Auto merge of #92518 - matthiaskrgr:rollup-fl8z4e7, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - #90102 (Remove `NullOp::Box`)
 - #92011 (Use field span in `rustc_macros` when emitting decode call)
 - #92402 (Suggest while let x = y when encountering while x = y)
 - #92409 (Couple of libtest cleanups)
 - #92418 (Fix spacing in pretty printed PatKind::Struct with no fields)
 - #92444 (Consolidate Result's and Option's methods into fewer impl blocks)

Failed merges:

 - #92483 (Stabilize `result_cloned` and `result_copied`)

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

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2461,7 +2461,11 @@ impl<'a> State<'a> {
                     self.print_path(path, true, 0);
                 }
                 self.nbsp();
-                self.word_space("{");
+                self.word("{");
+                let empty = fields.is_empty() && !etc;
+                if !empty {
+                    self.space();
+                }
                 self.commasep_cmnt(
                     Consistent,
                     &fields,
@@ -2482,7 +2486,9 @@ impl<'a> State<'a> {
                     }
                     self.word("..");
                 }
-                self.space();
+                if !empty {
+                    self.space();
+                }
                 self.word("}");
             }
             PatKind::Tuple(ref elts) => {

compiler/rustc_borrowck/src/lib.rs

@@ -1394,10 +1394,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
             Rvalue::NullaryOp(_op, _ty) => {
                 // nullary ops take no dynamic input; no borrowck effect.
-                //
-                // FIXME: is above actually true? Do we want to track
-                // the fact that uninitialized data can be created via
-                // `NullOp::Box`?
             }
 
             Rvalue::Aggregate(ref aggregate_kind, ref operands) => {

compiler/rustc_codegen_cranelift/src/base.rs

@@ -715,30 +715,6 @@ fn codegen_stmt<'tcx>(
                     let operand = operand.load_scalar(fx);
                     lval.write_cvalue(fx, CValue::by_val(operand, box_layout));
                 }
-                Rvalue::NullaryOp(NullOp::Box, content_ty) => {
-                    let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
-                    let content_ty = fx.monomorphize(content_ty);
-                    let layout = fx.layout_of(content_ty);
-                    let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
-                    let llalign = fx.bcx.ins().iconst(usize_type, layout.align.abi.bytes() as i64);
-                    let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
-
-                    // Allocate space:
-                    let def_id =
-                        match fx.tcx.lang_items().require(rustc_hir::LangItem::ExchangeMalloc) {
-                            Ok(id) => id,
-                            Err(s) => {
-                                fx.tcx
-                                    .sess
-                                    .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
-                            }
-                        };
-                    let instance = ty::Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
-                    let func_ref = fx.get_function_ref(instance);
-                    let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
-                    let ptr = fx.bcx.inst_results(call)[0];
-                    lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
-                }
                 Rvalue::NullaryOp(null_op, ty) => {
                     assert!(
                         lval.layout()
@@ -749,7 +725,6 @@ fn codegen_stmt<'tcx>(
                     let val = match null_op {
                         NullOp::SizeOf => layout.size.bytes(),
                         NullOp::AlignOf => layout.align.abi.bytes(),
-                        NullOp::Box => unreachable!(),
                     };
                     let val = CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), val.into());
                     lval.write_cvalue(fx, val);

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -8,7 +8,6 @@ use crate::traits::*;
 use crate::MemFlags;
 
 use rustc_apfloat::{ieee, Float, Round, Status};
-use rustc_hir::lang_items::LangItem;
 use rustc_middle::mir;
 use rustc_middle::ty::cast::{CastTy, IntTy};
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
@@ -486,39 +485,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 )
             }
 
-            mir::Rvalue::NullaryOp(mir::NullOp::Box, content_ty) => {
-                let content_ty = self.monomorphize(content_ty);
-                let content_layout = bx.cx().layout_of(content_ty);
-                let llsize = bx.cx().const_usize(content_layout.size.bytes());
-                let llalign = bx.cx().const_usize(content_layout.align.abi.bytes());
-                let box_layout = bx.cx().layout_of(bx.tcx().mk_box(content_ty));
-                let llty_ptr = bx.cx().backend_type(box_layout);
-
-                // Allocate space:
-                let def_id = match bx.tcx().lang_items().require(LangItem::ExchangeMalloc) {
-                    Ok(id) => id,
-                    Err(s) => {
-                        bx.cx().sess().fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
-                    }
-                };
-                let instance = ty::Instance::mono(bx.tcx(), def_id);
-                let r = bx.cx().get_fn_addr(instance);
-                let ty = bx.type_func(&[bx.type_isize(), bx.type_isize()], bx.type_i8p());
-                let call = bx.call(ty, r, &[llsize, llalign], None);
-                let val = bx.pointercast(call, llty_ptr);
-
-                let operand = OperandRef { val: OperandValue::Immediate(val), layout: box_layout };
-                (bx, operand)
-            }
-
             mir::Rvalue::NullaryOp(null_op, ty) => {
                 let ty = self.monomorphize(ty);
                 assert!(bx.cx().type_is_sized(ty));
                 let layout = bx.cx().layout_of(ty);
                 let val = match null_op {
                     mir::NullOp::SizeOf => layout.size.bytes(),
                     mir::NullOp::AlignOf => layout.align.abi.bytes(),
-                    mir::NullOp::Box => unreachable!(),
                 };
                 let val = bx.cx().const_usize(val);
                 let tcx = self.cx.tcx();

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -398,13 +398,6 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
         Err(ConstEvalErrKind::NeedsRfc("pointer arithmetic or comparison".to_string()).into())
     }
 
-    fn box_alloc(
-        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
-        _dest: &PlaceTy<'tcx>,
-    ) -> InterpResult<'tcx> {
-        Err(ConstEvalErrKind::NeedsRfc("heap allocations via `box` keyword".to_string()).into())
-    }
-
     fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
         // The step limit has already been hit in a previous call to `before_terminator`.
         if ecx.machine.steps_remaining == 0 {

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -156,7 +156,7 @@ pub enum StackPopCleanup {
     /// `ret` stores the block we jump to on a normal return, while `unwind`
     /// stores the block used for cleanup during unwinding.
     Goto { ret: Option<mir::BasicBlock>, unwind: StackPopUnwind },
-    /// Just do nothing: Used by Main and for the `box_alloc` hook in miri.
+    /// Just do nothing: Used by Main and for TLS hooks in miri.
     /// `cleanup` says whether locals are deallocated. Static computation
     /// wants them leaked to intern what they need (and just throw away
     /// the entire `ecx` when it is done).

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -212,12 +212,6 @@ pub trait Machine<'mir, 'tcx>: Sized {
         right: &ImmTy<'tcx, Self::PointerTag>,
     ) -> InterpResult<'tcx, (Scalar<Self::PointerTag>, bool, Ty<'tcx>)>;
 
-    /// Heap allocations via the `box` keyword.
-    fn box_alloc(
-        ecx: &mut InterpCx<'mir, 'tcx, Self>,
-        dest: &PlaceTy<'tcx, Self::PointerTag>,
-    ) -> InterpResult<'tcx>;
-
     /// Called to read the specified `local` from the `frame`.
     /// Since reading a ZST is not actually accessing memory or locals, this is never invoked
     /// for ZST reads.

compiler/rustc_const_eval/src/interpret/step.rs

@@ -271,10 +271,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.write_immediate(place.to_ref(self), &dest)?;
             }
 
-            NullaryOp(mir::NullOp::Box, _) => {
-                M::box_alloc(self, &dest)?;
-            }
-
             NullaryOp(null_op, ty) => {
                 let ty = self.subst_from_current_frame_and_normalize_erasing_regions(ty)?;
                 let layout = self.layout_of(ty)?;
@@ -289,7 +285,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let val = match null_op {
                     mir::NullOp::SizeOf => layout.size.bytes(),
                     mir::NullOp::AlignOf => layout.align.abi.bytes(),
-                    mir::NullOp::Box => unreachable!(),
                 };
                 self.write_scalar(Scalar::from_machine_usize(val, self), &dest)?;
             }

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -632,7 +632,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             }
 
             Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => {}
-            Rvalue::NullaryOp(NullOp::Box, _) => self.check_op(ops::HeapAllocation),
             Rvalue::ShallowInitBox(_, _) => {}
 
             Rvalue::UnaryOp(_, ref operand) => {

compiler/rustc_const_eval/src/transform/promote_consts.rs

@@ -508,7 +508,6 @@ impl<'tcx> Validator<'_, 'tcx> {
             }
 
             Rvalue::NullaryOp(op, _) => match op {
-                NullOp::Box => return Err(Unpromotable),
                 NullOp::SizeOf => {}
                 NullOp::AlignOf => {}
             },

compiler/rustc_hir_pretty/src/lib.rs

@@ -1874,7 +1874,11 @@ impl<'a> State<'a> {
             PatKind::Struct(ref qpath, ref fields, etc) => {
                 self.print_qpath(qpath, true);
                 self.nbsp();
-                self.word_space("{");
+                self.word("{");
+                let empty = fields.is_empty() && !etc;
+                if !empty {
+                    self.space();
+                }
                 self.commasep_cmnt(
                     Consistent,
                     &fields,
@@ -1895,7 +1899,9 @@ impl<'a> State<'a> {
                     }
                     self.word("..");
                 }
-                self.space();
+                if !empty {
+                    self.space();
+                }
                 self.word("}");
             }
             PatKind::Or(ref pats) => {

compiler/rustc_macros/src/serialize.rs

@@ -1,6 +1,7 @@
 use proc_macro2::TokenStream;
-use quote::quote;
+use quote::{quote, quote_spanned};
 use syn::parse_quote;
+use syn::spanned::Spanned;
 
 pub fn type_decodable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
     let decoder_ty = quote! { __D };
@@ -104,27 +105,30 @@ fn decodable_body(
 }
 
 fn decode_field(field: &syn::Field, index: usize, is_struct: bool) -> proc_macro2::TokenStream {
+    let field_span = field.ident.as_ref().map_or(field.ty.span(), |ident| ident.span());
+
     let decode_inner_method = if let syn::Type::Reference(_) = field.ty {
         quote! { ::rustc_middle::ty::codec::RefDecodable::decode }
     } else {
         quote! { ::rustc_serialize::Decodable::decode }
     };
     let (decode_method, opt_field_name) = if is_struct {
         let field_name = field.ident.as_ref().map_or_else(|| index.to_string(), |i| i.to_string());
-        (
-            proc_macro2::Ident::new("read_struct_field", proc_macro2::Span::call_site()),
-            quote! { #field_name, },
-        )
+        (proc_macro2::Ident::new("read_struct_field", field_span), quote! { #field_name, })
     } else {
-        (
-            proc_macro2::Ident::new("read_enum_variant_arg", proc_macro2::Span::call_site()),
-            quote! {},
-        )
+        (proc_macro2::Ident::new("read_enum_variant_arg", field_span), quote! {})
+    };
+
+    let __decoder = quote! { __decoder };
+    // Use the span of the field for the method call, so
+    // that backtraces will point to the field.
+    let decode_call = quote_spanned! {field_span=>
+        ::rustc_serialize::Decoder::#decode_method(
+                #__decoder, #opt_field_name #decode_inner_method)
     };
 
     quote! {
-        match ::rustc_serialize::Decoder::#decode_method(
-            __decoder, #opt_field_name #decode_inner_method) {
+        match #decode_call  {
             ::std::result::Result::Ok(__res) => __res,
             ::std::result::Result::Err(__err) => return ::std::result::Result::Err(__err),
         }

compiler/rustc_middle/src/mir/mod.rs

@@ -2336,8 +2336,6 @@ pub enum NullOp {
     SizeOf,
     /// Returns the minimum alignment of a type
     AlignOf,
-    /// Creates a new uninitialized box for a value of that type
-    Box,
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]

compiler/rustc_middle/src/mir/tcx.rs

@@ -195,7 +195,6 @@ impl<'tcx> Rvalue<'tcx> {
             }
             Rvalue::UnaryOp(UnOp::Not | UnOp::Neg, ref operand) => operand.ty(local_decls, tcx),
             Rvalue::Discriminant(ref place) => place.ty(local_decls, tcx).ty.discriminant_ty(tcx),
-            Rvalue::NullaryOp(NullOp::Box, t) => tcx.mk_box(t),
             Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => tcx.types.usize,
             Rvalue::Aggregate(ref ak, ref ops) => match **ak {
                 AggregateKind::Array(ty) => tcx.mk_array(ty, ops.len() as u64),
@@ -215,9 +214,7 @@ impl<'tcx> Rvalue<'tcx> {
     /// whether its only shallowly initialized (`Rvalue::Box`).
     pub fn initialization_state(&self) -> RvalueInitializationState {
         match *self {
-            Rvalue::NullaryOp(NullOp::Box, _) | Rvalue::ShallowInitBox(_, _) => {
-                RvalueInitializationState::Shallow
-            }
+            Rvalue::ShallowInitBox(_, _) => RvalueInitializationState::Shallow,
             _ => RvalueInitializationState::Deep,
         }
     }

compiler/rustc_mir_dataflow/src/move_paths/builder.rs

@@ -343,19 +343,7 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             | Rvalue::AddressOf(..)
             | Rvalue::Discriminant(..)
             | Rvalue::Len(..)
-            | Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _)
-            | Rvalue::NullaryOp(NullOp::Box, _) => {
-                // This returns an rvalue with uninitialized contents. We can't
-                // move out of it here because it is an rvalue - assignments always
-                // completely initialize their place.
-                //
-                // However, this does not matter - MIR building is careful to
-                // only emit a shallow free for the partially-initialized
-                // temporary.
-                //
-                // In any case, if we want to fix this, we have to register a
-                // special move and change the `statement_effect` functions.
-            }
+            | Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => {}
         }
     }
 

compiler/rustc_mir_transform/src/const_prop.rs

@@ -239,13 +239,6 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>
         throw_machine_stop_str!("pointer arithmetic or comparisons aren't supported in ConstProp")
     }
 
-    fn box_alloc(
-        _ecx: &mut InterpCx<'mir, 'tcx, Self>,
-        _dest: &PlaceTy<'tcx>,
-    ) -> InterpResult<'tcx> {
-        throw_machine_stop_str!("can't const prop heap allocations")
-    }
-
     fn access_local(
         _ecx: &InterpCx<'mir, 'tcx, Self>,
         frame: &Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>,

compiler/rustc_monomorphize/src/collector.rs

@@ -688,15 +688,6 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
                     _ => bug!(),
                 }
             }
-            mir::Rvalue::NullaryOp(mir::NullOp::Box, _) => {
-                let tcx = self.tcx;
-                let exchange_malloc_fn_def_id =
-                    tcx.require_lang_item(LangItem::ExchangeMalloc, None);
-                let instance = Instance::mono(tcx, exchange_malloc_fn_def_id);
-                if should_codegen_locally(tcx, &instance) {
-                    self.output.push(create_fn_mono_item(self.tcx, instance, span));
-                }
-            }
             mir::Rvalue::ThreadLocalRef(def_id) => {
                 assert!(self.tcx.is_thread_local_static(def_id));
                 let instance = Instance::mono(self.tcx, def_id);

compiler/rustc_resolve/src/late.rs

@@ -2379,7 +2379,9 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
             ExprKind::While(ref cond, ref block, label) => {
                 self.with_resolved_label(label, expr.id, |this| {
                     this.with_rib(ValueNS, NormalRibKind, |this| {
+                        let old = this.diagnostic_metadata.in_if_condition.replace(cond);
                         this.visit_expr(cond);
+                        this.diagnostic_metadata.in_if_condition = old;
                         this.visit_block(block);
                     })
                 });