Remove extern crate rustc_middle from rustc_mir_build.

compiler/rustc_mir_build/src/build/expr/as_constant.rs

@@ -9,6 +9,7 @@ use rustc_middle::thir::*;
 use rustc_middle::ty::{
     self, CanonicalUserType, CanonicalUserTypeAnnotation, TyCtxt, UserTypeAnnotationIndex,
 };
+use rustc_middle::{bug, span_bug};
 use rustc_target::abi::Size;
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {

compiler/rustc_mir_build/src/build/expr/as_place.rs

@@ -4,6 +4,7 @@ use crate::build::expr::category::Category;
 use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
 use crate::build::{BlockAnd, BlockAndExtension, Builder, Capture, CaptureMap};
 use rustc_hir::def_id::LocalDefId;
+use rustc_middle::bug;
 use rustc_middle::hir::place::Projection as HirProjection;
 use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
 use rustc_middle::middle::region;

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -9,6 +9,7 @@ use crate::build::expr::as_place::PlaceBase;
 use crate::build::expr::category::{Category, RvalueFunc};
 use crate::build::{BlockAnd, BlockAndExtension, Builder, NeedsTemporary};
 use rustc_hir::lang_items::LangItem;
+use rustc_middle::bug;
 use rustc_middle::middle::region;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::*;

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -7,6 +7,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir as hir;
 use rustc_middle::mir::*;
+use rustc_middle::span_bug;
 use rustc_middle::thir::*;
 use rustc_middle::ty::CanonicalUserTypeAnnotation;
 use rustc_span::source_map::Spanned;