Rollup merge of rust-lang#141811 - mejrs:bye_locals, r=compiler-errors

Unimplement unsized_locals

Implements rust-lang/compiler-team#630

Tracking issue here: rust-lang#111942

Note that this just removes the feature, not the implementation, and does not touch `unsized_fn_params`. This is because it is required to support `Box<dyn FnOnce()>: FnOnce()`.

There may be more that should be removed (possibly in follow up prs)
- the `forget_unsized` function and `forget` intrinsic.
- the `unsized_locals` test directory; I've just fixed up the tests for now
- various codegen support for unsized values and allocas

cc ``@JakobDegen`` ``@oli-obk`` ``@Noratrieb`` ``@programmerjake`` ``@bjorn3``

``@rustbot`` label F-unsized_locals

Fixes rust-lang#79409

Author: matthiaskrgr

tests/ui/large_stack_frames.rs

@@ -1,8 +1,7 @@
 //@ normalize-stderr-test: "\b10000(08|16|32)\b" -> "100$$PTR"
 //@ normalize-stderr-test: "\b2500(060|120)\b" -> "250$$PTR"
-#![allow(unused, incomplete_features)]
+#![allow(unused)]
 #![warn(clippy::large_stack_frames)]
-#![feature(unsized_locals)]
 
 use std::hint::black_box;
 
@@ -11,11 +10,6 @@ fn generic<T: Default>() {
     black_box(&x);
 }
 
-fn unsized_local() {
-    let x: dyn std::fmt::Display = *(Box::new(1) as Box<dyn std::fmt::Display>);
-    black_box(&x);
-}
-
 struct ArrayDefault<const N: usize>([u8; N]);
 
 impl<const N: usize> Default for ArrayDefault<N> {

tests/ui/large_stack_frames.stderr

@@ -1,5 +1,5 @@
 error: this function may allocate 250$PTR bytes on the stack
-  --> tests/ui/large_stack_frames.rs:27:4
+  --> tests/ui/large_stack_frames.rs:21:4
    |
 LL | fn many_small_arrays() {
    |    ^^^^^^^^^^^^^^^^^
@@ -13,23 +13,23 @@ LL |     let x5 = [0u8; 500_000];
    = help: to override `-D warnings` add `#[allow(clippy::large_stack_frames)]`
 
 error: this function may allocate 1000000 bytes on the stack
-  --> tests/ui/large_stack_frames.rs:38:4
+  --> tests/ui/large_stack_frames.rs:32:4
    |
 LL | fn large_return_value() -> ArrayDefault<1_000_000> {
    |    ^^^^^^^^^^^^^^^^^^      ----------------------- this is the largest part, at 1000000 bytes for type `ArrayDefault<1000000>`
    |
    = note: 1000000 bytes is larger than Clippy's configured `stack-size-threshold` of 512000
 
 error: this function may allocate 100$PTR bytes on the stack
-  --> tests/ui/large_stack_frames.rs:44:4
+  --> tests/ui/large_stack_frames.rs:38:4
    |
 LL | fn large_fn_arg(x: ArrayDefault<1_000_000>) {
    |    ^^^^^^^^^^^^ - `x` is the largest part, at 1000000 bytes for type `ArrayDefault<1000000>`
    |
    = note: 100$PTR bytes is larger than Clippy's configured `stack-size-threshold` of 512000
 
 error: this function may allocate 100$PTR bytes on the stack
-  --> tests/ui/large_stack_frames.rs:51:13
+  --> tests/ui/large_stack_frames.rs:45:13
    |
 LL |     let f = || black_box(&[0u8; 1_000_000]);
    |             ^^^^^^^^^^^^^^----------------^