Remove rustc_middle::mir::tcx module.

This is a really weird module. For example, what does `tcx` in
`rustc_middle::mir::tcx::PlaceTy` mean? The answer is "not much".

The top-level module comment says:

> Methods for the various MIR types. These are intended for use after
> building is complete.

Awfully broad for a module that has a handful of impl blocks for some
MIR types, none of which really relates to `TyCtxt`. `git blame`
indicates the comment is ancient, from 2015, and made sense then.

This module is now vestigial. This commit removes it and moves all the
code within into `rustc_middle::mir::statement`. Some specifics:

- `Place`, `PlaceRef`, `Rvalue`, `Operand`, `BorrowKind`: they all have `impl`
  blocks in both the `tcx` and `statement` modules. The commit merges
  the former into the latter.

- `BinOp`, `UnOp`: they only have `impl` blocks in `tcx`. The commit
  moves these into `statement`.

- `PlaceTy`, `RvalueInitializationState`: they are defined in `tcx`.
  This commit moves them into `statement` *and* makes them available in
  `mir::*`, like many other MIR types.

Author: nnethercote

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -18,12 +18,11 @@ use rustc_hir::intravisit::{Visitor, walk_block, walk_expr};
 use rustc_hir::{CoroutineDesugaring, CoroutineKind, CoroutineSource, LangItem, PatField};
 use rustc_middle::bug;
 use rustc_middle::hir::nested_filter::OnlyBodies;
-use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
     self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory,
     FakeBorrowKind, FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, MutBorrowKind,
-    Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement, StatementKind, Terminator,
-    TerminatorKind, VarBindingForm, VarDebugInfoContents,
+    Operand, Place, PlaceRef, PlaceTy, ProjectionElem, Rvalue, Statement, StatementKind,
+    Terminator, TerminatorKind, VarBindingForm, VarDebugInfoContents,
 };
 use rustc_middle::ty::print::PrintTraitRefExt as _;
 use rustc_middle::ty::{

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -13,10 +13,9 @@ use rustc_infer::infer::{
 };
 use rustc_infer::traits::SelectionError;
 use rustc_middle::bug;
-use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
     AggregateKind, CallSource, ConstOperand, ConstraintCategory, FakeReadCause, Local, LocalInfo,
-    LocalKind, Location, Operand, Place, PlaceRef, ProjectionElem, Rvalue, Statement,
+    LocalKind, Location, Operand, Place, PlaceRef, PlaceTy, ProjectionElem, Rvalue, Statement,
     StatementKind, Terminator, TerminatorKind, find_self_call,
 };
 use rustc_middle::ty::print::Print;

compiler/rustc_borrowck/src/lib.rs

@@ -33,7 +33,6 @@ use rustc_index::{IndexSlice, IndexVec};
 use rustc_infer::infer::{
     InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin, TyCtxtInferExt,
 };
-use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::fold::fold_regions;

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -19,7 +19,6 @@ use rustc_infer::infer::{
     BoundRegion, BoundRegionConversionTime, InferCtxt, NllRegionVariableOrigin,
 };
 use rustc_infer::traits::PredicateObligations;
-use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::traits::query::NoSolution;

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -1,7 +1,7 @@
 use rustc_abi::Primitive::{Int, Pointer};
 use rustc_abi::{Align, BackendRepr, FieldsShape, Size, TagEncoding, VariantIdx, Variants};
+use rustc_middle::mir::PlaceTy;
 use rustc_middle::mir::interpret::Scalar;
-use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, Ty};
 use rustc_middle::{bug, mir};

compiler/rustc_middle/src/mir/mod.rs

@@ -53,7 +53,6 @@ pub mod pretty;
 mod query;
 mod statement;
 mod syntax;
-pub mod tcx;
 mod terminator;
 
 pub mod traversal;

compiler/rustc_middle/src/mir/statement.rs

@@ -1125,7 +1125,7 @@ pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
 ///
 ///  1. The address in memory that the place refers to.
 ///  2. The provenance with which the place is being accessed.
-///  3. The type of the place and an optional variant index. See [`PlaceTy`][super::tcx::PlaceTy].
+///  3. The type of the place and an optional variant index. See [`PlaceTy`][super::PlaceTy].
 ///  4. Optionally, some metadata. This exists if and only if the type of the place is not `Sized`.
 ///
 /// We'll give a description below of how all pieces of the place except for the provenance are

compiler/rustc_middle/src/mir/syntax.rs

@@ -1,6 +1,5 @@
 use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_middle::mir::interpret::Scalar;
-use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty;

compiler/rustc_middle/src/mir/tcx.rs

@@ -1,7 +1,6 @@
 use std::mem;
 
 use rustc_index::IndexVec;
-use rustc_middle::mir::tcx::{PlaceTy, RvalueInitializationState};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_middle::{bug, span_bug};

compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs

@@ -7,7 +7,6 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexSet, StdEntry};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_index::IndexVec;
 use rustc_index::bit_set::DenseBitSet;
-use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt};

compiler/rustc_mir_dataflow/src/move_paths/builder.rs

@@ -185,7 +185,7 @@ where
             place.ty(self.elaborator.body(), self.tcx()).ty
         } else {
             // We don't have a slice with all the locals, since some are in the patch.
-            tcx::PlaceTy::from_ty(self.elaborator.patch_ref().local_ty(place.local))
+            PlaceTy::from_ty(self.elaborator.patch_ref().local_ty(place.local))
                 .multi_projection_ty(self.elaborator.tcx(), place.projection)
                 .ty
         }