Add UI tests for #[splat] with const, async, and unsafe functions

Author: Ajay-singh1

tests/ui/splat/splat-async-fn-tuple-fail.rs

@@ -0,0 +1,17 @@
+//@ edition:2024
+//! Test that using `#[splat]` incorrectly on async functions gives errors.
+
+#![allow(incomplete_features)]
+#![feature(splat)]
+
+async fn async_wrong_type(#[splat] _x: u32) {}
+//~^ ERROR cannot use splat attribute; the splatted argument type must be a tuple or unit, not a u32
+
+async fn async_multi_splat(#[splat] (_a, _b): (u32, i8), #[splat] (_c, _d): (u32, i8)) {}
+//~^ ERROR multiple `#[splat]`s are not allowed in the same function
+
+fn main() {
+    async_wrong_type(1u32);
+    async_multi_splat(1u32, 2i8, 3u32, 4i8);
+    //~^ ERROR this splatted function takes 3 arguments, but 4 were provided
+}

tests/ui/splat/splat-async-fn-tuple-fail.stderr

@@ -0,0 +1,27 @@
+error: multiple `#[splat]`s are not allowed in the same function
+  --> $DIR/splat-async-fn-tuple-fail.rs:10:28
+   |
+LL | async fn async_multi_splat(#[splat] (_a, _b): (u32, i8), #[splat] (_c, _d): (u32, i8)) {}
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: remove `#[splat]` from all but one argument
+
+error[E0277]: cannot use splat attribute; the splatted argument type must be a tuple or unit, not a u32 (u32)
+  --> $DIR/splat-async-fn-tuple-fail.rs:7:40
+   |
+LL | async fn async_wrong_type(#[splat] _x: u32) {}
+   |                                        ^^^
+...
+LL |     async_wrong_type(1u32);
+   |     ^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0057]: this splatted function takes 3 arguments, but 4 were provided
+  --> $DIR/splat-async-fn-tuple-fail.rs:15:5
+   |
+LL |     async_multi_splat(1u32, 2i8, 3u32, 4i8);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0057, E0277.
+For more information about an error, try `rustc --explain E0057`.

tests/ui/splat/splat-async-fn-tuple.rs

@@ -0,0 +1,18 @@
+//@ run-pass
+//@ edition:2024
+//! Test using `#[splat]` on tuple arguments of async functions.
+
+#![allow(incomplete_features)]
+#![feature(splat)]
+
+async fn async_tuple_args(#[splat] (_a, _b): (u32, i8)) {}
+
+async fn async_splat_non_terminal_arg(#[splat] (_a, _b): (u32, i8), _c: f64) {}
+
+fn main() {
+    let _ = async_tuple_args(1u32, 2i8);
+    let _ = async_tuple_args(1, 2);
+
+    let _ = async_splat_non_terminal_arg(1u32, 2i8, 3.5f64);
+    let _ = async_splat_non_terminal_arg(1, 2, 3.5);
+}

tests/ui/splat/splat-const-fn-tuple.rs

@@ -0,0 +1,17 @@
+//@ run-pass
+//! Test using `#[splat]` on tuple arguments of const functions.
+
+#![allow(incomplete_features)]
+#![feature(splat)]
+
+const fn sum(#[splat] (a, b): (u32, u32)) -> u32 {
+    a + b
+}
+
+const RESULT: u32 = sum(1, 2);
+
+fn main() {
+    assert_eq!(RESULT, 3);
+    assert_eq!(sum(12, 18) , 30);
+    assert_eq!(sum(1, 2), 3);
+}

tests/ui/splat/splat-unsafe-fn-tuple-fail.rs

@@ -0,0 +1,16 @@
+//! Test that using `#[splat]` incorrectly on unsafe functions gives errors.
+
+#![allow(incomplete_features)]
+#![feature(splat)]
+
+unsafe fn unsafe_wrong_type(#[splat] _x: u32) {}
+//~^ ERROR cannot use splat attribute; the splatted argument type must be a tuple or unit, not a u32
+
+unsafe fn unsafe_multi_splat(#[splat] (_a, _b): (u32, i8), #[splat] (_c, _d): (u32, i8)) {}
+//~^ ERROR multiple `#[splat]`s are not allowed in the same function
+
+fn main() {
+    unsafe {
+        unsafe_wrong_type(1u32);
+    }
+}

tests/ui/splat/splat-unsafe-fn-tuple-fail.stderr

@@ -0,0 +1,20 @@
+error: multiple `#[splat]`s are not allowed in the same function
+  --> $DIR/splat-unsafe-fn-tuple-fail.rs:9:30
+   |
+LL | unsafe fn unsafe_multi_splat(#[splat] (_a, _b): (u32, i8), #[splat] (_c, _d): (u32, i8)) {}
+   |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: remove `#[splat]` from all but one argument
+
+error[E0277]: cannot use splat attribute; the splatted argument type must be a tuple or unit, not a u32 (u32)
+  --> $DIR/splat-unsafe-fn-tuple-fail.rs:6:42
+   |
+LL | unsafe fn unsafe_wrong_type(#[splat] _x: u32) {}
+   |                                          ^^^
+...
+LL |         unsafe_wrong_type(1u32);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/splat/splat-unsafe-fn-tuple.rs

@@ -0,0 +1,19 @@
+//@ run-pass
+//! Test using `#[splat]` on tuple arguments of unsafe functions.
+
+#![allow(incomplete_features)]
+#![feature(splat)]
+
+unsafe fn unsafe_tuple_args(#[splat] (_a, _b): (u32, i8)) {}
+
+unsafe fn unsafe_splat_non_terminal_arg(#[splat] (_a, _b): (u32, i8), _c: f64) {}
+
+fn main() {
+    unsafe {
+        unsafe_tuple_args(1u32, 2i8);
+        unsafe_tuple_args(1, 2);
+
+        unsafe_splat_non_terminal_arg(1u32, 2i8, 3.5f64);
+        unsafe_splat_non_terminal_arg(1, 2, 3.5);
+    }
+}