use TypingEnv when no infcx is available

the behavior of the type system not only depends on the current
assumptions, but also the currentnphase of the compiler. This is
mostly necessary as we need to decide whether and how to reveal
opaque types. We track this via the `TypingMode`.

compiler/rustc_codegen_cranelift/src/base.rs

@@ -666,7 +666,7 @@ fn codegen_stmt<'tcx>(
                             let func_ref = fx.get_function_ref(
                                 Instance::resolve_for_fn_ptr(
                                     fx.tcx,
-                                    ParamEnv::reveal_all(),
+                                    ty::TypingEnv::fully_monomorphized(),
                                     def_id,
                                     args,
                                 )
@@ -841,14 +841,18 @@ fn codegen_stmt<'tcx>(
                     lval.write_cvalue(fx, CValue::by_val(operand, box_layout));
                 }
                 Rvalue::NullaryOp(ref null_op, ty) => {
-                    assert!(lval.layout().ty.is_sized(fx.tcx, ParamEnv::reveal_all()));
+                    assert!(lval.layout().ty.is_sized(fx.tcx, ty::ParamEnv::reveal_all()));
                     let layout = fx.layout_of(fx.monomorphize(ty));
                     let val = match null_op {
                         NullOp::SizeOf => layout.size.bytes(),
                         NullOp::AlignOf => layout.align.abi.bytes(),
                         NullOp::OffsetOf(fields) => fx
                             .tcx
-                            .offset_of_subfield(ParamEnv::reveal_all(), layout, fields.iter())
+                            .offset_of_subfield(
+                                ty::TypingEnv::fully_monomorphized(),
+                                layout,
+                                fields.iter(),
+                            )
                             .bytes(),
                         NullOp::UbChecks => {
                             let val = fx.tcx.sess.ub_checks();