Rollup merge of rust-lang#143303 - Kivooeo:tf28, r=tgross35

`tests/ui`: A New Order [28/28] FINAL PART

> [!NOTE]
>
> Intermediate commits are intended to help review, but will be squashed prior to merge.

Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang#133895.

r? `@tgross35`

Author: tgross35

tests/ui/allocator/weak-uninhabited-type.rs

@@ -0,0 +1,13 @@
+//! Checks that `Weak` pointers can be created with an empty enum type parameter.
+//! And generic `Weak` handles zero-variant enums without error.
+//!
+//! Regression test for <https://github.com/rust-lang/rust/issues/48493>
+
+//@ run-pass
+
+enum Void {}
+
+fn main() {
+    let _ = std::rc::Weak::<Void>::new();
+    let _ = std::sync::Weak::<Void>::new();
+}

tests/ui/binding/underscore-prefixed-function-argument.rs

@@ -0,0 +1,15 @@
+//! Test that argument names starting with `_` are usable.
+
+//@ run-pass
+
+fn good(_a: &isize) {}
+
+fn called<F>(_f: F)
+where
+    F: FnOnce(&isize),
+{
+}
+
+pub fn main() {
+    called(good);
+}

tests/ui/borrowck/ownership-struct-update-moved-error.rs

@@ -0,0 +1,19 @@
+//! Checks borrow after move error when using `self` consuming method with struct update syntax.
+
+struct Mine {
+    test: String,
+    other_val: isize,
+}
+
+impl Mine {
+    fn make_string_bar(mut self) -> Mine {
+        self.test = "Bar".to_string();
+        self
+    }
+}
+
+fn main() {
+    let start = Mine { test: "Foo".to_string(), other_val: 0 };
+    let end = Mine { other_val: 1, ..start.make_string_bar() };
+    println!("{}", start.test); //~ ERROR borrow of moved value: `start`
+}

tests/ui/walk-struct-literal-with.stderr renamed to tests/ui/borrowck/ownership-struct-update-moved-error.stderr

@@ -1,17 +1,17 @@
 error[E0382]: borrow of moved value: `start`
-  --> $DIR/walk-struct-literal-with.rs:16:20
+  --> $DIR/ownership-struct-update-moved-error.rs:18:20
    |
-LL |     let start = Mine{test:"Foo".to_string(), other_val:0};
+LL |     let start = Mine { test: "Foo".to_string(), other_val: 0 };
    |         ----- move occurs because `start` has type `Mine`, which does not implement the `Copy` trait
-LL |     let end = Mine{other_val:1, ..start.make_string_bar()};
-   |                                         ----------------- `start` moved due to this method call
+LL |     let end = Mine { other_val: 1, ..start.make_string_bar() };
+   |                                            ----------------- `start` moved due to this method call
 LL |     println!("{}", start.test);
    |                    ^^^^^^^^^^ value borrowed here after move
    |
 note: `Mine::make_string_bar` takes ownership of the receiver `self`, which moves `start`
-  --> $DIR/walk-struct-literal-with.rs:7:28
+  --> $DIR/ownership-struct-update-moved-error.rs:9:28
    |
-LL |     fn make_string_bar(mut self) -> Mine{
+LL |     fn make_string_bar(mut self) -> Mine {
    |                            ^^^^
    = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 

tests/ui/unused-move-capture.rs renamed to tests/ui/closures/no-capture-closure-call.rs

@@ -1,3 +1,5 @@
+//! Sanity check for no capture closures
+
 //@ run-pass
 
 pub fn main() {

tests/ui/unknown-llvm-arg.rs renamed to tests/ui/codegen/llvm-args-invalid-flag.rs

@@ -0,0 +1,12 @@
+//! Regression test for a crash caused by an "unsused move"
+//! (specifically, a variable bound to a `Box` used as a statement)
+//! leading to incorrect memory zero-filling after drop.
+//!
+//! Regression test for <https://github.com/rust-lang/rust/issues/3878>.
+
+//@ run-pass
+
+pub fn main() {
+    let y: Box<_> = Box::new(1);
+    drop(y);
+}

tests/ui/unknown-llvm-arg.stderr renamed to tests/ui/codegen/llvm-args-invalid-flag.stderr

@@ -1,26 +1,27 @@
+//! Check for correct initialization of `HashSet` with enums. This is a regression test for a
+//! codegen bug that caused the `HashSet` to appear as if it contained one of each enum variant.
+//!
+//! Regression test for <https://github.com/rust-lang/rust/issues/42918>
+
 //@ run-pass
-//
-#![allow(dead_code)]
 //@ compile-flags: -O
 
+#![allow(dead_code)]
+
 use std::collections::HashSet;
 
 #[derive(PartialEq, Debug, Hash, Eq, Clone, PartialOrd, Ord)]
 enum MyEnum {
     E0,
-
     E1,
-
     E2,
     E3,
     E4,
-
     E5,
     E6,
     E7,
 }
 
-
 fn main() {
     use MyEnum::*;
     let s: HashSet<_> = [E4, E1].iter().cloned().collect();