Set default move_size_limit to 4kB for large_assignments lint on nightly

Only enable it by default in the nightly compiler. The limit can be
changed on a per-crate basis with:

    #![feature(large_assignments)]
    #![move_size_limit = "8192"]

or with

    -Zmove-size-limit=8192

Author: Enselic

compiler/rustc_interface/src/passes.rs

@@ -716,6 +716,7 @@ pub fn create_global_ctxt<'tcx>(
 
     sess.time("setup_global_ctxt", || {
         gcx_cell.get_or_init(move || {
+            #[allow(large_assignments)]
             TyCtxt::create_global_ctxt(
                 sess,
                 crate_types,

compiler/rustc_interface/src/queries.rs

@@ -93,6 +93,7 @@ pub struct Queries<'tcx> {
 
 impl<'tcx> Queries<'tcx> {
     pub fn new(compiler: &'tcx Compiler) -> Queries<'tcx> {
+        #[allow(large_assignments)]
         Queries {
             compiler,
             gcx_cell: OnceLock::new(),

compiler/rustc_interface/src/tests.rs

@@ -1,4 +1,4 @@
-#![allow(rustc::bad_opt_access)]
+#![allow(rustc::bad_opt_access, large_assignments)]
 use crate::interface::parse_cfgspecs;
 
 use rustc_data_structures::fx::FxHashSet;

compiler/rustc_interface/src/util.rs

@@ -126,6 +126,7 @@ pub fn create_session(
     sess.parse_sess.config = cfg;
     sess.parse_sess.check_config = check_cfg;
 
+    #[allow(large_assignments)]
     (sess, codegen_backend)
 }
 

compiler/rustc_middle/src/middle/limits.rs

@@ -25,7 +25,15 @@ pub fn provide(providers: &mut Providers) {
             tcx.hir().krate_attrs(),
             tcx.sess,
             sym::move_size_limit,
-            tcx.sess.opts.unstable_opts.move_size_limit.unwrap_or(0),
+            // The check is enabled by default in nightly compilers without
+            // needing `#![feature(large_assignments)]` with a limit of 4096
+            // bytes. But if the user wants to use adjust `#![move_size_limit]`,
+            // then `#![feature(large_assignments)]` is needed.
+            tcx.sess.opts.unstable_opts.move_size_limit.unwrap_or(if tcx.sess.is_nightly_build() {
+                4096
+            } else {
+                0
+            }),
         ),
         type_length_limit: get_limit(
             tcx.hir().krate_attrs(),

compiler/rustc_middle/src/ty/context.rs

@@ -713,6 +713,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let common_lifetimes = CommonLifetimes::new(&interners);
         let common_consts = CommonConsts::new(&interners, &common_types);
 
+        #[allow(large_assignments)]
         GlobalCtxt {
             sess: s,
             crate_types,

compiler/rustc_query_impl/src/lib.rs

@@ -209,6 +209,7 @@ pub fn query_system<'tcx>(
     on_disk_cache: Option<OnDiskCache<'tcx>>,
     incremental: bool,
 ) -> QuerySystem<'tcx> {
+    #[allow(large_assignments)]
     QuerySystem {
         states: Default::default(),
         arenas: Default::default(),

compiler/rustc_session/src/session.rs

@@ -1312,7 +1312,7 @@ fn default_emitter(
 }
 
 // JUSTIFICATION: literally session construction
-#[allow(rustc::bad_opt_access)]
+#[allow(rustc::bad_opt_access, large_assignments)]
 pub fn build_session(
     handler: &EarlyErrorHandler,
     sopts: config::Options,

compiler/rustc_target/src/spec/apple/tests.rs

@@ -1,3 +1,5 @@
+#![allow(large_assignments)]
+
 use crate::spec::{
     aarch64_apple_darwin, aarch64_apple_ios_sim, aarch64_apple_watchos_sim, i686_apple_darwin,
     x86_64_apple_darwin, x86_64_apple_ios, x86_64_apple_tvos, x86_64_apple_watchos_sim,

library/alloc/benches/vec_deque.rs

@@ -1,3 +1,5 @@
+#![allow(large_assignments)]
+
 use core::iter::Iterator;
 use std::{
     collections::{vec_deque, VecDeque},

library/alloc/src/boxed.rs

@@ -837,6 +837,7 @@ impl<T, A: Allocator> Box<mem::MaybeUninit<T>, A> {
     ///
     /// ```
     /// #![feature(new_uninit)]
+    /// #![allow(large_assignments)]
     ///
     /// let big_box = Box::<[usize; 1024]>::new_uninit();
     ///

library/core/benches/array.rs

@@ -1,3 +1,5 @@
+#![allow(large_assignments)]
+
 use test::black_box;
 use test::Bencher;
 

library/core/benches/iter.rs

@@ -1,3 +1,5 @@
+#![allow(large_assignments)]
+
 use core::borrow::Borrow;
 use core::iter::*;
 use core::mem;

library/core/src/cell.rs

@@ -2042,6 +2042,7 @@ impl<T> UnsafeCell<T> {
     #[rustc_const_stable(feature = "const_unsafe_cell_new", since = "1.32.0")]
     #[inline(always)]
     pub const fn new(value: T) -> UnsafeCell<T> {
+        #[allow(large_assignments)]
         UnsafeCell { value }
     }
 

library/core/src/convert/mod.rs

@@ -713,6 +713,7 @@ where
     /// <code>[From]&lt;T&gt; for U</code> chooses to do.
     #[inline]
     fn into(self) -> U {
+        #[allow(large_assignments)]
         U::from(self)
     }
 }

library/core/src/hint.rs

@@ -290,6 +290,7 @@ pub fn spin_loop() {
 #[stable(feature = "bench_black_box", since = "1.66.0")]
 #[rustc_const_unstable(feature = "const_black_box", issue = "none")]
 pub const fn black_box<T>(dummy: T) -> T {
+    #[allow(large_assignments)]
     crate::intrinsics::black_box(dummy)
 }
 

library/core/src/mem/maybe_uninit.rs

@@ -97,6 +97,7 @@ use crate::slice;
 /// unnecessary moves.
 ///
 /// ```
+/// ##![allow(large_assignments)]
 /// use std::mem::MaybeUninit;
 ///
 /// unsafe fn make_vec(out: *mut Vec<i32>) {
@@ -117,6 +118,7 @@ use crate::slice;
 /// `MaybeUninit<T>` can be used to initialize a large array element-by-element:
 ///
 /// ```
+/// ##![allow(large_assignments)]
 /// use std::mem::{self, MaybeUninit};
 ///
 /// let data = {
@@ -145,6 +147,7 @@ use crate::slice;
 /// be found in low-level datastructures.
 ///
 /// ```
+/// ##![allow(large_assignments)]
 /// use std::mem::MaybeUninit;
 ///
 /// // Create an uninitialized array of `MaybeUninit`. The `assume_init` is

tests/ui/async-await/large_moves.attribute.stderr

@@ -28,12 +28,60 @@ LL |     let _ = NotBox::new([0; 9999]);
    = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
 
 error: moving 9999 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
+LL |             data,
+   |             ^^^^ value moved from here
+   |
+   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 1500 bytes
+  --> $DIR/large_moves.rs:37:13
+   |
+LL |     let _ = NotBox::new([0; 1500]);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 2500 bytes
   --> $DIR/large_moves.rs:41:13
    |
+LL |     let _ = NotBox::new([0; 2500]);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 5000 bytes
+  --> $DIR/large_moves.rs:47:13
+   |
+LL |     let _ = NotBox::new([0; 5000]);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 1500 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
+LL |             data,
+   |             ^^^^ value moved from here
+   |
+   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 2500 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
+LL |             data,
+   |             ^^^^ value moved from here
+   |
+   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 5000 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
 LL |             data,
    |             ^^^^ value moved from here
    |
    = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
 
-error: aborting due to 4 previous errors
+error: aborting due to 10 previous errors
 

tests/ui/async-await/large_moves.nothing.stderr

@@ -0,0 +1,55 @@
+error: moving 10024 bytes
+  --> $DIR/large_moves.rs:21:14
+   |
+LL |     let z = (x, 42);
+   |              ^ value moved from here
+   |
+   = note: The current maximum size is 4096, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+note: the lint level is defined here
+  --> $DIR/large_moves.rs:1:9
+   |
+LL | #![deny(large_assignments)]
+   |         ^^^^^^^^^^^^^^^^^
+
+error: moving 10024 bytes
+  --> $DIR/large_moves.rs:22:13
+   |
+LL |     let a = z.0;
+   |             ^^^ value moved from here
+   |
+   = note: The current maximum size is 4096, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 9999 bytes
+  --> $DIR/large_moves.rs:27:13
+   |
+LL |     let _ = NotBox::new([0; 9999]);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 4096, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 9999 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
+LL |             data,
+   |             ^^^^ value moved from here
+   |
+   = note: The current maximum size is 4096, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 5000 bytes
+  --> $DIR/large_moves.rs:47:13
+   |
+LL |     let _ = NotBox::new([0; 5000]);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 4096, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 5000 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
+LL |             data,
+   |             ^^^^ value moved from here
+   |
+   = note: The current maximum size is 4096, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: aborting due to 6 previous errors
+

tests/ui/async-await/large_moves.option.stderr

@@ -4,7 +4,7 @@ error: moving 10024 bytes
 LL |     let z = (x, 42);
    |              ^ value moved from here
    |
-   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
 note: the lint level is defined here
   --> $DIR/large_moves.rs:1:9
    |
@@ -17,23 +17,55 @@ error: moving 10024 bytes
 LL |     let a = z.0;
    |             ^^^ value moved from here
    |
-   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
 
 error: moving 9999 bytes
   --> $DIR/large_moves.rs:27:13
    |
 LL |     let _ = NotBox::new([0; 9999]);
    |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
    |
-   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
 
 error: moving 9999 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
+LL |             data,
+   |             ^^^^ value moved from here
+   |
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 2500 bytes
   --> $DIR/large_moves.rs:41:13
    |
+LL |     let _ = NotBox::new([0; 2500]);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 5000 bytes
+  --> $DIR/large_moves.rs:47:13
+   |
+LL |     let _ = NotBox::new([0; 5000]);
+   |             ^^^^^^^^^^^^^^^^^^^^^^ value moved from here
+   |
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 2500 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
+LL |             data,
+   |             ^^^^ value moved from here
+   |
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+
+error: moving 5000 bytes
+  --> $DIR/large_moves.rs:63:13
+   |
 LL |             data,
    |             ^^^^ value moved from here
    |
-   = note: The current maximum size is 1000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
+   = note: The current maximum size is 2000, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`
 
-error: aborting due to 4 previous errors
+error: aborting due to 8 previous errors