Rollup of 7 pull requests

compiler/rustc_hir/src/hir.rs

@@ -1395,7 +1395,7 @@ pub struct LetExpr<'hir> {
     pub pat: &'hir Pat<'hir>,
     pub ty: Option<&'hir Ty<'hir>>,
     pub init: &'hir Expr<'hir>,
-    /// `Recovered::Yes` when this let expressions is not in a syntanctically valid location.
+    /// `Recovered::Yes` when this let expressions is not in a syntactically valid location.
     /// Used to prevent building MIR in such situations.
     pub recovered: ast::Recovered,
 }

compiler/rustc_passes/messages.ftl

@@ -444,6 +444,9 @@ passes_macro_export_on_decl_macro =
 passes_macro_use =
     `#[{$name}]` only has an effect on `extern crate` and modules
 
+passes_may_dangle =
+    `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl
+
 passes_maybe_string_interpolation = you might have meant to use string interpolation in this string literal
 passes_missing_const_err =
     attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const`
@@ -475,8 +478,8 @@ passes_multiple_start_functions =
     .previous = previous `#[start]` function here
 
 passes_must_not_suspend =
-    `must_not_suspend` attribute should be applied to a struct, enum, or trait
-    .label = is not a struct, enum, or trait
+    `must_not_suspend` attribute should be applied to a struct, enum, union, or trait
+    .label = is not a struct, enum, union, or trait
 
 passes_must_use_async =
     `must_use` attribute on `async` functions applies to the anonymous `Future` returned by the function, not the value within

compiler/rustc_passes/src/check_attr.rs

@@ -189,6 +189,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 [sym::collapse_debuginfo, ..] => self.check_collapse_debuginfo(attr, span, target),
                 [sym::must_not_suspend, ..] => self.check_must_not_suspend(attr, span, target),
                 [sym::must_use, ..] => self.check_must_use(hir_id, attr, target),
+                [sym::may_dangle, ..] => self.check_may_dangle(hir_id, attr),
                 [sym::rustc_pass_by_value, ..] => self.check_pass_by_value(attr, span, target),
                 [sym::rustc_allow_incoherent_impl, ..] => {
                     self.check_allow_incoherent_impl(attr, span, target)
@@ -255,7 +256,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | sym::cfg_attr
                     // need to be fixed
                     | sym::cfi_encoding // FIXME(cfi_encoding)
-                    | sym::may_dangle // FIXME(dropck_eyepatch)
                     | sym::pointee // FIXME(derive_smart_pointer)
                     | sym::omit_gdb_pretty_printer_section // FIXME(omit_gdb_pretty_printer_section)
                     | sym::used // handled elsewhere to restrict to static items
@@ -1363,7 +1363,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    /// Checks if `#[must_not_suspend]` is applied to a function.
+    /// Checks if `#[must_not_suspend]` is applied to a struct, enum, union, or trait.
     fn check_must_not_suspend(&self, attr: &Attribute, span: Span, target: Target) {
         match target {
             Target::Struct | Target::Enum | Target::Union | Target::Trait => {}
@@ -1373,6 +1373,27 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
+    /// Checks if `#[may_dangle]` is applied to a lifetime or type generic parameter in `Drop` impl.
+    fn check_may_dangle(&self, hir_id: HirId, attr: &Attribute) {
+        if let hir::Node::GenericParam(param) = self.tcx.hir_node(hir_id)
+            && matches!(
+                param.kind,
+                hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. }
+            )
+            && matches!(param.source, hir::GenericParamSource::Generics)
+            && let parent_hir_id = self.tcx.parent_hir_id(hir_id)
+            && let hir::Node::Item(item) = self.tcx.hir_node(parent_hir_id)
+            && let hir::ItemKind::Impl(impl_) = item.kind
+            && let Some(trait_) = impl_.of_trait
+            && let Some(def_id) = trait_.trait_def_id()
+            && self.tcx.is_lang_item(def_id, hir::LangItem::Drop)
+        {
+            return;
+        }
+
+        self.dcx().emit_err(errors::InvalidMayDangle { attr_span: attr.span });
+    }
+
     /// Checks if `#[cold]` is applied to a non-function.
     fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
         match target {

compiler/rustc_passes/src/errors.rs

@@ -737,6 +737,13 @@ pub struct NonExportedMacroInvalidAttrs {
     pub attr_span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(passes_may_dangle)]
+pub struct InvalidMayDangle {
+    #[primary_span]
+    pub attr_span: Span,
+}
+
 #[derive(LintDiagnostic)]
 #[diag(passes_unused_duplicate)]
 pub struct UnusedDuplicate {

compiler/rustc_target/src/abi/call/mod.rs

@@ -642,7 +642,7 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
     pub fn make_indirect(&mut self) {
         match self.mode {
             PassMode::Direct(_) | PassMode::Pair(_, _) => {
-                self.mode = Self::indirect_pass_mode(&self.layout);
+                self.make_indirect_force();
             }
             PassMode::Indirect { attrs: _, meta_attrs: _, on_stack: false } => {
                 // already indirect
@@ -652,6 +652,11 @@ impl<'a, Ty> ArgAbi<'a, Ty> {
         }
     }
 
+    /// Same as make_indirect, but doesn't check the current `PassMode`.
+    pub fn make_indirect_force(&mut self) {
+        self.mode = Self::indirect_pass_mode(&self.layout);
+    }
+
     /// Pass this argument indirectly, by placing it at a fixed stack offset.
     /// This corresponds to the `byval` LLVM argument attribute.
     /// This is only valid for sized arguments.
@@ -871,10 +876,10 @@ impl<'a, Ty> FnAbi<'a, Ty> {
             }
             "x86_64" => match abi {
                 spec::abi::Abi::SysV64 { .. } => x86_64::compute_abi_info(cx, self),
-                spec::abi::Abi::Win64 { .. } => x86_win64::compute_abi_info(self),
+                spec::abi::Abi::Win64 { .. } => x86_win64::compute_abi_info(cx, self),
                 _ => {
                     if cx.target_spec().is_like_windows {
-                        x86_win64::compute_abi_info(self)
+                        x86_win64::compute_abi_info(cx, self)
                     } else {
                         x86_64::compute_abi_info(cx, self)
                     }
@@ -898,7 +903,7 @@ impl<'a, Ty> FnAbi<'a, Ty> {
             "csky" => csky::compute_abi_info(self),
             "mips" | "mips32r6" => mips::compute_abi_info(cx, self),
             "mips64" | "mips64r6" => mips64::compute_abi_info(cx, self),
-            "powerpc" => powerpc::compute_abi_info(self),
+            "powerpc" => powerpc::compute_abi_info(cx, self),
             "powerpc64" => powerpc64::compute_abi_info(cx, self),
             "s390x" => s390x::compute_abi_info(cx, self),
             "msp430" => msp430::compute_abi_info(self),

compiler/rustc_target/src/abi/call/powerpc.rs

@@ -1,4 +1,5 @@
 use crate::abi::call::{ArgAbi, FnAbi};
+use crate::spec::HasTargetSpec;
 
 fn classify_ret<Ty>(ret: &mut ArgAbi<'_, Ty>) {
     if ret.layout.is_aggregate() {
@@ -8,23 +9,30 @@ fn classify_ret<Ty>(ret: &mut ArgAbi<'_, Ty>) {
     }
 }
 
-fn classify_arg<Ty>(arg: &mut ArgAbi<'_, Ty>) {
+fn classify_arg<Ty>(cx: &impl HasTargetSpec, arg: &mut ArgAbi<'_, Ty>) {
+    if arg.is_ignore() {
+        // powerpc-unknown-linux-{gnu,musl,uclibc} doesn't ignore ZSTs.
+        if cx.target_spec().os == "linux"
+            && matches!(&*cx.target_spec().env, "gnu" | "musl" | "uclibc")
+            && arg.layout.is_zst()
+        {
+            arg.make_indirect_force();
+        }
+        return;
+    }
     if arg.layout.is_aggregate() {
         arg.make_indirect();
     } else {
         arg.extend_integer_width_to(32);
     }
 }
 
-pub fn compute_abi_info<Ty>(fn_abi: &mut FnAbi<'_, Ty>) {
+pub fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'_, Ty>) {
     if !fn_abi.ret.is_ignore() {
         classify_ret(&mut fn_abi.ret);
     }
 
     for arg in fn_abi.args.iter_mut() {
-        if arg.is_ignore() {
-            continue;
-        }
-        classify_arg(arg);
+        classify_arg(cx, arg);
     }
 }

compiler/rustc_target/src/abi/call/s390x.rs

@@ -3,6 +3,7 @@
 
 use crate::abi::call::{ArgAbi, FnAbi, Reg};
 use crate::abi::{HasDataLayout, TyAbiInterface};
+use crate::spec::HasTargetSpec;
 
 fn classify_ret<Ty>(ret: &mut ArgAbi<'_, Ty>) {
     if !ret.layout.is_aggregate() && ret.layout.size.bits() <= 64 {
@@ -15,12 +16,22 @@ fn classify_ret<Ty>(ret: &mut ArgAbi<'_, Ty>) {
 fn classify_arg<'a, Ty, C>(cx: &C, arg: &mut ArgAbi<'a, Ty>)
 where
     Ty: TyAbiInterface<'a, C> + Copy,
-    C: HasDataLayout,
+    C: HasDataLayout + HasTargetSpec,
 {
     if !arg.layout.is_sized() {
         // Not touching this...
         return;
     }
+    if arg.is_ignore() {
+        // s390x-unknown-linux-{gnu,musl,uclibc} doesn't ignore ZSTs.
+        if cx.target_spec().os == "linux"
+            && matches!(&*cx.target_spec().env, "gnu" | "musl" | "uclibc")
+            && arg.layout.is_zst()
+        {
+            arg.make_indirect_force();
+        }
+        return;
+    }
     if !arg.layout.is_aggregate() && arg.layout.size.bits() <= 64 {
         arg.extend_integer_width_to(64);
         return;
@@ -46,16 +57,13 @@ where
 pub fn compute_abi_info<'a, Ty, C>(cx: &C, fn_abi: &mut FnAbi<'a, Ty>)
 where
     Ty: TyAbiInterface<'a, C> + Copy,
-    C: HasDataLayout,
+    C: HasDataLayout + HasTargetSpec,
 {
     if !fn_abi.ret.is_ignore() {
         classify_ret(&mut fn_abi.ret);
     }
 
     for arg in fn_abi.args.iter_mut() {
-        if arg.is_ignore() {
-            continue;
-        }
         classify_arg(cx, arg);
     }
 }

compiler/rustc_target/src/abi/call/sparc64.rs

@@ -4,6 +4,7 @@ use crate::abi::call::{
     ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, CastTarget, FnAbi, Reg, Uniform,
 };
 use crate::abi::{self, HasDataLayout, Scalar, Size, TyAbiInterface, TyAndLayout};
+use crate::spec::HasTargetSpec;
 
 #[derive(Clone, Debug)]
 pub struct Sdata {
@@ -211,15 +212,22 @@ where
 pub fn compute_abi_info<'a, Ty, C>(cx: &C, fn_abi: &mut FnAbi<'a, Ty>)
 where
     Ty: TyAbiInterface<'a, C> + Copy,
-    C: HasDataLayout,
+    C: HasDataLayout + HasTargetSpec,
 {
     if !fn_abi.ret.is_ignore() {
         classify_arg(cx, &mut fn_abi.ret, Size::from_bytes(32));
     }
 
     for arg in fn_abi.args.iter_mut() {
         if arg.is_ignore() {
-            continue;
+            // sparc64-unknown-linux-{gnu,musl,uclibc} doesn't ignore ZSTs.
+            if cx.target_spec().os == "linux"
+                && matches!(&*cx.target_spec().env, "gnu" | "musl" | "uclibc")
+                && arg.layout.is_zst()
+            {
+                arg.make_indirect_force();
+            }
+            return;
         }
         classify_arg(cx, arg, Size::from_bytes(16));
     }

compiler/rustc_target/src/abi/call/x86_win64.rs

@@ -1,9 +1,10 @@
 use crate::abi::call::{ArgAbi, FnAbi, Reg};
 use crate::abi::{Abi, Float, Primitive};
+use crate::spec::HasTargetSpec;
 
 // Win64 ABI: https://docs.microsoft.com/en-us/cpp/build/parameter-passing
 
-pub fn compute_abi_info<Ty>(fn_abi: &mut FnAbi<'_, Ty>) {
+pub fn compute_abi_info<Ty>(cx: &impl HasTargetSpec, fn_abi: &mut FnAbi<'_, Ty>) {
     let fixup = |a: &mut ArgAbi<'_, Ty>| {
         match a.layout.abi {
             Abi::Uninhabited | Abi::Aggregate { sized: false } => {}
@@ -37,6 +38,13 @@ pub fn compute_abi_info<Ty>(fn_abi: &mut FnAbi<'_, Ty>) {
     }
     for arg in fn_abi.args.iter_mut() {
         if arg.is_ignore() {
+            // x86_64-pc-windows-gnu doesn't ignore ZSTs.
+            if cx.target_spec().os == "windows"
+                && cx.target_spec().env == "gnu"
+                && arg.layout.is_zst()
+            {
+                arg.make_indirect_force();
+            }
             continue;
         }
         fixup(arg);

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -4610,6 +4610,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         })
     }
 
+    // For E0277 when use `?` operator, suggest adding
+    // a suitable return type in `FnSig`, and a default
+    // return value at the end of the function's body.
     pub(super) fn suggest_add_result_as_return_type(
         &self,
         obligation: &PredicateObligation<'tcx>,
@@ -4620,19 +4623,47 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             return;
         }
 
+        // Only suggest for local function and associated method,
+        // because this suggest adding both return type in
+        // the `FnSig` and a default return value in the body, so it
+        // is not suitable for foreign function without a local body,
+        // and neighter for trait method which may be also implemented
+        // in other place, so shouldn't change it's FnSig.
+        fn choose_suggest_items<'tcx, 'hir>(
+            tcx: TyCtxt<'tcx>,
+            node: hir::Node<'hir>,
+        ) -> Option<(&'hir hir::FnDecl<'hir>, hir::BodyId)> {
+            match node {
+                hir::Node::Item(item) if let hir::ItemKind::Fn(sig, _, body_id) = item.kind => {
+                    Some((sig.decl, body_id))
+                }
+                hir::Node::ImplItem(item)
+                    if let hir::ImplItemKind::Fn(sig, body_id) = item.kind =>
+                {
+                    let parent = tcx.parent_hir_node(item.hir_id());
+                    if let hir::Node::Item(item) = parent
+                        && let hir::ItemKind::Impl(imp) = item.kind
+                        && imp.of_trait.is_none()
+                    {
+                        return Some((sig.decl, body_id));
+                    }
+                    None
+                }
+                _ => None,
+            }
+        }
+
         let node = self.tcx.hir_node_by_def_id(obligation.cause.body_id);
-        if let hir::Node::Item(item) = node
-            && let hir::ItemKind::Fn(sig, _, body_id) = item.kind
-            && let hir::FnRetTy::DefaultReturn(ret_span) = sig.decl.output
+        if let Some((fn_decl, body_id)) = choose_suggest_items(self.tcx, node)
+            && let hir::FnRetTy::DefaultReturn(ret_span) = fn_decl.output
             && self.tcx.is_diagnostic_item(sym::FromResidual, trait_pred.def_id())
             && trait_pred.skip_binder().trait_ref.args.type_at(0).is_unit()
             && let ty::Adt(def, _) = trait_pred.skip_binder().trait_ref.args.type_at(1).kind()
             && self.tcx.is_diagnostic_item(sym::Result, def.did())
         {
-            let body = self.tcx.hir().body(body_id);
             let mut sugg_spans =
                 vec![(ret_span, " -> Result<(), Box<dyn std::error::Error>>".to_string())];
-
+            let body = self.tcx.hir().body(body_id);
             if let hir::ExprKind::Block(b, _) = body.value.kind
                 && b.expr.is_none()
             {