Auto merge of rust-lang#129935 - RalfJung:unsupported_calling_convent…

…ions, r=compiler-errors

make unsupported_calling_conventions a hard error

This has been a future-compat lint (not shown in dependencies) since Rust 1.55, released 3 years ago. Hopefully that was enough time so this can be made a hard error now. Given that long timeframe, I think it's justified to skip the "show in dependencies" stage. There were [not many crates hitting this](rust-lang#86231 (comment)) even when the lint was originally added.

This should get cratered, and I assume then it needs a t-compiler FCP. (t-compiler because this looks entirely like an implementation oversight -- for the vast majority of ABIs, we already have a hard error, but some were initially missed, and we are finally fixing that.)

Fixes rust-lang#87678

compiler/rustc_hir_analysis/src/check/check.rs

@@ -22,7 +22,7 @@ use rustc_middle::ty::{
     AdtDef, GenericArgKind, ParamEnv, RegionKind, TypeSuperVisitable, TypeVisitable,
     TypeVisitableExt,
 };
-use rustc_session::lint::builtin::{UNINHABITED_STATIC, UNSUPPORTED_CALLING_CONVENTIONS};
+use rustc_session::lint::builtin::UNINHABITED_STATIC;
 use rustc_target::abi::FieldIdx;
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::traits::on_unimplemented::OnUnimplementedDirective;
@@ -36,36 +36,25 @@ use super::compare_impl_item::{check_type_bounds, compare_impl_method, compare_i
 use super::*;
 use crate::check::intrinsicck::InlineAsmCtxt;
 
-pub fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) {
-    match tcx.sess.target.is_abi_supported(abi) {
-        Some(true) => (),
-        Some(false) => {
-            struct_span_code_err!(
-                tcx.dcx(),
-                span,
-                E0570,
-                "`{abi}` is not a supported ABI for the current target",
-            )
-            .emit();
-        }
-        None => {
-            tcx.node_span_lint(UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, |lint| {
-                lint.primary_message("use of calling convention not supported on this target");
-            });
-        }
+pub fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
+    if !tcx.sess.target.is_abi_supported(abi) {
+        struct_span_code_err!(
+            tcx.dcx(),
+            span,
+            E0570,
+            "`{abi}` is not a supported ABI for the current target",
+        )
+        .emit();
     }
 }
 
 pub fn check_abi_fn_ptr(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) {
-    match tcx.sess.target.is_abi_supported(abi) {
-        Some(true) => (),
-        Some(false) | None => {
-            tcx.node_span_lint(UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS, hir_id, span, |lint| {
-                lint.primary_message(format!(
-                    "the calling convention {abi} is not supported on this target"
-                ));
-            });
-        }
+    if !tcx.sess.target.is_abi_supported(abi) {
+        tcx.node_span_lint(UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS, hir_id, span, |lint| {
+            lint.primary_message(format!(
+                "the calling convention {abi} is not supported on this target"
+            ));
+        });
     }
 }
 
@@ -705,7 +694,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) {
             let hir::ItemKind::ForeignMod { abi, items } = it.kind else {
                 return;
             };
-            check_abi(tcx, it.hir_id(), it.span, abi);
+            check_abi(tcx, it.span, abi);
 
             match abi {
                 Abi::RustIntrinsic => {

compiler/rustc_hir_typeck/src/lib.rs

@@ -155,7 +155,7 @@ fn typeck_with_fallback<'tcx>(
             tcx.fn_sig(def_id).instantiate_identity()
         };
 
-        check_abi(tcx, id, span, fn_sig.abi());
+        check_abi(tcx, span, fn_sig.abi());
 
         // Compute the function signature from point of view of inside the fn.
         let fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);

compiler/rustc_lint/src/lib.rs

@@ -598,6 +598,7 @@ fn register_builtins(store: &mut LintStore) {
         "converted into hard error, see PR #125380 \
          <https://github.com/rust-lang/rust/pull/125380> for more information",
     );
+    store.register_removed("unsupported_calling_conventions", "converted into hard error");
 }
 
 fn register_internals(store: &mut LintStore) {

compiler/rustc_lint_defs/src/builtin.rs

@@ -123,7 +123,6 @@ declare_lint_pass! {
         UNSAFE_OP_IN_UNSAFE_FN,
         UNSTABLE_NAME_COLLISIONS,
         UNSTABLE_SYNTAX_PRE_EXPANSION,
-        UNSUPPORTED_CALLING_CONVENTIONS,
         UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS,
         UNUSED_ASSIGNMENTS,
         UNUSED_ASSOCIATED_TYPE_BOUNDS,
@@ -3787,53 +3786,6 @@ declare_lint! {
     crate_level_only
 }
 
-declare_lint! {
-    /// The `unsupported_calling_conventions` lint is output whenever there is a use of the
-    /// `stdcall`, `fastcall`, `thiscall`, `vectorcall` calling conventions (or their unwind
-    /// variants) on targets that cannot meaningfully be supported for the requested target.
-    ///
-    /// For example `stdcall` does not make much sense for a x86_64 or, more apparently, powerpc
-    /// code, because this calling convention was never specified for those targets.
-    ///
-    /// Historically MSVC toolchains have fallen back to the regular C calling convention for
-    /// targets other than x86, but Rust doesn't really see a similar need to introduce a similar
-    /// hack across many more targets.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,ignore (needs specific targets)
-    /// extern "stdcall" fn stdcall() {}
-    /// ```
-    ///
-    /// This will produce:
-    ///
-    /// ```text
-    /// warning: use of calling convention not supported on this target
-    ///   --> $DIR/unsupported.rs:39:1
-    ///    |
-    /// LL | extern "stdcall" fn stdcall() {}
-    ///    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-    ///    |
-    ///    = note: `#[warn(unsupported_calling_conventions)]` on by default
-    ///    = warning: this was previously accepted by the compiler but is being phased out;
-    ///               it will become a hard error in a future release!
-    ///    = note: for more information, see issue ...
-    /// ```
-    ///
-    /// ### Explanation
-    ///
-    /// On most of the targets the behaviour of `stdcall` and similar calling conventions is not
-    /// defined at all, but was previously accepted due to a bug in the implementation of the
-    /// compiler.
-    pub UNSUPPORTED_CALLING_CONVENTIONS,
-    Warn,
-    "use of unsupported calling convention",
-    @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
-        reference: "issue #87678 <https://github.com/rust-lang/rust/issues/87678>",
-    };
-}
-
 declare_lint! {
     /// The `unsupported_fn_ptr_calling_conventions` lint is output whenever there is a use of
     /// a target dependent calling convention on a target that does not support this calling

compiler/rustc_target/src/spec/mod.rs

@@ -2757,10 +2757,9 @@ impl Target {
         }
     }
 
-    /// Returns a None if the UNSUPPORTED_CALLING_CONVENTIONS lint should be emitted
-    pub fn is_abi_supported(&self, abi: Abi) -> Option<bool> {
+    pub fn is_abi_supported(&self, abi: Abi) -> bool {
         use Abi::*;
-        Some(match abi {
+        match abi {
             Rust
             | C { .. }
             | System { .. }
@@ -2819,9 +2818,9 @@ impl Target {
             // architectures for which these calling conventions are actually well defined.
             Stdcall { .. } | Fastcall { .. } if self.arch == "x86" => true,
             Vectorcall { .. } if ["x86", "x86_64"].contains(&&self.arch[..]) => true,
-            // Return a `None` for other cases so that we know to emit a future compat lint.
-            Stdcall { .. } | Fastcall { .. } | Vectorcall { .. } => return None,
-        })
+            // Reject these calling conventions everywhere else.
+            Stdcall { .. } | Fastcall { .. } | Vectorcall { .. } => false,
+        }
     }
 
     /// Minimum integer size in bits that this target can perform atomic

src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.fixed

@@ -1,7 +1,7 @@
 #![warn(clippy::missing_const_for_fn)]
 #![allow(incomplete_features, clippy::let_and_return, clippy::missing_transmute_annotations)]
-#![allow(unsupported_calling_conventions)]
-#![feature(const_trait_impl)]
+#![feature(const_trait_impl, abi_vectorcall)]
+
 
 use std::mem::transmute;
 
@@ -212,8 +212,8 @@ mod extern_fn {
     //~^ ERROR: this could be a `const fn`
     const extern "system-unwind" fn system_unwind() {}
     //~^ ERROR: this could be a `const fn`
-    pub const extern "stdcall" fn std_call() {}
+    pub const extern "vectorcall" fn std_call() {}
     //~^ ERROR: this could be a `const fn`
-    pub const extern "stdcall-unwind" fn std_call_unwind() {}
+    pub const extern "vectorcall-unwind" fn std_call_unwind() {}
     //~^ ERROR: this could be a `const fn`
 }

src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.rs

@@ -1,7 +1,7 @@
 #![warn(clippy::missing_const_for_fn)]
 #![allow(incomplete_features, clippy::let_and_return, clippy::missing_transmute_annotations)]
-#![allow(unsupported_calling_conventions)]
-#![feature(const_trait_impl)]
+#![feature(const_trait_impl, abi_vectorcall)]
+
 
 use std::mem::transmute;
 
@@ -212,8 +212,8 @@ mod extern_fn {
     //~^ ERROR: this could be a `const fn`
     extern "system-unwind" fn system_unwind() {}
     //~^ ERROR: this could be a `const fn`
-    pub extern "stdcall" fn std_call() {}
+    pub extern "vectorcall" fn std_call() {}
     //~^ ERROR: this could be a `const fn`
-    pub extern "stdcall-unwind" fn std_call_unwind() {}
+    pub extern "vectorcall-unwind" fn std_call_unwind() {}
     //~^ ERROR: this could be a `const fn`
 }

src/tools/clippy/tests/ui/missing_const_for_fn/could_be_const.stderr

@@ -319,23 +319,23 @@ LL |     const extern "system-unwind" fn system_unwind() {}
 error: this could be a `const fn`
   --> tests/ui/missing_const_for_fn/could_be_const.rs:215:5
    |
-LL |     pub extern "stdcall" fn std_call() {}
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     pub extern "vectorcall" fn std_call() {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 help: make the function `const`
    |
-LL |     pub const extern "stdcall" fn std_call() {}
+LL |     pub const extern "vectorcall" fn std_call() {}
    |         +++++
 
 error: this could be a `const fn`
   --> tests/ui/missing_const_for_fn/could_be_const.rs:217:5
    |
-LL |     pub extern "stdcall-unwind" fn std_call_unwind() {}
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     pub extern "vectorcall-unwind" fn std_call_unwind() {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 help: make the function `const`
    |
-LL |     pub const extern "stdcall-unwind" fn std_call_unwind() {}
+LL |     pub const extern "vectorcall-unwind" fn std_call_unwind() {}
    |         +++++
 
 error: aborting due to 26 previous errors

tests/ui/abi/unsupported.aarch64.stderr

@@ -105,26 +105,22 @@ LL | extern "thiscall" {}
    | ^^^^^^^^^^^^^^^^^^^^
 
 warning: the calling convention "stdcall" is not supported on this target
-  --> $DIR/unsupported.rs:170:19
+  --> $DIR/unsupported.rs:165:19
    |
 LL | fn stdcall_ptr(f: extern "stdcall" fn()) {
    |                   ^^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #130260 <https://github.com/rust-lang/rust/issues/130260>
 
-warning: use of calling convention not supported on this target
-  --> $DIR/unsupported.rs:183:1
+error[E0570]: `"stdcall"` is not a supported ABI for the current target
+  --> $DIR/unsupported.rs:178:1
    |
 LL | extern "stdcall" {}
    | ^^^^^^^^^^^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
-   = note: `#[warn(unsupported_calling_conventions)]` on by default
 
 warning: the calling convention "C-cmse-nonsecure-call" is not supported on this target
-  --> $DIR/unsupported.rs:195:21
+  --> $DIR/unsupported.rs:185:21
    |
 LL | fn cmse_call_ptr(f: extern "C-cmse-nonsecure-call" fn()) {
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -133,7 +129,7 @@ LL | fn cmse_call_ptr(f: extern "C-cmse-nonsecure-call" fn()) {
    = note: for more information, see issue #130260 <https://github.com/rust-lang/rust/issues/130260>
 
 warning: the calling convention "C-cmse-nonsecure-entry" is not supported on this target
-  --> $DIR/unsupported.rs:203:22
+  --> $DIR/unsupported.rs:193:22
    |
 LL | fn cmse_entry_ptr(f: extern "C-cmse-nonsecure-entry" fn()) {
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -142,7 +138,7 @@ LL | fn cmse_entry_ptr(f: extern "C-cmse-nonsecure-entry" fn()) {
    = note: for more information, see issue #130260 <https://github.com/rust-lang/rust/issues/130260>
 
 error[E0570]: `"C-cmse-nonsecure-entry"` is not a supported ABI for the current target
-  --> $DIR/unsupported.rs:208:1
+  --> $DIR/unsupported.rs:198:1
    |
 LL | extern "C-cmse-nonsecure-entry" {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -189,21 +185,18 @@ error[E0570]: `"thiscall"` is not a supported ABI for the current target
 LL | extern "thiscall" fn thiscall() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-warning: use of calling convention not supported on this target
+error[E0570]: `"stdcall"` is not a supported ABI for the current target
   --> $DIR/unsupported.rs:159:1
    |
 LL | extern "stdcall" fn stdcall() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
 
 error[E0570]: `"C-cmse-nonsecure-entry"` is not a supported ABI for the current target
-  --> $DIR/unsupported.rs:201:1
+  --> $DIR/unsupported.rs:191:1
    |
 LL | extern "C-cmse-nonsecure-entry" fn cmse_entry() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 16 previous errors; 12 warnings emitted
+error: aborting due to 18 previous errors; 10 warnings emitted
 
 For more information about this error, try `rustc --explain E0570`.

tests/ui/abi/unsupported.arm.stderr

@@ -90,26 +90,22 @@ LL | extern "thiscall" {}
    | ^^^^^^^^^^^^^^^^^^^^
 
 warning: the calling convention "stdcall" is not supported on this target
-  --> $DIR/unsupported.rs:170:19
+  --> $DIR/unsupported.rs:165:19
    |
 LL | fn stdcall_ptr(f: extern "stdcall" fn()) {
    |                   ^^^^^^^^^^^^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #130260 <https://github.com/rust-lang/rust/issues/130260>
 
-warning: use of calling convention not supported on this target
-  --> $DIR/unsupported.rs:183:1
+error[E0570]: `"stdcall"` is not a supported ABI for the current target
+  --> $DIR/unsupported.rs:178:1
    |
 LL | extern "stdcall" {}
    | ^^^^^^^^^^^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
-   = note: `#[warn(unsupported_calling_conventions)]` on by default
 
 warning: the calling convention "C-cmse-nonsecure-call" is not supported on this target
-  --> $DIR/unsupported.rs:195:21
+  --> $DIR/unsupported.rs:185:21
    |
 LL | fn cmse_call_ptr(f: extern "C-cmse-nonsecure-call" fn()) {
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -118,7 +114,7 @@ LL | fn cmse_call_ptr(f: extern "C-cmse-nonsecure-call" fn()) {
    = note: for more information, see issue #130260 <https://github.com/rust-lang/rust/issues/130260>
 
 warning: the calling convention "C-cmse-nonsecure-entry" is not supported on this target
-  --> $DIR/unsupported.rs:203:22
+  --> $DIR/unsupported.rs:193:22
    |
 LL | fn cmse_entry_ptr(f: extern "C-cmse-nonsecure-entry" fn()) {
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -127,7 +123,7 @@ LL | fn cmse_entry_ptr(f: extern "C-cmse-nonsecure-entry" fn()) {
    = note: for more information, see issue #130260 <https://github.com/rust-lang/rust/issues/130260>
 
 error[E0570]: `"C-cmse-nonsecure-entry"` is not a supported ABI for the current target
-  --> $DIR/unsupported.rs:208:1
+  --> $DIR/unsupported.rs:198:1
    |
 LL | extern "C-cmse-nonsecure-entry" {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -168,21 +164,18 @@ error[E0570]: `"thiscall"` is not a supported ABI for the current target
 LL | extern "thiscall" fn thiscall() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-warning: use of calling convention not supported on this target
+error[E0570]: `"stdcall"` is not a supported ABI for the current target
   --> $DIR/unsupported.rs:159:1
    |
 LL | extern "stdcall" fn stdcall() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #87678 <https://github.com/rust-lang/rust/issues/87678>
 
 error[E0570]: `"C-cmse-nonsecure-entry"` is not a supported ABI for the current target
-  --> $DIR/unsupported.rs:201:1
+  --> $DIR/unsupported.rs:191:1
    |
 LL | extern "C-cmse-nonsecure-entry" fn cmse_entry() {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 14 previous errors; 11 warnings emitted
+error: aborting due to 16 previous errors; 9 warnings emitted
 
 For more information about this error, try `rustc --explain E0570`.