1 files changed, 27 insertions, 51 deletions
diff --git a/compiler/rustc_mir_transform/src/lower_slice_len.rs b/compiler/rustc_mir_transform/src/lower_slice_len.rs
index b7cc0db95..ae4878411 100644
--- a/compiler/rustc_mir_transform/src/lower_slice_len.rs
+++ b/compiler/rustc_mir_transform/src/lower_slice_len.rs
@@ -34,67 +34,43 @@ pub fn lower_slice_len_calls<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     }
 }
 
-struct SliceLenPatchInformation<'tcx> {
-    add_statement: Statement<'tcx>,
-    new_terminator_kind: TerminatorKind<'tcx>,
-}
-
 fn lower_slice_len_call<'tcx>(
     tcx: TyCtxt<'tcx>,
     block: &mut BasicBlockData<'tcx>,
     local_decls: &IndexSlice<Local, LocalDecl<'tcx>>,
     slice_len_fn_item_def_id: DefId,
 ) {
-    let mut patch_found: Option<SliceLenPatchInformation<'_>> = None;
-
     let terminator = block.terminator();
-    match &terminator.kind {
-        TerminatorKind::Call {
-            func,
-            args,
-            destination,
-            target: Some(bb),
-            call_source: CallSource::Normal,
-            ..
-        } => {
-            // some heuristics for fast rejection
-            if args.len() != 1 {
-                return;
-            }
-            let Some(arg) = args[0].place() else { return };
-            let func_ty = func.ty(local_decls, tcx);
-            match func_ty.kind() {
-                ty::FnDef(fn_def_id, _) if fn_def_id == &slice_len_fn_item_def_id => {
-                    // perform modifications
-                    // from something like `_5 = core::slice::<impl [u8]>::len(move _6) -> bb1`
-                    // into:
-                    // ```
-                    // _5 = Len(*_6)
-                    // goto bb1
-                    // ```
+    if let TerminatorKind::Call {
+        func,
+        args,
+        destination,
+        target: Some(bb),
+        call_source: CallSource::Normal,
+        ..
+    } = &terminator.kind
+        // some heuristics for fast rejection
+        && let [arg] = &args[..]
+        && let Some(arg) = arg.place()
+        && let ty::FnDef(fn_def_id, _) = func.ty(local_decls, tcx).kind()
+        && *fn_def_id == slice_len_fn_item_def_id
+    {
+        // perform modifications from something like:
+        //     _5 = core::slice::<impl [u8]>::len(move _6) -> bb1
+        // into:
+        //     _5 = Len(*_6)
+        //     goto bb1
 
-                    // make new RValue for Len
-                    let deref_arg = tcx.mk_place_deref(arg);
-                    let r_value = Rvalue::Len(deref_arg);
-                    let len_statement_kind =
-                        StatementKind::Assign(Box::new((*destination, r_value)));
-                    let add_statement =
-                        Statement { kind: len_statement_kind, source_info: terminator.source_info };
+        // make new RValue for Len
+        let deref_arg = tcx.mk_place_deref(arg);
+        let r_value = Rvalue::Len(deref_arg);
+        let len_statement_kind = StatementKind::Assign(Box::new((*destination, r_value)));
+        let add_statement =
+            Statement { kind: len_statement_kind, source_info: terminator.source_info };
 
-                    // modify terminator into simple Goto
-                    let new_terminator_kind = TerminatorKind::Goto { target: *bb };
-
-                    let patch = SliceLenPatchInformation { add_statement, new_terminator_kind };
-
-                    patch_found = Some(patch);
-                }
-                _ => {}
-            }
-        }
-        _ => {}
-    }
+        // modify terminator into simple Goto
+        let new_terminator_kind = TerminatorKind::Goto { target: *bb };
 
-    if let Some(SliceLenPatchInformation { add_statement, new_terminator_kind }) = patch_found {
         block.statements.push(add_statement);
         block.terminator_mut().kind = new_terminator_kind;
     }