Rollup merge of #135611 - chenyukang:yukang-fix-135341-ice-crash, r=oli-obk

Remove unnecessary assertion for reference error

Fixes #135341

From comment: https://github.com/rust-lang/rust/issues/135341#issuecomment-2594430504

r? ``@oli-obk``

tests/crashes/135341.rs

@@ -1,5 +0,0 @@
-//@ known-bug: #135341
-type A<T> = B;
-type B = _;
-
-pub fn main() {}

tests/ui/wf/ice-hir-wf-issue-135341.rs

@@ -0,0 +1,4 @@
+type A<T> = B;
+type B = _; //~ ERROR the placeholder `_` is not allowed within types on item signatures for type aliases
+
+fn main() {}

tests/ui/wf/ice-hir-wf-issue-135341.stderr

@@ -0,0 +1,9 @@
+error[E0121]: the placeholder `_` is not allowed within types on item signatures for type aliases
+  --> $DIR/ice-hir-wf-issue-135341.rs:2:10
+   |
+LL | type B = _;
+   |          ^ not allowed in type signatures
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0121`.