Auto merge of #91743 - cjgillot:enable_mir_inlining_inline_all, r=oli-obk

Enable MIR inlining

Continuation of https://github.com/rust-lang/rust/pull/82280 by `@wesleywiser.`

#82280 has shown nice compile time wins could be obtained by enabling MIR inlining.
Most of the issues in https://github.com/rust-lang/rust/issues/81567 are now fixed,
except the interaction with polymorphization which is worked around specifically.

I believe we can proceed with enabling MIR inlining in the near future
(preferably just after beta branching, in case we discover new issues).

Steps before merging:
- [x] figure out the interaction with polymorphization;
- [x] figure out how miri should deal with extern types;
- [x] silence the extra arithmetic overflow warnings;
- [x] remove the codegen fulfilment ICE;
- [x] remove the type normalization ICEs while compiling nalgebra;
- [ ] tweak the inlining threshold.

2 files changed, 6 insertions, 17 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index 2e6c7f47ac1..d09ab5fa3e8 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -100,7 +100,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                             def_id,
                             substs,
                             ty::ClosureKind::FnOnce,
-                        );
+                        )
+                        .ok_or_else(|| err_inval!(TooGeneric))?;
                         let fn_ptr = self.create_fn_alloc_ptr(FnVal::Instance(instance));
                         self.write_pointer(fn_ptr, dest)?;
                     }
diff --git a/compiler/rustc_const_eval/src/interpret/util.rs b/compiler/rustc_const_eval/src/interpret/util.rs
index b9866995e9f..9d7905ed9a8 100644
--- a/compiler/rustc_const_eval/src/interpret/util.rs
+++ b/compiler/rustc_const_eval/src/interpret/util.rs
@@ -44,22 +44,10 @@ where
                         let is_used = unused_params.contains(index).map_or(true, |unused| !unused);
                         // Only recurse when generic parameters in fns, closures and generators
                         // are used and require substitution.
-                        match (is_used, subst.needs_subst()) {
-                            // Just in case there are closures or generators within this subst,
-                            // recurse.
-                            (true, true) => return subst.visit_with(self),
-                            // Confirm that polymorphization replaced the parameter with
-                            // `ty::Param`/`ty::ConstKind::Param`.
-                            (false, true) if cfg!(debug_assertions) => match subst.unpack() {
-                                ty::subst::GenericArgKind::Type(ty) => {
-                                    assert!(matches!(ty.kind(), ty::Param(_)))
-                                }
-                                ty::subst::GenericArgKind::Const(ct) => {
-                                    assert!(matches!(ct.kind(), ty::ConstKind::Param(_)))
-                                }
-                                ty::subst::GenericArgKind::Lifetime(..) => (),
-                            },
-                            _ => {}
+                        // Just in case there are closures or generators within this subst,
+                        // recurse.
+                        if is_used && subst.needs_subst() {
+                            return subst.visit_with(self);
                         }
                     }
                     ControlFlow::CONTINUE