Rollup merge of #116161 - Soveu:varargs2, r=cjgillot

Stabilize `extended_varargs_abi_support`

I think that is everything? If there is any documentation regarding `extern` and/or varargs to correct, let me know, some quick greps suggest that there might be none.

Tracking issue: https://github.com/rust-lang/rust/issues/100189

compiler/rustc_feature/src/accepted.rs

@@ -193,6 +193,9 @@ declare_features! (
     (accepted, expr_fragment_specifier_2024, "1.83.0", Some(123742)),
     /// Allows arbitrary expressions in key-value attributes at parse time.
     (accepted, extended_key_value_attributes, "1.54.0", Some(78835)),
+    /// Allows using `efiapi`, `aapcs`, `sysv64` and `win64` as calling
+    /// convention for functions with varargs.
+    (accepted, extended_varargs_abi_support, "CURRENT_RUSTC_VERSION", Some(100189)),
     /// Allows resolving absolute paths as paths from other crates.
     (accepted, extern_absolute_paths, "1.30.0", Some(44660)),
     /// Allows `extern crate foo as bar;`. This puts `bar` into extern prelude.

compiler/rustc_feature/src/unstable.rs

@@ -475,9 +475,6 @@ declare_features! (
     (unstable, exhaustive_patterns, "1.13.0", Some(51085)),
     /// Allows explicit tail calls via `become` expression.
     (incomplete, explicit_tail_calls, "1.72.0", Some(112788)),
-    /// Allows using `efiapi`, `sysv64` and `win64` as calling convention
-    /// for functions with varargs.
-    (unstable, extended_varargs_abi_support, "1.65.0", Some(100189)),
     /// Allows defining `extern type`s.
     (unstable, extern_types, "1.23.0", Some(43467)),
     /// Allow using 128-bit (quad precision) floating point numbers.

compiler/rustc_hir_analysis/messages.ftl

@@ -590,7 +590,7 @@ hir_analysis_value_of_associated_struct_already_specified =
     .label = re-bound here
     .previous_bound_label = `{$item_name}` bound here first
 
-hir_analysis_variadic_function_compatible_convention = C-variadic function must have a compatible calling convention, like {$conventions}
+hir_analysis_variadic_function_compatible_convention = C-variadic function must have a compatible calling convention, like `C`, `cdecl`, `system`, `aapcs`, `win64`, `sysv64` or `efiapi`
     .label = C-variadic function must have a compatible calling convention
 
 hir_analysis_variances_of = {$variances}

compiler/rustc_hir_analysis/src/errors.rs

@@ -672,11 +672,10 @@ pub(crate) struct MainFunctionGenericParameters {
 
 #[derive(Diagnostic)]
 #[diag(hir_analysis_variadic_function_compatible_convention, code = E0045)]
-pub(crate) struct VariadicFunctionCompatibleConvention<'a> {
+pub(crate) struct VariadicFunctionCompatibleConvention {
     #[primary_span]
     #[label]
     pub span: Span,
-    pub conventions: &'a str,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_hir_analysis/src/lib.rs

@@ -98,9 +98,7 @@ use rustc_middle::middle;
 use rustc_middle::mir::interpret::GlobalId;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, Const, Ty, TyCtxt};
-use rustc_session::parse::feature_err;
 use rustc_span::Span;
-use rustc_span::symbol::sym;
 use rustc_trait_selection::traits;
 
 use self::hir_ty_lowering::{FeedConstTy, HirTyLowerer};
@@ -113,34 +111,9 @@ fn require_c_abi_if_c_variadic(
     abi: ExternAbi,
     span: Span,
 ) {
-    const CONVENTIONS_UNSTABLE: &str =
-        "`C`, `cdecl`, `system`, `aapcs`, `win64`, `sysv64` or `efiapi`";
-    const CONVENTIONS_STABLE: &str = "`C` or `cdecl`";
-    const UNSTABLE_EXPLAIN: &str =
-        "using calling conventions other than `C` or `cdecl` for varargs functions is unstable";
-
-    if !decl.c_variadic || matches!(abi, ExternAbi::C { .. } | ExternAbi::Cdecl { .. }) {
-        return;
+    if decl.c_variadic && !abi.supports_varargs() {
+        tcx.dcx().emit_err(errors::VariadicFunctionCompatibleConvention { span });
     }
-
-    let extended_abi_support = tcx.features().extended_varargs_abi_support();
-    let conventions = match (extended_abi_support, abi.supports_varargs()) {
-        // User enabled additional ABI support for varargs and function ABI matches those ones.
-        (true, true) => return,
-
-        // Using this ABI would be ok, if the feature for additional ABI support was enabled.
-        // Return CONVENTIONS_STABLE, because we want the other error to look the same.
-        (false, true) => {
-            feature_err(&tcx.sess, sym::extended_varargs_abi_support, span, UNSTABLE_EXPLAIN)
-                .emit();
-            CONVENTIONS_STABLE
-        }
-
-        (false, false) => CONVENTIONS_STABLE,
-        (true, false) => CONVENTIONS_UNSTABLE,
-    };
-
-    tcx.dcx().emit_err(errors::VariadicFunctionCompatibleConvention { span, conventions });
 }
 
 pub fn provide(providers: &mut Providers) {