Explain that associated types and consts can't be accessed directly on the trait's path
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@ -2075,7 +2075,30 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
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}
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let mut err = self.need_type_info_err(body_id, span, self_ty, ErrorCode::E0283);
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err.note(&format!("cannot resolve `{}`", predicate));
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if let (Ok(ref snippet), ObligationCauseCode::BindingObligation(ref def_id, _)) =
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if let ObligationCauseCode::ItemObligation(def_id) = obligation.cause.code {
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if let Some(assoc_item) = self.tcx.opt_associated_item(def_id) {
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if let ty::AssocKind::Const | ty::AssocKind::Type = assoc_item.kind {
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err.note(&format!(
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"{}s cannot be accessed directly on a `trait`, they can only be \
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accessed through a specific `impl`",
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assoc_item.kind.suggestion_descr(),
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));
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err.span_suggestion(
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span,
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"use the fully qualified path to an implementation",
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format!(
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"<Type as {}>::{}",
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self.tcx.def_path_str(trait_ref.def_id()),
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assoc_item.ident
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),
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Applicability::HasPlaceholders,
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);
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}
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}
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} else if let (
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Ok(ref snippet),
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ObligationCauseCode::BindingObligation(ref def_id, _),
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) =
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(self.tcx.sess.source_map().span_to_snippet(span), &obligation.cause.code)
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{
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let generics = self.tcx.generics_of(*def_id);
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@ -5,9 +5,13 @@ LL | const C: usize;
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| --------------- required by `A::C`
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LL |
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LL | fn f() -> ([u8; A::C], [u8; A::C]);
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| ^^^^ cannot infer type
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| ^^^^
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| |
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| cannot infer type
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| help: use the fully qualified path to an implementation: `<Type as A>::C`
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= note: cannot resolve `_: A`
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= note: associated constants cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
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error[E0283]: type annotations needed
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--> $DIR/issue-63496.rs:4:33
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@ -16,9 +20,13 @@ LL | const C: usize;
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| --------------- required by `A::C`
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LL |
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LL | fn f() -> ([u8; A::C], [u8; A::C]);
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| ^^^^ cannot infer type
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| ^^^^
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| |
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| cannot infer type
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| help: use the fully qualified path to an implementation: `<Type as A>::C`
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= note: cannot resolve `_: A`
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= note: associated constants cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
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error: aborting due to 2 previous errors
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@ -13,9 +13,13 @@ error[E0283]: type annotations needed
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LL | const X: usize;
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| --------------- required by `Bar::X`
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LL | fn return_n(&self) -> [u8; Bar::X];
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| ^^^^^^ cannot infer type
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| ^^^^^^
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| |
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| cannot infer type
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| help: use the fully qualified path to an implementation: `<Type as Bar>::X`
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= note: cannot resolve `_: Bar`
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= note: associated constants cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
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error: aborting due to 2 previous errors
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@ -11,9 +11,13 @@ LL | const SIZE: usize;
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| ------------------ required by `Foo::SIZE`
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LL |
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LL | fn new(slice: &[u8; Foo::SIZE]) -> Self;
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| ^^^^^^^^^ cannot infer type
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| ^^^^^^^^^
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| |
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| cannot infer type
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| help: use the fully qualified path to an implementation: `<Type as Foo>::SIZE`
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= note: cannot resolve `_: Foo`
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= note: associated constants cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
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error: aborting due to 2 previous errors
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