Auto merge of #113802 - cjgillot:check-debuginfo, r=compiler-errors

Substitute types before checking inlining compatibility.

Addresses #112332 and #113781

I don't have a minimal test, but I this seems to remove the ICE locally.

This whole pre-inlining validation mirrors the "real" MIR validation pass to verify that inlined MIR will still pass validation.
The debuginfo loop is added because MIR validation check projections in debuginfo.
Likewise, MIR validation only checks `is_subtype`, so there is no reason for a stronger check.

The types were not being substituted in `check_equal`, so we were not bailing out of inlining if the substituted MIR callee body would not pass validation.

compiler/rustc_mir_transform/src/inline.rs

@@ -440,6 +440,10 @@ impl<'tcx> Inliner<'tcx> {
             validation: Ok(()),
         };
 
+        for var_debug_info in callee_body.var_debug_info.iter() {
+            checker.visit_var_debug_info(var_debug_info);
+        }
+
         // Traverse the MIR manually so we can account for the effects of inlining on the CFG.
         let mut work_list = vec![START_BLOCK];
         let mut visited = BitSet::new_empty(callee_body.basic_blocks.len());
@@ -847,7 +851,16 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
         if let ProjectionElem::Field(f, ty) = elem {
             let parent_ty = place_ref.ty(&self.callee_body.local_decls, self.tcx);
             let check_equal = |this: &mut Self, f_ty| {
-                if !util::is_equal_up_to_subtyping(this.tcx, this.param_env, ty, f_ty) {
+                // Fast path if there is nothing to substitute.
+                if ty == f_ty {
+                    return;
+                }
+                let ty = this.instance.subst_mir(this.tcx, ty::EarlyBinder::bind(&ty));
+                let f_ty = this.instance.subst_mir(this.tcx, ty::EarlyBinder::bind(&f_ty));
+                if ty == f_ty {
+                    return;
+                }
+                if !util::is_subtype(this.tcx, this.param_env, ty, f_ty) {
                     trace!(?ty, ?f_ty);
                     this.validation = Err("failed to normalize projection type");
                     return;