImplItemKind::Method(sig, body_id))
}
ImplItemKind::Type(ref ty) => (
self.lower_generics(&i.generics, ImplTraitContext::Disallowed),
hir::ImplItemKind::Type(self.lower_ty(ty, ImplTraitContext::Disallowed)),
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::ImplItemKind::Type(self.lower_ty(ty, ImplTraitContext::disallowed())),
),
ImplItemKind::Existential(ref bounds) => (
self.lower_generics(&i.generics, ImplTraitContext::Disallowed),
self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
hir::ImplItemKind::Existential(
self.lower_param_bounds(bounds, ImplTraitContext::Disallowed),
self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
),
),
ImplItemKind::Macro(..) => panic!("Shouldn't exist any more"),
@@ -3349,7 +3374,8 @@ impl<'a> LoweringContext<'a> {
hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
}
ForeignItemKind::Static(ref t, m) => {
hir::ForeignItemKind::Static(self.lower_ty(t, ImplTraitContext::Disallowed), m)
hir::ForeignItemKind::Static(
self.lower_ty(t, ImplTraitContext::disallowed()), m)
}
ForeignItemKind::Ty => hir::ForeignItemKind::Type,
ForeignItemKind::Macro(_) => panic!("shouldn't exist here"),
@@ -3488,7 +3514,7 @@ impl<'a> LoweringContext<'a> {
&None,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
);
self.check_self_struct_ctor_feature(&qpath);
hir::PatKind::TupleStruct(
@@ -3503,7 +3529,7 @@ impl<'a> LoweringContext<'a> {
qself,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
);
self.check_self_struct_ctor_feature(&qpath);
hir::PatKind::Path(qpath)
@@ -3514,7 +3540,7 @@ impl<'a> LoweringContext<'a> {
&None,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
);

let fs = fields
@@ -3608,7 +3634,7 @@ impl<'a> LoweringContext<'a> {
ParamMode::Optional,
0,
ParenthesizedGenericArgs::Err,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
);
let args = args.iter().map(|x| self.lower_expr(x)).collect();
hir::ExprKind::MethodCall(hir_seg, seg.ident.span, args)
@@ -3627,11 +3653,11 @@ impl<'a> LoweringContext<'a> {
ExprKind::Lit(ref l) => hir::ExprKind::Lit(P((**l).clone())),
ExprKind::Cast(ref expr, ref ty) => {
let expr = P(self.lower_expr(expr));
hir::ExprKind::Cast(expr, self.lower_ty(ty, ImplTraitContext::Disallowed))
hir::ExprKind::Cast(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
}
ExprKind::Type(ref expr, ref ty) => {
let expr = P(self.lower_expr(expr));
hir::ExprKind::Type(expr, self.lower_ty(ty, ImplTraitContext::Disallowed))
hir::ExprKind::Type(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
}
ExprKind::AddrOf(m, ref ohs) => {
let m = self.lower_mutability(m);
@@ -3900,7 +3926,7 @@ impl<'a> LoweringContext<'a> {
qself,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
);
self.check_self_struct_ctor_feature(&qpath);
hir::ExprKind::Path(qpath)
@@ -3965,7 +3991,7 @@ impl<'a> LoweringContext<'a> {
&None,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed,
ImplTraitContext::disallowed(),
),
fields.iter().map(|x| self.lower_field(x)).collect(),
maybe_expr.as_ref().map(|x| P(self.lower_expr(x))),
4 changes: 4 additions & 0 deletions src/test/ui/feature-gates/feature-gate-impl_trait_in_bindings.stderr
View file
Original file line number Diff line number Diff line change
@@ -9,12 +9,16 @@ error[E0562]: `impl Trait` not allowed outside of function and inherent method r
|
LL | const FOO: impl Copy = 42;
| ^^^^^^^^^
|
= help: add #![feature(impl_trait_in_bindings)] to the crate attributes to enable

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/feature-gate-impl_trait_in_bindings.rs:13:13
|
LL | static BAR: impl Copy = 42;
| ^^^^^^^^^
|
= help: add #![feature(impl_trait_in_bindings)] to the crate attributes to enable

error: aborting due to 3 previous errors

2 changes: 2 additions & 0 deletions src/test/ui/impl-trait/where-allowed.stderr
View file
Original file line number Diff line number Diff line change
@@ -231,6 +231,8 @@ error[E0562]: `impl Trait` not allowed outside of function and inherent method r
|
LL | let _in_local_variable: impl Fn() = || {};
| ^^^^^^^^^
|
= help: add #![feature(impl_trait_in_bindings)] to the crate attributes to enable

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:232:46