Check inlinee arity in mir inliner

compiler/rustc_mir_transform/src/inline.rs

@@ -268,6 +268,10 @@ impl<'tcx> Inliner<'tcx> {
                 bug!("Closure arguments are not passed as a tuple");
             };
 
+            if arg_tuple_tys.len() + self_arg_ty.map_or(0, |_| 1) != callee_body.args_iter().len() {
+                return Err("arg arity mismatch");
+            }
+
             for (arg_ty, input) in
                 self_arg_ty.into_iter().chain(arg_tuple_tys).zip(callee_body.args_iter())
             {
@@ -278,6 +282,10 @@ impl<'tcx> Inliner<'tcx> {
                 }
             }
         } else {
+            if args.len() != callee_body.args_iter().len() {
+                return Err("arg arity mismatch");
+            }
+
             for (arg, input) in args.iter().zip(callee_body.args_iter()) {
                 let input_type = callee_body.local_decls[input].ty;
                 let arg_ty = arg.node.ty(&caller_body.local_decls, self.tcx);

tests/ui/mir/inline-wrong-args.rs

@@ -0,0 +1,16 @@
+//@ compile-flags: -Zvalidate-mir -Zinline-mir -Zinline-mir-threshold=500
+
+struct Foo<T>([T; 2]);
+
+impl<T: Default + Copy> Default for Foo<T> {
+    fn default(&self) -> Self {
+        //~^ ERROR method `default` has a `&self` declaration in the impl, but not in the trait
+        Foo([Default::default(); 2])
+    }
+}
+
+fn field_array() {
+    let Foo([a, b]): Foo<i32> = Default::default();
+}
+
+fn main() {}

tests/ui/mir/inline-wrong-args.stderr

@@ -0,0 +1,11 @@
+error[E0185]: method `default` has a `&self` declaration in the impl, but not in the trait
+  --> $DIR/inline-wrong-args.rs:6:5
+   |
+LL |     fn default(&self) -> Self {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ `&self` used in impl
+   |
+   = note: `default` from trait: `fn() -> Self`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0185`.