Rollup merge of #148131 - tmiasko:deduce-spread-arg, r=wesleywiser

Skip parameter attribute deduction for MIR with `spread_arg`

When a MIR argument is spread at ABI level, deduced attributes are potentially misapplied, since a spread argument can correspond to zero or more arguments at ABI level.

Disable deduction for MIR using spread argument for the time being.

compiler/rustc_mir_transform/src/deduce_param_attrs.rs

@@ -195,6 +195,11 @@ pub(super) fn deduced_param_attrs<'tcx>(
 
     // Grab the optimized MIR. Analyze it to determine which arguments have been mutated.
     let body: &Body<'tcx> = tcx.optimized_mir(def_id);
+    // Arguments spread at ABI level are currently unsupported.
+    if body.spread_arg.is_some() {
+        return &[];
+    }
+
     let mut deduce = DeduceParamAttrs::new(body);
     deduce.visit_body(body);
     tracing::trace!(?deduce.usage);