Add UI tests for #[splat] unhappy path and generics cases

Author: Ajay-singh1

tests/ui/splat/splat-generics-inside-tuple.rs

@@ -0,0 +1,31 @@
+// tests/ui/splat/splat-generics-inside-tuple.rs
+
+//@ run-pass
+//! Test using `#[splat]` on tuples with generics inside the splatted tuple.
+#![allow(incomplete_features)]
+#![feature(splat)]
+
+fn generic_second<T>(#[splat] _s: (u32, T)) {}
+
+fn generic_first<T>(#[splat] _s: (T, u32)) {}
+
+fn generic_both<T, U>(#[splat] _s: (T, U)) {}
+
+fn generic_triple<T, U, V>(#[splat] _s: (T, U, V)) {}
+
+fn main() {
+    generic_second(1u32, 2i8);
+    generic_second(1u32, 2.0f64);
+    generic_second(1u32, "hello");
+
+    generic_first(1i8, 2u32);
+    generic_first(2.0f64, 2u32);
+    generic_first("hello", 2u32);
+
+    generic_both(1u32, 2i8);
+    generic_both("hello", 2.0f64);
+    generic_both(true, "world");
+
+    generic_triple(1u32, 2.0f64, "hello");
+    generic_triple(true, 42i32, 3.14f32);
+}

tests/ui/splat/splat-invalid-trait-impl.rs

@@ -0,0 +1,29 @@
+// tests/ui/splat/splat-invalid-trait-impl.rs
+
+//! Test that `#[splat]` trait impls with mismatched tuple element types are rejected.
+#![allow(incomplete_features)]
+#![feature(splat)]
+
+trait FooTrait {
+    fn method(#[splat] _: (u32, i8));
+}
+
+struct Foo;
+struct Foo1;
+struct Foo2;
+
+impl FooTrait for Foo {
+    fn method(#[splat] _: (u32, f32)) {}
+    //~^ ERROR 
+}
+
+impl FooTrait for Foo1 {
+    fn method(#[splat] _: (f32, i8)) {}
+    //~^ ERROR
+}
+
+impl FooTrait for Foo2 {
+    fn method(#[splat] _: (f32, f64)) {}
+    //~^ ERROR
+}
+fn main() {}

tests/ui/splat/splat-invalid-trait-impl.stderr

@@ -0,0 +1,60 @@
+error[E0053]: method `method` has an incompatible type for trait
+  --> $DIR/splat-invalid-trait-impl.rs:16:27
+   |
+LL |     fn method(#[splat] _: (u32, f32)) {}
+   |                           ^^^^^^^^^^ expected `i8`, found `f32`
+   |
+note: type in trait
+  --> $DIR/splat-invalid-trait-impl.rs:8:27
+   |
+LL |     fn method(#[splat] _: (u32, i8));
+   |                           ^^^^^^^^^
+   = note: expected signature `fn(#[splat] (_, i8))`
+              found signature `fn(#[splat] (_, f32))`
+help: change the parameter type to match the trait
+   |
+LL -     fn method(#[splat] _: (u32, f32)) {}
+LL +     fn method(#[splat] _: (u32, i8)) {}
+   |
+
+error[E0053]: method `method` has an incompatible type for trait
+  --> $DIR/splat-invalid-trait-impl.rs:21:27
+   |
+LL |     fn method(#[splat] _: (f32, i8)) {}
+   |                           ^^^^^^^^^ expected `u32`, found `f32`
+   |
+note: type in trait
+  --> $DIR/splat-invalid-trait-impl.rs:8:27
+   |
+LL |     fn method(#[splat] _: (u32, i8));
+   |                           ^^^^^^^^^
+   = note: expected signature `fn(#[splat] (u32, _))`
+              found signature `fn(#[splat] (f32, _))`
+help: change the parameter type to match the trait
+   |
+LL -     fn method(#[splat] _: (f32, i8)) {}
+LL +     fn method(#[splat] _: (u32, i8)) {}
+   |
+
+error[E0053]: method `method` has an incompatible type for trait
+  --> $DIR/splat-invalid-trait-impl.rs:26:27
+   |
+LL |     fn method(#[splat] _: (f32, f64)) {}
+   |                           ^^^^^^^^^^ expected `u32`, found `f32`
+   |
+note: type in trait
+  --> $DIR/splat-invalid-trait-impl.rs:8:27
+   |
+LL |     fn method(#[splat] _: (u32, i8));
+   |                           ^^^^^^^^^
+   = note: expected signature `fn(#[splat] (u32, i8))`
+              found signature `fn(#[splat] (f32, f64))`
+help: change the parameter type to match the trait
+   |
+LL -     fn method(#[splat] _: (f32, f64)) {}
+LL +     fn method(#[splat] _: (u32, i8)) {}
+   |
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0053`.