Revert "Rollup merge of #134371 - scottmcm:fix-134352, r=oli-obk"

This reverts commit 7c301ecdf5e806b7aa3c44e4a185049fabbc4381, reversing
changes made to dffaad83327454430129802f240121f8c7866208.

(cherry picked from commit 0bb4880581a6963e0b895f9550e9147c68b9537a)

3 files changed, 7 insertions, 48 deletions

diff --git a/compiler/rustc_mir_build/src/builder/expr/as_place.rs b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
index 01aec70f437..2c88a48424f 100644
--- a/compiler/rustc_mir_build/src/builder/expr/as_place.rs
+++ b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
@@ -647,31 +647,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
         match place_ty.kind() {
             ty::Array(_elem_ty, len_const) => {
-                let ty_const = if let Some((_, len_ty)) = len_const.try_to_valtree()
-                    && len_ty != self.tcx.types.usize
-                {
-                    // Bad const generics can give us a constant from the type that's
-                    // not actually a `usize`, so in that case give an error instead.
-                    // FIXME: It'd be nice if the type checker made sure this wasn't
-                    // possible, instead.
-                    let err = self.tcx.dcx().span_delayed_bug(
-                        span,
-                        format!(
-                            "Array length should have already been a type error, as it's {len_ty:?}"
-                        ),
-                    );
-                    ty::Const::new_error(self.tcx, err)
-                } else {
-                    // We know how long an array is, so just use that as a constant
-                    // directly -- no locals needed. We do need one statement so
-                    // that borrow- and initialization-checking consider it used,
-                    // though. FIXME: Do we really *need* to count this as a use?
-                    // Could partial array tracking work off something else instead?
-                    self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
-                    *len_const
-                };
-
-                let const_ = Const::from_ty_const(ty_const, usize_ty, self.tcx);
+                // We know how long an array is, so just use that as a constant
+                // directly -- no locals needed. We do need one statement so
+                // that borrow- and initialization-checking consider it used,
+                // though. FIXME: Do we really *need* to count this as a use?
+                // Could partial array tracking work off something else instead?
+                self.cfg.push_fake_read(block, source_info, FakeReadCause::ForIndex, place);
+                let const_ = Const::from_ty_const(*len_const, usize_ty, self.tcx);
                 Operand::Constant(Box::new(ConstOperand { span, user_ty: None, const_ }))
             }
             ty::Slice(_elem_ty) => {
diff --git a/tests/ui/const-generics/issues/index_array_bad_type.rs b/tests/ui/const-generics/issues/index_array_bad_type.rs
deleted file mode 100644
index 41e4dba026c..00000000000
--- a/tests/ui/const-generics/issues/index_array_bad_type.rs
+++ /dev/null
@@ -1,15 +0,0 @@
-//@ check-fail
-//@ compile-flags: -C opt-level=0
-
-#![crate_type = "lib"]
-
-// This used to fail in the known-panics lint, as the MIR was ill-typed due to
-// the length constant not actually having type usize.
-// https://github.com/rust-lang/rust/issues/134352
-
-pub struct BadStruct<const N: i64>(pub [u8; N]);
-//~^ ERROR: the constant `N` is not of type `usize`
-
-pub fn bad_array_length_type(value: BadStruct<3>) -> u8 {
-    value.0[0]
-}
diff --git a/tests/ui/const-generics/issues/index_array_bad_type.stderr b/tests/ui/const-generics/issues/index_array_bad_type.stderr
deleted file mode 100644
index e4417192150..00000000000
--- a/tests/ui/const-generics/issues/index_array_bad_type.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: the constant `N` is not of type `usize`
-  --> $DIR/index_array_bad_type.rs:10:40
-   |
-LL | pub struct BadStruct<const N: i64>(pub [u8; N]);
-   |                                        ^^^^^^^ expected `usize`, found `i64`
-
-error: aborting due to 1 previous error
-