use rustc_span::symbol::{kw, sym};
use rustc_span::Span;
use std::mem;
+use std::ops::DerefMut;
const MORE_EXTERN: &str =
"for more information, visit https://doc.rust-lang.org/std/keyword.extern.html";
for predicate in &generics.where_clause.predicates {
if let WherePredicate::EqPredicate(ref predicate) = *predicate {
- self.err_handler()
- .struct_span_err(
- predicate.span,
- "equality constraints are not yet supported in `where` clauses",
- )
- .span_label(predicate.span, "not supported")
- .note(
- "see issue #20041 <https://github.com/rust-lang/rust/issues/20041> \
- for more information",
- )
- .emit();
+ deny_equality_constraints(self, predicate, generics);
}
}
}
}
+fn deny_equality_constraints(
+ this: &mut AstValidator<'_>,
+ predicate: &WhereEqPredicate,
+ generics: &Generics,
+) {
+ let mut err = this.err_handler().struct_span_err(
+ predicate.span,
+ "equality constraints are not yet supported in `where` clauses",
+ );
+ err.span_label(predicate.span, "not supported");
+
+ // Given `<A as Foo>::Bar = RhsTy`, suggest `A: Foo<Bar = RhsTy>`.
+ if let TyKind::Path(Some(qself), full_path) = &predicate.lhs_ty.kind {
+ if let TyKind::Path(None, path) = &qself.ty.kind {
+ match &path.segments[..] {
+ [PathSegment { ident, args: None, .. }] => {
+ for param in &generics.params {
+ if param.ident == *ident {
+ let param = ident;
+ match &full_path.segments[qself.position..] {
+ [PathSegment { ident, .. }] => {
+ // Make a new `Path` from `foo::Bar` to `Foo<Bar = RhsTy>`.
+ let mut assoc_path = full_path.clone();
+ // Remove `Bar` from `Foo::Bar`.
+ assoc_path.segments.pop();
+ let len = assoc_path.segments.len() - 1;
+ // Build `<Bar = RhsTy>`.
+ let arg = AngleBracketedArg::Constraint(AssocTyConstraint {
+ id: rustc_ast::node_id::DUMMY_NODE_ID,
+ ident: *ident,
+ kind: AssocTyConstraintKind::Equality {
+ ty: predicate.rhs_ty.clone(),
+ },
+ span: ident.span,
+ });
+ // Add `<Bar = RhsTy>` to `Foo`.
+ match &mut assoc_path.segments[len].args {
+ Some(args) => match args.deref_mut() {
+ GenericArgs::Parenthesized(_) => continue,
+ GenericArgs::AngleBracketed(args) => {
+ args.args.push(arg);
+ }
+ },
+ empty_args => {
+ *empty_args = AngleBracketedArgs {
+ span: ident.span,
+ args: vec![arg],
+ }
+ .into();
+ }
+ }
+ err.span_suggestion_verbose(
+ predicate.span,
+ &format!(
+ "if `{}` is an associated type you're trying to set, \
+ use the associated type binding syntax",
+ ident
+ ),
+ format!(
+ "{}: {}",
+ param,
+ pprust::path_to_string(&assoc_path)
+ ),
+ Applicability::MaybeIncorrect,
+ );
+ }
+ _ => {}
+ };
+ }
+ }
+ }
+ _ => {}
+ }
+ }
+ }
+ err.note(
+ "see issue #20041 <https://github.com/rust-lang/rust/issues/20041> for more information",
+ );
+ err.emit();
+}
+
pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) -> bool {
let mut validator = AstValidator {
session,
+error: equality constraints are not yet supported in `where` clauses
+ --> $DIR/missing-bounds.rs:37:33
+ |
+LL | impl<B: Add> Add for E<B> where <B as Add>::Output = B {
+ | ^^^^^^^^^^^^^^^^^^^^^^ not supported
+ |
+ = note: see issue #20041 <https://github.com/rust-lang/rust/issues/20041> for more information
+help: if `Output` is an associated type you're trying to set, use the associated type binding syntax
+ |
+LL | impl<B: Add> Add for E<B> where B: Add<Output = B> {
+ | ^^^^^^^^^^^^^^^^^^
+
error[E0308]: mismatched types
--> $DIR/missing-bounds.rs:11:11
|
LL | impl<B: std::ops::Add<Output = B>> Add for D<B> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-error: aborting due to 3 previous errors
+error[E0308]: mismatched types
+ --> $DIR/missing-bounds.rs:42:14
+ |
+LL | impl<B: Add> Add for E<B> where <B as Add>::Output = B {
+ | - this type parameter
+...
+LL | Self(self.0 + rhs.0)
+ | ^^^^^^^^^^^^^^ expected type parameter `B`, found associated type
+ |
+ = note: expected type parameter `B`
+ found associated type `<B as std::ops::Add>::Output`
+help: consider further restricting type parameter `B`
+ |
+LL | impl<B: Add> Add for E<B> where <B as Add>::Output = B, B: std::ops::Add<Output = B> {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
Some errors have detailed explanations: E0308, E0369.
For more information about an error, try `rustc --explain E0308`.