Rollup of 9 pull requests

Cargo.lock

@@ -3786,6 +3786,7 @@ dependencies = [
  "rustc_middle",
  "rustc_session",
  "rustc_span",
+ "rustc_target",
  "rustc_trait_selection",
  "smallvec",
  "tracing",

compiler/rustc_abi/src/extern_abi.rs

@@ -12,66 +12,93 @@ use crate::AbiFromStrErr;
 #[cfg(test)]
 mod tests;
 
-use ExternAbi as Abi;
-
+/// ABI we expect to see within `extern "{abi}"`
 #[derive(Clone, Copy, Debug)]
 #[cfg_attr(feature = "nightly", derive(Encodable, Decodable))]
 pub enum ExternAbi {
-    // Some of the ABIs come first because every time we add a new ABI, we have to re-bless all the
-    // hashing tests. These are used in many places, so giving them stable values reduces test
-    // churn. The specific values are meaningless.
-    Rust,
+    /* universal */
+    /// presumed C ABI for the platform
     C {
         unwind: bool,
     },
-    Cdecl {
+    /// ABI of the "system" interface, e.g. the Win32 API, always "aliasing"
+    System {
         unwind: bool,
     },
-    Stdcall {
+
+    /// that's us!
+    Rust,
+    /// the mostly-unused `unboxed_closures` ABI, effectively now an impl detail unless someone
+    /// puts in the work to make it viable again... but would we need a special ABI?
+    RustCall,
+    /// For things unlikely to be called, where reducing register pressure in
+    /// `extern "Rust"` callers is worth paying extra cost in the callee.
+    /// Stronger than just `#[cold]` because `fn` pointers might be incompatible.
+    RustCold,
+
+    /// Unstable impl detail that directly uses Rust types to describe the ABI to LLVM.
+    /// Even normally-compatible Rust types can become ABI-incompatible with this ABI!
+    Unadjusted,
+
+    /// UEFI ABI, usually an alias of C, but sometimes an arch-specific alias
+    /// and only valid on platforms that have a UEFI standard
+    EfiApi,
+
+    /* arm */
+    /// Arm Architecture Procedure Call Standard, sometimes `ExternAbi::C` is an alias for this
+    Aapcs {
         unwind: bool,
     },
-    Fastcall {
+    /// extremely constrained barely-C ABI for TrustZone
+    CCmseNonSecureCall,
+    /// extremely constrained barely-C ABI for TrustZone
+    CCmseNonSecureEntry,
+
+    /* gpu */
+    /// An entry-point function called by the GPU's host
+    // FIXME: should not be callable from Rust on GPU targets, is for host's use only
+    GpuKernel,
+    /// An entry-point function called by the GPU's host
+    // FIXME: why do we have two of these?
+    PtxKernel,
+
+    /* interrupt */
+    AvrInterrupt,
+    AvrNonBlockingInterrupt,
+    Msp430Interrupt,
+    RiscvInterruptM,
+    RiscvInterruptS,
+    X86Interrupt,
+
+    /* x86 */
+    /// `ExternAbi::C` but spelled funny because x86
+    Cdecl {
         unwind: bool,
     },
-    Vectorcall {
+    /// gnu-stdcall on "unix" and win-stdcall on "windows"
+    Stdcall {
         unwind: bool,
     },
-    Thiscall {
+    /// gnu-fastcall on "unix" and win-fastcall on "windows"
+    Fastcall {
         unwind: bool,
     },
-    Aapcs {
+    /// windows C++ ABI
+    Thiscall {
         unwind: bool,
     },
-    Win64 {
+    /// uses AVX and stuff
+    Vectorcall {
         unwind: bool,
     },
+
+    /* x86_64 */
     SysV64 {
         unwind: bool,
     },
-    PtxKernel,
-    Msp430Interrupt,
-    X86Interrupt,
-    /// An entry-point function called by the GPU's host
-    // FIXME: should not be callable from Rust on GPU targets, is for host's use only
-    GpuKernel,
-    EfiApi,
-    AvrInterrupt,
-    AvrNonBlockingInterrupt,
-    CCmseNonSecureCall,
-    CCmseNonSecureEntry,
-    System {
+    Win64 {
         unwind: bool,
     },
-    RustCall,
-    /// *Not* a stable ABI, just directly use the Rust types to describe the ABI for LLVM. Even
-    /// normally ABI-compatible Rust types can become ABI-incompatible with this ABI!
-    Unadjusted,
-    /// For things unlikely to be called, where reducing register pressure in
-    /// `extern "Rust"` callers is worth paying extra cost in the callee.
-    /// Stronger than just `#[cold]` because `fn` pointers might be incompatible.
-    RustCold,
-    RiscvInterruptM,
-    RiscvInterruptS,
 }
 
 macro_rules! abi_impls {
@@ -224,7 +251,7 @@ pub fn all_names() -> Vec<&'static str> {
 
 impl ExternAbi {
     /// Default ABI chosen for `extern fn` declarations without an explicit ABI.
-    pub const FALLBACK: Abi = Abi::C { unwind: false };
+    pub const FALLBACK: ExternAbi = ExternAbi::C { unwind: false };
 
     pub fn name(self) -> &'static str {
         self.as_str()

compiler/rustc_errors/src/lib.rs

@@ -1529,7 +1529,7 @@ impl DiagCtxtInner {
             // Future breakages aren't emitted if they're `Level::Allow` or
             // `Level::Expect`, but they still need to be constructed and
             // stashed below, so they'll trigger the must_produce_diag check.
-            assert_matches!(diagnostic.level, Error | Warning | Allow | Expect);
+            assert_matches!(diagnostic.level, Error | ForceWarning | Warning | Allow | Expect);
             self.future_breakage_diagnostics.push(diagnostic.clone());
         }
 

compiler/rustc_hir_analysis/Cargo.toml

@@ -26,6 +26,7 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
+rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
 tracing = "0.1"

compiler/rustc_hir_analysis/src/check/check.rs

@@ -4,14 +4,15 @@ use std::ops::ControlFlow;
 use rustc_abi::FieldIdx;
 use rustc_attr_data_structures::ReprAttr::ReprPacked;
 use rustc_data_structures::unord::{UnordMap, UnordSet};
-use rustc_errors::MultiSpan;
 use rustc_errors::codes::*;
+use rustc_errors::{EmissionGuarantee, MultiSpan};
 use rustc_hir::def::{CtorKind, DefKind};
 use rustc_hir::{LangItem, Node, intravisit};
 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
 use rustc_infer::traits::{Obligation, ObligationCauseCode};
 use rustc_lint_defs::builtin::{
-    REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS, UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS,
+    REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS, UNSUPPORTED_CALLING_CONVENTIONS,
+    UNSUPPORTED_FN_PTR_CALLING_CONVENTIONS,
 };
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::resolve_bound_vars::ResolvedArg;
@@ -24,6 +25,7 @@ use rustc_middle::ty::{
     TypeVisitable, TypeVisitableExt, fold_regions,
 };
 use rustc_session::lint::builtin::UNINHABITED_STATIC;
+use rustc_target::spec::{AbiMap, AbiMapping};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::traits::on_unimplemented::OnUnimplementedDirective;
 use rustc_trait_selection::traits;
@@ -35,25 +37,56 @@ use {rustc_attr_data_structures as attrs, rustc_hir as hir};
 use super::compare_impl_item::check_type_bounds;
 use super::*;
 
-pub fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: ExternAbi) {
-    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(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: ExternAbi) {
+    // FIXME: this should be checked earlier, e.g. in `rustc_ast_lowering`, to fix
+    // things like #86232.
+    fn add_help<T: EmissionGuarantee>(abi: ExternAbi, diag: &mut Diag<'_, T>) {
+        if let ExternAbi::Cdecl { unwind } = abi {
+            let c_abi = ExternAbi::C { unwind };
+            diag.help(format!("use `extern {c_abi}` instead",));
+        } else if let ExternAbi::Stdcall { unwind } = abi {
+            let c_abi = ExternAbi::C { unwind };
+            let system_abi = ExternAbi::System { unwind };
+            diag.help(format!(
+                "if you need `extern {abi}` on win32 and `extern {c_abi}` everywhere else, \
+                use `extern {system_abi}`"
+            ));
+        }
+    }
+
+    match AbiMap::from_target(&tcx.sess.target).canonize_abi(abi, false) {
+        AbiMapping::Direct(..) => (),
+        AbiMapping::Invalid => {
+            let mut err = struct_span_code_err!(
+                tcx.dcx(),
+                span,
+                E0570,
+                "`{abi}` is not a supported ABI for the current target",
+            );
+            add_help(abi, &mut err);
+            err.emit();
+        }
+        AbiMapping::Deprecated(..) => {
+            tcx.node_span_lint(UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, |lint| {
+                lint.primary_message("use of calling convention not supported on this target");
+                add_help(abi, lint);
+            });
+        }
     }
 }
 
 pub fn check_abi_fn_ptr(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: ExternAbi) {
-    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"
-            ));
-        });
+    // This is always an FCW, even for `AbiMapping::Invalid`, since we started linting later than
+    // in `check_abi` above.
+    match AbiMap::from_target(&tcx.sess.target).canonize_abi(abi, false) {
+        AbiMapping::Direct(..) => (),
+        AbiMapping::Deprecated(..) | AbiMapping::Invalid => {
+            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"
+                ));
+            });
+        }
     }
 }
 
@@ -779,7 +812,7 @@ 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.span, abi);
+            check_abi(tcx, it.hir_id(), it.span, abi);
 
             for item in items {
                 let def_id = item.id.owner_id.def_id;

compiler/rustc_hir_typeck/src/lib.rs

@@ -150,7 +150,7 @@ fn typeck_with_inspect<'tcx>(
             tcx.fn_sig(def_id).instantiate_identity()
         };
 
-        check_abi(tcx, span, fn_sig.abi());
+        check_abi(tcx, id, span, fn_sig.abi());
 
         // Compute the function signature from point of view of inside the fn.
         let mut fn_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), fn_sig);

compiler/rustc_infer/src/infer/mod.rs

@@ -823,6 +823,13 @@ impl<'tcx> InferCtxt<'tcx> {
         ty::Region::new_var(self.tcx, region_var)
     }
 
+    pub fn next_term_var_of_kind(&self, term: ty::Term<'tcx>, span: Span) -> ty::Term<'tcx> {
+        match term.kind() {
+            ty::TermKind::Ty(_) => self.next_ty_var(span).into(),
+            ty::TermKind::Const(_) => self.next_const_var(span).into(),
+        }
+    }
+
     /// Return the universe that the region `r` was created in. For
     /// most regions (e.g., `'static`, named regions from the user,
     /// etc) this is the root universe U0. For inference variables or

compiler/rustc_lint/src/lib.rs

@@ -599,7 +599,6 @@ 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");
     store.register_removed(
         "cenum_impl_drop_cast",
         "converted into hard error, \

compiler/rustc_lint_defs/src/builtin.rs

@@ -3621,6 +3621,54 @@ declare_lint! {
     crate_level_only
 }
 
+declare_lint! {
+    /// The `unsupported_calling_conventions` lint is output whenever there is a use of the
+    /// `stdcall`, `fastcall`, and `cdecl` 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::FutureReleaseError,
+        report_in_deps: true,
+        reference: "issue #137018 <https://github.com/rust-lang/rust/issues/137018>",
+    };
+}
+
 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_metadata/messages.ftl

@@ -272,6 +272,9 @@ metadata_raw_dylib_no_nul =
 metadata_raw_dylib_only_windows =
     link kind `raw-dylib` is only supported on Windows targets
 
+metadata_raw_dylib_unsupported_abi =
+    ABI not supported by `#[link(kind = "raw-dylib")]` on this architecture
+
 metadata_renaming_no_link =
     renaming of the library `{$lib_name}` was specified, however this crate contains no `#[link(...)]` attributes referencing this library
 
@@ -319,12 +322,6 @@ metadata_unknown_link_modifier =
 
 metadata_unknown_target_modifier_unsafe_allowed = unknown target modifier `{$flag_name}`, requested by `-Cunsafe-allow-abi-mismatch={$flag_name}`
 
-metadata_unsupported_abi =
-    ABI not supported by `#[link(kind = "raw-dylib")]` on this architecture
-
-metadata_unsupported_abi_i686 =
-    ABI not supported by `#[link(kind = "raw-dylib")]` on i686
-
 metadata_wasm_c_abi =
     older versions of the `wasm-bindgen` crate are incompatible with current versions of Rust; please update to `wasm-bindgen` v0.2.88
 

compiler/rustc_metadata/src/errors.rs

@@ -300,15 +300,8 @@ pub struct NoLinkModOverride {
 }
 
 #[derive(Diagnostic)]
-#[diag(metadata_unsupported_abi_i686)]
-pub struct UnsupportedAbiI686 {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(metadata_unsupported_abi)]
-pub struct UnsupportedAbi {
+#[diag(metadata_raw_dylib_unsupported_abi)]
+pub struct RawDylibUnsupportedAbi {
     #[primary_span]
     pub span: Span,
 }