Auto merge of rust-lang#108471 - clubby789:unbox-the-syntax, r=Nilstrieb,est31

Remove `box_syntax`

r? `@Nilstrieb`

This removes the feature `box_syntax`, which allows the use of `box <expr>` to create a Box, and finalises removing use of the feature from the compiler. `box_patterns` (allowing the use of `box <pat>` in a pattern) is unaffected.
It also removes `ast::ExprKind::Box` - the only way to create a 'box' expression now is with the rustc-internal `#[rustc_box]` attribute.
As a temporary measure to help users move away, `box <expr>` now parses the inner expression, and emits a `MachineApplicable` lint to replace it with `Box::new`

Closes rust-lang#49733

Author: bors

clippy_lints/src/suspicious_operation_groupings.rs

@@ -596,8 +596,7 @@ fn ident_difference_expr_with_base_location(
         | (MethodCall(_), MethodCall(_))
         | (Call(_, _), Call(_, _))
         | (ConstBlock(_), ConstBlock(_))
-        | (Array(_), Array(_))
-        | (Box(_), Box(_)) => {
+        | (Array(_), Array(_)) => {
             // keep going
         },
         _ => {

clippy_utils/src/ast_utils.rs

@@ -143,7 +143,7 @@ pub fn eq_expr(l: &Expr, r: &Expr) -> bool {
         (Paren(l), _) => eq_expr(l, r),
         (_, Paren(r)) => eq_expr(l, r),
         (Err, Err) => true,
-        (Box(l), Box(r)) | (Try(l), Try(r)) | (Await(l), Await(r)) => eq_expr(l, r),
+        (Try(l), Try(r)) | (Await(l), Await(r)) => eq_expr(l, r),
         (Array(l), Array(r)) => over(l, r, |l, r| eq_expr(l, r)),
         (Tup(l), Tup(r)) => over(l, r, |l, r| eq_expr(l, r)),
         (Repeat(le, ls), Repeat(re, rs)) => eq_expr(le, re) && eq_expr(&ls.value, &rs.value),

clippy_utils/src/sugg.rs

@@ -188,7 +188,6 @@ impl<'a> Sugg<'a> {
         match expr.kind {
             _ if expr.span.ctxt() != ctxt => Sugg::NonParen(snippet_with_context(cx, expr.span, ctxt, default, app).0),
             ast::ExprKind::AddrOf(..)
-            | ast::ExprKind::Box(..)
             | ast::ExprKind::Closure { .. }
             | ast::ExprKind::If(..)
             | ast::ExprKind::Let(..)

tests/ui/boxed_local.rs

@@ -1,4 +1,3 @@
-#![feature(box_syntax)]
 #![feature(lint_reasons)]
 #![allow(
     clippy::borrowed_box,
@@ -34,7 +33,7 @@ fn ok_box_trait(boxed_trait: &Box<dyn Z>) {
 }
 
 fn warn_call() {
-    let x = box A;
+    let x = Box::new(A);
     x.foo();
 }
 
@@ -43,41 +42,41 @@ fn warn_arg(x: Box<A>) {
 }
 
 fn nowarn_closure_arg() {
-    let x = Some(box A);
+    let x = Some(Box::new(A));
     x.map_or((), |x| take_ref(&x));
 }
 
 fn warn_rename_call() {
-    let x = box A;
+    let x = Box::new(A);
 
     let y = x;
     y.foo(); // via autoderef
 }
 
 fn warn_notuse() {
-    let bz = box A;
+    let bz = Box::new(A);
 }
 
 fn warn_pass() {
-    let bz = box A;
+    let bz = Box::new(A);
     take_ref(&bz); // via deref coercion
 }
 
 fn nowarn_return() -> Box<A> {
-    box A // moved out, "escapes"
+    Box::new(A) // moved out, "escapes"
 }
 
 fn nowarn_move() {
-    let bx = box A;
+    let bx = Box::new(A);
     drop(bx) // moved in, "escapes"
 }
 fn nowarn_call() {
-    let bx = box A;
+    let bx = Box::new(A);
     bx.clone(); // method only available to Box, not via autoderef
 }
 
 fn nowarn_pass() {
-    let bx = box A;
+    let bx = Box::new(A);
     take_box(&bx); // fn needs &Box
 }
 
@@ -86,30 +85,20 @@ fn take_ref(x: &A) {}
 
 fn nowarn_ref_take() {
     // false positive, should actually warn
-    let x = box A;
+    let x = Box::new(A);
     let y = &x;
     take_box(y);
 }
 
 fn nowarn_match() {
-    let x = box A; // moved into a match
+    let x = Box::new(A); // moved into a match
     match x {
         y => drop(y),
     }
 }
 
 fn warn_match() {
-    let x = box A;
-    match &x {
-        // not moved
-        y => (),
-    }
-}
-
-fn nowarn_large_array() {
-    // should not warn, is large array
-    // and should not be on stack
-    let x = box [1; 10000];
+    let x = Box::new(A);
     match &x {
         // not moved
         y => (),

tests/ui/boxed_local.stderr

@@ -1,25 +1,25 @@
 error: local variable doesn't need to be boxed here
-  --> $DIR/boxed_local.rs:41:13
+  --> $DIR/boxed_local.rs:40:13
    |
 LL | fn warn_arg(x: Box<A>) {
    |             ^
    |
    = note: `-D clippy::boxed-local` implied by `-D warnings`
 
 error: local variable doesn't need to be boxed here
-  --> $DIR/boxed_local.rs:132:12
+  --> $DIR/boxed_local.rs:121:12
    |
 LL | pub fn new(_needs_name: Box<PeekableSeekable<&()>>) -> () {}
    |            ^^^^^^^^^^^
 
 error: local variable doesn't need to be boxed here
-  --> $DIR/boxed_local.rs:196:44
+  --> $DIR/boxed_local.rs:185:44
    |
 LL |         fn default_impl_x(self: Box<Self>, x: Box<u32>) -> u32 {
    |                                            ^
 
 error: local variable doesn't need to be boxed here
-  --> $DIR/boxed_local.rs:203:16
+  --> $DIR/boxed_local.rs:192:16
    |
 LL |         fn foo(x: Box<u32>) {}
    |                ^

tests/ui/no_effect.rs

@@ -1,4 +1,4 @@
-#![feature(box_syntax, fn_traits, unboxed_closures)]
+#![feature(fn_traits, unboxed_closures)]
 #![warn(clippy::no_effect_underscore_binding)]
 #![allow(dead_code, path_statements)]
 #![allow(clippy::deref_addrof, clippy::redundant_field_names, clippy::uninlined_format_args)]
@@ -102,7 +102,6 @@ fn main() {
     *&42;
     &6;
     (5, 6, 7);
-    box 42;
     ..;
     5..;
     ..5;

tests/ui/no_effect.stderr

@@ -81,106 +81,100 @@ LL |     (5, 6, 7);
 error: statement with no effect
   --> $DIR/no_effect.rs:105:5
    |
-LL |     box 42;
-   |     ^^^^^^^
-
-error: statement with no effect
-  --> $DIR/no_effect.rs:106:5
-   |
 LL |     ..;
    |     ^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:107:5
+  --> $DIR/no_effect.rs:106:5
    |
 LL |     5..;
    |     ^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:108:5
+  --> $DIR/no_effect.rs:107:5
    |
 LL |     ..5;
    |     ^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:109:5
+  --> $DIR/no_effect.rs:108:5
    |
 LL |     5..6;
    |     ^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:110:5
+  --> $DIR/no_effect.rs:109:5
    |
 LL |     5..=6;
    |     ^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:111:5
+  --> $DIR/no_effect.rs:110:5
    |
 LL |     [42, 55];
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:112:5
+  --> $DIR/no_effect.rs:111:5
    |
 LL |     [42, 55][1];
    |     ^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:113:5
+  --> $DIR/no_effect.rs:112:5
    |
 LL |     (42, 55).1;
    |     ^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:114:5
+  --> $DIR/no_effect.rs:113:5
    |
 LL |     [42; 55];
    |     ^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:115:5
+  --> $DIR/no_effect.rs:114:5
    |
 LL |     [42; 55][13];
    |     ^^^^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:117:5
+  --> $DIR/no_effect.rs:116:5
    |
 LL |     || x += 5;
    |     ^^^^^^^^^^
 
 error: statement with no effect
-  --> $DIR/no_effect.rs:119:5
+  --> $DIR/no_effect.rs:118:5
    |
 LL |     FooString { s: s };
    |     ^^^^^^^^^^^^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:120:5
+  --> $DIR/no_effect.rs:119:5
    |
 LL |     let _unused = 1;
    |     ^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::no-effect-underscore-binding` implied by `-D warnings`
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:121:5
+  --> $DIR/no_effect.rs:120:5
    |
 LL |     let _penguin = || println!("Some helpful closure");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:122:5
+  --> $DIR/no_effect.rs:121:5
    |
 LL |     let _duck = Struct { field: 0 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: binding to `_` prefixed variable with no side-effect
-  --> $DIR/no_effect.rs:123:5
+  --> $DIR/no_effect.rs:122:5
    |
 LL |     let _cat = [2, 4, 6, 8][2];
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 30 previous errors
+error: aborting due to 29 previous errors
 

tests/ui/unnecessary_operation.fixed

@@ -1,6 +1,5 @@
 // run-rustfix
 
-#![feature(box_syntax)]
 #![allow(clippy::deref_addrof, dead_code, unused, clippy::no_effect)]
 #![warn(clippy::unnecessary_operation)]
 
@@ -59,7 +58,6 @@ fn main() {
     5;6;get_number();
     get_number();
     get_number();
-    get_number();
     5;get_number();
     42;get_number();
     assert!([42, 55].len() > get_usize());

tests/ui/unnecessary_operation.rs

@@ -1,6 +1,5 @@
 // run-rustfix
 
-#![feature(box_syntax)]
 #![allow(clippy::deref_addrof, dead_code, unused, clippy::no_effect)]
 #![warn(clippy::unnecessary_operation)]
 
@@ -57,7 +56,6 @@ fn main() {
     *&get_number();
     &get_number();
     (5, 6, get_number());
-    box get_number();
     get_number()..;
     ..get_number();
     5..get_number();