Rollup merge of rust-lang#115373 - lqd:come-on-bors, r=compiler-errors

Fix bors missing a commit when merging rust-lang#115355

bors incorrectly merged an outdated version of PR rust-lang#115355 (via rollup rust-lang#115370):
- it [recorded r+](rust-lang#115355 (comment)) as approving commit rust-lang@325b585, and thus merged the original revision rust-lang@7762ac7
- but the branch at the time was at commit rust-lang@eefa07d, so bors missed the `compiler/rustc_trait_selection/src/solve/search_graph/mod.rs` cleanup in commit rust-lang@0e1e964 😓

Thankfully the change that bors missed was small, and this new PR corrects the situation (as I'd rather avoid having confusing multiple merge commits of PR rust-lang#115355 in the git history)

r? ``@compiler-errors``

compiler/rustc_trait_selection/src/solve/search_graph/mod.rs

@@ -51,13 +51,9 @@ pub(super) struct SearchGraph<'tcx> {
 
 impl<'tcx> SearchGraph<'tcx> {
     pub(super) fn new(tcx: TyCtxt<'tcx>, mode: SolverMode) -> SearchGraph<'tcx> {
-        let local_overflow_limit = {
-            let recursion_limit = tcx.recursion_limit().0;
-            if recursion_limit == 0 { 0 } else { recursion_limit.ilog2() as usize }
-        };
         Self {
             mode,
-            local_overflow_limit,
+            local_overflow_limit: tcx.recursion_limit().0.checked_ilog2().unwrap_or(0) as usize,
             stack: Default::default(),
             provisional_cache: ProvisionalCache::empty(),
         }