Check const_fn_pointer feature in mir context

Author: filtsin

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -218,18 +218,14 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             _ => bug!("{} cannot be cast to a fn ptr", operand.layout.ty),
                         }
                     }
-                    mir::CastKind::Pointer(PointerCast::UnsafeFnPointer) => {
-                        // This is a no-op at the LLVM level.
-                        operand.val
-                    }
-                    mir::CastKind::Pointer(PointerCast::NotConstFnPointer) => {
+                    mir::CastKind::Pointer(
+                        PointerCast::UnsafeFnPointer
+                        | PointerCast::NotConstFnPointer
+                        | PointerCast::UnsafeNotConstFnPointer,
+                    ) => {
                         // This is a no-op at the LLVM level.
                         operand.val
                     }
-                    mir::CastKind::Pointer(PointerCast::UnsafeNotConstFnPointer) => {
-                        // This is a no-op at the LLVM level
-                        operand.val
-                    }
                     mir::CastKind::Pointer(PointerCast::Unsize) => {
                         assert!(bx.cx().is_backend_scalar_pair(cast));
                         match operand.val {

compiler/rustc_middle/src/ty/layout.rs

@@ -2340,15 +2340,16 @@ impl<'tcx> ty::Instance<'tcx> {
 
                 let env_ty = tcx.closure_env_ty(def_id, substs).unwrap();
 
-                sig.map_bound(|sig|
-                  tcx.mk_fn_sig(
-                    iter::once(env_ty.skip_binder()).chain(sig.inputs().iter().cloned()),
-                    sig.output(),
-                    sig.c_variadic,
-                    sig.unsafety,
-                    sig.abi,
-                    hir::Constness::NotConst,
-                ))
+                sig.map_bound(|sig| {
+                    tcx.mk_fn_sig(
+                        iter::once(env_ty.skip_binder()).chain(sig.inputs().iter().cloned()),
+                        sig.output(),
+                        sig.c_variadic,
+                        sig.unsafety,
+                        sig.abi,
+                        hir::Constness::NotConst,
+                    )
+                })
             }
             ty::Generator(_, substs, _) => {
                 let sig = substs.as_generator().poly_sig();

compiler/rustc_mir/src/transform/check_consts/validation.rs

@@ -748,7 +748,8 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
                     ty::FnPtr(fn_sig) => {
                         // At this point, we are calling a function by raw pointer because
                         // we know that it is const
-                        if fn_sig.constness() == hir::Constness::Const {
+                        if self.ccx.tcx.features().const_fn_pointer &&
+                          fn_sig.constness() == hir::Constness::Const {
                             return;
                         }
                         self.check_op(ops::FnCallIndirect);