tests: add test for #105111

Enabling a tied feature should not enable the other feature
automatically. This was fixed by something in #128796, probably #128221
or #128679.

tests/ui/target-feature/tied-features-no-implication-1.paca.stderr

@@ -0,0 +1,4 @@
+error: the target features paca, pacg must all be either enabled or disabled together
+
+error: aborting due to 1 previous error
+

tests/ui/target-feature/tied-features-no-implication-1.pacg.stderr

@@ -0,0 +1,4 @@
+error: the target features paca, pacg must all be either enabled or disabled together
+
+error: aborting due to 1 previous error
+

tests/ui/target-feature/tied-features-no-implication-1.rs

@@ -0,0 +1,20 @@
+//@ revisions: paca pacg
+//@ compile-flags: --crate-type=rlib --target=aarch64-unknown-linux-gnu
+//@ needs-llvm-components: aarch64
+//@[paca] compile-flags: -Ctarget-feature=+paca
+//@[paca] error-pattern: the target features paca, pacg must all be either enabled or disabled together
+//@[pacg] compile-flags: -Ctarget-feature=+pacg
+//@[paca] error-pattern: the target features paca, pacg must all be either enabled or disabled together
+#![feature(no_core, lang_items)]
+#![no_core]
+
+#[lang="sized"]
+trait Sized {}
+
+// In this test, demonstrate that +paca and +pacg both result in the tied feature error if there
+// isn't something causing an error.
+// See tied-features-no-implication.rs
+
+#[cfg(target_feature = "pacg")]
+pub unsafe fn foo() {
+}

tests/ui/target-feature/tied-features-no-implication.paca.stderr

@@ -0,0 +1,4 @@
+error: the target features paca, pacg must all be either enabled or disabled together
+
+error: aborting due to 1 previous error
+

tests/ui/target-feature/tied-features-no-implication.pacg.stderr

@@ -0,0 +1,14 @@
+error[E0428]: the name `foo` is defined multiple times
+  --> $DIR/tied-features-no-implication.rs:28:1
+   |
+LL | fn foo() {}
+   | -------- previous definition of the value `foo` here
+...
+LL | pub unsafe fn foo() {
+   | ^^^^^^^^^^^^^^^^^^^ `foo` redefined here
+   |
+   = note: `foo` must be defined only once in the value namespace of this module
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0428`.

tests/ui/target-feature/tied-features-no-implication.rs

@@ -0,0 +1,29 @@
+//@ revisions: paca pacg
+//@ compile-flags: --crate-type=rlib --target=aarch64-unknown-linux-gnu
+//@ needs-llvm-components: aarch64
+//@[paca] compile-flags: -Ctarget-feature=+paca
+//@[paca] error-pattern: the target features paca, pacg must all be either enabled or disabled together
+//@[pacg] compile-flags: -Ctarget-feature=+pacg
+//@[pacg] error-pattern: the name `foo` is defined multiple times
+#![feature(no_core, lang_items)]
+#![no_core]
+
+#[lang="sized"]
+trait Sized {}
+
+// Can't use `compile_error!` here without `core`/`std` but requiring these makes this test only
+// work if you have libcore built in the sysroot for `aarch64-unknown-linux-gnu`. Can't run this
+// test on any aarch64 platform because they all have different default available features - as
+// written, this test depends on `aarch64-unknown-linux-gnu` having -paca,-pacg by default.
+// Cause a multiple definition error instead.
+fn foo() {}
+
+// Enabling one of the tied features does not imply the other is enabled.
+//
+// With +paca, this multiple definition doesn't cause an error because +paca hasn't implied
+// +pacg. With +pacg, the multiple definition error is emitted (and the tied feature error would
+// be).
+
+#[cfg(target_feature = "pacg")]
+pub unsafe fn foo() {
+}