Auto merge of #141984 - matthiaskrgr:rollup-wy6j9ca, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang/rust#137725 (Add `iter` macro)
 - rust-lang/rust#141455 (std: abort the process on failure to allocate a TLS key)
 - rust-lang/rust#141569 (Replace ad-hoc ABI "adjustments" with an `AbiMap` to `CanonAbi`)
 - rust-lang/rust#141698 (Use the informative error as the main const eval error message)
 - rust-lang/rust#141925 (Remove bootstrap cfgs from library/)
 - rust-lang/rust#141943 (Remove pre-expansion AST stats.)
 - rust-lang/rust#141945 (Remove `Path::is_ident`.)
 - rust-lang/rust#141957 (Add missing `dyn` keywords to tests that do not test for them Part 2)

r? `@ghost`
`@rustbot` modify labels: rollup

40 files changed, 711 insertions, 579 deletions

diff --git a/compiler/rustc_abi/src/canon_abi.rs b/compiler/rustc_abi/src/canon_abi.rs
new file mode 100644
index 00000000000..2cf7648a859
--- /dev/null
+++ b/compiler/rustc_abi/src/canon_abi.rs
@@ -0,0 +1,136 @@
+use std::fmt;
+
+#[cfg(feature = "nightly")]
+use rustc_macros::HashStable_Generic;
+
+use crate::ExternAbi;
+
+/// Calling convention to determine codegen
+///
+/// CanonAbi erases certain distinctions ExternAbi preserves, but remains target-dependent.
+/// There are still both target-specific variants and aliasing variants, though much fewer.
+/// The reason for this step is the frontend may wish to show an ExternAbi but implement that ABI
+/// using a different ABI than the string per se, or describe irrelevant differences, e.g.
+/// - extern "system"
+/// - extern "cdecl"
+/// - extern "C-unwind"
+/// In that sense, this erases mere syntactic distinctions to create a canonical *directive*,
+/// rather than picking the "actual" ABI.
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum CanonAbi {
+    // NOTE: the use of nested variants for some ABIs is for many targets they don't matter,
+    // and this pushes the complexity of their reasoning to target-specific code,
+    // allowing a `match` to easily exhaustively ignore these subcategories of variants.
+    // Otherwise it is very tempting to avoid matching exhaustively!
+    C,
+    Rust,
+    RustCold,
+
+    /// ABIs relevant to 32-bit Arm targets
+    Arm(ArmCall),
+    /// ABI relevant to GPUs: the entry point for a GPU kernel
+    GpuKernel,
+
+    /// ABIs relevant to bare-metal interrupt targets
+    // FIXME(workingjubilee): a particular reason for this nesting is we might not need these?
+    // interrupt ABIs should have the same properties:
+    // - uncallable by Rust calls, as LLVM rejects it in most cases
+    // - uses a preserve-all-registers *callee* convention
+    // - should always return `-> !` (effectively... it can't use normal `ret`)
+    // what differs between targets is
+    // - allowed arguments: x86 differs slightly, having 2-3 arguments which are handled magically
+    // - may need special prologues/epilogues for some interrupts, without affecting "call ABI"
+    Interrupt(InterruptKind),
+
+    /// ABIs relevant to Windows or x86 targets
+    X86(X86Call),
+}
+
+impl fmt::Display for CanonAbi {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.to_erased_extern_abi().as_str().fmt(f)
+    }
+}
+
+impl CanonAbi {
+    /// convert to the ExternAbi that *shares a string* with this CanonAbi
+    ///
+    /// A target-insensitive mapping of CanonAbi to ExternAbi, convenient for "forwarding" impls.
+    /// Importantly, the set of CanonAbi values is a logical *subset* of ExternAbi values,
+    /// so this is injective: if you take an ExternAbi to a CanonAbi and back, you have lost data.
+    const fn to_erased_extern_abi(self) -> ExternAbi {
+        match self {
+            CanonAbi::C => ExternAbi::C { unwind: false },
+            CanonAbi::Rust => ExternAbi::Rust,
+            CanonAbi::RustCold => ExternAbi::RustCold,
+            CanonAbi::Arm(arm_call) => match arm_call {
+                ArmCall::Aapcs => ExternAbi::Aapcs { unwind: false },
+                ArmCall::CCmseNonSecureCall => ExternAbi::CCmseNonSecureCall,
+                ArmCall::CCmseNonSecureEntry => ExternAbi::CCmseNonSecureEntry,
+            },
+            CanonAbi::GpuKernel => ExternAbi::GpuKernel,
+            CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+                InterruptKind::Avr => ExternAbi::AvrInterrupt,
+                InterruptKind::AvrNonBlocking => ExternAbi::AvrNonBlockingInterrupt,
+                InterruptKind::Msp430 => ExternAbi::Msp430Interrupt,
+                InterruptKind::RiscvMachine => ExternAbi::RiscvInterruptM,
+                InterruptKind::RiscvSupervisor => ExternAbi::RiscvInterruptS,
+                InterruptKind::X86 => ExternAbi::X86Interrupt,
+            },
+            CanonAbi::X86(x86_call) => match x86_call {
+                X86Call::Fastcall => ExternAbi::Fastcall { unwind: false },
+                X86Call::Stdcall => ExternAbi::Stdcall { unwind: false },
+                X86Call::SysV64 => ExternAbi::SysV64 { unwind: false },
+                X86Call::Thiscall => ExternAbi::Thiscall { unwind: false },
+                X86Call::Vectorcall => ExternAbi::Vectorcall { unwind: false },
+                X86Call::Win64 => ExternAbi::Win64 { unwind: false },
+            },
+        }
+    }
+}
+
+/// Callee codegen for interrupts
+///
+/// This is named differently from the "Call" enums because it is different:
+/// these "ABI" differences are not relevant to callers, since there is "no caller".
+/// These only affect callee codegen. making their categorization as distinct ABIs a bit peculiar.
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum InterruptKind {
+    Avr,
+    AvrNonBlocking,
+    Msp430,
+    RiscvMachine,
+    RiscvSupervisor,
+    X86,
+}
+
+/// ABIs defined for x86-{32,64}
+///
+/// One of SysV64 or Win64 may alias the C ABI, and arguably Win64 is cross-platform now?
+#[derive(Clone, Copy, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum X86Call {
+    /// "fastcall" has both GNU and Windows variants
+    Fastcall,
+    /// "stdcall" has both GNU and Windows variants
+    Stdcall,
+    SysV64,
+    Thiscall,
+    Vectorcall,
+    Win64,
+}
+
+/// ABIs defined for 32-bit Arm
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum ArmCall {
+    Aapcs,
+    CCmseNonSecureCall,
+    CCmseNonSecureEntry,
+}
diff --git a/compiler/rustc_abi/src/extern_abi.rs b/compiler/rustc_abi/src/extern_abi.rs
index 55f4845d216..c48920e5f1b 100644
--- a/compiler/rustc_abi/src/extern_abi.rs
+++ b/compiler/rustc_abi/src/extern_abi.rs
@@ -7,6 +7,8 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableOrd};
 #[cfg(feature = "nightly")]
 use rustc_macros::{Decodable, Encodable};
 
+use crate::AbiFromStrErr;
+
 #[cfg(test)]
 mod tests;
 
@@ -99,11 +101,6 @@ macro_rules! abi_impls {
     }
 }
 
-#[derive(Debug)]
-pub enum AbiFromStrErr {
-    Unknown,
-}
-
 abi_impls! {
     ExternAbi = {
             C { unwind: false } =><= "C",
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index 59b74d29221..b806d0aba31 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -55,13 +55,14 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_Generic};
 
 mod callconv;
+mod canon_abi;
+mod extern_abi;
 mod layout;
 #[cfg(test)]
 mod tests;
 
-mod extern_abi;
-
 pub use callconv::{Heterogeneous, HomogeneousAggregate, Reg, RegKind};
+pub use canon_abi::{ArmCall, CanonAbi, InterruptKind, X86Call};
 pub use extern_abi::{ExternAbi, all_names};
 #[cfg(feature = "nightly")]
 pub use layout::{FIRST_VARIANT, FieldIdx, Layout, TyAbiInterface, TyAndLayout, VariantIdx};
@@ -1895,3 +1896,11 @@ pub enum StructKind {
     /// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
     Prefixed(Size, Align),
 }
+
+#[derive(Clone, Debug)]
+pub enum AbiFromStrErr {
+    /// not a known ABI
+    Unknown,
+    /// no "-unwind" variant can be used here
+    NoExplicitUnwind,
+}
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 5c122ff0bbc..c9a8adec31a 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -99,8 +99,15 @@ pub struct Path {
 
 impl PartialEq<Symbol> for Path {
     #[inline]
-    fn eq(&self, symbol: &Symbol) -> bool {
-        matches!(&self.segments[..], [segment] if segment.ident.name == *symbol)
+    fn eq(&self, name: &Symbol) -> bool {
+        if let [segment] = self.segments.as_ref()
+            && segment.args.is_none()
+            && segment.ident.name == *name
+        {
+            true
+        } else {
+            false
+        }
     }
 }
 
@@ -120,17 +127,6 @@ impl Path {
         Path { segments: thin_vec![PathSegment::from_ident(ident)], span: ident.span, tokens: None }
     }
 
-    pub fn is_ident(&self, name: Symbol) -> bool {
-        if let [segment] = self.segments.as_ref()
-            && segment.args.is_none()
-            && segment.ident.name == name
-        {
-            true
-        } else {
-            false
-        }
-    }
-
     pub fn is_global(&self) -> bool {
         self.segments.first().is_some_and(|segment| segment.ident.name == kw::PathRoot)
     }
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 9f3aed9216c..537d4a2a6af 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1,4 +1,3 @@
-use std::assert_matches::assert_matches;
 use std::ops::ControlFlow;
 use std::sync::Arc;
 
@@ -1199,11 +1198,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let closure_def_id = self.local_def_id(closure_id);
         let (binder_clause, generic_params) = self.lower_closure_binder(binder);
 
-        assert_matches!(
-            coroutine_kind,
-            CoroutineKind::Async { .. },
-            "only async closures are supported currently"
-        );
+        let coroutine_desugaring = match coroutine_kind {
+            CoroutineKind::Async { .. } => hir::CoroutineDesugaring::Async,
+            CoroutineKind::Gen { .. } => hir::CoroutineDesugaring::Gen,
+            CoroutineKind::AsyncGen { span, .. } => {
+                span_bug!(span, "only async closures and `iter!` closures are supported currently")
+            }
+        };
 
         let body = self.with_new_scopes(fn_decl_span, |this| {
             let inner_decl =
@@ -1247,7 +1248,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             // Lower this as a `CoroutineClosure`. That will ensure that HIR typeck
             // knows that a `FnDecl` output type like `-> &str` actually means
             // "coroutine that returns &str", rather than directly returning a `&str`.
-            kind: hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async),
+            kind: hir::ClosureKind::CoroutineClosure(coroutine_desugaring),
             constness: hir::Constness::NotConst,
         });
         hir::ExprKind::Closure(c)
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 915613a3913..3682d25d341 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -477,11 +477,12 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
         for span in spans {
             if (!visitor.features.coroutines() && !span.allows_unstable(sym::coroutines))
                 && (!visitor.features.gen_blocks() && !span.allows_unstable(sym::gen_blocks))
+                && (!visitor.features.yield_expr() && !span.allows_unstable(sym::yield_expr))
             {
                 #[allow(rustc::untranslatable_diagnostic)]
-                // Don't know which of the two features to include in the
-                // error message, so I am arbitrarily picking one.
-                feature_err(&visitor.sess, sym::coroutines, *span, "yield syntax is experimental")
+                // Emit yield_expr as the error, since that will be sufficient. You can think of it
+                // as coroutines and gen_blocks imply yield_expr.
+                feature_err(&visitor.sess, sym::yield_expr, *span, "yield syntax is experimental")
                     .emit();
             }
         }
diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index c6b29fe36fd..0c46e0c0c22 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -52,7 +52,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             assert_matches!(
                 self.tcx().coroutine_kind(self.tcx().coroutine_for_closure(mir_def_id)),
                 Some(hir::CoroutineKind::Desugared(
-                    hir::CoroutineDesugaring::Async,
+                    hir::CoroutineDesugaring::Async | hir::CoroutineDesugaring::Gen,
                     hir::CoroutineSource::Closure
                 )),
                 "this needs to be modified if we're lowering non-async closures"
diff --git a/compiler/rustc_builtin_macros/src/iter.rs b/compiler/rustc_builtin_macros/src/iter.rs
new file mode 100644
index 00000000000..7ad83903a1b
--- /dev/null
+++ b/compiler/rustc_builtin_macros/src/iter.rs
@@ -0,0 +1,53 @@
+use rustc_ast::ptr::P;
+use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::{CoroutineKind, DUMMY_NODE_ID, Expr, ast, token};
+use rustc_errors::PResult;
+use rustc_expand::base::{self, DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
+use rustc_span::Span;
+
+pub(crate) fn expand<'cx>(
+    cx: &'cx mut ExtCtxt<'_>,
+    sp: Span,
+    tts: TokenStream,
+) -> MacroExpanderResult<'cx> {
+    let closure = match parse_closure(cx, sp, tts) {
+        Ok(parsed) => parsed,
+        Err(err) => {
+            return ExpandResult::Ready(DummyResult::any(sp, err.emit()));
+        }
+    };
+
+    ExpandResult::Ready(base::MacEager::expr(closure))
+}
+
+fn parse_closure<'a>(
+    cx: &mut ExtCtxt<'a>,
+    span: Span,
+    stream: TokenStream,
+) -> PResult<'a, P<Expr>> {
+    let mut closure_parser = cx.new_parser_from_tts(stream);
+
+    let coroutine_kind = Some(CoroutineKind::Gen {
+        span,
+        closure_id: DUMMY_NODE_ID,
+        return_impl_trait_id: DUMMY_NODE_ID,
+    });
+
+    let mut closure = closure_parser.parse_expr()?;
+    match &mut closure.kind {
+        ast::ExprKind::Closure(c) => {
+            if let Some(kind) = c.coroutine_kind {
+                cx.dcx().span_err(kind.span(), "only plain closures allowed in `iter!`");
+            }
+            c.coroutine_kind = coroutine_kind;
+            if closure_parser.token != token::Eof {
+                closure_parser.unexpected()?;
+            }
+            Ok(closure)
+        }
+        _ => {
+            cx.dcx().span_err(closure.span, "`iter!` body must be a closure");
+            Err(closure_parser.unexpected().unwrap_err())
+        }
+    }
+}
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index 667d90429f2..aa52c3bd281 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -47,6 +47,7 @@ mod errors;
 mod format;
 mod format_foreign;
 mod global_allocator;
+mod iter;
 mod log_syntax;
 mod pattern_type;
 mod source_util;
@@ -95,6 +96,7 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         include: source_util::expand_include,
         include_bytes: source_util::expand_include_bytes,
         include_str: source_util::expand_include_str,
+        iter: iter::expand,
         line: source_util::expand_line,
         log_syntax: log_syntax::expand_log_syntax,
         module_path: source_util::expand_mod,
diff --git a/compiler/rustc_codegen_cranelift/src/abi/mod.rs b/compiler/rustc_codegen_cranelift/src/abi/mod.rs
index 5f7bf3821d7..fe5b220117f 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/mod.rs
@@ -10,7 +10,7 @@ use std::mem;
 use cranelift_codegen::ir::{ArgumentPurpose, SigRef};
 use cranelift_codegen::isa::CallConv;
 use cranelift_module::ModuleError;
-use rustc_abi::ExternAbi;
+use rustc_abi::{CanonAbi, ExternAbi, X86Call};
 use rustc_codegen_ssa::base::is_call_from_compiler_builtins_to_upstream_monomorphization;
 use rustc_codegen_ssa::errors::CompilerBuiltinsCannotCall;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
@@ -19,7 +19,7 @@ use rustc_middle::ty::layout::FnAbiOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_session::Session;
 use rustc_span::source_map::Spanned;
-use rustc_target::callconv::{Conv, FnAbi, PassMode};
+use rustc_target::callconv::{FnAbi, PassMode};
 use smallvec::SmallVec;
 
 use self::pass_mode::*;
@@ -42,32 +42,27 @@ fn clif_sig_from_fn_abi<'tcx>(
     Signature { params, returns, call_conv }
 }
 
-pub(crate) fn conv_to_call_conv(sess: &Session, c: Conv, default_call_conv: CallConv) -> CallConv {
+pub(crate) fn conv_to_call_conv(
+    sess: &Session,
+    c: CanonAbi,
+    default_call_conv: CallConv,
+) -> CallConv {
     match c {
-        Conv::Rust | Conv::C => default_call_conv,
-        Conv::Cold | Conv::PreserveMost | Conv::PreserveAll => CallConv::Cold,
-        Conv::X86_64SysV => CallConv::SystemV,
-        Conv::X86_64Win64 => CallConv::WindowsFastcall,
-
-        // Should already get a back compat warning
-        Conv::X86Fastcall | Conv::X86Stdcall | Conv::X86ThisCall | Conv::X86VectorCall => {
-            default_call_conv
-        }
-
-        Conv::X86Intr | Conv::RiscvInterrupt { .. } => {
-            sess.dcx().fatal(format!("interrupt call conv {c:?} not yet implemented"))
+        CanonAbi::Rust | CanonAbi::C => default_call_conv,
+        CanonAbi::RustCold => CallConv::Cold,
+
+        CanonAbi::X86(x86_call) => match x86_call {
+            X86Call::SysV64 => CallConv::SystemV,
+            X86Call::Win64 => CallConv::WindowsFastcall,
+            // Should already get a back compat warning
+            _ => default_call_conv,
+        },
+
+        CanonAbi::Interrupt(_) | CanonAbi::Arm(_) => {
+            sess.dcx().fatal("call conv {c:?} is not yet implemented")
         }
-
-        Conv::ArmAapcs => sess.dcx().fatal("aapcs call conv not yet implemented"),
-        Conv::CCmseNonSecureCall => {
-            sess.dcx().fatal("C-cmse-nonsecure-call call conv is not yet implemented");
-        }
-        Conv::CCmseNonSecureEntry => {
-            sess.dcx().fatal("C-cmse-nonsecure-entry call conv is not yet implemented");
-        }
-
-        Conv::Msp430Intr | Conv::GpuKernel | Conv::AvrInterrupt | Conv::AvrNonBlockingInterrupt => {
-            unreachable!("tried to use {c:?} call conv which only exists on an unsupported target");
+        CanonAbi::GpuKernel => {
+            unreachable!("tried to use {c:?} call conv which only exists on an unsupported target")
         }
     }
 }
@@ -610,7 +605,7 @@ pub(crate) fn codegen_terminator_call<'tcx>(
         target: CallTarget,
         call_args: &mut Vec<Value>,
     ) {
-        if fn_abi.conv != Conv::C {
+        if fn_abi.conv != CanonAbi::C {
             fx.tcx.dcx().span_fatal(
                 source_info.span,
                 format!("Variadic call for non-C abi {:?}", fn_abi.conv),
diff --git a/compiler/rustc_codegen_gcc/src/abi.rs b/compiler/rustc_codegen_gcc/src/abi.rs
index 0c499ba6237..3d0c258f576 100644
--- a/compiler/rustc_codegen_gcc/src/abi.rs
+++ b/compiler/rustc_codegen_gcc/src/abi.rs
@@ -1,7 +1,7 @@
 #[cfg(feature = "master")]
 use gccjit::FnAttribute;
 use gccjit::{ToLValue, ToRValue, Type};
-use rustc_abi::{Reg, RegKind};
+use rustc_abi::{ArmCall, CanonAbi, InterruptKind, Reg, RegKind, X86Call};
 use rustc_codegen_ssa::traits::{AbiBuilderMethods, BaseTypeCodegenMethods};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::bug;
@@ -10,8 +10,6 @@ use rustc_middle::ty::layout::LayoutOf;
 #[cfg(feature = "master")]
 use rustc_session::config;
 use rustc_target::callconv::{ArgAttributes, CastTarget, FnAbi, PassMode};
-#[cfg(feature = "master")]
-use rustc_target::callconv::{Conv, RiscvInterruptKind};
 
 use crate::builder::Builder;
 use crate::context::CodegenCx;
@@ -238,29 +236,16 @@ impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
 }
 
 #[cfg(feature = "master")]
-pub fn conv_to_fn_attribute<'gcc>(conv: Conv, arch: &str) -> Option<FnAttribute<'gcc>> {
+pub fn conv_to_fn_attribute<'gcc>(conv: CanonAbi, arch: &str) -> Option<FnAttribute<'gcc>> {
     let attribute = match conv {
-        Conv::C | Conv::Rust => return None,
-        Conv::CCmseNonSecureCall => {
-            if arch == "arm" {
-                FnAttribute::ArmCmseNonsecureCall
-            } else {
-                return None;
-            }
-        }
-        Conv::CCmseNonSecureEntry => {
-            if arch == "arm" {
-                FnAttribute::ArmCmseNonsecureEntry
-            } else {
-                return None;
-            }
-        }
-        Conv::Cold => FnAttribute::Cold,
-        // NOTE: the preserve attributes are not yet implemented in GCC:
-        // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110899
-        Conv::PreserveMost => return None,
-        Conv::PreserveAll => return None,
-        Conv::GpuKernel => {
+        CanonAbi::C | CanonAbi::Rust => return None,
+        CanonAbi::Arm(arm_call) => match arm_call {
+            ArmCall::CCmseNonSecureCall => FnAttribute::ArmCmseNonsecureCall,
+            ArmCall::CCmseNonSecureEntry => FnAttribute::ArmCmseNonsecureEntry,
+            ArmCall::Aapcs => FnAttribute::ArmPcs("aapcs"),
+        },
+        CanonAbi::RustCold => FnAttribute::Cold,
+        CanonAbi::GpuKernel => {
             if arch == "amdgpu" {
                 FnAttribute::GcnAmdGpuHsaKernel
             } else if arch == "nvptx64" {
@@ -270,26 +255,24 @@ pub fn conv_to_fn_attribute<'gcc>(conv: Conv, arch: &str) -> Option<FnAttribute<
             }
         }
         // TODO(antoyo): check if those AVR attributes are mapped correctly.
-        Conv::AvrInterrupt => FnAttribute::AvrSignal,
-        Conv::AvrNonBlockingInterrupt => FnAttribute::AvrInterrupt,
-        Conv::ArmAapcs => FnAttribute::ArmPcs("aapcs"),
-        Conv::Msp430Intr => FnAttribute::Msp430Interrupt,
-        Conv::RiscvInterrupt { kind } => {
-            let kind = match kind {
-                RiscvInterruptKind::Machine => "machine",
-                RiscvInterruptKind::Supervisor => "supervisor",
-            };
-            FnAttribute::RiscvInterrupt(kind)
-        }
-        Conv::X86Fastcall => FnAttribute::X86FastCall,
-        Conv::X86Intr => FnAttribute::X86Interrupt,
-        Conv::X86Stdcall => FnAttribute::X86Stdcall,
-        Conv::X86ThisCall => FnAttribute::X86ThisCall,
-        // NOTE: the vectorcall calling convention is not yet implemented in GCC:
-        // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89485
-        Conv::X86VectorCall => return None,
-        Conv::X86_64SysV => FnAttribute::X86SysvAbi,
-        Conv::X86_64Win64 => FnAttribute::X86MsAbi,
+        CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+            InterruptKind::Avr => FnAttribute::AvrSignal,
+            InterruptKind::AvrNonBlocking => FnAttribute::AvrInterrupt,
+            InterruptKind::Msp430 => FnAttribute::Msp430Interrupt,
+            InterruptKind::RiscvMachine => FnAttribute::RiscvInterrupt("machine"),
+            InterruptKind::RiscvSupervisor => FnAttribute::RiscvInterrupt("supervisor"),
+            InterruptKind::X86 => FnAttribute::X86Interrupt,
+        },
+        CanonAbi::X86(x86_call) => match x86_call {
+            X86Call::Fastcall => FnAttribute::X86FastCall,
+            X86Call::Stdcall => FnAttribute::X86Stdcall,
+            X86Call::Thiscall => FnAttribute::X86ThisCall,
+            // // NOTE: the vectorcall calling convention is not yet implemented in GCC:
+            // // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89485
+            X86Call::Vectorcall => return None,
+            X86Call::SysV64 => FnAttribute::X86SysvAbi,
+            X86Call::Win64 => FnAttribute::X86MsAbi,
+        },
     };
     Some(attribute)
 }
diff --git a/compiler/rustc_codegen_gcc/src/int.rs b/compiler/rustc_codegen_gcc/src/int.rs
index 9b5b0fde6e2..eb4acd8ade9 100644
--- a/compiler/rustc_codegen_gcc/src/int.rs
+++ b/compiler/rustc_codegen_gcc/src/int.rs
@@ -3,11 +3,11 @@
 //! 128-bit integers on 32-bit platforms and thus require to be handled manually.
 
 use gccjit::{BinaryOp, ComparisonOp, FunctionType, Location, RValue, ToRValue, Type, UnaryOp};
-use rustc_abi::{Endian, ExternAbi};
+use rustc_abi::{CanonAbi, Endian, ExternAbi};
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc_codegen_ssa::traits::{BackendTypes, BaseTypeCodegenMethods, BuilderMethods, OverflowOp};
 use rustc_middle::ty::{self, Ty};
-use rustc_target::callconv::{ArgAbi, ArgAttributes, Conv, FnAbi, PassMode};
+use rustc_target::callconv::{ArgAbi, ArgAttributes, FnAbi, PassMode};
 
 use crate::builder::{Builder, ToGccComp};
 use crate::common::{SignType, TypeReflection};
@@ -397,7 +397,7 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             ret: arg_abi,
             c_variadic: false,
             fixed_count: 3,
-            conv: Conv::C,
+            conv: CanonAbi::C,
             can_unwind: false,
         };
         fn_abi.adjust_for_foreign_abi(self.cx, ExternAbi::C { unwind: false });
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index c87e70864e5..119cd634f98 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -2,7 +2,10 @@ use std::borrow::Borrow;
 use std::cmp;
 
 use libc::c_uint;
-use rustc_abi::{BackendRepr, HasDataLayout, Primitive, Reg, RegKind, Size};
+use rustc_abi::{
+    ArmCall, BackendRepr, CanonAbi, HasDataLayout, InterruptKind, Primitive, Reg, RegKind, Size,
+    X86Call,
+};
 use rustc_codegen_ssa::MemFlags;
 use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
 use rustc_codegen_ssa::mir::place::{PlaceRef, PlaceValue};
@@ -12,7 +15,7 @@ use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::{bug, ty};
 use rustc_session::config;
 use rustc_target::callconv::{
-    ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, CastTarget, Conv, FnAbi, PassMode,
+    ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, CastTarget, FnAbi, PassMode,
 };
 use rustc_target::spec::SanitizerSet;
 use smallvec::SmallVec;
@@ -409,11 +412,17 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         if !self.can_unwind {
             func_attrs.push(llvm::AttributeKind::NoUnwind.create_attr(cx.llcx));
         }
-        if let Conv::RiscvInterrupt { kind } = self.conv {
-            func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", kind.as_str()));
-        }
-        if let Conv::CCmseNonSecureEntry = self.conv {
-            func_attrs.push(llvm::CreateAttrString(cx.llcx, "cmse_nonsecure_entry"))
+        match self.conv {
+            CanonAbi::Interrupt(InterruptKind::RiscvMachine) => {
+                func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", "machine"))
+            }
+            CanonAbi::Interrupt(InterruptKind::RiscvSupervisor) => {
+                func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", "supervisor"))
+            }
+            CanonAbi::Arm(ArmCall::CCmseNonSecureEntry) => {
+                func_attrs.push(llvm::CreateAttrString(cx.llcx, "cmse_nonsecure_entry"))
+            }
+            _ => (),
         }
         attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &{ func_attrs });
 
@@ -600,7 +609,7 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             llvm::SetInstructionCallConv(callsite, cconv);
         }
 
-        if self.conv == Conv::CCmseNonSecureCall {
+        if self.conv == CanonAbi::Arm(ArmCall::CCmseNonSecureCall) {
             // This will probably get ignored on all targets but those supporting the TrustZone-M
             // extension (thumbv8m targets).
             let cmse_nonsecure_call = llvm::CreateAttrString(bx.cx.llcx, "cmse_nonsecure_call");
@@ -636,17 +645,11 @@ impl AbiBuilderMethods for Builder<'_, '_, '_> {
 }
 
 impl llvm::CallConv {
-    pub(crate) fn from_conv(conv: Conv, arch: &str) -> Self {
+    pub(crate) fn from_conv(conv: CanonAbi, arch: &str) -> Self {
         match conv {
-            Conv::C
-            | Conv::Rust
-            | Conv::CCmseNonSecureCall
-            | Conv::CCmseNonSecureEntry
-            | Conv::RiscvInterrupt { .. } => llvm::CCallConv,
-            Conv::Cold => llvm::ColdCallConv,
-            Conv::PreserveMost => llvm::PreserveMost,
-            Conv::PreserveAll => llvm::PreserveAll,
-            Conv::GpuKernel => {
+            CanonAbi::C | CanonAbi::Rust => llvm::CCallConv,
+            CanonAbi::RustCold => llvm::PreserveMost,
+            CanonAbi::GpuKernel => {
                 if arch == "amdgpu" {
                     llvm::AmdgpuKernel
                 } else if arch == "nvptx64" {
@@ -655,17 +658,25 @@ impl llvm::CallConv {
                     panic!("Architecture {arch} does not support GpuKernel calling convention");
                 }
             }
-            Conv::AvrInterrupt => llvm::AvrInterrupt,
-            Conv::AvrNonBlockingInterrupt => llvm::AvrNonBlockingInterrupt,
-            Conv::ArmAapcs => llvm::ArmAapcsCallConv,
-            Conv::Msp430Intr => llvm::Msp430Intr,
-            Conv::X86Fastcall => llvm::X86FastcallCallConv,
-            Conv::X86Intr => llvm::X86_Intr,
-            Conv::X86Stdcall => llvm::X86StdcallCallConv,
-            Conv::X86ThisCall => llvm::X86_ThisCall,
-            Conv::X86VectorCall => llvm::X86_VectorCall,
-            Conv::X86_64SysV => llvm::X86_64_SysV,
-            Conv::X86_64Win64 => llvm::X86_64_Win64,
+            CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+                InterruptKind::Avr => llvm::AvrInterrupt,
+                InterruptKind::AvrNonBlocking => llvm::AvrNonBlockingInterrupt,
+                InterruptKind::Msp430 => llvm::Msp430Intr,
+                InterruptKind::RiscvMachine | InterruptKind::RiscvSupervisor => llvm::CCallConv,
+                InterruptKind::X86 => llvm::X86_Intr,
+            },
+            CanonAbi::Arm(arm_call) => match arm_call {
+                ArmCall::Aapcs => llvm::ArmAapcsCallConv,
+                ArmCall::CCmseNonSecureCall | ArmCall::CCmseNonSecureEntry => llvm::CCallConv,
+            },
+            CanonAbi::X86(x86_call) => match x86_call {
+                X86Call::Fastcall => llvm::X86FastcallCallConv,
+                X86Call::Stdcall => llvm::X86StdcallCallConv,
+                X86Call::SysV64 => llvm::X86_64_SysV,
+                X86Call::Thiscall => llvm::X86_ThisCall,
+                X86Call::Vectorcall => llvm::X86_VectorCall,
+                X86Call::Win64 => llvm::X86_64_Win64,
+            },
         }
     }
 }
diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index e26f999773d..92b9b6e132e 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -1,5 +1,6 @@
 use std::collections::hash_map::Entry::*;
 
+use rustc_abi::{CanonAbi, X86Call};
 use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, NO_ALLOC_SHIM_IS_UNSTABLE, global_fn_name};
 use rustc_data_structures::unord::UnordMap;
 use rustc_hir::def::DefKind;
@@ -14,7 +15,6 @@ use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, Instance, SymbolNam
 use rustc_middle::util::Providers;
 use rustc_session::config::{CrateType, OomStrategy};
 use rustc_symbol_mangling::mangle_internal_symbol;
-use rustc_target::callconv::Conv;
 use rustc_target::spec::{SanitizerSet, TlsModel};
 use tracing::debug;
 
@@ -652,7 +652,7 @@ pub(crate) fn symbol_name_for_instance_in_crate<'tcx>(
 fn calling_convention_for_symbol<'tcx>(
     tcx: TyCtxt<'tcx>,
     symbol: ExportedSymbol<'tcx>,
-) -> (Conv, &'tcx [rustc_target::callconv::ArgAbi<'tcx, Ty<'tcx>>]) {
+) -> (CanonAbi, &'tcx [rustc_target::callconv::ArgAbi<'tcx, Ty<'tcx>>]) {
     let instance = match symbol {
         ExportedSymbol::NonGeneric(def_id) | ExportedSymbol::Generic(def_id, _)
             if tcx.is_static(def_id) =>
@@ -683,7 +683,7 @@ fn calling_convention_for_symbol<'tcx>(
         })
         .map(|fnabi| (fnabi.conv, &fnabi.args[..]))
         // FIXME(workingjubilee): why don't we know the convention here?
-        .unwrap_or((Conv::Rust, &[]))
+        .unwrap_or((CanonAbi::Rust, &[]))
 }
 
 /// This is the symbol name of the given instance as seen by the linker.
@@ -717,14 +717,14 @@ pub(crate) fn linking_symbol_name_for_instance_in_crate<'tcx>(
         _ => return undecorated,
     };
 
-    let (conv, args) = calling_convention_for_symbol(tcx, symbol);
+    let (callconv, args) = calling_convention_for_symbol(tcx, symbol);
 
     // Decorate symbols with prefixes, suffixes and total number of bytes of arguments.
     // Reference: https://docs.microsoft.com/en-us/cpp/build/reference/decorated-names?view=msvc-170
-    let (prefix, suffix) = match conv {
-        Conv::X86Fastcall => ("@", "@"),
-        Conv::X86Stdcall => ("_", "@"),
-        Conv::X86VectorCall => ("", "@@"),
+    let (prefix, suffix) = match callconv {
+        CanonAbi::X86(X86Call::Fastcall) => ("@", "@"),
+        CanonAbi::X86(X86Call::Stdcall) => ("_", "@"),
+        CanonAbi::X86(X86Call::Vectorcall) => ("", "@@"),
         _ => {
             if let Some(prefix) = prefix {
                 undecorated.insert(0, prefix);
@@ -758,9 +758,9 @@ pub(crate) fn extend_exported_symbols<'tcx>(
     symbol: ExportedSymbol<'tcx>,
     instantiating_crate: CrateNum,
 ) {
-    let (conv, _) = calling_convention_for_symbol(tcx, symbol);
+    let (callconv, _) = calling_convention_for_symbol(tcx, symbol);
 
-    if conv != Conv::GpuKernel || tcx.sess.target.os != "amdhsa" {
+    if callconv != CanonAbi::GpuKernel || tcx.sess.target.os != "amdhsa" {
         return;
     }
 
diff --git a/compiler/rustc_const_eval/messages.ftl b/compiler/rustc_const_eval/messages.ftl
index 7d4afc9d3d9..5bce6fb7ab2 100644
--- a/compiler/rustc_const_eval/messages.ftl
+++ b/compiler/rustc_const_eval/messages.ftl
@@ -89,9 +89,9 @@ const_eval_dyn_call_not_a_method =
     `dyn` call trying to call something that is not a method
 
 const_eval_error = {$error_kind ->
-    [static] could not evaluate static initializer
-    [const] evaluation of constant value failed
-    [const_with_path] evaluation of `{$instance}` failed
+    [static] evaluation of static initializer failed here
+    [const] evaluation of constant value failed here
+    [const_with_path] evaluation of `{$instance}` failed here
     *[other] {""}
 }
 
@@ -118,7 +118,7 @@ const_eval_frame_note_inner = inside {$where_ ->
 const_eval_frame_note_last = the failure occurred here
 
 const_eval_incompatible_calling_conventions =
-    calling a function with calling convention {$callee_conv} using calling convention {$caller_conv}
+    calling a function with calling convention "{$callee_conv}" using calling convention "{$caller_conv}"
 
 const_eval_incompatible_return_types =
     calling a function with return type {$callee_ty} passing return place of type {$caller_ty}
diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index b67a3ce03a9..6167f8cd4b5 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -589,12 +589,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             Rvalue::Aggregate(kind, ..) => {
                 if let AggregateKind::Coroutine(def_id, ..) = kind.as_ref()
-                    && let Some(
-                        coroutine_kind @ hir::CoroutineKind::Desugared(
-                            hir::CoroutineDesugaring::Async,
-                            _,
-                        ),
-                    ) = self.tcx.coroutine_kind(def_id)
+                    && let Some(coroutine_kind) = self.tcx.coroutine_kind(def_id)
                 {
                     self.check_op(ops::Coroutine(coroutine_kind));
                 }
diff --git a/compiler/rustc_const_eval/src/check_consts/ops.rs b/compiler/rustc_const_eval/src/check_consts/ops.rs
index 177ba56b165..d701646719a 100644
--- a/compiler/rustc_const_eval/src/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/check_consts/ops.rs
@@ -486,24 +486,25 @@ impl<'tcx> NonConstOp<'tcx> for IntrinsicUnstable {
 pub(crate) struct Coroutine(pub hir::CoroutineKind);
 impl<'tcx> NonConstOp<'tcx> for Coroutine {
     fn status_in_item(&self, _: &ConstCx<'_, 'tcx>) -> Status {
-        if let hir::CoroutineKind::Desugared(
-            hir::CoroutineDesugaring::Async,
-            hir::CoroutineSource::Block,
-        ) = self.0
-        {
-            Status::Unstable {
+        match self.0 {
+            hir::CoroutineKind::Desugared(
+                hir::CoroutineDesugaring::Async,
+                hir::CoroutineSource::Block,
+            )
+            // FIXME(coroutines): eventually we want to gate const coroutine coroutines behind a
+            // different feature.
+            | hir::CoroutineKind::Coroutine(_) => Status::Unstable {
                 gate: sym::const_async_blocks,
                 gate_already_checked: false,
                 safe_to_expose_on_stable: false,
                 is_function_call: false,
-            }
-        } else {
-            Status::Forbidden
+            },
+            _ => Status::Forbidden,
         }
     }
 
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        let msg = format!("{:#}s are not allowed in {}s", self.0, ccx.const_kind());
+        let msg = format!("{} are not allowed in {}s", self.0.to_plural_string(), ccx.const_kind());
         if let Status::Unstable { gate, .. } = self.status_in_item(ccx) {
             ccx.tcx.sess.create_feature_err(errors::UnallowedOpInConstContext { span, msg }, gate)
         } else {
diff --git a/compiler/rustc_const_eval/src/const_eval/error.rs b/compiler/rustc_const_eval/src/const_eval/error.rs
index ffb32fa41eb..08fc03d9c46 100644
--- a/compiler/rustc_const_eval/src/const_eval/error.rs
+++ b/compiler/rustc_const_eval/src/const_eval/error.rs
@@ -1,6 +1,6 @@
 use std::mem;
 
-use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, Diagnostic, IntoDiagArg};
+use rustc_errors::{Diag, DiagArgName, DiagArgValue, DiagMessage, IntoDiagArg};
 use rustc_middle::mir::AssertKind;
 use rustc_middle::mir::interpret::{Provenance, ReportedErrorInfo};
 use rustc_middle::query::TyCtxtAt;
@@ -131,10 +131,10 @@ pub fn get_span_and_frames<'tcx>(
 
 /// Create a diagnostic for a const eval error.
 ///
-/// This will use the `mk` function for creating the error which will get passed labels according to
-/// the `InterpError` and the span and a stacktrace of current execution according to
-/// `get_span_and_frames`.
-pub(super) fn report<'tcx, C, F, E>(
+/// This will use the `mk` function for adding more information to the error.
+/// You can use it to add a stacktrace of current execution according to
+/// `get_span_and_frames` or just give context on where the const eval error happened.
+pub(super) fn report<'tcx, C, F>(
     tcx: TyCtxt<'tcx>,
     error: InterpErrorKind<'tcx>,
     span: Span,
@@ -143,8 +143,7 @@ pub(super) fn report<'tcx, C, F, E>(
 ) -> ErrorHandled
 where
     C: FnOnce() -> (Span, Vec<FrameNote>),
-    F: FnOnce(Span, Vec<FrameNote>) -> E,
-    E: Diagnostic<'tcx>,
+    F: FnOnce(&mut Diag<'_>, Span, Vec<FrameNote>),
 {
     // Special handling for certain errors
     match error {
@@ -163,8 +162,7 @@ where
         _ => {
             let (our_span, frames) = get_span_and_frames();
             let span = span.substitute_dummy(our_span);
-            let err = mk(span, frames);
-            let mut err = tcx.dcx().create_err(err);
+            let mut err = tcx.dcx().struct_span_err(our_span, error.diagnostic_message());
             // We allow invalid programs in infallible promoteds since invalid layouts can occur
             // anyway (e.g. due to size overflow). And we allow OOM as that can happen any time.
             let allowed_in_infallible = matches!(
@@ -172,11 +170,9 @@ where
                 InterpErrorKind::ResourceExhaustion(_) | InterpErrorKind::InvalidProgram(_)
             );
 
-            let msg = error.diagnostic_message();
             error.add_args(&mut err);
 
-            // Use *our* span to label the interp error
-            err.span_label(our_span, msg);
+            mk(&mut err, span, frames);
             let g = err.emit();
             let reported = if allowed_in_infallible {
                 ReportedErrorInfo::allowed_in_infallible(g)
diff --git a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
index a79ba6a6342..01625b91353 100644
--- a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
@@ -2,6 +2,7 @@ use std::sync::atomic::Ordering::Relaxed;
 
 use either::{Left, Right};
 use rustc_abi::{self as abi, BackendRepr};
+use rustc_errors::E0080;
 use rustc_hir::def::DefKind;
 use rustc_middle::mir::interpret::{AllocId, ErrorHandled, InterpErrorInfo, ReportedErrorInfo};
 use rustc_middle::mir::{self, ConstAlloc, ConstValue};
@@ -290,12 +291,18 @@ pub fn eval_to_const_value_raw_provider<'tcx>(
             |error| {
                 let span = tcx.def_span(def_id);
 
+                // FIXME(oli-obk): why don't we have any tests for this code path?
                 super::report(
                     tcx,
                     error.into_kind(),
                     span,
                     || (span, vec![]),
-                    |span, _| errors::NullaryIntrinsicError { span },
+                    |diag, span, _| {
+                        diag.span_label(
+                            span,
+                            crate::fluent_generated::const_eval_nullary_intrinsic_fail,
+                        );
+                    },
                 )
             },
         );
@@ -443,11 +450,15 @@ fn report_eval_error<'tcx>(
         error,
         DUMMY_SP,
         || super::get_span_and_frames(ecx.tcx, ecx.stack()),
-        |span, frames| errors::ConstEvalError {
-            span,
-            error_kind: kind,
-            instance,
-            frame_notes: frames,
+        |diag, span, frames| {
+            // FIXME(oli-obk): figure out how to use structured diagnostics again.
+            diag.code(E0080);
+            diag.span_label(span, crate::fluent_generated::const_eval_error);
+            diag.arg("instance", instance);
+            diag.arg("error_kind", kind);
+            for frame in frames {
+                diag.subdiagnostic(frame);
+            }
         },
     )
 }
@@ -477,6 +488,15 @@ fn report_validation_error<'tcx>(
         error,
         DUMMY_SP,
         || crate::const_eval::get_span_and_frames(ecx.tcx, ecx.stack()),
-        move |span, frames| errors::ValidationFailure { span, ub_note: (), frames, raw_bytes },
+        move |diag, span, frames| {
+            // FIXME(oli-obk): figure out how to use structured diagnostics again.
+            diag.code(E0080);
+            diag.span_label(span, crate::fluent_generated::const_eval_validation_failure);
+            diag.note(crate::fluent_generated::const_eval_validation_failure_note);
+            for frame in frames {
+                diag.subdiagnostic(frame);
+            }
+            diag.subdiagnostic(raw_bytes);
+        },
     )
 }
diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index 7c35e47bbf8..037cbf777e7 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -439,38 +439,6 @@ pub struct LiveDrop<'tcx> {
     pub dropped_at: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(const_eval_error, code = E0080)]
-pub struct ConstEvalError {
-    #[primary_span]
-    pub span: Span,
-    /// One of "const", "const_with_path", and "static"
-    pub error_kind: &'static str,
-    pub instance: String,
-    #[subdiagnostic]
-    pub frame_notes: Vec<FrameNote>,
-}
-
-#[derive(Diagnostic)]
-#[diag(const_eval_nullary_intrinsic_fail)]
-pub struct NullaryIntrinsicError {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(const_eval_validation_failure, code = E0080)]
-pub struct ValidationFailure {
-    #[primary_span]
-    pub span: Span,
-    #[note(const_eval_validation_failure_note)]
-    pub ub_note: (),
-    #[subdiagnostic]
-    pub frames: Vec<FrameNote>,
-    #[subdiagnostic]
-    pub raw_bytes: RawBytesNote,
-}
-
 pub trait ReportErrorExt {
     /// Returns the diagnostic message for this error.
     fn diagnostic_message(&self) -> DiagMessage;
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 4f05e1c816c..433d5f98829 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -2061,12 +2061,19 @@ impl CoroutineKind {
             CoroutineKind::Coroutine(mov) => mov,
         }
     }
-}
 
-impl CoroutineKind {
     pub fn is_fn_like(self) -> bool {
         matches!(self, CoroutineKind::Desugared(_, CoroutineSource::Fn))
     }
+
+    pub fn to_plural_string(&self) -> String {
+        match self {
+            CoroutineKind::Desugared(d, CoroutineSource::Fn) => format!("{d:#}fn bodies"),
+            CoroutineKind::Desugared(d, CoroutineSource::Block) => format!("{d:#}blocks"),
+            CoroutineKind::Desugared(d, CoroutineSource::Closure) => format!("{d:#}closure bodies"),
+            CoroutineKind::Coroutine(_) => "coroutines".to_string(),
+        }
+    }
 }
 
 impl fmt::Display for CoroutineKind {
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index b1cb3ef4d79..cd3746be1d1 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -204,14 +204,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 )
             }
             hir::ClosureKind::CoroutineClosure(kind) => {
-                // async closures always return the type ascribed after the `->` (if present),
-                // and yield `()`.
                 let (bound_return_ty, bound_yield_ty) = match kind {
+                    hir::CoroutineDesugaring::Gen => {
+                        // `iter!` closures always return unit and yield the `Iterator::Item` type
+                        // that we have to infer.
+                        (tcx.types.unit, self.infcx.next_ty_var(expr_span))
+                    }
                     hir::CoroutineDesugaring::Async => {
+                        // async closures always return the type ascribed after the `->` (if present),
+                        // and yield `()`.
                         (bound_sig.skip_binder().output(), tcx.types.unit)
                     }
-                    hir::CoroutineDesugaring::Gen | hir::CoroutineDesugaring::AsyncGen => {
-                        todo!("`gen` and `async gen` closures not supported yet")
+                    hir::CoroutineDesugaring::AsyncGen => {
+                        todo!("`async gen` closures not supported yet")
                     }
                 };
                 // Compute all of the variables that will be used to populate the coroutine.
@@ -465,7 +470,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             if let Some(trait_def_id) = trait_def_id {
                 let found_kind = match closure_kind {
-                    hir::ClosureKind::Closure => self.tcx.fn_trait_kind_from_def_id(trait_def_id),
+                    hir::ClosureKind::Closure
+                    // FIXME(iter_macro): Someday we'll probably want iterator closures instead of
+                    // just using Fn* for iterators.
+                    | hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Gen) => {
+                        self.tcx.fn_trait_kind_from_def_id(trait_def_id)
+                    }
                     hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async) => self
                         .tcx
                         .async_fn_trait_kind_from_def_id(trait_def_id)
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 5bc7559d29a..f4045eeea4d 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -60,10 +60,6 @@ pub fn parse<'a>(sess: &'a Session) -> ast::Crate {
             guar.raise_fatal();
         });
 
-    if sess.opts.unstable_opts.input_stats {
-        input_stats::print_ast_stats(&krate, "PRE EXPANSION AST STATS", "ast-stats-1");
-    }
-
     rustc_builtin_macros::cmdline_attrs::inject(
         &mut krate,
         &sess.psess,
@@ -298,7 +294,7 @@ fn early_lint_checks(tcx: TyCtxt<'_>, (): ()) {
     let mut lint_buffer = resolver.lint_buffer.steal();
 
     if sess.opts.unstable_opts.input_stats {
-        input_stats::print_ast_stats(krate, "POST EXPANSION AST STATS", "ast-stats-2");
+        input_stats::print_ast_stats(krate, "POST EXPANSION AST STATS", "ast-stats");
     }
 
     // Needs to go *after* expansion to be able to check the results of macro expansion.
diff --git a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
index cfeaee07776..5478e54a606 100644
--- a/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
+++ b/compiler/rustc_monomorphize/src/mono_checks/abi_check.rs
@@ -1,6 +1,6 @@
 //! This module ensures that if a function's ABI requires a particular target feature,
 //! that target feature is enabled both on the callee and all callers.
-use rustc_abi::{BackendRepr, RegKind};
+use rustc_abi::{BackendRepr, CanonAbi, RegKind, X86Call};
 use rustc_hir::{CRATE_HIR_ID, HirId};
 use rustc_middle::mir::{self, Location, traversal};
 use rustc_middle::ty::layout::LayoutCx;
@@ -8,7 +8,7 @@ use rustc_middle::ty::{self, Instance, InstanceKind, Ty, TyCtxt, TypingEnv};
 use rustc_session::lint::builtin::WASM_C_ABI;
 use rustc_span::def_id::DefId;
 use rustc_span::{DUMMY_SP, Span, Symbol, sym};
-use rustc_target::callconv::{ArgAbi, Conv, FnAbi, PassMode};
+use rustc_target::callconv::{ArgAbi, FnAbi, PassMode};
 use rustc_target::spec::{HasWasmCAbiOpt, WasmCAbi};
 
 use crate::errors;
@@ -72,7 +72,7 @@ fn do_check_simd_vector_abi<'tcx>(
         }
     }
     // The `vectorcall` ABI is special in that it requires SSE2 no matter which types are being passed.
-    if abi.conv == Conv::X86VectorCall && !have_feature(sym::sse2) {
+    if abi.conv == CanonAbi::X86(X86Call::Vectorcall) && !have_feature(sym::sse2) {
         let (span, _hir_id) = loc();
         tcx.dcx().emit_err(errors::AbiRequiredTargetFeature {
             span,
@@ -128,7 +128,7 @@ fn do_check_wasm_abi<'tcx>(
     if !(tcx.sess.target.arch == "wasm32"
         && tcx.sess.target.os == "unknown"
         && tcx.wasm_c_abi_opt() == WasmCAbi::Legacy { with_lint: true }
-        && abi.conv == Conv::C)
+        && abi.conv == CanonAbi::C)
     {
         return;
     }
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 1a44f4af8a6..adfea3641e6 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -834,7 +834,7 @@ impl<'a> Parser<'a> {
         // guides recovery in case we write `&raw expr`.
         if borrow_kind == ast::BorrowKind::Ref
             && mutbl == ast::Mutability::Not
-            && matches!(&expr.kind, ExprKind::Path(None, p) if p.is_ident(kw::Raw))
+            && matches!(&expr.kind, ExprKind::Path(None, p) if *p == kw::Raw)
         {
             self.expected_token_types.insert(TokenType::KwMut);
             self.expected_token_types.insert(TokenType::KwConst);
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index ccc3410674b..c37cb0881c3 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -713,7 +713,7 @@ impl<'a> Parser<'a> {
 
     /// Parses the rest of a block expression or function body.
     /// Precondition: already parsed the '{'.
-    pub(crate) fn parse_block_tail(
+    pub fn parse_block_tail(
         &mut self,
         lo: Span,
         s: BlockCheckMode,
diff --git a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/mod.rs b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/mod.rs
index 562e288afaa..82e18ad497b 100644
--- a/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/mod.rs
+++ b/compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/mod.rs
@@ -4,10 +4,11 @@
 //! For more information about LLVM CFI and cross-language LLVM CFI support for the Rust compiler,
 //! see design document in the tracking issue #89653.
 
+use rustc_abi::CanonAbi;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::bug;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
-use rustc_target::callconv::{Conv, FnAbi, PassMode};
+use rustc_target::callconv::{FnAbi, PassMode};
 use tracing::instrument;
 
 mod encode;
@@ -45,7 +46,7 @@ pub fn typeid_for_fnabi<'tcx>(
     let mut encode_ty_options = EncodeTyOptions::from_bits(options.bits())
         .unwrap_or_else(|| bug!("typeid_for_fnabi: invalid option(s) `{:?}`", options.bits()));
     match fn_abi.conv {
-        Conv::C => {
+        CanonAbi::C => {
             encode_ty_options.insert(EncodeTyOptions::GENERALIZE_REPR_C);
         }
         _ => {
diff --git a/compiler/rustc_smir/src/rustc_smir/convert/abi.rs b/compiler/rustc_smir/src/rustc_smir/convert/abi.rs
index 7ccc785a400..06dfaf079a3 100644
--- a/compiler/rustc_smir/src/rustc_smir/convert/abi.rs
+++ b/compiler/rustc_smir/src/rustc_smir/convert/abi.rs
@@ -2,8 +2,9 @@
 
 #![allow(rustc::usage_of_qualified_ty)]
 
+use rustc_abi::{ArmCall, CanonAbi, InterruptKind, X86Call};
 use rustc_middle::ty;
-use rustc_target::callconv::{self, Conv};
+use rustc_target::callconv;
 use stable_mir::abi::{
     AddressSpace, ArgAbi, CallConvention, FieldsShape, FloatLength, FnAbi, IntegerLength, Layout,
     LayoutShape, PassMode, Primitive, Scalar, TagEncoding, TyAndLayout, ValueAbi, VariantsShape,
@@ -69,7 +70,7 @@ impl<'tcx> Stable<'tcx> for callconv::FnAbi<'tcx, ty::Ty<'tcx>> {
 
     fn stable(&self, tables: &mut Tables<'_>) -> Self::T {
         assert!(self.args.len() >= self.fixed_count as usize);
-        assert!(!self.c_variadic || matches!(self.conv, Conv::C));
+        assert!(!self.c_variadic || matches!(self.conv, CanonAbi::C));
         FnAbi {
             args: self.args.as_ref().stable(tables),
             ret: self.ret.stable(tables),
@@ -92,31 +93,37 @@ impl<'tcx> Stable<'tcx> for callconv::ArgAbi<'tcx, ty::Ty<'tcx>> {
     }
 }
 
-impl<'tcx> Stable<'tcx> for callconv::Conv {
+impl<'tcx> Stable<'tcx> for CanonAbi {
     type T = CallConvention;
 
     fn stable(&self, _tables: &mut Tables<'_>) -> Self::T {
         match self {
-            Conv::C => CallConvention::C,
-            Conv::Rust => CallConvention::Rust,
-            Conv::Cold => CallConvention::Cold,
-            Conv::PreserveMost => CallConvention::PreserveMost,
-            Conv::PreserveAll => CallConvention::PreserveAll,
-            Conv::ArmAapcs => CallConvention::ArmAapcs,
-            Conv::CCmseNonSecureCall => CallConvention::CCmseNonSecureCall,
-            Conv::CCmseNonSecureEntry => CallConvention::CCmseNonSecureEntry,
-            Conv::Msp430Intr => CallConvention::Msp430Intr,
-            Conv::X86Fastcall => CallConvention::X86Fastcall,
-            Conv::X86Intr => CallConvention::X86Intr,
-            Conv::X86Stdcall => CallConvention::X86Stdcall,
-            Conv::X86ThisCall => CallConvention::X86ThisCall,
-            Conv::X86VectorCall => CallConvention::X86VectorCall,
-            Conv::X86_64SysV => CallConvention::X86_64SysV,
-            Conv::X86_64Win64 => CallConvention::X86_64Win64,
-            Conv::GpuKernel => CallConvention::GpuKernel,
-            Conv::AvrInterrupt => CallConvention::AvrInterrupt,
-            Conv::AvrNonBlockingInterrupt => CallConvention::AvrNonBlockingInterrupt,
-            Conv::RiscvInterrupt { .. } => CallConvention::RiscvInterrupt,
+            CanonAbi::C => CallConvention::C,
+            CanonAbi::Rust => CallConvention::Rust,
+            CanonAbi::RustCold => CallConvention::Cold,
+            CanonAbi::Arm(arm_call) => match arm_call {
+                ArmCall::Aapcs => CallConvention::ArmAapcs,
+                ArmCall::CCmseNonSecureCall => CallConvention::CCmseNonSecureCall,
+                ArmCall::CCmseNonSecureEntry => CallConvention::CCmseNonSecureEntry,
+            },
+            CanonAbi::GpuKernel => CallConvention::GpuKernel,
+            CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+                InterruptKind::Avr => CallConvention::AvrInterrupt,
+                InterruptKind::AvrNonBlocking => CallConvention::AvrNonBlockingInterrupt,
+                InterruptKind::Msp430 => CallConvention::Msp430Intr,
+                InterruptKind::RiscvMachine | InterruptKind::RiscvSupervisor => {
+                    CallConvention::RiscvInterrupt
+                }
+                InterruptKind::X86 => CallConvention::X86Intr,
+            },
+            CanonAbi::X86(x86_call) => match x86_call {
+                X86Call::Fastcall => CallConvention::X86Fastcall,
+                X86Call::Stdcall => CallConvention::X86Stdcall,
+                X86Call::SysV64 => CallConvention::X86_64SysV,
+                X86Call::Thiscall => CallConvention::X86ThisCall,
+                X86Call::Vectorcall => CallConvention::X86VectorCall,
+                X86Call::Win64 => CallConvention::X86_64Win64,
+            },
         }
     }
 }
diff --git a/compiler/rustc_target/src/callconv/arm.rs b/compiler/rustc_target/src/callconv/arm.rs
index 0a5dcc66347..70830fa07b6 100644
--- a/compiler/rustc_target/src/callconv/arm.rs
+++ b/compiler/rustc_target/src/callconv/arm.rs
@@ -1,6 +1,6 @@
-use rustc_abi::{HasDataLayout, TyAbiInterface};
+use rustc_abi::{ArmCall, CanonAbi, HasDataLayout, TyAbiInterface};
 
-use crate::callconv::{ArgAbi, Conv, FnAbi, Reg, RegKind, Uniform};
+use crate::callconv::{ArgAbi, FnAbi, Reg, RegKind, Uniform};
 use crate::spec::HasTargetSpec;
 
 fn is_homogeneous_aggregate<'a, Ty, C>(cx: &C, arg: &mut ArgAbi<'a, Ty>) -> Option<Uniform>
@@ -90,7 +90,7 @@ where
     // If this is a target with a hard-float ABI, and the function is not explicitly
     // `extern "aapcs"`, then we must use the VFP registers for homogeneous aggregates.
     let vfp = cx.target_spec().llvm_target.ends_with("hf")
-        && fn_abi.conv != Conv::ArmAapcs
+        && fn_abi.conv != CanonAbi::Arm(ArmCall::Aapcs)
         && !fn_abi.c_variadic;
 
     if !fn_abi.ret.is_ignore() {
diff --git a/compiler/rustc_target/src/callconv/mod.rs b/compiler/rustc_target/src/callconv/mod.rs
index 907614520a2..d2e49cea647 100644
--- a/compiler/rustc_target/src/callconv/mod.rs
+++ b/compiler/rustc_target/src/callconv/mod.rs
@@ -1,13 +1,12 @@
-use std::fmt::Display;
-use std::str::FromStr;
 use std::{fmt, iter};
 
 use rustc_abi::{
-    AddressSpace, Align, BackendRepr, ExternAbi, HasDataLayout, Primitive, Reg, RegKind, Scalar,
-    Size, TyAbiInterface, TyAndLayout,
+    AddressSpace, Align, BackendRepr, CanonAbi, ExternAbi, HasDataLayout, Primitive, Reg, RegKind,
+    Scalar, Size, TyAbiInterface, TyAndLayout,
 };
 use rustc_macros::HashStable_Generic;
 
+pub use crate::spec::AbiMap;
 use crate::spec::{HasTargetSpec, HasWasmCAbiOpt, HasX86AbiOpt, RustcAbi, WasmCAbi};
 
 mod aarch64;
@@ -530,41 +529,6 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
-pub enum Conv {
-    // General language calling conventions, for which every target
-    // should have its own backend (e.g. LLVM) support.
-    C,
-    Rust,
-
-    Cold,
-    PreserveMost,
-    PreserveAll,
-
-    // Target-specific calling conventions.
-    ArmAapcs,
-    CCmseNonSecureCall,
-    CCmseNonSecureEntry,
-
-    Msp430Intr,
-
-    GpuKernel,
-
-    X86Fastcall,
-    X86Intr,
-    X86Stdcall,
-    X86ThisCall,
-    X86VectorCall,
-
-    X86_64SysV,
-    X86_64Win64,
-
-    AvrInterrupt,
-    AvrNonBlockingInterrupt,
-
-    RiscvInterrupt { kind: RiscvInterruptKind },
-}
-
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
 pub enum RiscvInterruptKind {
     Machine,
     Supervisor,
@@ -605,7 +569,7 @@ pub struct FnAbi<'a, Ty> {
     /// This can be used to know whether an argument is variadic or not.
     pub fixed_count: u32,
     /// The calling convention of this function.
-    pub conv: Conv,
+    pub conv: CanonAbi,
     /// Indicates if an unwind may happen across a call to this function.
     pub can_unwind: bool,
 }
@@ -696,7 +660,6 @@ impl<'a, Ty> FnAbi<'a, Ty> {
             "sparc" => sparc::compute_abi_info(cx, self),
             "sparc64" => sparc64::compute_abi_info(cx, self),
             "nvptx64" => {
-                let abi = cx.target_spec().adjust_abi(abi, self.c_variadic);
                 if abi == ExternAbi::PtxKernel || abi == ExternAbi::GpuKernel {
                     nvptx64::compute_ptx_kernel_abi_info(cx, self)
                 } else {
@@ -863,70 +826,6 @@ impl<'a, Ty> FnAbi<'a, Ty> {
     }
 }
 
-impl FromStr for Conv {
-    type Err = String;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        match s {
-            "C" => Ok(Conv::C),
-            "Rust" => Ok(Conv::Rust),
-            "RustCold" => Ok(Conv::Rust),
-            "ArmAapcs" => Ok(Conv::ArmAapcs),
-            "CCmseNonSecureCall" => Ok(Conv::CCmseNonSecureCall),
-            "CCmseNonSecureEntry" => Ok(Conv::CCmseNonSecureEntry),
-            "Msp430Intr" => Ok(Conv::Msp430Intr),
-            "X86Fastcall" => Ok(Conv::X86Fastcall),
-            "X86Intr" => Ok(Conv::X86Intr),
-            "X86Stdcall" => Ok(Conv::X86Stdcall),
-            "X86ThisCall" => Ok(Conv::X86ThisCall),
-            "X86VectorCall" => Ok(Conv::X86VectorCall),
-            "X86_64SysV" => Ok(Conv::X86_64SysV),
-            "X86_64Win64" => Ok(Conv::X86_64Win64),
-            "GpuKernel" => Ok(Conv::GpuKernel),
-            "AvrInterrupt" => Ok(Conv::AvrInterrupt),
-            "AvrNonBlockingInterrupt" => Ok(Conv::AvrNonBlockingInterrupt),
-            "RiscvInterrupt(machine)" => {
-                Ok(Conv::RiscvInterrupt { kind: RiscvInterruptKind::Machine })
-            }
-            "RiscvInterrupt(supervisor)" => {
-                Ok(Conv::RiscvInterrupt { kind: RiscvInterruptKind::Supervisor })
-            }
-            _ => Err(format!("'{s}' is not a valid value for entry function call convention.")),
-        }
-    }
-}
-
-fn conv_to_externabi(conv: &Conv) -> ExternAbi {
-    match conv {
-        Conv::C => ExternAbi::C { unwind: false },
-        Conv::Rust => ExternAbi::Rust,
-        Conv::PreserveMost => ExternAbi::RustCold,
-        Conv::ArmAapcs => ExternAbi::Aapcs { unwind: false },
-        Conv::CCmseNonSecureCall => ExternAbi::CCmseNonSecureCall,
-        Conv::CCmseNonSecureEntry => ExternAbi::CCmseNonSecureEntry,
-        Conv::Msp430Intr => ExternAbi::Msp430Interrupt,
-        Conv::GpuKernel => ExternAbi::GpuKernel,
-        Conv::X86Fastcall => ExternAbi::Fastcall { unwind: false },
-        Conv::X86Intr => ExternAbi::X86Interrupt,
-        Conv::X86Stdcall => ExternAbi::Stdcall { unwind: false },
-        Conv::X86ThisCall => ExternAbi::Thiscall { unwind: false },
-        Conv::X86VectorCall => ExternAbi::Vectorcall { unwind: false },
-        Conv::X86_64SysV => ExternAbi::SysV64 { unwind: false },
-        Conv::X86_64Win64 => ExternAbi::Win64 { unwind: false },
-        Conv::AvrInterrupt => ExternAbi::AvrInterrupt,
-        Conv::AvrNonBlockingInterrupt => ExternAbi::AvrNonBlockingInterrupt,
-        Conv::RiscvInterrupt { kind: RiscvInterruptKind::Machine } => ExternAbi::RiscvInterruptM,
-        Conv::RiscvInterrupt { kind: RiscvInterruptKind::Supervisor } => ExternAbi::RiscvInterruptS,
-        Conv::Cold | Conv::PreserveAll => unreachable!(),
-    }
-}
-
-impl Display for Conv {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}", conv_to_externabi(self))
-    }
-}
-
 // Some types are used a lot. Make sure they don't unintentionally get bigger.
 #[cfg(target_pointer_width = "64")]
 mod size_asserts {
diff --git a/compiler/rustc_target/src/json.rs b/compiler/rustc_target/src/json.rs
index 8d6f8f4c6f6..4fcc477921b 100644
--- a/compiler/rustc_target/src/json.rs
+++ b/compiler/rustc_target/src/json.rs
@@ -92,38 +92,6 @@ impl<A: ToJson> ToJson for Option<A> {
     }
 }
 
-impl ToJson for crate::callconv::Conv {
-    fn to_json(&self) -> Json {
-        let buf: String;
-        let s = match self {
-            Self::C => "C",
-            Self::Rust => "Rust",
-            Self::Cold => "Cold",
-            Self::PreserveMost => "PreserveMost",
-            Self::PreserveAll => "PreserveAll",
-            Self::ArmAapcs => "ArmAapcs",
-            Self::CCmseNonSecureCall => "CCmseNonSecureCall",
-            Self::CCmseNonSecureEntry => "CCmseNonSecureEntry",
-            Self::Msp430Intr => "Msp430Intr",
-            Self::X86Fastcall => "X86Fastcall",
-            Self::X86Intr => "X86Intr",
-            Self::X86Stdcall => "X86Stdcall",
-            Self::X86ThisCall => "X86ThisCall",
-            Self::X86VectorCall => "X86VectorCall",
-            Self::X86_64SysV => "X86_64SysV",
-            Self::X86_64Win64 => "X86_64Win64",
-            Self::GpuKernel => "GpuKernel",
-            Self::AvrInterrupt => "AvrInterrupt",
-            Self::AvrNonBlockingInterrupt => "AvrNonBlockingInterrupt",
-            Self::RiscvInterrupt { kind } => {
-                buf = format!("RiscvInterrupt({})", kind.as_str());
-                &buf
-            }
-        };
-        Json::String(s.to_owned())
-    }
-}
-
 impl ToJson for TargetMetadata {
     fn to_json(&self) -> Json {
         json!({
@@ -140,3 +108,9 @@ impl ToJson for rustc_abi::Endian {
         self.as_str().to_json()
     }
 }
+
+impl ToJson for rustc_abi::CanonAbi {
+    fn to_json(&self) -> Json {
+        self.to_string().to_json()
+    }
+}
diff --git a/compiler/rustc_target/src/spec/abi_map.rs b/compiler/rustc_target/src/spec/abi_map.rs
new file mode 100644
index 00000000000..d9101f79f04
--- /dev/null
+++ b/compiler/rustc_target/src/spec/abi_map.rs
@@ -0,0 +1,187 @@
+use rustc_abi::{ArmCall, CanonAbi, ExternAbi, InterruptKind, X86Call};
+
+use crate::spec::Target;
+
+/// Mapping for ExternAbi to CanonAbi according to a Target
+///
+/// A maybe-transitional structure circa 2025 for hosting future experiments in
+/// encapsulating arch-specific ABI lowering details to make them more testable.
+#[derive(Clone, Debug)]
+pub struct AbiMap {
+    arch: Arch,
+    os: OsKind,
+}
+
+#[derive(Copy, Clone, Debug)]
+pub enum AbiMapping {
+    /// this ABI is exactly mapped for this platform
+    Direct(CanonAbi),
+    /// we don't yet warn on this, but we will
+    Deprecated(CanonAbi),
+    Invalid,
+}
+
+impl AbiMapping {
+    pub fn into_option(self) -> Option<CanonAbi> {
+        match self {
+            Self::Direct(abi) | Self::Deprecated(abi) => Some(abi),
+            Self::Invalid => None,
+        }
+    }
+
+    pub fn unwrap(self) -> CanonAbi {
+        self.into_option().unwrap()
+    }
+
+    pub fn is_mapped(self) -> bool {
+        self.into_option().is_some()
+    }
+}
+
+impl AbiMap {
+    pub fn from_target(target: &Target) -> Self {
+        // the purpose of this little exercise is to force listing what affects these mappings
+        let arch = match &*target.arch {
+            "aarch64" => Arch::Aarch64,
+            "amdgpu" => Arch::Amdgpu,
+            "arm" if target.llvm_target.starts_with("thumbv8m") => Arch::Arm(ArmVer::ThumbV8M),
+            "arm" => Arch::Arm(ArmVer::Other),
+            "avr" => Arch::Avr,
+            "msp430" => Arch::Msp430,
+            "nvptx64" => Arch::Nvptx,
+            "riscv32" | "riscv64" => Arch::Riscv,
+            "x86" => Arch::X86,
+            "x86_64" => Arch::X86_64,
+            _ => Arch::Other,
+        };
+        let os = if target.is_like_windows { OsKind::Windows } else { OsKind::Other };
+        AbiMap { arch, os }
+    }
+
+    pub fn canonize_abi(&self, extern_abi: ExternAbi, has_c_varargs: bool) -> AbiMapping {
+        let AbiMap { os, arch } = *self;
+
+        let canon_abi = match (extern_abi, arch) {
+            // infallible lowerings
+            (ExternAbi::C { .. }, _) => CanonAbi::C,
+            (ExternAbi::Rust | ExternAbi::RustCall, _) => CanonAbi::Rust,
+            (ExternAbi::Unadjusted, _) => CanonAbi::C,
+
+            (ExternAbi::RustCold, _) if self.os == OsKind::Windows => CanonAbi::Rust,
+            (ExternAbi::RustCold, _) => CanonAbi::RustCold,
+
+            (ExternAbi::System { .. }, Arch::X86) if os == OsKind::Windows && !has_c_varargs => {
+                CanonAbi::X86(X86Call::Stdcall)
+            }
+            (ExternAbi::System { .. }, _) => CanonAbi::C,
+
+            // fallible lowerings
+            (ExternAbi::EfiApi, Arch::Arm(..)) => CanonAbi::Arm(ArmCall::Aapcs),
+            (ExternAbi::EfiApi, Arch::X86_64) => CanonAbi::X86(X86Call::Win64),
+            (ExternAbi::EfiApi, Arch::Aarch64 | Arch::Riscv | Arch::X86) => CanonAbi::C,
+            (ExternAbi::EfiApi, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::Aapcs { .. }, Arch::Arm(..)) => CanonAbi::Arm(ArmCall::Aapcs),
+            (ExternAbi::Aapcs { .. }, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::CCmseNonSecureCall, Arch::Arm(ArmVer::ThumbV8M)) => {
+                CanonAbi::Arm(ArmCall::CCmseNonSecureCall)
+            }
+            (ExternAbi::CCmseNonSecureEntry, Arch::Arm(ArmVer::ThumbV8M)) => {
+                CanonAbi::Arm(ArmCall::CCmseNonSecureEntry)
+            }
+            (ExternAbi::CCmseNonSecureCall | ExternAbi::CCmseNonSecureEntry, ..) => {
+                return AbiMapping::Invalid;
+            }
+
+            (ExternAbi::Cdecl { .. }, Arch::X86) => CanonAbi::C,
+            (ExternAbi::Cdecl { .. }, _) => return AbiMapping::Deprecated(CanonAbi::C),
+
+            (ExternAbi::Fastcall { .. }, Arch::X86) => CanonAbi::X86(X86Call::Fastcall),
+            (ExternAbi::Fastcall { .. }, _) if os == OsKind::Windows => {
+                return AbiMapping::Deprecated(CanonAbi::C);
+            }
+            (ExternAbi::Fastcall { .. }, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::Stdcall { .. }, Arch::X86) => CanonAbi::X86(X86Call::Stdcall),
+            (ExternAbi::Stdcall { .. }, _) if os == OsKind::Windows => {
+                return AbiMapping::Deprecated(CanonAbi::C);
+            }
+            (ExternAbi::Stdcall { .. }, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::Thiscall { .. }, Arch::X86) => CanonAbi::X86(X86Call::Thiscall),
+            (ExternAbi::Thiscall { .. }, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::Vectorcall { .. }, Arch::X86 | Arch::X86_64) => {
+                CanonAbi::X86(X86Call::Vectorcall)
+            }
+            (ExternAbi::Vectorcall { .. }, _) if os == OsKind::Windows => {
+                return AbiMapping::Deprecated(CanonAbi::C);
+            }
+            (ExternAbi::Vectorcall { .. }, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::SysV64 { .. }, Arch::X86_64) => CanonAbi::X86(X86Call::SysV64),
+            (ExternAbi::Win64 { .. }, Arch::X86_64) => CanonAbi::X86(X86Call::Win64),
+            (ExternAbi::SysV64 { .. } | ExternAbi::Win64 { .. }, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::PtxKernel, Arch::Nvptx) => CanonAbi::GpuKernel,
+            (ExternAbi::GpuKernel, Arch::Amdgpu | Arch::Nvptx) => CanonAbi::GpuKernel,
+            (ExternAbi::PtxKernel | ExternAbi::GpuKernel, _) => return AbiMapping::Invalid,
+
+            (ExternAbi::AvrInterrupt, Arch::Avr) => CanonAbi::Interrupt(InterruptKind::Avr),
+            (ExternAbi::AvrNonBlockingInterrupt, Arch::Avr) => {
+                CanonAbi::Interrupt(InterruptKind::AvrNonBlocking)
+            }
+            (ExternAbi::Msp430Interrupt, Arch::Msp430) => {
+                CanonAbi::Interrupt(InterruptKind::Msp430)
+            }
+            (ExternAbi::RiscvInterruptM, Arch::Riscv) => {
+                CanonAbi::Interrupt(InterruptKind::RiscvMachine)
+            }
+            (ExternAbi::RiscvInterruptS, Arch::Riscv) => {
+                CanonAbi::Interrupt(InterruptKind::RiscvSupervisor)
+            }
+            (ExternAbi::X86Interrupt, Arch::X86 | Arch::X86_64) => {
+                CanonAbi::Interrupt(InterruptKind::X86)
+            }
+            (
+                ExternAbi::AvrInterrupt
+                | ExternAbi::AvrNonBlockingInterrupt
+                | ExternAbi::Msp430Interrupt
+                | ExternAbi::RiscvInterruptM
+                | ExternAbi::RiscvInterruptS
+                | ExternAbi::X86Interrupt,
+                _,
+            ) => return AbiMapping::Invalid,
+        };
+
+        AbiMapping::Direct(canon_abi)
+    }
+}
+
+#[derive(Debug, PartialEq, Copy, Clone)]
+enum Arch {
+    Aarch64,
+    Amdgpu,
+    Arm(ArmVer),
+    Avr,
+    Msp430,
+    Nvptx,
+    Riscv,
+    X86,
+    X86_64,
+    /// Architectures which don't need other considerations for ABI lowering
+    Other,
+}
+
+#[derive(Debug, PartialEq, Copy, Clone)]
+enum OsKind {
+    Windows,
+    Other,
+}
+
+#[derive(Debug, PartialEq, Copy, Clone)]
+enum ArmVer {
+    ThumbV8M,
+    Other,
+}
diff --git a/compiler/rustc_target/src/spec/json.rs b/compiler/rustc_target/src/spec/json.rs
index be71da76b4a..54b06d9f9b4 100644
--- a/compiler/rustc_target/src/spec/json.rs
+++ b/compiler/rustc_target/src/spec/json.rs
@@ -2,10 +2,12 @@ use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::str::FromStr;
 
+use rustc_abi::ExternAbi;
 use serde_json::Value;
 
 use super::{Target, TargetKind, TargetOptions, TargetWarnings};
 use crate::json::{Json, ToJson};
+use crate::spec::AbiMap;
 
 impl Target {
     /// Loads a target descriptor from a JSON object.
@@ -515,18 +517,6 @@ impl Target {
                     }
                 }
             } );
-            ($key_name:ident, Conv) => ( {
-                let name = (stringify!($key_name)).replace("_", "-");
-                obj.remove(&name).and_then(|o| o.as_str().and_then(|s| {
-                    match super::Conv::from_str(s) {
-                        Ok(c) => {
-                            base.$key_name = c;
-                            Some(Ok(()))
-                        }
-                        Err(e) => Some(Err(e))
-                    }
-                })).unwrap_or(Ok(()))
-            } );
         }
 
         if let Some(j) = obj.remove("target-endian") {
@@ -660,9 +650,23 @@ impl Target {
         key!(supports_stack_protector, bool);
         key!(small_data_threshold_support, SmallDataThresholdSupport)?;
         key!(entry_name);
-        key!(entry_abi, Conv)?;
         key!(supports_xray, bool);
 
+        // we're going to run `update_from_cli`, but that won't change the target's AbiMap
+        // FIXME: better factor the Target definition so we enforce this on a type level
+        let abi_map = AbiMap::from_target(&base);
+
+        if let Some(abi_str) = obj.remove("entry-abi") {
+            if let Json::String(abi_str) = abi_str {
+                match abi_str.parse::<ExternAbi>() {
+                    Ok(abi) => base.options.entry_abi = abi_map.canonize_abi(abi, false).unwrap(),
+                    Err(_) => return Err(format!("{abi_str} is not a valid ExternAbi")),
+                }
+            } else {
+                incorrect_type.push("entry-abi".to_owned())
+            }
+        }
+
         base.update_from_cli();
         base.check_consistency(TargetKind::Json)?;
 
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index 303be54a6d7..6529c2d72c8 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -43,7 +43,7 @@ use std::str::FromStr;
 use std::{fmt, io};
 
 use rustc_abi::{
-    Align, Endian, ExternAbi, Integer, Size, TargetDataLayout, TargetDataLayoutErrors,
+    Align, CanonAbi, Endian, ExternAbi, Integer, Size, TargetDataLayout, TargetDataLayoutErrors,
 };
 use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_fs_util::try_canonicalize;
@@ -53,15 +53,16 @@ use rustc_span::{Symbol, kw, sym};
 use serde_json::Value;
 use tracing::debug;
 
-use crate::callconv::Conv;
 use crate::json::{Json, ToJson};
 use crate::spec::crt_objects::CrtObjects;
 
 pub mod crt_objects;
 
+mod abi_map;
 mod base;
 mod json;
 
+pub use abi_map::AbiMap;
 pub use base::apple;
 pub use base::avr::ef_avr_arch;
 
@@ -2655,9 +2656,9 @@ pub struct TargetOptions {
     /// Default value is "main"
     pub entry_name: StaticCow<str>,
 
-    /// The ABI of entry function.
-    /// Default value is `Conv::C`, i.e. C call convention
-    pub entry_abi: Conv,
+    /// The ABI of the entry function.
+    /// Default value is `CanonAbi::C`
+    pub entry_abi: CanonAbi,
 
     /// Whether the target supports XRay instrumentation.
     pub supports_xray: bool,
@@ -2888,7 +2889,7 @@ impl Default for TargetOptions {
             generate_arange_section: true,
             supports_stack_protector: true,
             entry_name: "main".into(),
-            entry_abi: Conv::C,
+            entry_abi: CanonAbi::C,
             supports_xray: false,
             small_data_threshold_support: SmallDataThresholdSupport::DefaultForArch,
         }
@@ -2914,114 +2915,9 @@ impl DerefMut for Target {
 }
 
 impl Target {
-    /// Given a function ABI, turn it into the correct ABI for this target.
-    pub fn adjust_abi(&self, abi: ExternAbi, c_variadic: bool) -> ExternAbi {
-        use ExternAbi::*;
-        match abi {
-            // On Windows, `extern "system"` behaves like msvc's `__stdcall`.
-            // `__stdcall` only applies on x86 and on non-variadic functions:
-            // https://learn.microsoft.com/en-us/cpp/cpp/stdcall?view=msvc-170
-            System { unwind } => {
-                if self.is_like_windows && self.arch == "x86" && !c_variadic {
-                    Stdcall { unwind }
-                } else {
-                    C { unwind }
-                }
-            }
-
-            EfiApi => {
-                if self.arch == "arm" {
-                    Aapcs { unwind: false }
-                } else if self.arch == "x86_64" {
-                    Win64 { unwind: false }
-                } else {
-                    C { unwind: false }
-                }
-            }
-
-            // See commentary in `is_abi_supported`.
-            Stdcall { unwind } | Thiscall { unwind } | Fastcall { unwind } => {
-                if self.arch == "x86" { abi } else { C { unwind } }
-            }
-            Vectorcall { unwind } => {
-                if ["x86", "x86_64"].contains(&&*self.arch) {
-                    abi
-                } else {
-                    C { unwind }
-                }
-            }
-
-            // The Windows x64 calling convention we use for `extern "Rust"`
-            // <https://learn.microsoft.com/en-us/cpp/build/x64-software-conventions#register-volatility-and-preservation>
-            // expects the callee to save `xmm6` through `xmm15`, but `PreserveMost`
-            // (that we use by default for `extern "rust-cold"`) doesn't save any of those.
-            // So to avoid bloating callers, just use the Rust convention here.
-            RustCold if self.is_like_windows && self.arch == "x86_64" => Rust,
-
-            abi => abi,
-        }
-    }
-
     pub fn is_abi_supported(&self, abi: ExternAbi) -> bool {
-        use ExternAbi::*;
-        match abi {
-            Rust | C { .. } | System { .. } | RustCall | Unadjusted | Cdecl { .. } | RustCold => {
-                true
-            }
-            EfiApi => {
-                ["arm", "aarch64", "riscv32", "riscv64", "x86", "x86_64"].contains(&&self.arch[..])
-            }
-            X86Interrupt => ["x86", "x86_64"].contains(&&self.arch[..]),
-            Aapcs { .. } => "arm" == self.arch,
-            CCmseNonSecureCall | CCmseNonSecureEntry => {
-                ["thumbv8m.main-none-eabi", "thumbv8m.main-none-eabihf", "thumbv8m.base-none-eabi"]
-                    .contains(&&self.llvm_target[..])
-            }
-            Win64 { .. } | SysV64 { .. } => self.arch == "x86_64",
-            PtxKernel => self.arch == "nvptx64",
-            GpuKernel => ["amdgpu", "nvptx64"].contains(&&self.arch[..]),
-            Msp430Interrupt => self.arch == "msp430",
-            RiscvInterruptM | RiscvInterruptS => ["riscv32", "riscv64"].contains(&&self.arch[..]),
-            AvrInterrupt | AvrNonBlockingInterrupt => self.arch == "avr",
-            Thiscall { .. } => self.arch == "x86",
-            // On windows these fall-back to platform native calling convention (C) when the
-            // architecture is not supported.
-            //
-            // This is I believe a historical accident that has occurred as part of Microsoft
-            // striving to allow most of the code to "just" compile when support for 64-bit x86
-            // was added and then later again, when support for ARM architectures was added.
-            //
-            // This is well documented across MSDN. Support for this in Rust has been added in
-            // #54576. This makes much more sense in context of Microsoft's C++ than it does in
-            // Rust, but there isn't much leeway remaining here to change it back at the time this
-            // comment has been written.
-            //
-            // Following are the relevant excerpts from the MSDN documentation.
-            //
-            // > The __vectorcall calling convention is only supported in native code on x86 and
-            // x64 processors that include Streaming SIMD Extensions 2 (SSE2) and above.
-            // > ...
-            // > On ARM machines, __vectorcall is accepted and ignored by the compiler.
-            //
-            // -- https://docs.microsoft.com/en-us/cpp/cpp/vectorcall?view=msvc-160
-            //
-            // > On ARM and x64 processors, __stdcall is accepted and ignored by the compiler;
-            //
-            // -- https://docs.microsoft.com/en-us/cpp/cpp/stdcall?view=msvc-160
-            //
-            // > In most cases, keywords or compiler switches that specify an unsupported
-            // > convention on a particular platform are ignored, and the platform default
-            // > convention is used.
-            //
-            // -- https://docs.microsoft.com/en-us/cpp/cpp/argument-passing-and-naming-conventions
-            Stdcall { .. } | Fastcall { .. } | Vectorcall { .. } if self.is_like_windows => true,
-            // Outside of Windows we want to only support these calling conventions for the
-            // 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,
-            // Reject these calling conventions everywhere else.
-            Stdcall { .. } | Fastcall { .. } | Vectorcall { .. } => false,
-        }
+        let abi_map = AbiMap::from_target(self);
+        abi_map.canonize_abi(abi, false).is_mapped()
     }
 
     /// Minimum integer size in bits that this target can perform atomic
diff --git a/compiler/rustc_target/src/spec/targets/x86_64_unknown_uefi.rs b/compiler/rustc_target/src/spec/targets/x86_64_unknown_uefi.rs
index 07f853dacaf..0cf6a879462 100644
--- a/compiler/rustc_target/src/spec/targets/x86_64_unknown_uefi.rs
+++ b/compiler/rustc_target/src/spec/targets/x86_64_unknown_uefi.rs
@@ -5,7 +5,8 @@
 // The win64 ABI is used. It differs from the sysv64 ABI, so we must use a windows target with
 // LLVM. "x86_64-unknown-windows" is used to get the minimal subset of windows-specific features.
 
-use crate::callconv::Conv;
+use rustc_abi::{CanonAbi, X86Call};
+
 use crate::spec::{RustcAbi, Target, TargetMetadata, base};
 
 pub(crate) fn target() -> Target {
@@ -13,7 +14,7 @@ pub(crate) fn target() -> Target {
     base.cpu = "x86-64".into();
     base.plt_by_default = false;
     base.max_atomic_width = Some(64);
-    base.entry_abi = Conv::X86_64Win64;
+    base.entry_abi = CanonAbi::X86(X86Call::Win64);
 
     // We disable MMX and SSE for now, even though UEFI allows using them. Problem is, you have to
     // enable these CPU features explicitly before their first use, otherwise their instructions
diff --git a/compiler/rustc_trait_selection/messages.ftl b/compiler/rustc_trait_selection/messages.ftl
index 9b949a0a795..8232da4df43 100644
--- a/compiler/rustc_trait_selection/messages.ftl
+++ b/compiler/rustc_trait_selection/messages.ftl
@@ -72,8 +72,6 @@ trait_selection_adjust_signature_remove_borrow = consider adjusting the signatur
 
 trait_selection_ascribe_user_type_prove_predicate = ...so that the where clause holds
 
-trait_selection_async_closure_not_fn = async closure does not implement `{$kind}` because it captures state from its environment
-
 trait_selection_await_both_futures = consider `await`ing on both `Future`s
 trait_selection_await_future = consider `await`ing on the `Future`
 trait_selection_await_note = calling an async function returns a future
@@ -123,6 +121,8 @@ trait_selection_closure_kind_requirement = the requirement to implement `{$trait
 
 trait_selection_compare_impl_item_obligation = ...so that the definition in impl matches the definition from the trait
 trait_selection_consider_specifying_length = consider specifying the actual array length
+trait_selection_coro_closure_not_fn = {$coro_kind}closure does not implement `{$kind}` because it captures state from its environment
+
 trait_selection_data_flows = ...but data{$label_var1_exists ->
     [true] {" "}from `{$label_var1}`
     *[false] {""}
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
index 9b5e421e0e4..fc5be111144 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -42,9 +42,7 @@ use super::{
 use crate::error_reporting::TypeErrCtxt;
 use crate::error_reporting::infer::TyCategory;
 use crate::error_reporting::traits::report_dyn_incompatibility;
-use crate::errors::{
-    AsyncClosureNotFn, ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch,
-};
+use crate::errors::{ClosureFnMutLabel, ClosureFnOnceLabel, ClosureKindMismatch, CoroClosureNotFn};
 use crate::infer::{self, InferCtxt, InferCtxtExt as _};
 use crate::traits::query::evaluate_obligation::InferCtxtExt as _;
 use crate::traits::{
@@ -886,9 +884,18 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         // is unimplemented is because async closures don't implement `Fn`/`FnMut`
         // if they have captures.
         if has_self_borrows && expected_kind != ty::ClosureKind::FnOnce {
-            let mut err = self.dcx().create_err(AsyncClosureNotFn {
+            let coro_kind = match self
+                .tcx
+                .coroutine_kind(self.tcx.coroutine_for_closure(closure_def_id))
+                .unwrap()
+            {
+                rustc_hir::CoroutineKind::Desugared(desugaring, _) => desugaring.to_string(),
+                coro => coro.to_string(),
+            };
+            let mut err = self.dcx().create_err(CoroClosureNotFn {
                 span: self.tcx.def_span(closure_def_id),
                 kind: expected_kind.as_str(),
+                coro_kind,
             });
             self.note_obligation_cause(&mut err, &obligation);
             return Some(err.emit());
diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index 779c861637a..0bea308ed5c 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -201,11 +201,12 @@ pub struct ClosureFnMutLabel {
 }
 
 #[derive(Diagnostic)]
-#[diag(trait_selection_async_closure_not_fn)]
-pub(crate) struct AsyncClosureNotFn {
+#[diag(trait_selection_coro_closure_not_fn)]
+pub(crate) struct CoroClosureNotFn {
     #[primary_span]
     pub span: Span,
     pub kind: &'static str,
+    pub coro_kind: String,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index 7d869b27445..97ecf9702e6 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -11,7 +11,7 @@ use std::ops::ControlFlow;
 use hir::LangItem;
 use hir::def_id::DefId;
 use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
-use rustc_hir as hir;
+use rustc_hir::{self as hir, CoroutineDesugaring, CoroutineKind};
 use rustc_infer::traits::{Obligation, PolyTraitObligation, SelectionError};
 use rustc_middle::ty::fast_reject::DeepRejectCtxt;
 use rustc_middle::ty::{self, Ty, TypeVisitableExt, TypingMode, elaborate};
@@ -438,6 +438,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         }
     }
 
+    #[instrument(level = "debug", skip(self, candidates))]
     fn assemble_async_closure_candidates(
         &mut self,
         obligation: &PolyTraitObligation<'tcx>,
@@ -446,15 +447,30 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let goal_kind =
             self.tcx().async_fn_trait_kind_from_def_id(obligation.predicate.def_id()).unwrap();
 
+        debug!("self_ty = {:?}", obligation.self_ty().skip_binder().kind());
         match *obligation.self_ty().skip_binder().kind() {
-            ty::CoroutineClosure(_, args) => {
+            ty::CoroutineClosure(def_id, args) => {
                 if let Some(closure_kind) =
                     args.as_coroutine_closure().kind_ty().to_opt_closure_kind()
                     && !closure_kind.extends(goal_kind)
                 {
                     return;
                 }
-                candidates.vec.push(AsyncClosureCandidate);
+
+                // Make sure this is actually an async closure.
+                let Some(coroutine_kind) =
+                    self.tcx().coroutine_kind(self.tcx().coroutine_for_closure(def_id))
+                else {
+                    bug!("coroutine with no kind");
+                };
+
+                debug!(?coroutine_kind);
+                match coroutine_kind {
+                    CoroutineKind::Desugared(CoroutineDesugaring::Async, _) => {
+                        candidates.vec.push(AsyncClosureCandidate);
+                    }
+                    _ => (),
+                }
             }
             // Closures and fn pointers implement `AsyncFn*` if their return types
             // implement `Future`, which is checked later.
diff --git a/compiler/rustc_ty_utils/src/abi.rs b/compiler/rustc_ty_utils/src/abi.rs
index 2b49d7ac8b5..83d7416b03e 100644
--- a/compiler/rustc_ty_utils/src/abi.rs
+++ b/compiler/rustc_ty_utils/src/abi.rs
@@ -13,7 +13,7 @@ use rustc_middle::ty::{self, InstanceKind, Ty, TyCtxt};
 use rustc_session::config::OptLevel;
 use rustc_span::def_id::DefId;
 use rustc_target::callconv::{
-    ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, Conv, FnAbi, PassMode, RiscvInterruptKind,
+    AbiMap, ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, FnAbi, PassMode,
 };
 use tracing::debug;
 
@@ -240,45 +240,6 @@ fn fn_sig_for_fn_abi<'tcx>(
     }
 }
 
-#[inline]
-fn conv_from_spec_abi(tcx: TyCtxt<'_>, abi: ExternAbi, c_variadic: bool) -> Conv {
-    use rustc_abi::ExternAbi::*;
-    match tcx.sess.target.adjust_abi(abi, c_variadic) {
-        Rust | RustCall => Conv::Rust,
-
-        // This is intentionally not using `Conv::Cold`, as that has to preserve
-        // even SIMD registers, which is generally not a good trade-off.
-        RustCold => Conv::PreserveMost,
-
-        // It's the ABI's job to select this, not ours.
-        System { .. } => bug!("system abi should be selected elsewhere"),
-        EfiApi => bug!("eficall abi should be selected elsewhere"),
-
-        Stdcall { .. } => Conv::X86Stdcall,
-        Fastcall { .. } => Conv::X86Fastcall,
-        Vectorcall { .. } => Conv::X86VectorCall,
-        Thiscall { .. } => Conv::X86ThisCall,
-        C { .. } => Conv::C,
-        Unadjusted => Conv::C,
-        Win64 { .. } => Conv::X86_64Win64,
-        SysV64 { .. } => Conv::X86_64SysV,
-        Aapcs { .. } => Conv::ArmAapcs,
-        CCmseNonSecureCall => Conv::CCmseNonSecureCall,
-        CCmseNonSecureEntry => Conv::CCmseNonSecureEntry,
-        PtxKernel => Conv::GpuKernel,
-        Msp430Interrupt => Conv::Msp430Intr,
-        X86Interrupt => Conv::X86Intr,
-        GpuKernel => Conv::GpuKernel,
-        AvrInterrupt => Conv::AvrInterrupt,
-        AvrNonBlockingInterrupt => Conv::AvrNonBlockingInterrupt,
-        RiscvInterruptM => Conv::RiscvInterrupt { kind: RiscvInterruptKind::Machine },
-        RiscvInterruptS => Conv::RiscvInterrupt { kind: RiscvInterruptKind::Supervisor },
-
-        // These API constants ought to be more specific...
-        Cdecl { .. } => Conv::C,
-    }
-}
-
 fn fn_abi_of_fn_ptr<'tcx>(
     tcx: TyCtxt<'tcx>,
     query: ty::PseudoCanonicalInput<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>,
@@ -529,7 +490,8 @@ fn fn_abi_new_uncached<'tcx>(
     };
     let sig = tcx.normalize_erasing_regions(cx.typing_env, sig);
 
-    let conv = conv_from_spec_abi(cx.tcx(), sig.abi, sig.c_variadic);
+    let abi_map = AbiMap::from_target(&tcx.sess.target);
+    let conv = abi_map.canonize_abi(sig.abi, sig.c_variadic).unwrap();
 
     let mut inputs = sig.inputs();
     let extra_args = if sig.abi == ExternAbi::RustCall {