Auto merge of #147193 - BoxyUwU:shallow_resolve_to_root, r=<try>

Shallow resolve ty vars to their root var

Author: rust-bors[bot]

compiler/rustc_infer/src/infer/mod.rs

@@ -1125,7 +1125,9 @@ impl<'tcx> InferCtxt<'tcx> {
                     // Note: if these two lines are combined into one we get
                     // dynamic borrow errors on `self.inner`.
                     let known = self.inner.borrow_mut().type_variables().probe(v).known();
-                    known.map_or(ty, |t| self.shallow_resolve(t))
+                    known.map_or(Ty::new_var(self.tcx, self.root_var(v)), |t| {
+                        self.shallow_resolve(t)
+                    })
                 }
 
                 ty::IntVar(v) => {

tests/ui/coercion/issue-88097.rs

@@ -3,6 +3,9 @@
 // behavior has been fixed.
 
 //@ check-pass
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
 
 fn peculiar() -> impl Fn(u8) -> u8 {
     return |x| x + 1