(ty::Param(p), ty::Alias(ty::Projection, proj)) | (ty::Alias(ty::Projection, proj), ty::Param(p))
if tcx.def_kind(proj.def_id) != DefKind::ImplTraitPlaceholder =>
{
- let generics = tcx.generics_of(body_owner_def_id);
- let p_span = tcx.def_span(generics.type_param(p, tcx).def_id);
+ let p_def_id = tcx
+ .generics_of(body_owner_def_id)
+ .type_param(p, tcx)
+ .def_id;
+ let p_span = tcx.def_span(p_def_id);
if !sp.contains(p_span) {
diag.span_label(p_span, "this type parameter");
}
let hir = tcx.hir();
let mut note = true;
- if let Some(generics) = generics
- .type_param(p, tcx)
- .def_id
+ let parent = p_def_id
.as_local()
- .map(|id| hir.local_def_id_to_hir_id(id))
- .and_then(|id| tcx.hir().find_parent(id))
- .as_ref()
- .and_then(|node| node.generics())
+ .and_then(|id| {
+ let local_id = hir.local_def_id_to_hir_id(id);
+ let generics = tcx.hir().find_parent(local_id)?.generics()?;
+ Some((id, generics))
+ });
+ if let Some((local_id, generics)) = parent
{
// Synthesize the associated type restriction `Add<Output = Expected>`.
// FIXME: extract this logic for use in other diagnostics.
let (trait_ref, assoc_substs) = proj.trait_ref_and_own_substs(tcx);
- let path =
- tcx.def_path_str_with_substs(trait_ref.def_id, trait_ref.substs);
let item_name = tcx.item_name(proj.def_id);
let item_args = self.format_generic_args(assoc_substs);
- let path = if path.ends_with('>') {
- format!(
- "{}, {}{} = {}>",
- &path[..path.len() - 1],
- item_name,
- item_args,
- p
- )
+ // Here, we try to see if there's an existing
+ // trait implementation that matches the one that
+ // we're suggesting to restrict. If so, find the
+ // "end", whether it be at the end of the trait
+ // or the end of the generic arguments.
+ let mut matching_span = None;
+ let mut matched_end_of_args = false;
+ for bound in generics.bounds_for_param(local_id) {
+ let potential_spans = bound
+ .bounds
+ .iter()
+ .find_map(|bound| {
+ let bound_trait_path = bound.trait_ref()?.path;
+ let def_id = bound_trait_path.res.opt_def_id()?;
+ let generic_args = bound_trait_path.segments.iter().last().map(|path| path.args());
+ (def_id == trait_ref.def_id).then_some((bound_trait_path.span, generic_args))
+ });
+
+ if let Some((end_of_trait, end_of_args)) = potential_spans {
+ let args_span = end_of_args.and_then(|args| args.span());
+ matched_end_of_args = args_span.is_some();
+ matching_span = args_span
+ .or_else(|| Some(end_of_trait))
+ .map(|span| span.shrink_to_hi());
+ break;
+ }
+ }
+
+ if matched_end_of_args {
+ // Append suggestion to the end of our args
+ let path = format!(", {}{} = {}",item_name, item_args, p);
+ note = !suggest_constraining_type_param(
+ tcx,
+ generics,
+ diag,
+ &format!("{}", proj.self_ty()),
+ &path,
+ None,
+ matching_span,
+ );
} else {
- format!("{}<{}{} = {}>", path, item_name, item_args, p)
- };
- note = !suggest_constraining_type_param(
- tcx,
- generics,
- diag,
- &format!("{}", proj.self_ty()),
- &path,
- None,
- );
+ // Suggest adding a bound to an existing trait
+ // or if the trait doesn't exist, add the trait
+ // and the suggested bounds.
+ let path = format!("<{}{} = {}>", item_name, item_args, p);
+ note = !suggest_constraining_type_param(
+ tcx,
+ generics,
+ diag,
+ &format!("{}", proj.self_ty()),
+ &path,
+ None,
+ matching_span,
+ );
+ }
}
if note {
diag.note("you might be missing a type parameter or trait bound");
diag.help(
"given a type parameter `T` and a method `foo`:
```
-trait Trait<T> { fn foo(&tcx) -> T; }
+trait Trait<T> { fn foo(&self) -> T; }
```
the only ways to implement method `foo` are:
- constrain `T` with an explicit type:
```
impl Trait<String> for X {
- fn foo(&tcx) -> String { String::new() }
+ fn foo(&self) -> String { String::new() }
}
```
- add a trait bound to `T` and call a method on that trait that returns `Self`:
```
impl<T: std::default::Default> Trait<T> for X {
- fn foo(&tcx) -> T { <T as std::default::Default>::default() }
+ fn foo(&self) -> T { <T as std::default::Default>::default() }
}
```
- change `foo` to return an argument of type `T`:
```
impl<T> Trait<T> for X {
- fn foo(&tcx, x: T) -> T { x }
+ fn foo(&self, x: T) -> T { x }
}
```",
);
);
}
}
+ (ty::FnPtr(_), ty::FnDef(def, _))
+ if let hir::def::DefKind::Fn = tcx.def_kind(def) => {
+ diag.note(
+ "when the arguments and return types match, functions can be coerced \
+ to function pointers",
+ );
+ }
_ => {}
}
debug!(
```
trait Trait {
type T;
-fn foo(&tcx) -> Self::T;
+fn foo(&self) -> Self::T;
}
```
the only way of implementing method `foo` is to constrain `T` with an explicit associated type:
```
impl Trait for X {
type T = String;
-fn foo(&tcx) -> Self::T { String::new() }
+fn foo(&self) -> Self::T { String::new() }
}
```",
);
ty::AssocKind::Fn == item.kind && Some(item.name) != current_method_ident
})
.filter_map(|item| {
- let method = tcx.fn_sig(item.def_id);
+ let method = tcx.fn_sig(item.def_id).subst_identity();
match *method.output().skip_binder().kind() {
ty::Alias(ty::Projection, ty::AliasTy { def_id: item_def_id, .. })
if item_def_id == proj_ty_item_def_id =>
projects / rust.git / blobdiff