resolve: Add some asserts for unexpected lifetime rib combinations

compiler/rustc_resolve/src/late.rs

@@ -1423,9 +1423,10 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                                     } else {
                                         LifetimeUseSet::Many
                                     }),
-                                    LifetimeRibKind::Generics { .. }
-                                    | LifetimeRibKind::ConstGeneric
-                                    | LifetimeRibKind::AnonConst => None,
+                                    LifetimeRibKind::Generics { .. } => None,
+                                    LifetimeRibKind::ConstGeneric | LifetimeRibKind::AnonConst => {
+                                        span_bug!(ident.span, "unexpected rib kind: {:?}", rib.kind)
+                                    }
                                 })
                                 .unwrap_or(LifetimeUseSet::Many);
                             debug!(?use_ctxt, ?use_set);
@@ -1460,7 +1461,11 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                     );
                     return;
                 }
-                _ => {}
+                LifetimeRibKind::AnonymousCreateParameter { .. }
+                | LifetimeRibKind::Elided(_)
+                | LifetimeRibKind::Generics { .. }
+                | LifetimeRibKind::ElisionFailure
+                | LifetimeRibKind::AnonymousReportError => {}
             }
         }
 
@@ -1534,9 +1539,11 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                     return;
                 }
                 LifetimeRibKind::Item => break,
-                LifetimeRibKind::Generics { .. }
-                | LifetimeRibKind::ConstGeneric
-                | LifetimeRibKind::AnonConst => {}
+                LifetimeRibKind::Generics { .. } | LifetimeRibKind::ConstGeneric => {}
+                LifetimeRibKind::AnonConst => {
+                    // There is always an `Elided(LifetimeRes::Static)` inside an `AnonConst`.
+                    span_bug!(lifetime.ident.span, "unexpected rib kind: {:?}", rib.kind)
+                }
             }
         }
         self.record_lifetime_res(lifetime.id, LifetimeRes::Error, elision_candidate);
@@ -1751,9 +1758,11 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                         self.report_missing_lifetime_specifiers(vec![missing_lifetime], None);
                         break;
                     }
-                    LifetimeRibKind::Generics { .. }
-                    | LifetimeRibKind::ConstGeneric
-                    | LifetimeRibKind::AnonConst => {}
+                    LifetimeRibKind::Generics { .. } | LifetimeRibKind::ConstGeneric => {}
+                    LifetimeRibKind::AnonConst => {
+                        // There is always an `Elided(LifetimeRes::Static)` inside an `AnonConst`.
+                        span_bug!(elided_lifetime_span, "unexpected rib kind: {:?}", rib.kind)
+                    }
                 }
             }
 
@@ -3938,7 +3947,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         fn_id: NodeId,
         async_node_id: Option<(NodeId, Span)>,
     ) {
-        if let Some((async_node_id, _)) = async_node_id {
+        if let Some((async_node_id, span)) = async_node_id {
             let mut extra_lifetime_params =
                 self.r.extra_lifetime_params_map.get(&fn_id).cloned().unwrap_or_default();
             for rib in self.lifetime_ribs.iter().rev() {
@@ -3952,7 +3961,12 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                             extra_lifetime_params.extend(earlier_fresh);
                         }
                     }
-                    _ => {}
+                    LifetimeRibKind::Generics { .. } => {}
+                    _ => {
+                        // We are in a function definition. We should only find `Generics`
+                        // and `AnonymousCreateParameter` inside the innermost `Item`.
+                        span_bug!(span, "unexpected rib kind: {:?}", rib.kind)
+                    }
                 }
             }
             self.r.extra_lifetime_params_map.insert(async_node_id, extra_lifetime_params);

src/test/ui/lifetimes/unusual-rib-combinations.rs

@@ -0,0 +1,28 @@
+#![feature(inline_const)]
+
+struct S<'a>(&'a u8);
+fn foo() {}
+
+// Paren generic args in AnonConst
+fn a() -> [u8; foo::()] {
+//~^ ERROR parenthesized type parameters may only be used with a `Fn` trait
+//~| ERROR mismatched types
+    panic!()
+}
+
+// Paren generic args in ConstGeneric
+fn b<const C: u8()>() {}
+//~^ ERROR parenthesized type parameters may only be used with a `Fn` trait
+
+// Paren generic args in AnonymousReportError
+fn c<T = u8()>() {}
+//~^ ERROR parenthesized type parameters may only be used with a `Fn` trait
+//~| ERROR defaults for type parameters are only allowed in
+//~| WARN this was previously accepted
+
+// Elided lifetime in path in ConstGeneric
+fn d<const C: S>() {}
+//~^ ERROR missing lifetime specifier
+//~| ERROR `S<'static>` is forbidden as the type of a const generic parameter
+
+fn main() {}

src/test/ui/lifetimes/unusual-rib-combinations.stderr

@@ -0,0 +1,61 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/unusual-rib-combinations.rs:24:15
+   |
+LL | fn d<const C: S>() {}
+   |               ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL | fn d<'a, const C: S<'a>>() {}
+   |      +++           ++++
+
+error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
+  --> $DIR/unusual-rib-combinations.rs:7:16
+   |
+LL | fn a() -> [u8; foo::()] {
+   |                ^^^^^^^ only `Fn` traits may use parentheses
+
+error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
+  --> $DIR/unusual-rib-combinations.rs:14:15
+   |
+LL | fn b<const C: u8()>() {}
+   |               ^^^^ only `Fn` traits may use parentheses
+
+error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
+  --> $DIR/unusual-rib-combinations.rs:18:10
+   |
+LL | fn c<T = u8()>() {}
+   |          ^^^^ only `Fn` traits may use parentheses
+
+error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/unusual-rib-combinations.rs:18:6
+   |
+LL | fn c<T = u8()>() {}
+   |      ^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
+   = note: `#[deny(invalid_type_param_default)]` on by default
+
+error[E0308]: mismatched types
+  --> $DIR/unusual-rib-combinations.rs:7:16
+   |
+LL | fn a() -> [u8; foo::()] {
+   |                ^^^^^^^ expected `usize`, found fn item
+   |
+   = note: expected type `usize`
+           found fn item `fn() {foo}`
+
+error: `S<'static>` is forbidden as the type of a const generic parameter
+  --> $DIR/unusual-rib-combinations.rs:24:15
+   |
+LL | fn d<const C: S>() {}
+   |               ^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+   = help: more complex types are supported with `#![feature(adt_const_params)]`
+
+error: aborting due to 7 previous errors
+
+Some errors have detailed explanations: E0106, E0214, E0308.
+For more information about an error, try `rustc --explain E0106`.