Auto merge of #132173 - veluca93:abi_checks, r=RalfJung,compiler-errors

Emit warning when calling/declaring functions with unavailable vectors.

On some architectures, vector types may have a different ABI depending on whether the relevant target features are enabled. (The ABI when the feature is disabled is often not specified, but LLVM implements some de-facto ABI.)

As discussed in rust-lang/lang-team#235, this turns out to very easily lead to unsound code.

This commit makes it a post-monomorphization future-incompat warning to declare or call functions using those vector types in a context in which the corresponding target features are disabled, if using an ABI for which the difference is relevant. This ensures that these functions are always called with a consistent ABI.

See the [nomination comment](https://github.com/rust-lang/rust/pull/127731#issuecomment-2288558187) for more discussion.

Part of #116558

r? RalfJung

4 files changed, 10 insertions, 12 deletions

diff --git a/tests/ui/layout/post-mono-layout-cycle-2.rs b/tests/ui/layout/post-mono-layout-cycle-2.rs
index 356f1e777c7..e9a5292fbbd 100644
--- a/tests/ui/layout/post-mono-layout-cycle-2.rs
+++ b/tests/ui/layout/post-mono-layout-cycle-2.rs
@@ -45,7 +45,6 @@ where
     T: Blah,
 {
     async fn ice(&mut self) {
-        //~^ ERROR a cycle occurred during layout computation
         let arr: [(); 0] = [];
         self.t.iter(arr.into_iter()).await;
     }
diff --git a/tests/ui/layout/post-mono-layout-cycle-2.stderr b/tests/ui/layout/post-mono-layout-cycle-2.stderr
index ad01c2694fa..2e8d237844e 100644
--- a/tests/ui/layout/post-mono-layout-cycle-2.stderr
+++ b/tests/ui/layout/post-mono-layout-cycle-2.stderr
@@ -12,12 +12,12 @@ LL |           Blah::iter(self, iterator).await
    |
    = note: a recursive `async fn` call must introduce indirection such as `Box::pin` to avoid an infinitely sized future
 
-error: a cycle occurred during layout computation
-  --> $DIR/post-mono-layout-cycle-2.rs:47:5
+note: the above error was encountered while instantiating `fn Wrap::<()>::ice`
+  --> $DIR/post-mono-layout-cycle-2.rs:56:9
    |
-LL |     async fn ice(&mut self) {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^
+LL |         t.ice();
+   |         ^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0733`.
diff --git a/tests/ui/layout/post-mono-layout-cycle.rs b/tests/ui/layout/post-mono-layout-cycle.rs
index 8d136190c00..6753c01267e 100644
--- a/tests/ui/layout/post-mono-layout-cycle.rs
+++ b/tests/ui/layout/post-mono-layout-cycle.rs
@@ -14,7 +14,6 @@ struct Wrapper<T: Trait> {
 }
 
 fn abi<T: Trait>(_: Option<Wrapper<T>>) {}
-//~^ ERROR a cycle occurred during layout computation
 
 fn indirect<T: Trait>() {
     abi::<T>(None);
diff --git a/tests/ui/layout/post-mono-layout-cycle.stderr b/tests/ui/layout/post-mono-layout-cycle.stderr
index 47f7f30b1cb..7f246b3d409 100644
--- a/tests/ui/layout/post-mono-layout-cycle.stderr
+++ b/tests/ui/layout/post-mono-layout-cycle.stderr
@@ -5,12 +5,12 @@ error[E0391]: cycle detected when computing layout of `Wrapper<()>`
    = note: cycle used when computing layout of `core::option::Option<Wrapper<()>>`
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
-error: a cycle occurred during layout computation
-  --> $DIR/post-mono-layout-cycle.rs:16:1
+note: the above error was encountered while instantiating `fn abi::<()>`
+  --> $DIR/post-mono-layout-cycle.rs:19:5
    |
-LL | fn abi<T: Trait>(_: Option<Wrapper<T>>) {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     abi::<T>(None);
+   |     ^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0391`.