rustc_mir_build/thir/cx/
expr.rs

1use itertools::Itertools;
2use rustc_abi::{FIRST_VARIANT, FieldIdx};
3use rustc_ast::UnsafeBinderCastKind;
4use rustc_data_structures::stack::ensure_sufficient_stack;
5use rustc_hir as hir;
6use rustc_hir::attrs::AttributeKind;
7use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
8use rustc_hir::find_attr;
9use rustc_index::Idx;
10use rustc_middle::hir::place::{
11    Place as HirPlace, PlaceBase as HirPlaceBase, ProjectionKind as HirProjectionKind,
12};
13use rustc_middle::middle::region;
14use rustc_middle::mir::{self, AssignOp, BinOp, BorrowKind, UnOp};
15use rustc_middle::thir::*;
16use rustc_middle::ty::adjustment::{
17    Adjust, Adjustment, AutoBorrow, AutoBorrowMutability, PointerCoercion,
18};
19use rustc_middle::ty::{
20    self, AdtKind, GenericArgs, InlineConstArgs, InlineConstArgsParts, ScalarInt, Ty, UpvarArgs,
21};
22use rustc_middle::{bug, span_bug};
23use rustc_span::{Span, sym};
24use tracing::{debug, info, instrument, trace};
25
26use crate::errors::*;
27use crate::thir::cx::ThirBuildCx;
28
29impl<'tcx> ThirBuildCx<'tcx> {
30    /// Create a THIR expression for the given HIR expression. This expands all
31    /// adjustments and directly adds the type information from the
32    /// `typeck_results`. See the [dev-guide] for more details.
33    ///
34    /// (The term "mirror" in this case does not refer to "flipped" or
35    /// "reversed".)
36    ///
37    /// [dev-guide]: https://rustc-dev-guide.rust-lang.org/thir.html
38    pub(crate) fn mirror_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) -> ExprId {
39        // `mirror_expr` is recursing very deep. Make sure the stack doesn't overflow.
40        ensure_sufficient_stack(|| self.mirror_expr_inner(expr))
41    }
42
43    pub(crate) fn mirror_exprs(&mut self, exprs: &'tcx [hir::Expr<'tcx>]) -> Box<[ExprId]> {
44        // `mirror_exprs` may also recurse deeply, so it needs protection from stack overflow.
45        // Note that we *could* forward to `mirror_expr` for that, but we can consolidate the
46        // overhead of stack growth by doing it outside the iteration.
47        ensure_sufficient_stack(|| exprs.iter().map(|expr| self.mirror_expr_inner(expr)).collect())
48    }
49
50    #[instrument(level = "trace", skip(self, hir_expr))]
51    pub(super) fn mirror_expr_inner(&mut self, hir_expr: &'tcx hir::Expr<'tcx>) -> ExprId {
52        let expr_scope =
53            region::Scope { local_id: hir_expr.hir_id.local_id, data: region::ScopeData::Node };
54
55        trace!(?hir_expr.hir_id, ?hir_expr.span);
56
57        let mut expr = self.make_mirror_unadjusted(hir_expr);
58
59        trace!(?expr.ty);
60
61        // Now apply adjustments, if any.
62        if self.apply_adjustments {
63            for adjustment in self.typeck_results.expr_adjustments(hir_expr) {
64                trace!(?expr, ?adjustment);
65                let span = expr.span;
66                expr = self.apply_adjustment(hir_expr, expr, adjustment, span);
67            }
68        }
69
70        trace!(?expr.ty, "after adjustments");
71
72        // Finally, wrap this up in the expr's scope.
73        expr = Expr {
74            temp_lifetime: expr.temp_lifetime,
75            ty: expr.ty,
76            span: hir_expr.span,
77            kind: ExprKind::Scope {
78                region_scope: expr_scope,
79                value: self.thir.exprs.push(expr),
80                lint_level: LintLevel::Explicit(hir_expr.hir_id),
81            },
82        };
83
84        // OK, all done!
85        self.thir.exprs.push(expr)
86    }
87
88    #[instrument(level = "trace", skip(self, expr, span))]
89    fn apply_adjustment(
90        &mut self,
91        hir_expr: &'tcx hir::Expr<'tcx>,
92        mut expr: Expr<'tcx>,
93        adjustment: &Adjustment<'tcx>,
94        mut span: Span,
95    ) -> Expr<'tcx> {
96        let Expr { temp_lifetime, .. } = expr;
97
98        // Adjust the span from the block, to the last expression of the
99        // block. This is a better span when returning a mutable reference
100        // with too short a lifetime. The error message will use the span
101        // from the assignment to the return place, which should only point
102        // at the returned value, not the entire function body.
103        //
104        // fn return_short_lived<'a>(x: &'a mut i32) -> &'static mut i32 {
105        //      x
106        //   // ^ error message points at this expression.
107        // }
108        let mut adjust_span = |expr: &mut Expr<'tcx>| {
109            if let ExprKind::Block { block } = expr.kind
110                && let Some(last_expr) = self.thir[block].expr
111            {
112                span = self.thir[last_expr].span;
113                expr.span = span;
114            }
115        };
116
117        let kind = match adjustment.kind {
118            Adjust::Pointer(cast) => {
119                if cast == PointerCoercion::Unsize {
120                    adjust_span(&mut expr);
121                }
122
123                let is_from_as_cast = if let hir::Node::Expr(hir::Expr {
124                    kind: hir::ExprKind::Cast(..),
125                    span: cast_span,
126                    ..
127                }) = self.tcx.parent_hir_node(hir_expr.hir_id)
128                {
129                    // Use the whole span of the `x as T` expression for the coercion.
130                    span = *cast_span;
131                    true
132                } else {
133                    false
134                };
135                ExprKind::PointerCoercion {
136                    cast,
137                    source: self.thir.exprs.push(expr),
138                    is_from_as_cast,
139                }
140            }
141            Adjust::NeverToAny if adjustment.target.is_never() => return expr,
142            Adjust::NeverToAny => ExprKind::NeverToAny { source: self.thir.exprs.push(expr) },
143            Adjust::Deref(None) => {
144                adjust_span(&mut expr);
145                ExprKind::Deref { arg: self.thir.exprs.push(expr) }
146            }
147            Adjust::Deref(Some(deref)) => {
148                // We don't need to do call adjust_span here since
149                // deref coercions always start with a built-in deref.
150                let call_def_id = deref.method_call(self.tcx);
151                let overloaded_callee =
152                    Ty::new_fn_def(self.tcx, call_def_id, self.tcx.mk_args(&[expr.ty.into()]));
153
154                expr = Expr {
155                    temp_lifetime,
156                    ty: Ty::new_ref(self.tcx, self.tcx.lifetimes.re_erased, expr.ty, deref.mutbl),
157                    span,
158                    kind: ExprKind::Borrow {
159                        borrow_kind: deref.mutbl.to_borrow_kind(),
160                        arg: self.thir.exprs.push(expr),
161                    },
162                };
163
164                let expr = Box::new([self.thir.exprs.push(expr)]);
165
166                self.overloaded_place(
167                    hir_expr,
168                    adjustment.target,
169                    Some(overloaded_callee),
170                    expr,
171                    deref.span,
172                )
173            }
174            Adjust::Borrow(AutoBorrow::Ref(m)) => ExprKind::Borrow {
175                borrow_kind: m.to_borrow_kind(),
176                arg: self.thir.exprs.push(expr),
177            },
178            Adjust::Borrow(AutoBorrow::RawPtr(mutability)) => {
179                ExprKind::RawBorrow { mutability, arg: self.thir.exprs.push(expr) }
180            }
181            Adjust::ReborrowPin(mutbl) => {
182                debug!("apply ReborrowPin adjustment");
183                // Rewrite `$expr` as `Pin { __pointer: &(mut)? *($expr).__pointer }`
184
185                // We'll need these types later on
186                let pin_ty_args = match expr.ty.kind() {
187                    ty::Adt(_, args) => args,
188                    _ => bug!("ReborrowPin with non-Pin type"),
189                };
190                let pin_ty = pin_ty_args.iter().next().unwrap().expect_ty();
191                let ptr_target_ty = match pin_ty.kind() {
192                    ty::Ref(_, ty, _) => *ty,
193                    _ => bug!("ReborrowPin with non-Ref type"),
194                };
195
196                // pointer = ($expr).__pointer
197                let pointer_target = ExprKind::Field {
198                    lhs: self.thir.exprs.push(expr),
199                    variant_index: FIRST_VARIANT,
200                    name: FieldIdx::ZERO,
201                };
202                let arg = Expr { temp_lifetime, ty: pin_ty, span, kind: pointer_target };
203                let arg = self.thir.exprs.push(arg);
204
205                // arg = *pointer
206                let expr = ExprKind::Deref { arg };
207                let arg = self.thir.exprs.push(Expr {
208                    temp_lifetime,
209                    ty: ptr_target_ty,
210                    span,
211                    kind: expr,
212                });
213
214                // expr = &mut target
215                let borrow_kind = match mutbl {
216                    hir::Mutability::Mut => BorrowKind::Mut { kind: mir::MutBorrowKind::Default },
217                    hir::Mutability::Not => BorrowKind::Shared,
218                };
219                let new_pin_target =
220                    Ty::new_ref(self.tcx, self.tcx.lifetimes.re_erased, ptr_target_ty, mutbl);
221                let expr = self.thir.exprs.push(Expr {
222                    temp_lifetime,
223                    ty: new_pin_target,
224                    span,
225                    kind: ExprKind::Borrow { borrow_kind, arg },
226                });
227
228                // kind = Pin { __pointer: pointer }
229                let pin_did = self.tcx.require_lang_item(rustc_hir::LangItem::Pin, span);
230                let args = self.tcx.mk_args(&[new_pin_target.into()]);
231                let kind = ExprKind::Adt(Box::new(AdtExpr {
232                    adt_def: self.tcx.adt_def(pin_did),
233                    variant_index: FIRST_VARIANT,
234                    args,
235                    fields: Box::new([FieldExpr { name: FieldIdx::ZERO, expr }]),
236                    user_ty: None,
237                    base: AdtExprBase::None,
238                }));
239
240                debug!(?kind);
241                kind
242            }
243        };
244
245        Expr { temp_lifetime, ty: adjustment.target, span, kind }
246    }
247
248    /// Lowers a cast expression.
249    ///
250    /// Dealing with user type annotations is left to the caller.
251    fn mirror_expr_cast(
252        &mut self,
253        source: &'tcx hir::Expr<'tcx>,
254        temp_lifetime: TempLifetime,
255        span: Span,
256    ) -> ExprKind<'tcx> {
257        let tcx = self.tcx;
258
259        // Check to see if this cast is a "coercion cast", where the cast is actually done
260        // using a coercion (or is a no-op).
261        if self.typeck_results.is_coercion_cast(source.hir_id) {
262            // Convert the lexpr to a vexpr.
263            ExprKind::Use { source: self.mirror_expr(source) }
264        } else if self.typeck_results.expr_ty(source).is_ref() {
265            // Special cased so that we can type check that the element
266            // type of the source matches the pointed to type of the
267            // destination.
268            ExprKind::PointerCoercion {
269                source: self.mirror_expr(source),
270                cast: PointerCoercion::ArrayToPointer,
271                is_from_as_cast: true,
272            }
273        } else if let hir::ExprKind::Path(ref qpath) = source.kind
274            && let res = self.typeck_results.qpath_res(qpath, source.hir_id)
275            && let ty = self.typeck_results.node_type(source.hir_id)
276            && let ty::Adt(adt_def, args) = ty.kind()
277            && let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Const), variant_ctor_id) = res
278        {
279            // Check whether this is casting an enum variant discriminant.
280            // To prevent cycles, we refer to the discriminant initializer,
281            // which is always an integer and thus doesn't need to know the
282            // enum's layout (or its tag type) to compute it during const eval.
283            // Example:
284            // enum Foo {
285            //     A,
286            //     B = A as isize + 4,
287            // }
288            // The correct solution would be to add symbolic computations to miri,
289            // so we wouldn't have to compute and store the actual value
290
291            let idx = adt_def.variant_index_with_ctor_id(variant_ctor_id);
292            let (discr_did, discr_offset) = adt_def.discriminant_def_for_variant(idx);
293
294            use rustc_middle::ty::util::IntTypeExt;
295            let ty = adt_def.repr().discr_type();
296            let discr_ty = ty.to_ty(tcx);
297
298            let size = tcx
299                .layout_of(self.typing_env.as_query_input(discr_ty))
300                .unwrap_or_else(|e| panic!("could not compute layout for {discr_ty:?}: {e:?}"))
301                .size;
302
303            let (lit, overflowing) = ScalarInt::truncate_from_uint(discr_offset as u128, size);
304            if overflowing {
305                // An erroneous enum with too many variants for its repr will emit E0081 and E0370
306                self.tcx.dcx().span_delayed_bug(
307                    source.span,
308                    "overflowing enum wasn't rejected by hir analysis",
309                );
310            }
311            let kind = ExprKind::NonHirLiteral { lit, user_ty: None };
312            let offset = self.thir.exprs.push(Expr { temp_lifetime, ty: discr_ty, span, kind });
313
314            let source = match discr_did {
315                // in case we are offsetting from a computed discriminant
316                // and not the beginning of discriminants (which is always `0`)
317                Some(did) => {
318                    let kind = ExprKind::NamedConst { def_id: did, args, user_ty: None };
319                    let lhs =
320                        self.thir.exprs.push(Expr { temp_lifetime, ty: discr_ty, span, kind });
321                    let bin = ExprKind::Binary { op: BinOp::Add, lhs, rhs: offset };
322                    self.thir.exprs.push(Expr { temp_lifetime, ty: discr_ty, span, kind: bin })
323                }
324                None => offset,
325            };
326
327            ExprKind::Cast { source }
328        } else {
329            // Default to `ExprKind::Cast` for all explicit casts.
330            // MIR building then picks the right MIR casts based on the types.
331            ExprKind::Cast { source: self.mirror_expr(source) }
332        }
333    }
334
335    #[instrument(level = "debug", skip(self), ret)]
336    fn make_mirror_unadjusted(&mut self, expr: &'tcx hir::Expr<'tcx>) -> Expr<'tcx> {
337        let tcx = self.tcx;
338        let expr_ty = self.typeck_results.expr_ty(expr);
339        let (temp_lifetime, backwards_incompatible) =
340            self.rvalue_scopes.temporary_scope(self.region_scope_tree, expr.hir_id.local_id);
341
342        let kind = match expr.kind {
343            // Here comes the interesting stuff:
344            hir::ExprKind::MethodCall(segment, receiver, args, fn_span) => {
345                // Rewrite a.b(c) into UFCS form like Trait::b(a, c)
346                let expr = self.method_callee(expr, segment.ident.span, None);
347                info!("Using method span: {:?}", expr.span);
348                let args = std::iter::once(receiver)
349                    .chain(args.iter())
350                    .map(|expr| self.mirror_expr(expr))
351                    .collect();
352                ExprKind::Call {
353                    ty: expr.ty,
354                    fun: self.thir.exprs.push(expr),
355                    args,
356                    from_hir_call: true,
357                    fn_span,
358                }
359            }
360
361            hir::ExprKind::Call(fun, ref args) => {
362                if self.typeck_results.is_method_call(expr) {
363                    // The callee is something implementing Fn, FnMut, or FnOnce.
364                    // Find the actual method implementation being called and
365                    // build the appropriate UFCS call expression with the
366                    // callee-object as expr parameter.
367
368                    // rewrite f(u, v) into FnOnce::call_once(f, (u, v))
369
370                    let method = self.method_callee(expr, fun.span, None);
371
372                    let arg_tys = args.iter().map(|e| self.typeck_results.expr_ty_adjusted(e));
373                    let tupled_args = Expr {
374                        ty: Ty::new_tup_from_iter(tcx, arg_tys),
375                        temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
376                        span: expr.span,
377                        kind: ExprKind::Tuple { fields: self.mirror_exprs(args) },
378                    };
379                    let tupled_args = self.thir.exprs.push(tupled_args);
380
381                    ExprKind::Call {
382                        ty: method.ty,
383                        fun: self.thir.exprs.push(method),
384                        args: Box::new([self.mirror_expr(fun), tupled_args]),
385                        from_hir_call: true,
386                        fn_span: expr.span,
387                    }
388                } else if let ty::FnDef(def_id, _) = self.typeck_results.expr_ty(fun).kind()
389                    && let Some(intrinsic) = self.tcx.intrinsic(def_id)
390                    && intrinsic.name == sym::box_new
391                {
392                    // We don't actually evaluate `fun` here, so make sure that doesn't miss any side-effects.
393                    if !matches!(fun.kind, hir::ExprKind::Path(_)) {
394                        span_bug!(
395                            expr.span,
396                            "`box_new` intrinsic can only be called via path expression"
397                        );
398                    }
399                    let value = &args[0];
400                    return Expr {
401                        temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
402                        ty: expr_ty,
403                        span: expr.span,
404                        kind: ExprKind::Box { value: self.mirror_expr(value) },
405                    };
406                } else {
407                    // Tuple-like ADTs are represented as ExprKind::Call. We convert them here.
408                    let adt_data = if let hir::ExprKind::Path(ref qpath) = fun.kind
409                        && let Some(adt_def) = expr_ty.ty_adt_def()
410                    {
411                        match qpath {
412                            hir::QPath::Resolved(_, path) => match path.res {
413                                Res::Def(DefKind::Ctor(_, CtorKind::Fn), ctor_id) => {
414                                    Some((adt_def, adt_def.variant_index_with_ctor_id(ctor_id)))
415                                }
416                                Res::SelfCtor(..) => Some((adt_def, FIRST_VARIANT)),
417                                _ => None,
418                            },
419                            hir::QPath::TypeRelative(_ty, _) => {
420                                if let Some((DefKind::Ctor(_, CtorKind::Fn), ctor_id)) =
421                                    self.typeck_results.type_dependent_def(fun.hir_id)
422                                {
423                                    Some((adt_def, adt_def.variant_index_with_ctor_id(ctor_id)))
424                                } else {
425                                    None
426                                }
427                            }
428                            _ => None,
429                        }
430                    } else {
431                        None
432                    };
433                    if let Some((adt_def, index)) = adt_data {
434                        let node_args = self.typeck_results.node_args(fun.hir_id);
435                        let user_provided_types = self.typeck_results.user_provided_types();
436                        let user_ty =
437                            user_provided_types.get(fun.hir_id).copied().map(|mut u_ty| {
438                                if let ty::UserTypeKind::TypeOf(did, _) = &mut u_ty.value.kind {
439                                    *did = adt_def.did();
440                                }
441                                Box::new(u_ty)
442                            });
443                        debug!("make_mirror_unadjusted: (call) user_ty={:?}", user_ty);
444
445                        let field_refs = args
446                            .iter()
447                            .enumerate()
448                            .map(|(idx, e)| FieldExpr {
449                                name: FieldIdx::new(idx),
450                                expr: self.mirror_expr(e),
451                            })
452                            .collect();
453                        ExprKind::Adt(Box::new(AdtExpr {
454                            adt_def,
455                            args: node_args,
456                            variant_index: index,
457                            fields: field_refs,
458                            user_ty,
459                            base: AdtExprBase::None,
460                        }))
461                    } else {
462                        ExprKind::Call {
463                            ty: self.typeck_results.node_type(fun.hir_id),
464                            fun: self.mirror_expr(fun),
465                            args: self.mirror_exprs(args),
466                            from_hir_call: true,
467                            fn_span: expr.span,
468                        }
469                    }
470                }
471            }
472
473            hir::ExprKind::Use(expr, span) => {
474                ExprKind::ByUse { expr: self.mirror_expr(expr), span }
475            }
476
477            hir::ExprKind::AddrOf(hir::BorrowKind::Ref, mutbl, arg) => {
478                ExprKind::Borrow { borrow_kind: mutbl.to_borrow_kind(), arg: self.mirror_expr(arg) }
479            }
480
481            hir::ExprKind::AddrOf(hir::BorrowKind::Raw, mutability, arg) => {
482                ExprKind::RawBorrow { mutability, arg: self.mirror_expr(arg) }
483            }
484
485            // Make `&pin mut $expr` and `&pin const $expr` into
486            // `Pin { __pointer: &mut { $expr } }` and `Pin { __pointer: &$expr }`.
487            hir::ExprKind::AddrOf(hir::BorrowKind::Pin, mutbl, arg_expr) => match expr_ty.kind() {
488                &ty::Adt(adt_def, args) if tcx.is_lang_item(adt_def.did(), hir::LangItem::Pin) => {
489                    let ty = args.type_at(0);
490                    let arg_ty = self.typeck_results.expr_ty(arg_expr);
491                    let mut arg = self.mirror_expr(arg_expr);
492                    // For `&pin mut $place` where `$place` is not `Unpin`, move the place
493                    // `$place` to ensure it will not be used afterwards.
494                    if mutbl.is_mut() && !arg_ty.is_unpin(self.tcx, self.typing_env) {
495                        let block = self.thir.blocks.push(Block {
496                            targeted_by_break: false,
497                            region_scope: region::Scope {
498                                local_id: arg_expr.hir_id.local_id,
499                                data: region::ScopeData::Node,
500                            },
501                            span: arg_expr.span,
502                            stmts: Box::new([]),
503                            expr: Some(arg),
504                            safety_mode: BlockSafety::Safe,
505                        });
506                        let (temp_lifetime, backwards_incompatible) = self
507                            .rvalue_scopes
508                            .temporary_scope(self.region_scope_tree, arg_expr.hir_id.local_id);
509                        arg = self.thir.exprs.push(Expr {
510                            temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
511                            ty: arg_ty,
512                            span: arg_expr.span,
513                            kind: ExprKind::Block { block },
514                        });
515                    }
516                    let expr = self.thir.exprs.push(Expr {
517                        temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
518                        ty,
519                        span: expr.span,
520                        kind: ExprKind::Borrow { borrow_kind: mutbl.to_borrow_kind(), arg },
521                    });
522                    ExprKind::Adt(Box::new(AdtExpr {
523                        adt_def,
524                        variant_index: FIRST_VARIANT,
525                        args,
526                        fields: Box::new([FieldExpr { name: FieldIdx::from(0u32), expr }]),
527                        user_ty: None,
528                        base: AdtExprBase::None,
529                    }))
530                }
531                _ => span_bug!(expr.span, "unexpected type for pinned borrow: {:?}", expr_ty),
532            },
533
534            hir::ExprKind::Block(blk, _) => ExprKind::Block { block: self.mirror_block(blk) },
535
536            hir::ExprKind::Assign(lhs, rhs, _) => {
537                ExprKind::Assign { lhs: self.mirror_expr(lhs), rhs: self.mirror_expr(rhs) }
538            }
539
540            hir::ExprKind::AssignOp(op, lhs, rhs) => {
541                if self.typeck_results.is_method_call(expr) {
542                    let lhs = self.mirror_expr(lhs);
543                    let rhs = self.mirror_expr(rhs);
544                    self.overloaded_operator(expr, Box::new([lhs, rhs]))
545                } else {
546                    ExprKind::AssignOp {
547                        op: assign_op(op.node),
548                        lhs: self.mirror_expr(lhs),
549                        rhs: self.mirror_expr(rhs),
550                    }
551                }
552            }
553
554            hir::ExprKind::Lit(lit) => ExprKind::Literal { lit, neg: false },
555
556            hir::ExprKind::Binary(op, lhs, rhs) => {
557                if self.typeck_results.is_method_call(expr) {
558                    let lhs = self.mirror_expr(lhs);
559                    let rhs = self.mirror_expr(rhs);
560                    self.overloaded_operator(expr, Box::new([lhs, rhs]))
561                } else {
562                    match op.node {
563                        hir::BinOpKind::And => ExprKind::LogicalOp {
564                            op: LogicalOp::And,
565                            lhs: self.mirror_expr(lhs),
566                            rhs: self.mirror_expr(rhs),
567                        },
568                        hir::BinOpKind::Or => ExprKind::LogicalOp {
569                            op: LogicalOp::Or,
570                            lhs: self.mirror_expr(lhs),
571                            rhs: self.mirror_expr(rhs),
572                        },
573                        _ => {
574                            let op = bin_op(op.node);
575                            ExprKind::Binary {
576                                op,
577                                lhs: self.mirror_expr(lhs),
578                                rhs: self.mirror_expr(rhs),
579                            }
580                        }
581                    }
582                }
583            }
584
585            hir::ExprKind::Index(lhs, index, brackets_span) => {
586                if self.typeck_results.is_method_call(expr) {
587                    let lhs = self.mirror_expr(lhs);
588                    let index = self.mirror_expr(index);
589                    self.overloaded_place(
590                        expr,
591                        expr_ty,
592                        None,
593                        Box::new([lhs, index]),
594                        brackets_span,
595                    )
596                } else {
597                    ExprKind::Index { lhs: self.mirror_expr(lhs), index: self.mirror_expr(index) }
598                }
599            }
600
601            hir::ExprKind::Unary(hir::UnOp::Deref, arg) => {
602                if self.typeck_results.is_method_call(expr) {
603                    let arg = self.mirror_expr(arg);
604                    self.overloaded_place(expr, expr_ty, None, Box::new([arg]), expr.span)
605                } else {
606                    ExprKind::Deref { arg: self.mirror_expr(arg) }
607                }
608            }
609
610            hir::ExprKind::Unary(hir::UnOp::Not, arg) => {
611                if self.typeck_results.is_method_call(expr) {
612                    let arg = self.mirror_expr(arg);
613                    self.overloaded_operator(expr, Box::new([arg]))
614                } else {
615                    ExprKind::Unary { op: UnOp::Not, arg: self.mirror_expr(arg) }
616                }
617            }
618
619            hir::ExprKind::Unary(hir::UnOp::Neg, arg) => {
620                if self.typeck_results.is_method_call(expr) {
621                    let arg = self.mirror_expr(arg);
622                    self.overloaded_operator(expr, Box::new([arg]))
623                } else if let hir::ExprKind::Lit(lit) = arg.kind {
624                    ExprKind::Literal { lit, neg: true }
625                } else {
626                    ExprKind::Unary { op: UnOp::Neg, arg: self.mirror_expr(arg) }
627                }
628            }
629
630            hir::ExprKind::Struct(qpath, fields, ref base) => match expr_ty.kind() {
631                ty::Adt(adt, args) => match adt.adt_kind() {
632                    AdtKind::Struct | AdtKind::Union => {
633                        let user_provided_types = self.typeck_results.user_provided_types();
634                        let user_ty = user_provided_types.get(expr.hir_id).copied().map(Box::new);
635                        debug!("make_mirror_unadjusted: (struct/union) user_ty={:?}", user_ty);
636                        ExprKind::Adt(Box::new(AdtExpr {
637                            adt_def: *adt,
638                            variant_index: FIRST_VARIANT,
639                            args,
640                            user_ty,
641                            fields: self.field_refs(fields),
642                            base: match base {
643                                hir::StructTailExpr::Base(base) => AdtExprBase::Base(FruInfo {
644                                    base: self.mirror_expr(base),
645                                    field_types: self.typeck_results.fru_field_types()[expr.hir_id]
646                                        .iter()
647                                        .copied()
648                                        .collect(),
649                                }),
650                                hir::StructTailExpr::DefaultFields(_) => {
651                                    AdtExprBase::DefaultFields(
652                                        self.typeck_results.fru_field_types()[expr.hir_id]
653                                            .iter()
654                                            .copied()
655                                            .collect(),
656                                    )
657                                }
658                                hir::StructTailExpr::None => AdtExprBase::None,
659                            },
660                        }))
661                    }
662                    AdtKind::Enum => {
663                        let res = self.typeck_results.qpath_res(qpath, expr.hir_id);
664                        match res {
665                            Res::Def(DefKind::Variant, variant_id) => {
666                                assert!(matches!(
667                                    base,
668                                    hir::StructTailExpr::None
669                                        | hir::StructTailExpr::DefaultFields(_)
670                                ));
671
672                                let index = adt.variant_index_with_id(variant_id);
673                                let user_provided_types = self.typeck_results.user_provided_types();
674                                let user_ty =
675                                    user_provided_types.get(expr.hir_id).copied().map(Box::new);
676                                debug!("make_mirror_unadjusted: (variant) user_ty={:?}", user_ty);
677                                ExprKind::Adt(Box::new(AdtExpr {
678                                    adt_def: *adt,
679                                    variant_index: index,
680                                    args,
681                                    user_ty,
682                                    fields: self.field_refs(fields),
683                                    base: match base {
684                                        hir::StructTailExpr::DefaultFields(_) => {
685                                            AdtExprBase::DefaultFields(
686                                                self.typeck_results.fru_field_types()[expr.hir_id]
687                                                    .iter()
688                                                    .copied()
689                                                    .collect(),
690                                            )
691                                        }
692                                        hir::StructTailExpr::Base(base) => {
693                                            span_bug!(base.span, "unexpected res: {:?}", res);
694                                        }
695                                        hir::StructTailExpr::None => AdtExprBase::None,
696                                    },
697                                }))
698                            }
699                            _ => {
700                                span_bug!(expr.span, "unexpected res: {:?}", res);
701                            }
702                        }
703                    }
704                },
705                _ => {
706                    span_bug!(expr.span, "unexpected type for struct literal: {:?}", expr_ty);
707                }
708            },
709
710            hir::ExprKind::Closure(hir::Closure { .. }) => {
711                let closure_ty = self.typeck_results.expr_ty(expr);
712                let (def_id, args, movability) = match *closure_ty.kind() {
713                    ty::Closure(def_id, args) => (def_id, UpvarArgs::Closure(args), None),
714                    ty::Coroutine(def_id, args) => {
715                        (def_id, UpvarArgs::Coroutine(args), Some(tcx.coroutine_movability(def_id)))
716                    }
717                    ty::CoroutineClosure(def_id, args) => {
718                        (def_id, UpvarArgs::CoroutineClosure(args), None)
719                    }
720                    _ => {
721                        span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
722                    }
723                };
724                let def_id = def_id.expect_local();
725
726                let upvars = self
727                    .tcx
728                    .closure_captures(def_id)
729                    .iter()
730                    .zip_eq(args.upvar_tys())
731                    .map(|(captured_place, ty)| {
732                        let upvars = self.capture_upvar(expr, captured_place, ty);
733                        self.thir.exprs.push(upvars)
734                    })
735                    .collect();
736
737                // Convert the closure fake reads, if any, from hir `Place` to ExprRef
738                let fake_reads = match self.typeck_results.closure_fake_reads.get(&def_id) {
739                    Some(fake_reads) => fake_reads
740                        .iter()
741                        .map(|(place, cause, hir_id)| {
742                            let expr = self.convert_captured_hir_place(expr, place.clone());
743                            (self.thir.exprs.push(expr), *cause, *hir_id)
744                        })
745                        .collect(),
746                    None => Vec::new(),
747                };
748
749                ExprKind::Closure(Box::new(ClosureExpr {
750                    closure_id: def_id,
751                    args,
752                    upvars,
753                    movability,
754                    fake_reads,
755                }))
756            }
757
758            hir::ExprKind::Path(ref qpath) => {
759                let res = self.typeck_results.qpath_res(qpath, expr.hir_id);
760                self.convert_path_expr(expr, res)
761            }
762
763            hir::ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(Box::new(InlineAsmExpr {
764                asm_macro: asm.asm_macro,
765                template: asm.template,
766                operands: asm
767                    .operands
768                    .iter()
769                    .map(|(op, _op_sp)| match *op {
770                        hir::InlineAsmOperand::In { reg, expr } => {
771                            InlineAsmOperand::In { reg, expr: self.mirror_expr(expr) }
772                        }
773                        hir::InlineAsmOperand::Out { reg, late, ref expr } => {
774                            InlineAsmOperand::Out {
775                                reg,
776                                late,
777                                expr: expr.map(|expr| self.mirror_expr(expr)),
778                            }
779                        }
780                        hir::InlineAsmOperand::InOut { reg, late, expr } => {
781                            InlineAsmOperand::InOut { reg, late, expr: self.mirror_expr(expr) }
782                        }
783                        hir::InlineAsmOperand::SplitInOut { reg, late, in_expr, ref out_expr } => {
784                            InlineAsmOperand::SplitInOut {
785                                reg,
786                                late,
787                                in_expr: self.mirror_expr(in_expr),
788                                out_expr: out_expr.map(|expr| self.mirror_expr(expr)),
789                            }
790                        }
791                        hir::InlineAsmOperand::Const { ref anon_const } => {
792                            let ty = self.typeck_results.node_type(anon_const.hir_id);
793                            let did = anon_const.def_id.to_def_id();
794                            let typeck_root_def_id = tcx.typeck_root_def_id(did);
795                            let parent_args = tcx.erase_regions(GenericArgs::identity_for_item(
796                                tcx,
797                                typeck_root_def_id,
798                            ));
799                            let args =
800                                InlineConstArgs::new(tcx, InlineConstArgsParts { parent_args, ty })
801                                    .args;
802
803                            let uneval = mir::UnevaluatedConst::new(did, args);
804                            let value = mir::Const::Unevaluated(uneval, ty);
805                            InlineAsmOperand::Const { value, span: tcx.def_span(did) }
806                        }
807                        hir::InlineAsmOperand::SymFn { expr } => {
808                            InlineAsmOperand::SymFn { value: self.mirror_expr(expr) }
809                        }
810                        hir::InlineAsmOperand::SymStatic { path: _, def_id } => {
811                            InlineAsmOperand::SymStatic { def_id }
812                        }
813                        hir::InlineAsmOperand::Label { block } => {
814                            InlineAsmOperand::Label { block: self.mirror_block(block) }
815                        }
816                    })
817                    .collect(),
818                options: asm.options,
819                line_spans: asm.line_spans,
820            })),
821
822            hir::ExprKind::OffsetOf(_, _) => {
823                let data = self.typeck_results.offset_of_data();
824                let &(container, ref indices) = data.get(expr.hir_id).unwrap();
825                let fields = tcx.mk_offset_of_from_iter(indices.iter().copied());
826
827                ExprKind::OffsetOf { container, fields }
828            }
829
830            hir::ExprKind::ConstBlock(ref anon_const) => {
831                let ty = self.typeck_results.node_type(anon_const.hir_id);
832                let did = anon_const.def_id.to_def_id();
833                let typeck_root_def_id = tcx.typeck_root_def_id(did);
834                let parent_args =
835                    tcx.erase_regions(GenericArgs::identity_for_item(tcx, typeck_root_def_id));
836                let args = InlineConstArgs::new(tcx, InlineConstArgsParts { parent_args, ty }).args;
837
838                ExprKind::ConstBlock { did, args }
839            }
840            // Now comes the rote stuff:
841            hir::ExprKind::Repeat(v, _) => {
842                let ty = self.typeck_results.expr_ty(expr);
843                let ty::Array(_, count) = ty.kind() else {
844                    span_bug!(expr.span, "unexpected repeat expr ty: {:?}", ty);
845                };
846
847                ExprKind::Repeat { value: self.mirror_expr(v), count: *count }
848            }
849            hir::ExprKind::Ret(v) => ExprKind::Return { value: v.map(|v| self.mirror_expr(v)) },
850            hir::ExprKind::Become(call) => ExprKind::Become { value: self.mirror_expr(call) },
851            hir::ExprKind::Break(dest, ref value) => {
852                if find_attr!(self.tcx.hir_attrs(expr.hir_id), AttributeKind::ConstContinue(_)) {
853                    match dest.target_id {
854                        Ok(target_id) => {
855                            let (Some(value), Some(_)) = (value, dest.label) else {
856                                let span = expr.span;
857                                self.tcx.dcx().emit_fatal(ConstContinueMissingLabelOrValue { span })
858                            };
859
860                            ExprKind::ConstContinue {
861                                label: region::Scope {
862                                    local_id: target_id.local_id,
863                                    data: region::ScopeData::Node,
864                                },
865                                value: self.mirror_expr(value),
866                            }
867                        }
868                        Err(err) => bug!("invalid loop id for break: {}", err),
869                    }
870                } else {
871                    match dest.target_id {
872                        Ok(target_id) => ExprKind::Break {
873                            label: region::Scope {
874                                local_id: target_id.local_id,
875                                data: region::ScopeData::Node,
876                            },
877                            value: value.map(|value| self.mirror_expr(value)),
878                        },
879                        Err(err) => bug!("invalid loop id for break: {}", err),
880                    }
881                }
882            }
883            hir::ExprKind::Continue(dest) => match dest.target_id {
884                Ok(loop_id) => ExprKind::Continue {
885                    label: region::Scope {
886                        local_id: loop_id.local_id,
887                        data: region::ScopeData::Node,
888                    },
889                },
890                Err(err) => bug!("invalid loop id for continue: {}", err),
891            },
892            hir::ExprKind::Let(let_expr) => ExprKind::Let {
893                expr: self.mirror_expr(let_expr.init),
894                pat: self.pattern_from_hir(let_expr.pat),
895            },
896            hir::ExprKind::If(cond, then, else_opt) => ExprKind::If {
897                if_then_scope: region::Scope {
898                    local_id: then.hir_id.local_id,
899                    data: {
900                        if expr.span.at_least_rust_2024() {
901                            region::ScopeData::IfThenRescope
902                        } else {
903                            region::ScopeData::IfThen
904                        }
905                    },
906                },
907                cond: self.mirror_expr(cond),
908                then: self.mirror_expr(then),
909                else_opt: else_opt.map(|el| self.mirror_expr(el)),
910            },
911            hir::ExprKind::Match(discr, arms, match_source) => ExprKind::Match {
912                scrutinee: self.mirror_expr(discr),
913                arms: arms.iter().map(|a| self.convert_arm(a)).collect(),
914                match_source,
915            },
916            hir::ExprKind::Loop(body, ..) => {
917                if find_attr!(self.tcx.hir_attrs(expr.hir_id), AttributeKind::LoopMatch(_)) {
918                    let dcx = self.tcx.dcx();
919
920                    // Accept either `state = expr` or `state = expr;`.
921                    let loop_body_expr = match body.stmts {
922                        [] => match body.expr {
923                            Some(expr) => expr,
924                            None => dcx.emit_fatal(LoopMatchMissingAssignment { span: body.span }),
925                        },
926                        [single] if body.expr.is_none() => match single.kind {
927                            hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr) => expr,
928                            _ => dcx.emit_fatal(LoopMatchMissingAssignment { span: body.span }),
929                        },
930                        [first @ last] | [first, .., last] => dcx
931                            .emit_fatal(LoopMatchBadStatements { span: first.span.to(last.span) }),
932                    };
933
934                    let hir::ExprKind::Assign(state, rhs_expr, _) = loop_body_expr.kind else {
935                        dcx.emit_fatal(LoopMatchMissingAssignment { span: loop_body_expr.span })
936                    };
937
938                    let hir::ExprKind::Block(block_body, _) = rhs_expr.kind else {
939                        dcx.emit_fatal(LoopMatchBadRhs { span: rhs_expr.span })
940                    };
941
942                    // The labeled block should contain one match expression, but defining items is
943                    // allowed.
944                    for stmt in block_body.stmts {
945                        if !matches!(stmt.kind, rustc_hir::StmtKind::Item(_)) {
946                            dcx.emit_fatal(LoopMatchBadStatements { span: stmt.span })
947                        }
948                    }
949
950                    let Some(block_body_expr) = block_body.expr else {
951                        dcx.emit_fatal(LoopMatchBadRhs { span: block_body.span })
952                    };
953
954                    let hir::ExprKind::Match(scrutinee, arms, _match_source) = block_body_expr.kind
955                    else {
956                        dcx.emit_fatal(LoopMatchBadRhs { span: block_body_expr.span })
957                    };
958
959                    fn local(
960                        cx: &mut ThirBuildCx<'_>,
961                        expr: &rustc_hir::Expr<'_>,
962                    ) -> Option<hir::HirId> {
963                        if let hir::ExprKind::Path(hir::QPath::Resolved(_, path)) = expr.kind
964                            && let Res::Local(hir_id) = path.res
965                            && !cx.is_upvar(hir_id)
966                        {
967                            return Some(hir_id);
968                        }
969
970                        None
971                    }
972
973                    let Some(scrutinee_hir_id) = local(self, scrutinee) else {
974                        dcx.emit_fatal(LoopMatchInvalidMatch { span: scrutinee.span })
975                    };
976
977                    if local(self, state) != Some(scrutinee_hir_id) {
978                        dcx.emit_fatal(LoopMatchInvalidUpdate {
979                            scrutinee: scrutinee.span,
980                            lhs: state.span,
981                        })
982                    }
983
984                    ExprKind::LoopMatch {
985                        state: self.mirror_expr(state),
986                        region_scope: region::Scope {
987                            local_id: block_body.hir_id.local_id,
988                            data: region::ScopeData::Node,
989                        },
990
991                        match_data: Box::new(LoopMatchMatchData {
992                            scrutinee: self.mirror_expr(scrutinee),
993                            arms: arms.iter().map(|a| self.convert_arm(a)).collect(),
994                            span: block_body_expr.span,
995                        }),
996                    }
997                } else {
998                    let block_ty = self.typeck_results.node_type(body.hir_id);
999                    let (temp_lifetime, backwards_incompatible) = self
1000                        .rvalue_scopes
1001                        .temporary_scope(self.region_scope_tree, body.hir_id.local_id);
1002                    let block = self.mirror_block(body);
1003                    let body = self.thir.exprs.push(Expr {
1004                        ty: block_ty,
1005                        temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1006                        span: self.thir[block].span,
1007                        kind: ExprKind::Block { block },
1008                    });
1009                    ExprKind::Loop { body }
1010                }
1011            }
1012            hir::ExprKind::Field(source, ..) => ExprKind::Field {
1013                lhs: self.mirror_expr(source),
1014                variant_index: FIRST_VARIANT,
1015                name: self.typeck_results.field_index(expr.hir_id),
1016            },
1017            hir::ExprKind::Cast(source, cast_ty) => {
1018                // Check for a user-given type annotation on this `cast`
1019                let user_provided_types = self.typeck_results.user_provided_types();
1020                let user_ty = user_provided_types.get(cast_ty.hir_id);
1021
1022                debug!(
1023                    "cast({:?}) has ty w/ hir_id {:?} and user provided ty {:?}",
1024                    expr, cast_ty.hir_id, user_ty,
1025                );
1026
1027                let cast = self.mirror_expr_cast(
1028                    source,
1029                    TempLifetime { temp_lifetime, backwards_incompatible },
1030                    expr.span,
1031                );
1032
1033                if let Some(user_ty) = user_ty {
1034                    // NOTE: Creating a new Expr and wrapping a Cast inside of it may be
1035                    //       inefficient, revisit this when performance becomes an issue.
1036                    let cast_expr = self.thir.exprs.push(Expr {
1037                        temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1038                        ty: expr_ty,
1039                        span: expr.span,
1040                        kind: cast,
1041                    });
1042                    debug!("make_mirror_unadjusted: (cast) user_ty={:?}", user_ty);
1043
1044                    ExprKind::ValueTypeAscription {
1045                        source: cast_expr,
1046                        user_ty: Some(Box::new(*user_ty)),
1047                        user_ty_span: cast_ty.span,
1048                    }
1049                } else {
1050                    cast
1051                }
1052            }
1053            hir::ExprKind::Type(source, ty) => {
1054                let user_provided_types = self.typeck_results.user_provided_types();
1055                let user_ty = user_provided_types.get(ty.hir_id).copied().map(Box::new);
1056                debug!("make_mirror_unadjusted: (type) user_ty={:?}", user_ty);
1057                let mirrored = self.mirror_expr(source);
1058                if source.is_syntactic_place_expr() {
1059                    ExprKind::PlaceTypeAscription {
1060                        source: mirrored,
1061                        user_ty,
1062                        user_ty_span: ty.span,
1063                    }
1064                } else {
1065                    ExprKind::ValueTypeAscription {
1066                        source: mirrored,
1067                        user_ty,
1068                        user_ty_span: ty.span,
1069                    }
1070                }
1071            }
1072
1073            hir::ExprKind::UnsafeBinderCast(UnsafeBinderCastKind::Unwrap, source, _ty) => {
1074                // FIXME(unsafe_binders): Take into account the ascribed type, too.
1075                let mirrored = self.mirror_expr(source);
1076                if source.is_syntactic_place_expr() {
1077                    ExprKind::PlaceUnwrapUnsafeBinder { source: mirrored }
1078                } else {
1079                    ExprKind::ValueUnwrapUnsafeBinder { source: mirrored }
1080                }
1081            }
1082            hir::ExprKind::UnsafeBinderCast(UnsafeBinderCastKind::Wrap, source, _ty) => {
1083                // FIXME(unsafe_binders): Take into account the ascribed type, too.
1084                let mirrored = self.mirror_expr(source);
1085                ExprKind::WrapUnsafeBinder { source: mirrored }
1086            }
1087
1088            hir::ExprKind::DropTemps(source) => ExprKind::Use { source: self.mirror_expr(source) },
1089            hir::ExprKind::Array(fields) => ExprKind::Array { fields: self.mirror_exprs(fields) },
1090            hir::ExprKind::Tup(fields) => ExprKind::Tuple { fields: self.mirror_exprs(fields) },
1091
1092            hir::ExprKind::Yield(v, _) => ExprKind::Yield { value: self.mirror_expr(v) },
1093            hir::ExprKind::Err(_) => unreachable!("cannot lower a `hir::ExprKind::Err` to THIR"),
1094        };
1095
1096        Expr {
1097            temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1098            ty: expr_ty,
1099            span: expr.span,
1100            kind,
1101        }
1102    }
1103
1104    fn user_args_applied_to_res(
1105        &mut self,
1106        hir_id: hir::HirId,
1107        res: Res,
1108    ) -> Option<Box<ty::CanonicalUserType<'tcx>>> {
1109        debug!("user_args_applied_to_res: res={:?}", res);
1110        let user_provided_type = match res {
1111            // A reference to something callable -- e.g., a fn, method, or
1112            // a tuple-struct or tuple-variant. This has the type of a
1113            // `Fn` but with the user-given generic parameters.
1114            Res::Def(DefKind::Fn, _)
1115            | Res::Def(DefKind::AssocFn, _)
1116            | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
1117            | Res::Def(DefKind::Const, _)
1118            | Res::Def(DefKind::AssocConst, _) => {
1119                self.typeck_results.user_provided_types().get(hir_id).copied().map(Box::new)
1120            }
1121
1122            // A unit struct/variant which is used as a value (e.g.,
1123            // `None`). This has the type of the enum/struct that defines
1124            // this variant -- but with the generic parameters given by the
1125            // user.
1126            Res::Def(DefKind::Ctor(_, CtorKind::Const), _) => {
1127                self.user_args_applied_to_ty_of_hir_id(hir_id).map(Box::new)
1128            }
1129
1130            // `Self` is used in expression as a tuple struct constructor or a unit struct constructor
1131            Res::SelfCtor(_) => self.user_args_applied_to_ty_of_hir_id(hir_id).map(Box::new),
1132
1133            _ => bug!("user_args_applied_to_res: unexpected res {:?} at {:?}", res, hir_id),
1134        };
1135        debug!("user_args_applied_to_res: user_provided_type={:?}", user_provided_type);
1136        user_provided_type
1137    }
1138
1139    fn method_callee(
1140        &mut self,
1141        expr: &hir::Expr<'_>,
1142        span: Span,
1143        overloaded_callee: Option<Ty<'tcx>>,
1144    ) -> Expr<'tcx> {
1145        let (temp_lifetime, backwards_incompatible) =
1146            self.rvalue_scopes.temporary_scope(self.region_scope_tree, expr.hir_id.local_id);
1147        let (ty, user_ty) = match overloaded_callee {
1148            Some(fn_def) => (fn_def, None),
1149            None => {
1150                let (kind, def_id) =
1151                    self.typeck_results.type_dependent_def(expr.hir_id).unwrap_or_else(|| {
1152                        span_bug!(expr.span, "no type-dependent def for method callee")
1153                    });
1154                let user_ty = self.user_args_applied_to_res(expr.hir_id, Res::Def(kind, def_id));
1155                debug!("method_callee: user_ty={:?}", user_ty);
1156                (
1157                    Ty::new_fn_def(self.tcx, def_id, self.typeck_results.node_args(expr.hir_id)),
1158                    user_ty,
1159                )
1160            }
1161        };
1162        Expr {
1163            temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1164            ty,
1165            span,
1166            kind: ExprKind::ZstLiteral { user_ty },
1167        }
1168    }
1169
1170    fn convert_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) -> ArmId {
1171        let arm = Arm {
1172            pattern: self.pattern_from_hir(&arm.pat),
1173            guard: arm.guard.as_ref().map(|g| self.mirror_expr(g)),
1174            body: self.mirror_expr(arm.body),
1175            lint_level: LintLevel::Explicit(arm.hir_id),
1176            scope: region::Scope { local_id: arm.hir_id.local_id, data: region::ScopeData::Node },
1177            span: arm.span,
1178        };
1179        self.thir.arms.push(arm)
1180    }
1181
1182    fn convert_path_expr(&mut self, expr: &'tcx hir::Expr<'tcx>, res: Res) -> ExprKind<'tcx> {
1183        let args = self.typeck_results.node_args(expr.hir_id);
1184        match res {
1185            // A regular function, constructor function or a constant.
1186            Res::Def(DefKind::Fn, _)
1187            | Res::Def(DefKind::AssocFn, _)
1188            | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
1189            | Res::SelfCtor(_) => {
1190                let user_ty = self.user_args_applied_to_res(expr.hir_id, res);
1191                ExprKind::ZstLiteral { user_ty }
1192            }
1193
1194            Res::Def(DefKind::ConstParam, def_id) => {
1195                let hir_id = self.tcx.local_def_id_to_hir_id(def_id.expect_local());
1196                let generics = self.tcx.generics_of(hir_id.owner);
1197                let Some(&index) = generics.param_def_id_to_index.get(&def_id) else {
1198                    span_bug!(
1199                        expr.span,
1200                        "Should have already errored about late bound consts: {def_id:?}"
1201                    );
1202                };
1203                let name = self.tcx.hir_name(hir_id);
1204                let param = ty::ParamConst::new(index, name);
1205
1206                ExprKind::ConstParam { param, def_id }
1207            }
1208
1209            Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
1210                let user_ty = self.user_args_applied_to_res(expr.hir_id, res);
1211                ExprKind::NamedConst { def_id, args, user_ty }
1212            }
1213
1214            Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id) => {
1215                let user_provided_types = self.typeck_results.user_provided_types();
1216                let user_ty = user_provided_types.get(expr.hir_id).copied().map(Box::new);
1217                debug!("convert_path_expr: user_ty={:?}", user_ty);
1218                let ty = self.typeck_results.node_type(expr.hir_id);
1219                match ty.kind() {
1220                    // A unit struct/variant which is used as a value.
1221                    // We return a completely different ExprKind here to account for this special case.
1222                    ty::Adt(adt_def, args) => ExprKind::Adt(Box::new(AdtExpr {
1223                        adt_def: *adt_def,
1224                        variant_index: adt_def.variant_index_with_ctor_id(def_id),
1225                        args,
1226                        user_ty,
1227                        fields: Box::new([]),
1228                        base: AdtExprBase::None,
1229                    })),
1230                    _ => bug!("unexpected ty: {:?}", ty),
1231                }
1232            }
1233
1234            // A source Rust `path::to::STATIC` is a place expr like *&ident is.
1235            // In THIR, we make them exactly equivalent by inserting the implied *& or *&raw,
1236            // but distinguish between &STATIC and &THREAD_LOCAL as they have different semantics
1237            Res::Def(DefKind::Static { .. }, id) => {
1238                // this is &raw for extern static or static mut, and & for other statics
1239                let ty = self.tcx.static_ptr_ty(id, self.typing_env);
1240                let (temp_lifetime, backwards_incompatible) = self
1241                    .rvalue_scopes
1242                    .temporary_scope(self.region_scope_tree, expr.hir_id.local_id);
1243                let kind = if self.tcx.is_thread_local_static(id) {
1244                    ExprKind::ThreadLocalRef(id)
1245                } else {
1246                    let alloc_id = self.tcx.reserve_and_set_static_alloc(id);
1247                    ExprKind::StaticRef { alloc_id, ty, def_id: id }
1248                };
1249                ExprKind::Deref {
1250                    arg: self.thir.exprs.push(Expr {
1251                        ty,
1252                        temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1253                        span: expr.span,
1254                        kind,
1255                    }),
1256                }
1257            }
1258
1259            Res::Local(var_hir_id) => self.convert_var(var_hir_id),
1260
1261            _ => span_bug!(expr.span, "res `{:?}` not yet implemented", res),
1262        }
1263    }
1264
1265    fn convert_var(&mut self, var_hir_id: hir::HirId) -> ExprKind<'tcx> {
1266        // We want upvars here not captures.
1267        // Captures will be handled in MIR.
1268        let is_upvar = self.is_upvar(var_hir_id);
1269
1270        debug!(
1271            "convert_var({:?}): is_upvar={}, body_owner={:?}",
1272            var_hir_id, is_upvar, self.body_owner
1273        );
1274
1275        if is_upvar {
1276            ExprKind::UpvarRef {
1277                closure_def_id: self.body_owner,
1278                var_hir_id: LocalVarId(var_hir_id),
1279            }
1280        } else {
1281            ExprKind::VarRef { id: LocalVarId(var_hir_id) }
1282        }
1283    }
1284
1285    fn overloaded_operator(
1286        &mut self,
1287        expr: &'tcx hir::Expr<'tcx>,
1288        args: Box<[ExprId]>,
1289    ) -> ExprKind<'tcx> {
1290        let fun = self.method_callee(expr, expr.span, None);
1291        let fun = self.thir.exprs.push(fun);
1292        ExprKind::Call {
1293            ty: self.thir[fun].ty,
1294            fun,
1295            args,
1296            from_hir_call: false,
1297            fn_span: expr.span,
1298        }
1299    }
1300
1301    fn overloaded_place(
1302        &mut self,
1303        expr: &'tcx hir::Expr<'tcx>,
1304        place_ty: Ty<'tcx>,
1305        overloaded_callee: Option<Ty<'tcx>>,
1306        args: Box<[ExprId]>,
1307        span: Span,
1308    ) -> ExprKind<'tcx> {
1309        // For an overloaded *x or x[y] expression of type T, the method
1310        // call returns an &T and we must add the deref so that the types
1311        // line up (this is because `*x` and `x[y]` represent places):
1312
1313        // Reconstruct the output assuming it's a reference with the
1314        // same region and mutability as the receiver. This holds for
1315        // `Deref(Mut)::deref(_mut)` and `Index(Mut)::index(_mut)`.
1316        let ty::Ref(region, _, mutbl) = *self.thir[args[0]].ty.kind() else {
1317            span_bug!(span, "overloaded_place: receiver is not a reference");
1318        };
1319        let ref_ty = Ty::new_ref(self.tcx, region, place_ty, mutbl);
1320
1321        // construct the complete expression `foo()` for the overloaded call,
1322        // which will yield the &T type
1323        let (temp_lifetime, backwards_incompatible) =
1324            self.rvalue_scopes.temporary_scope(self.region_scope_tree, expr.hir_id.local_id);
1325        let fun = self.method_callee(expr, span, overloaded_callee);
1326        let fun = self.thir.exprs.push(fun);
1327        let fun_ty = self.thir[fun].ty;
1328        let ref_expr = self.thir.exprs.push(Expr {
1329            temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1330            ty: ref_ty,
1331            span,
1332            kind: ExprKind::Call { ty: fun_ty, fun, args, from_hir_call: false, fn_span: span },
1333        });
1334
1335        // construct and return a deref wrapper `*foo()`
1336        ExprKind::Deref { arg: ref_expr }
1337    }
1338
1339    fn convert_captured_hir_place(
1340        &mut self,
1341        closure_expr: &'tcx hir::Expr<'tcx>,
1342        place: HirPlace<'tcx>,
1343    ) -> Expr<'tcx> {
1344        let (temp_lifetime, backwards_incompatible) = self
1345            .rvalue_scopes
1346            .temporary_scope(self.region_scope_tree, closure_expr.hir_id.local_id);
1347        let var_ty = place.base_ty;
1348
1349        // The result of capture analysis in `rustc_hir_typeck/src/upvar.rs` represents a captured path
1350        // as it's seen for use within the closure and not at the time of closure creation.
1351        //
1352        // That is we see expect to see it start from a captured upvar and not something that is local
1353        // to the closure's parent.
1354        let var_hir_id = match place.base {
1355            HirPlaceBase::Upvar(upvar_id) => upvar_id.var_path.hir_id,
1356            base => bug!("Expected an upvar, found {:?}", base),
1357        };
1358
1359        let mut captured_place_expr = Expr {
1360            temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1361            ty: var_ty,
1362            span: closure_expr.span,
1363            kind: self.convert_var(var_hir_id),
1364        };
1365
1366        for proj in place.projections.iter() {
1367            let kind = match proj.kind {
1368                HirProjectionKind::Deref => {
1369                    ExprKind::Deref { arg: self.thir.exprs.push(captured_place_expr) }
1370                }
1371                HirProjectionKind::Field(field, variant_index) => ExprKind::Field {
1372                    lhs: self.thir.exprs.push(captured_place_expr),
1373                    variant_index,
1374                    name: field,
1375                },
1376                HirProjectionKind::OpaqueCast => {
1377                    ExprKind::Use { source: self.thir.exprs.push(captured_place_expr) }
1378                }
1379                HirProjectionKind::UnwrapUnsafeBinder => ExprKind::PlaceUnwrapUnsafeBinder {
1380                    source: self.thir.exprs.push(captured_place_expr),
1381                },
1382                HirProjectionKind::Index | HirProjectionKind::Subslice => {
1383                    // We don't capture these projections, so we can ignore them here
1384                    continue;
1385                }
1386            };
1387
1388            captured_place_expr = Expr {
1389                temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1390                ty: proj.ty,
1391                span: closure_expr.span,
1392                kind,
1393            };
1394        }
1395
1396        captured_place_expr
1397    }
1398
1399    fn capture_upvar(
1400        &mut self,
1401        closure_expr: &'tcx hir::Expr<'tcx>,
1402        captured_place: &'tcx ty::CapturedPlace<'tcx>,
1403        upvar_ty: Ty<'tcx>,
1404    ) -> Expr<'tcx> {
1405        let upvar_capture = captured_place.info.capture_kind;
1406        let captured_place_expr =
1407            self.convert_captured_hir_place(closure_expr, captured_place.place.clone());
1408        let (temp_lifetime, backwards_incompatible) = self
1409            .rvalue_scopes
1410            .temporary_scope(self.region_scope_tree, closure_expr.hir_id.local_id);
1411
1412        match upvar_capture {
1413            ty::UpvarCapture::ByValue => captured_place_expr,
1414            ty::UpvarCapture::ByUse => {
1415                let span = captured_place_expr.span;
1416                let expr_id = self.thir.exprs.push(captured_place_expr);
1417
1418                Expr {
1419                    temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1420                    ty: upvar_ty,
1421                    span: closure_expr.span,
1422                    kind: ExprKind::ByUse { expr: expr_id, span },
1423                }
1424            }
1425            ty::UpvarCapture::ByRef(upvar_borrow) => {
1426                let borrow_kind = match upvar_borrow {
1427                    ty::BorrowKind::Immutable => BorrowKind::Shared,
1428                    ty::BorrowKind::UniqueImmutable => {
1429                        BorrowKind::Mut { kind: mir::MutBorrowKind::ClosureCapture }
1430                    }
1431                    ty::BorrowKind::Mutable => {
1432                        BorrowKind::Mut { kind: mir::MutBorrowKind::Default }
1433                    }
1434                };
1435                Expr {
1436                    temp_lifetime: TempLifetime { temp_lifetime, backwards_incompatible },
1437                    ty: upvar_ty,
1438                    span: closure_expr.span,
1439                    kind: ExprKind::Borrow {
1440                        borrow_kind,
1441                        arg: self.thir.exprs.push(captured_place_expr),
1442                    },
1443                }
1444            }
1445        }
1446    }
1447
1448    fn is_upvar(&mut self, var_hir_id: hir::HirId) -> bool {
1449        self.tcx
1450            .upvars_mentioned(self.body_owner)
1451            .is_some_and(|upvars| upvars.contains_key(&var_hir_id))
1452    }
1453
1454    /// Converts a list of named fields (i.e., for struct-like struct/enum ADTs) into FieldExpr.
1455    fn field_refs(&mut self, fields: &'tcx [hir::ExprField<'tcx>]) -> Box<[FieldExpr]> {
1456        fields
1457            .iter()
1458            .map(|field| FieldExpr {
1459                name: self.typeck_results.field_index(field.hir_id),
1460                expr: self.mirror_expr(field.expr),
1461            })
1462            .collect()
1463    }
1464}
1465
1466trait ToBorrowKind {
1467    fn to_borrow_kind(&self) -> BorrowKind;
1468}
1469
1470impl ToBorrowKind for AutoBorrowMutability {
1471    fn to_borrow_kind(&self) -> BorrowKind {
1472        use rustc_middle::ty::adjustment::AllowTwoPhase;
1473        match *self {
1474            AutoBorrowMutability::Mut { allow_two_phase_borrow } => BorrowKind::Mut {
1475                kind: match allow_two_phase_borrow {
1476                    AllowTwoPhase::Yes => mir::MutBorrowKind::TwoPhaseBorrow,
1477                    AllowTwoPhase::No => mir::MutBorrowKind::Default,
1478                },
1479            },
1480            AutoBorrowMutability::Not => BorrowKind::Shared,
1481        }
1482    }
1483}
1484
1485impl ToBorrowKind for hir::Mutability {
1486    fn to_borrow_kind(&self) -> BorrowKind {
1487        match *self {
1488            hir::Mutability::Mut => BorrowKind::Mut { kind: mir::MutBorrowKind::Default },
1489            hir::Mutability::Not => BorrowKind::Shared,
1490        }
1491    }
1492}
1493
1494fn bin_op(op: hir::BinOpKind) -> BinOp {
1495    match op {
1496        hir::BinOpKind::Add => BinOp::Add,
1497        hir::BinOpKind::Sub => BinOp::Sub,
1498        hir::BinOpKind::Mul => BinOp::Mul,
1499        hir::BinOpKind::Div => BinOp::Div,
1500        hir::BinOpKind::Rem => BinOp::Rem,
1501        hir::BinOpKind::BitXor => BinOp::BitXor,
1502        hir::BinOpKind::BitAnd => BinOp::BitAnd,
1503        hir::BinOpKind::BitOr => BinOp::BitOr,
1504        hir::BinOpKind::Shl => BinOp::Shl,
1505        hir::BinOpKind::Shr => BinOp::Shr,
1506        hir::BinOpKind::Eq => BinOp::Eq,
1507        hir::BinOpKind::Lt => BinOp::Lt,
1508        hir::BinOpKind::Le => BinOp::Le,
1509        hir::BinOpKind::Ne => BinOp::Ne,
1510        hir::BinOpKind::Ge => BinOp::Ge,
1511        hir::BinOpKind::Gt => BinOp::Gt,
1512        _ => bug!("no equivalent for ast binop {:?}", op),
1513    }
1514}
1515
1516fn assign_op(op: hir::AssignOpKind) -> AssignOp {
1517    match op {
1518        hir::AssignOpKind::AddAssign => AssignOp::AddAssign,
1519        hir::AssignOpKind::SubAssign => AssignOp::SubAssign,
1520        hir::AssignOpKind::MulAssign => AssignOp::MulAssign,
1521        hir::AssignOpKind::DivAssign => AssignOp::DivAssign,
1522        hir::AssignOpKind::RemAssign => AssignOp::RemAssign,
1523        hir::AssignOpKind::BitXorAssign => AssignOp::BitXorAssign,
1524        hir::AssignOpKind::BitAndAssign => AssignOp::BitAndAssign,
1525        hir::AssignOpKind::BitOrAssign => AssignOp::BitOrAssign,
1526        hir::AssignOpKind::ShlAssign => AssignOp::ShlAssign,
1527        hir::AssignOpKind::ShrAssign => AssignOp::ShrAssign,
1528    }
1529}
rustc_mir_build/thir/cx/expr.rs

rustc_mir_build/thir/cx/
expr.rs
