Rollup merge of #72879 - RalfJung:miri-tctx-at, r=oli-obk

Miri: avoid tracking current location three times

Miri tracks the current instruction to execute in the call stack, but it also additionally has two `TyCtxtAt` that carry a `Span` that also tracks the current instruction. That is quite silly, so this PR uses `TyCtxt` instead, and then uses a method for computing the current span when a `TyCtxtAt` is needed. Having less redundant (semi-)global state seems like a good improvement to me. :D

To keep the ConstProp errors the same, I had to add the option to `error_to_const_error` to overwrite the span. Also for some reason this changes cycle errors a bit -- not sure if we are now better or worse as giving those queries the right span. (It is unfortunately quite easy to accidentally use `DUMMY_SP` by calling the query on a `TyCtxt` instead of a `TyCtxtAt`.)

r? @oli-obk @eddyb

23 files changed, 141 insertions, 123 deletions

diff --git a/src/librustc_middle/ty/util.rs b/src/librustc_middle/ty/util.rs
index 866a35ebfa6..ff284b709c2 100644
--- a/src/librustc_middle/ty/util.rs
+++ b/src/librustc_middle/ty/util.rs
@@ -705,6 +705,7 @@ impl<'tcx> ty::TyS<'tcx> {
     /// optimization as well as the rules around static values. Note
     /// that the `Freeze` trait is not exposed to end users and is
     /// effectively an implementation detail.
+    // FIXME: use `TyCtxtAt` instead of separate `Span`.
     pub fn is_freeze(
         &'tcx self,
         tcx: TyCtxt<'tcx>,
diff --git a/src/librustc_mir/const_eval/error.rs b/src/librustc_mir/const_eval/error.rs
index b165a69433d..5deae94fe0c 100644
--- a/src/librustc_mir/const_eval/error.rs
+++ b/src/librustc_mir/const_eval/error.rs
@@ -2,7 +2,7 @@ use std::error::Error;
 use std::fmt;
 
 use rustc_middle::mir::AssertKind;
-use rustc_span::Symbol;
+use rustc_span::{Span, Symbol};
 
 use super::InterpCx;
 use crate::interpret::{ConstEvalErr, InterpErrorInfo, Machine};
@@ -53,8 +53,9 @@ impl Error for ConstEvalErrKind {}
 pub fn error_to_const_error<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>>(
     ecx: &InterpCx<'mir, 'tcx, M>,
     error: InterpErrorInfo<'tcx>,
+    span: Option<Span>,
 ) -> ConstEvalErr<'tcx> {
     error.print_backtrace();
     let stacktrace = ecx.generate_stacktrace();
-    ConstEvalErr { error: error.kind, stacktrace, span: ecx.tcx.span }
+    ConstEvalErr { error: error.kind, stacktrace, span: span.unwrap_or_else(|| ecx.cur_span()) }
 }
diff --git a/src/librustc_mir/const_eval/eval_queries.rs b/src/librustc_mir/const_eval/eval_queries.rs
index 2c0a40b4c54..d62300b3f55 100644
--- a/src/librustc_mir/const_eval/eval_queries.rs
+++ b/src/librustc_mir/const_eval/eval_queries.rs
@@ -27,7 +27,7 @@ fn eval_body_using_ecx<'mir, 'tcx>(
     body: &'mir mir::Body<'tcx>,
 ) -> InterpResult<'tcx, MPlaceTy<'tcx>> {
     debug!("eval_body_using_ecx: {:?}, {:?}", cid, ecx.param_env);
-    let tcx = ecx.tcx.tcx;
+    let tcx = *ecx.tcx;
     let layout = ecx.layout_of(body.return_ty().subst(tcx, cid.instance.substs))?;
     assert!(!layout.is_unsized());
     let ret = ecx.allocate(layout, MemoryKind::Stack);
@@ -81,13 +81,14 @@ fn eval_body_using_ecx<'mir, 'tcx>(
 /// parameter. These bounds are passed to `mk_eval_cx` via the `ParamEnv` argument.
 pub(super) fn mk_eval_cx<'mir, 'tcx>(
     tcx: TyCtxt<'tcx>,
-    span: Span,
+    root_span: Span,
     param_env: ty::ParamEnv<'tcx>,
     can_access_statics: bool,
 ) -> CompileTimeEvalContext<'mir, 'tcx> {
     debug!("mk_eval_cx: {:?}", param_env);
     InterpCx::new(
-        tcx.at(span),
+        tcx,
+        root_span,
         param_env,
         CompileTimeInterpreter::new(tcx.sess.const_eval_limit()),
         MemoryExtra { can_access_statics },
@@ -163,7 +164,7 @@ pub(super) fn op_to_const<'tcx>(
                         0,
                     ),
                 };
-                let len = b.to_machine_usize(&ecx.tcx.tcx).unwrap();
+                let len = b.to_machine_usize(ecx).unwrap();
                 let start = start.try_into().unwrap();
                 let len: usize = len.try_into().unwrap();
                 ConstValue::Slice { data, start, end: start + len }
@@ -212,7 +213,7 @@ fn validate_and_turn_into_const<'tcx>(
     })();
 
     val.map_err(|error| {
-        let err = error_to_const_error(&ecx, error);
+        let err = error_to_const_error(&ecx, error, None);
         err.struct_error(ecx.tcx, "it is undefined behavior to use this value", |mut diag| {
             diag.note(note_on_undefined_behavior_error());
             diag.emit();
@@ -299,9 +300,9 @@ pub fn const_eval_raw_provider<'tcx>(
 
     let is_static = tcx.is_static(def_id);
 
-    let span = tcx.def_span(cid.instance.def_id());
     let mut ecx = InterpCx::new(
-        tcx.at(span),
+        tcx,
+        tcx.def_span(cid.instance.def_id()),
         key.param_env,
         CompileTimeInterpreter::new(tcx.sess.const_eval_limit()),
         MemoryExtra { can_access_statics: is_static },
@@ -311,12 +312,15 @@ pub fn const_eval_raw_provider<'tcx>(
     res.and_then(|body| eval_body_using_ecx(&mut ecx, cid, &body))
         .map(|place| RawConst { alloc_id: place.ptr.assert_ptr().alloc_id, ty: place.layout.ty })
         .map_err(|error| {
-            let err = error_to_const_error(&ecx, error);
+            let err = error_to_const_error(&ecx, error, None);
             // errors in statics are always emitted as fatal errors
             if is_static {
                 // Ensure that if the above error was either `TooGeneric` or `Reported`
                 // an error must be reported.
-                let v = err.report_as_error(ecx.tcx, "could not evaluate static initializer");
+                let v = err.report_as_error(
+                    ecx.tcx.at(ecx.cur_span()),
+                    "could not evaluate static initializer",
+                );
 
                 // If this is `Reveal:All`, then we need to make sure an error is reported but if
                 // this is `Reveal::UserFacing`, then it's expected that we could get a
@@ -372,13 +376,16 @@ pub fn const_eval_raw_provider<'tcx>(
                         // anything else (array lengths, enum initializers, constant patterns) are
                         // reported as hard errors
                         } else {
-                            err.report_as_error(ecx.tcx, "evaluation of constant value failed")
+                            err.report_as_error(
+                                ecx.tcx.at(ecx.cur_span()),
+                                "evaluation of constant value failed",
+                            )
                         }
                     }
                 }
             } else {
                 // use of broken constant from other crate
-                err.report_as_error(ecx.tcx, "could not evaluate constant")
+                err.report_as_error(ecx.tcx.at(ecx.cur_span()), "could not evaluate constant")
             }
         })
 }
diff --git a/src/librustc_mir/interpret/cast.rs b/src/librustc_mir/interpret/cast.rs
index 0fd695586eb..cfe856abe36 100644
--- a/src/librustc_mir/interpret/cast.rs
+++ b/src/librustc_mir/interpret/cast.rs
@@ -268,11 +268,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             (&ty::Array(_, length), &ty::Slice(_)) => {
                 let ptr = self.read_immediate(src)?.to_scalar()?;
                 // u64 cast is from usize to u64, which is always good
-                let val = Immediate::new_slice(
-                    ptr,
-                    length.eval_usize(self.tcx.tcx, self.param_env),
-                    self,
-                );
+                let val =
+                    Immediate::new_slice(ptr, length.eval_usize(*self.tcx, self.param_env), self);
                 self.write_immediate(val, dest)
             }
             (&ty::Dynamic(..), &ty::Dynamic(..)) => {
diff --git a/src/librustc_mir/interpret/eval_context.rs b/src/librustc_mir/interpret/eval_context.rs
index b44152a5188..22f4691c22b 100644
--- a/src/librustc_mir/interpret/eval_context.rs
+++ b/src/librustc_mir/interpret/eval_context.rs
@@ -33,6 +33,8 @@ pub struct InterpCx<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
     pub machine: M,
 
     /// The results of the type checker, from rustc.
+    /// The span in this is the "root" of the evaluation, i.e., the const
+    /// we are evaluating (if this is CTFE).
     pub tcx: TyCtxtAt<'tcx>,
 
     /// Bounds in scope for polymorphic evaluations.
@@ -202,7 +204,7 @@ where
     }
 }
 
-impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> LayoutOf for InterpCx<'mir, 'tcx, M> {
+impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> LayoutOf for InterpCx<'mir, 'tcx, M> {
     type Ty = Ty<'tcx>;
     type TyAndLayout = InterpResult<'tcx, TyAndLayout<'tcx>>;
 
@@ -285,14 +287,15 @@ pub(super) fn from_known_layout<'tcx>(
 
 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     pub fn new(
-        tcx: TyCtxtAt<'tcx>,
+        tcx: TyCtxt<'tcx>,
+        root_span: Span,
         param_env: ty::ParamEnv<'tcx>,
         machine: M,
         memory_extra: M::MemoryExtra,
     ) -> Self {
         InterpCx {
             machine,
-            tcx,
+            tcx: tcx.at(root_span),
             param_env,
             memory: Memory::new(tcx, memory_extra),
             vtables: FxHashMap::default(),
@@ -300,9 +303,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
     }
 
     #[inline(always)]
-    pub fn set_span(&mut self, span: Span) {
-        self.tcx.span = span;
-        self.memory.tcx.span = span;
+    pub fn cur_span(&self) -> Span {
+        self.stack()
+            .last()
+            .and_then(|f| f.current_source_info())
+            .map(|si| si.span)
+            .unwrap_or(self.tcx.span)
     }
 
     #[inline(always)]
@@ -385,7 +391,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
     #[inline]
     pub fn type_is_freeze(&self, ty: Ty<'tcx>) -> bool {
-        ty.is_freeze(*self.tcx, self.param_env, DUMMY_SP)
+        ty.is_freeze(*self.tcx, self.param_env, self.tcx.span)
     }
 
     pub fn load_mir(
@@ -554,7 +560,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let size = size.align_to(align);
 
                 // Check if this brought us over the size limit.
-                if size.bytes() >= self.tcx.data_layout().obj_size_bound() {
+                if size.bytes() >= self.tcx.data_layout.obj_size_bound() {
                     throw_ub!(InvalidMeta("total size is bigger than largest supported object"));
                 }
                 Ok(Some((size, align)))
@@ -570,7 +576,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let elem = layout.field(self, 0)?;
 
                 // Make sure the slice is not too big.
-                let size = elem.size.checked_mul(len, &*self.tcx).ok_or_else(|| {
+                let size = elem.size.checked_mul(len, self).ok_or_else(|| {
                     err_ub!(InvalidMeta("slice is bigger than largest supported object"))
                 })?;
                 Ok(Some((size, elem.align.abi)))
diff --git a/src/librustc_mir/interpret/intern.rs b/src/librustc_mir/interpret/intern.rs
index 02a7f24a1e3..3c724c79b40 100644
--- a/src/librustc_mir/interpret/intern.rs
+++ b/src/librustc_mir/interpret/intern.rs
@@ -111,7 +111,7 @@ fn intern_shallow<'rt, 'mir, 'tcx, M: CompileTimeMachine<'mir, 'tcx>>(
     if let InternMode::Static(mutability) = mode {
         // For this, we need to take into account `UnsafeCell`. When `ty` is `None`, we assume
         // no interior mutability.
-        let frozen = ty.map_or(true, |ty| ty.is_freeze(ecx.tcx.tcx, ecx.param_env, ecx.tcx.span));
+        let frozen = ty.map_or(true, |ty| ty.is_freeze(*ecx.tcx, ecx.param_env, ecx.tcx.span));
         // For statics, allocation mutability is the combination of the place mutability and
         // the type mutability.
         // The entire allocation needs to be mutable if it contains an `UnsafeCell` anywhere.
@@ -253,8 +253,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx>> ValueVisitor<'mir
                         // caused (by somehow getting a mutable reference in a `const`).
                         if ref_mutability == Mutability::Mut {
                             match referenced_ty.kind {
-                                ty::Array(_, n)
-                                    if n.eval_usize(tcx.tcx, self.ecx.param_env) == 0 => {}
+                                ty::Array(_, n) if n.eval_usize(*tcx, self.ecx.param_env) == 0 => {}
                                 ty::Slice(_)
                                     if mplace.meta.unwrap_meta().to_machine_usize(self.ecx)?
                                         == 0 => {}
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index 115a472cabe..47e5b8b4fce 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -347,7 +347,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
                 let elem = args[2];
                 let input = args[0];
-                let (len, e_ty) = input.layout.ty.simd_size_and_type(self.tcx.tcx);
+                let (len, e_ty) = input.layout.ty.simd_size_and_type(*self.tcx);
                 assert!(
                     index < len,
                     "Index `{}` must be in bounds of vector type `{}`: `[0, {})`",
@@ -374,7 +374,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
             sym::simd_extract => {
                 let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
-                let (len, e_ty) = args[0].layout.ty.simd_size_and_type(self.tcx.tcx);
+                let (len, e_ty) = args[0].layout.ty.simd_size_and_type(*self.tcx);
                 assert!(
                     index < len,
                     "index `{}` is out-of-bounds of vector type `{}` with length `{}`",
diff --git a/src/librustc_mir/interpret/memory.rs b/src/librustc_mir/interpret/memory.rs
index d7f64542aa7..8af1a8ac608 100644
--- a/src/librustc_mir/interpret/memory.rs
+++ b/src/librustc_mir/interpret/memory.rs
@@ -14,7 +14,7 @@ use std::ptr;
 
 use rustc_ast::ast::Mutability;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_middle::ty::{self, query::TyCtxtAt, Instance, ParamEnv};
+use rustc_middle::ty::{self, Instance, ParamEnv, TyCtxt};
 use rustc_target::abi::{Align, HasDataLayout, Size, TargetDataLayout};
 
 use super::{
@@ -115,7 +115,7 @@ pub struct Memory<'mir, 'tcx, M: Machine<'mir, 'tcx>> {
     pub extra: M::MemoryExtra,
 
     /// Lets us implement `HasDataLayout`, which is awfully convenient.
-    pub tcx: TyCtxtAt<'tcx>,
+    pub tcx: TyCtxt<'tcx>,
 }
 
 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for Memory<'mir, 'tcx, M> {
@@ -126,7 +126,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> HasDataLayout for Memory<'mir, 'tcx, M>
 }
 
 impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
-    pub fn new(tcx: TyCtxtAt<'tcx>, extra: M::MemoryExtra) -> Self {
+    pub fn new(tcx: TyCtxt<'tcx>, extra: M::MemoryExtra) -> Self {
         Memory {
             alloc_map: M::MemoryMap::default(),
             extra_fn_ptr_map: FxHashMap::default(),
@@ -425,7 +425,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
     /// `M::tag_allocation`.
     fn get_global_alloc(
         memory_extra: &M::MemoryExtra,
-        tcx: TyCtxtAt<'tcx>,
+        tcx: TyCtxt<'tcx>,
         id: AllocId,
         is_write: bool,
     ) -> InterpResult<'tcx, Cow<'tcx, Allocation<M::PointerTag, M::AllocExtra>>> {
@@ -455,7 +455,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
                     throw_unsup!(ReadForeignStatic(def_id))
                 }
                 trace!("get_global_alloc: Need to compute {:?}", def_id);
-                let instance = Instance::mono(tcx.tcx, def_id);
+                let instance = Instance::mono(tcx, def_id);
                 let gid = GlobalId { instance, promoted: None };
                 // Use the raw query here to break validation cycles. Later uses of the static
                 // will call the full query anyway.
@@ -664,14 +664,14 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
     pub fn dump_allocs(&self, mut allocs: Vec<AllocId>) {
         // Cannot be a closure because it is generic in `Tag`, `Extra`.
         fn write_allocation_track_relocs<'tcx, Tag: Copy + fmt::Debug, Extra>(
-            tcx: TyCtxtAt<'tcx>,
+            tcx: TyCtxt<'tcx>,
             allocs_to_print: &mut VecDeque<AllocId>,
             alloc: &Allocation<Tag, Extra>,
         ) {
             for &(_, target_id) in alloc.relocations().values() {
                 allocs_to_print.push_back(target_id);
             }
-            pretty::write_allocation(tcx.tcx, alloc, &mut std::io::stderr()).unwrap();
+            pretty::write_allocation(tcx, alloc, &mut std::io::stderr()).unwrap();
         }
 
         allocs.sort();
@@ -820,7 +820,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
                 return Ok(());
             }
         };
-        let tcx = self.tcx.tcx;
+        let tcx = self.tcx;
         self.get_raw_mut(ptr.alloc_id)?.write_bytes(&tcx, ptr, src)
     }
 
@@ -846,7 +846,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
                 return Ok(());
             }
         };
-        let tcx = self.tcx.tcx;
+        let tcx = self.tcx;
         let allocation = self.get_raw_mut(ptr.alloc_id)?;
 
         for idx in 0..len {
@@ -888,7 +888,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
         let relocations =
             self.get_raw(src.alloc_id)?.prepare_relocation_copy(self, src, size, dest, length);
 
-        let tcx = self.tcx.tcx;
+        let tcx = self.tcx;
 
         // This checks relocation edges on the src.
         let src_bytes =
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index db4473154c4..38f5988d0eb 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -651,12 +651,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 // Convert discriminant to variant index, and catch invalid discriminants.
                 let index = match op.layout.ty.kind {
                     ty::Adt(adt, _) => {
-                        adt.discriminants(self.tcx.tcx).find(|(_, var)| var.val == discr_bits)
+                        adt.discriminants(*self.tcx).find(|(_, var)| var.val == discr_bits)
                     }
                     ty::Generator(def_id, substs, _) => {
                         let substs = substs.as_generator();
                         substs
-                            .discriminants(def_id, self.tcx.tcx)
+                            .discriminants(def_id, *self.tcx)
                             .find(|(_, var)| var.val == discr_bits)
                     }
                     _ => bug!("tagged layout for non-adt non-generator"),
diff --git a/src/librustc_mir/interpret/place.rs b/src/librustc_mir/interpret/place.rs
index 3f0800b12b5..24b191e9b53 100644
--- a/src/librustc_mir/interpret/place.rs
+++ b/src/librustc_mir/interpret/place.rs
@@ -404,7 +404,10 @@ where
                     // to get some code to work that probably ought to work.
                     field_layout.align.abi
                 }
-                None => bug!("Cannot compute offset for extern type field at non-0 offset"),
+                None => span_bug!(
+                    self.cur_span(),
+                    "cannot compute offset for extern type field at non-0 offset"
+                ),
             };
             (base.meta, offset.align_to(align))
         } else {
@@ -440,7 +443,11 @@ where
                 assert!(!field_layout.is_unsized());
                 base.offset(offset, MemPlaceMeta::None, field_layout, self)
             }
-            _ => bug!("`mplace_index` called on non-array type {:?}", base.layout.ty),
+            _ => span_bug!(
+                self.cur_span(),
+                "`mplace_index` called on non-array type {:?}",
+                base.layout.ty
+            ),
         }
     }
 
@@ -454,7 +461,7 @@ where
         let len = base.len(self)?; // also asserts that we have a type where this makes sense
         let stride = match base.layout.fields {
             FieldsShape::Array { stride, .. } => stride,
-            _ => bug!("mplace_array_fields: expected an array layout"),
+            _ => span_bug!(self.cur_span(), "mplace_array_fields: expected an array layout"),
         };
         let layout = base.layout.field(self, 0)?;
         let dl = &self.tcx.data_layout;
@@ -484,7 +491,9 @@ where
         // (that have count 0 in their layout).
         let from_offset = match base.layout.fields {
             FieldsShape::Array { stride, .. } => stride * from, // `Size` multiplication is checked
-            _ => bug!("Unexpected layout of index access: {:#?}", base.layout),
+            _ => {
+                span_bug!(self.cur_span(), "unexpected layout of index access: {:#?}", base.layout)
+            }
         };
 
         // Compute meta and new layout
@@ -497,7 +506,9 @@ where
                 let len = Scalar::from_machine_usize(inner_len, self);
                 (MemPlaceMeta::Meta(len), base.layout.ty)
             }
-            _ => bug!("cannot subslice non-array type: `{:?}`", base.layout.ty),
+            _ => {
+                span_bug!(self.cur_span(), "cannot subslice non-array type: `{:?}`", base.layout.ty)
+            }
         };
         let layout = self.layout_of(ty)?;
         base.offset(from_offset, meta, layout, self)
@@ -768,7 +779,7 @@ where
             None => return Ok(()), // zero-sized access
         };
 
-        let tcx = &*self.tcx;
+        let tcx = *self.tcx;
         // FIXME: We should check that there are dest.layout.size many bytes available in
         // memory.  The code below is not sufficient, with enough padding it might not
         // cover all the bytes!
@@ -776,12 +787,14 @@ where
             Immediate::Scalar(scalar) => {
                 match dest.layout.abi {
                     Abi::Scalar(_) => {} // fine
-                    _ => {
-                        bug!("write_immediate_to_mplace: invalid Scalar layout: {:#?}", dest.layout)
-                    }
+                    _ => span_bug!(
+                        self.cur_span(),
+                        "write_immediate_to_mplace: invalid Scalar layout: {:#?}",
+                        dest.layout
+                    ),
                 }
                 self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(
-                    tcx,
+                    &tcx,
                     ptr,
                     scalar,
                     dest.layout.size,
@@ -793,7 +806,8 @@ where
                 // which `ptr.offset(b_offset)` cannot possibly fail to satisfy.
                 let (a, b) = match dest.layout.abi {
                     Abi::ScalarPair(ref a, ref b) => (&a.value, &b.value),
-                    _ => bug!(
+                    _ => span_bug!(
+                        self.cur_span(),
                         "write_immediate_to_mplace: invalid ScalarPair layout: {:#?}",
                         dest.layout
                     ),
@@ -806,8 +820,8 @@ where
                 // but that does not work: We could be a newtype around a pair, then the
                 // fields do not match the `ScalarPair` components.
 
-                self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(tcx, ptr, a_val, a_size)?;
-                self.memory.get_raw_mut(b_ptr.alloc_id)?.write_scalar(tcx, b_ptr, b_val, b_size)
+                self.memory.get_raw_mut(ptr.alloc_id)?.write_scalar(&tcx, ptr, a_val, a_size)?;
+                self.memory.get_raw_mut(b_ptr.alloc_id)?.write_scalar(&tcx, b_ptr, b_val, b_size)
             }
         }
     }
@@ -841,9 +855,9 @@ where
     ) -> InterpResult<'tcx> {
         // We do NOT compare the types for equality, because well-typed code can
         // actually "transmute" `&mut T` to `&T` in an assignment without a cast.
-        if !mir_assign_valid_types(self.tcx.tcx, src.layout, dest.layout) {
+        if !mir_assign_valid_types(*self.tcx, src.layout, dest.layout) {
             span_bug!(
-                self.tcx.span,
+                self.cur_span(),
                 "type mismatch when copying!\nsrc: {:?},\ndest: {:?}",
                 src.layout.ty,
                 dest.layout.ty,
@@ -898,7 +912,7 @@ where
         src: OpTy<'tcx, M::PointerTag>,
         dest: PlaceTy<'tcx, M::PointerTag>,
     ) -> InterpResult<'tcx> {
-        if mir_assign_valid_types(self.tcx.tcx, src.layout, dest.layout) {
+        if mir_assign_valid_types(*self.tcx, src.layout, dest.layout) {
             // Fast path: Just use normal `copy_op`
             return self.copy_op(src, dest);
         }
@@ -910,7 +924,7 @@ where
             // on `typeck_tables().has_errors` at all const eval entry points.
             debug!("Size mismatch when transmuting!\nsrc: {:#?}\ndest: {:#?}", src, dest);
             self.tcx.sess.delay_span_bug(
-                self.tcx.span,
+                self.cur_span(),
                 "size-changing transmute, should have been caught by transmute checking",
             );
             throw_inval!(TransmuteSizeDiff(src.layout.ty, dest.layout.ty));
diff --git a/src/librustc_mir/interpret/step.rs b/src/librustc_mir/interpret/step.rs
index 02a709ab1a1..16c6396799e 100644
--- a/src/librustc_mir/interpret/step.rs
+++ b/src/librustc_mir/interpret/step.rs
@@ -76,7 +76,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
     fn statement(&mut self, stmt: &mir::Statement<'tcx>) -> InterpResult<'tcx> {
         info!("{:?}", stmt);
-        self.set_span(stmt.source_info.span);
 
         use rustc_middle::mir::StatementKind::*;
 
@@ -279,7 +278,6 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
     fn terminator(&mut self, terminator: &mir::Terminator<'tcx>) -> InterpResult<'tcx> {
         info!("{:?}", terminator.kind);
-        self.set_span(terminator.source_info.span);
 
         self.eval_terminator(terminator)?;
         if !self.stack().is_empty() {
diff --git a/src/librustc_mir/interpret/traits.rs b/src/librustc_mir/interpret/traits.rs
index b9f9d37df76..a1d124bb760 100644
--- a/src/librustc_mir/interpret/traits.rs
+++ b/src/librustc_mir/interpret/traits.rs
@@ -2,7 +2,7 @@ use std::convert::TryFrom;
 
 use rustc_middle::mir::interpret::{InterpResult, Pointer, PointerArithmetic, Scalar};
 use rustc_middle::ty::{self, Instance, Ty, TypeFoldable};
-use rustc_target::abi::{Align, HasDataLayout, LayoutOf, Size};
+use rustc_target::abi::{Align, LayoutOf, Size};
 
 use super::{FnVal, InterpCx, Machine, MemoryKind};
 
@@ -49,8 +49,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let size = layout.size.bytes();
         let align = layout.align.abi.bytes();
 
+        let tcx = *self.tcx;
         let ptr_size = self.pointer_size();
-        let ptr_align = self.tcx.data_layout.pointer_align.abi;
+        let ptr_align = tcx.data_layout.pointer_align.abi;
         // /////////////////////////////////////////////////////////////////////////////////////////
         // If you touch this code, be sure to also make the corresponding changes to
         // `get_vtable` in `rust_codegen_llvm/meth.rs`.
@@ -60,33 +61,32 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             ptr_align,
             MemoryKind::Vtable,
         );
-        let tcx = &*self.tcx;
 
-        let drop = Instance::resolve_drop_in_place(*tcx, ty);
+        let drop = Instance::resolve_drop_in_place(tcx, ty);
         let drop = self.memory.create_fn_alloc(FnVal::Instance(drop));
 
         // No need to do any alignment checks on the memory accesses below, because we know the
         // allocation is correctly aligned as we created it above. Also we're only offsetting by
         // multiples of `ptr_align`, which means that it will stay aligned to `ptr_align`.
         let vtable_alloc = self.memory.get_raw_mut(vtable.alloc_id)?;
-        vtable_alloc.write_ptr_sized(tcx, vtable, drop.into())?;
+        vtable_alloc.write_ptr_sized(&tcx, vtable, drop.into())?;
 
-        let size_ptr = vtable.offset(ptr_size, tcx)?;
-        vtable_alloc.write_ptr_sized(tcx, size_ptr, Scalar::from_uint(size, ptr_size).into())?;
-        let align_ptr = vtable.offset(ptr_size * 2, tcx)?;
-        vtable_alloc.write_ptr_sized(tcx, align_ptr, Scalar::from_uint(align, ptr_size).into())?;
+        let size_ptr = vtable.offset(ptr_size, &tcx)?;
+        vtable_alloc.write_ptr_sized(&tcx, size_ptr, Scalar::from_uint(size, ptr_size).into())?;
+        let align_ptr = vtable.offset(ptr_size * 2, &tcx)?;
+        vtable_alloc.write_ptr_sized(&tcx, align_ptr, Scalar::from_uint(align, ptr_size).into())?;
 
         for (i, method) in methods.iter().enumerate() {
             if let Some((def_id, substs)) = *method {
                 // resolve for vtable: insert shims where needed
                 let instance =
-                    ty::Instance::resolve_for_vtable(*tcx, self.param_env, def_id, substs)
+                    ty::Instance::resolve_for_vtable(tcx, self.param_env, def_id, substs)
                         .ok_or_else(|| err_inval!(TooGeneric))?;
                 let fn_ptr = self.memory.create_fn_alloc(FnVal::Instance(instance));
                 // We cannot use `vtable_allic` as we are creating fn ptrs in this loop.
-                let method_ptr = vtable.offset(ptr_size * (3 + i as u64), tcx)?;
+                let method_ptr = vtable.offset(ptr_size * (3 + i as u64), &tcx)?;
                 self.memory.get_raw_mut(vtable.alloc_id)?.write_ptr_sized(
-                    tcx,
+                    &tcx,
                     method_ptr,
                     fn_ptr.into(),
                 )?;
@@ -171,7 +171,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             alloc.read_ptr_sized(self, vtable.offset(pointer_size * 2, self)?)?.not_undef()?;
         let align = u64::try_from(self.force_bits(align, pointer_size)?).unwrap();
 
-        if size >= self.tcx.data_layout().obj_size_bound() {
+        if size >= self.tcx.data_layout.obj_size_bound() {
             throw_ub_format!(
                 "invalid vtable: \
                 size is bigger than largest supported object"
diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs
index 0ff60cbd55d..d50f052d405 100644
--- a/src/librustc_mir/transform/const_prop.rs
+++ b/src/librustc_mir/transform/const_prop.rs
@@ -313,7 +313,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         let param_env = tcx.param_env(def_id).with_reveal_all();
 
         let span = tcx.def_span(def_id);
-        let mut ecx = InterpCx::new(tcx.at(span), param_env, ConstPropMachine::new(), ());
+        let mut ecx = InterpCx::new(tcx, span, param_env, ConstPropMachine::new(), ());
         let can_const_prop = CanConstProp::check(body);
 
         let ret = ecx
@@ -404,9 +404,8 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         match self.ecx.eval_const_to_op(c.literal, None) {
             Ok(op) => Some(op),
             Err(error) => {
-                // Make sure errors point at the constant.
-                self.ecx.set_span(c.span);
-                let err = error_to_const_error(&self.ecx, error);
+                let tcx = self.ecx.tcx.at(c.span);
+                let err = error_to_const_error(&self.ecx, error, Some(c.span));
                 if let Some(lint_root) = self.lint_root(source_info) {
                     let lint_only = match c.literal.val {
                         // Promoteds must lint and not error as the user didn't ask for them
@@ -418,17 +417,12 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                     if lint_only {
                         // Out of backwards compatibility we cannot report hard errors in unused
                         // generic functions using associated constants of the generic parameters.
-                        err.report_as_lint(
-                            self.ecx.tcx,
-                            "erroneous constant used",
-                            lint_root,
-                            Some(c.span),
-                        );
+                        err.report_as_lint(tcx, "erroneous constant used", lint_root, Some(c.span));
                     } else {
-                        err.report_as_error(self.ecx.tcx, "erroneous constant used");
+                        err.report_as_error(tcx, "erroneous constant used");
                     }
                 } else {
-                    err.report_as_error(self.ecx.tcx, "erroneous constant used");
+                    err.report_as_error(tcx, "erroneous constant used");
                 }
                 None
             }
@@ -851,7 +845,6 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
     fn visit_statement(&mut self, statement: &mut Statement<'tcx>, location: Location) {
         trace!("visit_statement: {:?}", statement);
         let source_info = statement.source_info;
-        self.ecx.set_span(source_info.span);
         self.source_info = Some(source_info);
         if let StatementKind::Assign(box (place, ref mut rval)) = statement.kind {
             let place_ty: Ty<'tcx> = place.ty(&self.local_decls, self.tcx).ty;
@@ -864,7 +857,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
                         if let Some(value) = self.get_const(place) {
                             if self.should_const_prop(value) {
                                 trace!("replacing {:?} with {:?}", rval, value);
-                                self.replace_with_const(rval, value, statement.source_info);
+                                self.replace_with_const(rval, value, source_info);
                                 if can_const_prop == ConstPropMode::FullConstProp
                                     || can_const_prop == ConstPropMode::OnlyInsideOwnBlock
                                 {
@@ -927,7 +920,6 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
 
     fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, location: Location) {
         let source_info = terminator.source_info;
-        self.ecx.set_span(source_info.span);
         self.source_info = Some(source_info);
         self.super_terminator(terminator, location);
         match &mut terminator.kind {
diff --git a/src/test/ui/consts/const-eval/infinite_loop.stderr b/src/test/ui/consts/const-eval/infinite_loop.stderr
index ebdb73c4467..3386e6e588e 100644
--- a/src/test/ui/consts/const-eval/infinite_loop.stderr
+++ b/src/test/ui/consts/const-eval/infinite_loop.stderr
@@ -23,10 +23,10 @@ LL |             n = if n % 2 == 0 { n/2 } else { 3*n + 1 };
    = help: add `#![feature(const_if_match)]` to the crate attributes to enable
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/infinite_loop.rs:8:20
+  --> $DIR/infinite_loop.rs:8:17
    |
 LL |             n = if n % 2 == 0 { n/2 } else { 3*n + 1 };
-   |                    ^^^^^^^^^^ exceeded interpreter step limit (see `#[const_eval_limit]`)
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ exceeded interpreter step limit (see `#[const_eval_limit]`)
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/consts/const-size_of-cycle.stderr b/src/test/ui/consts/const-size_of-cycle.stderr
index 5fd7fe4480e..0aa30665f59 100644
--- a/src/test/ui/consts/const-size_of-cycle.stderr
+++ b/src/test/ui/consts/const-size_of-cycle.stderr
@@ -17,8 +17,8 @@ LL |     bytes: [u8; std::mem::size_of::<Foo>()]
 note: ...which requires const-evaluating `std::mem::size_of`...
   --> $SRC_DIR/libcore/mem/mod.rs:LL:COL
    |
-LL |     intrinsics::size_of::<T>()
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL | pub const fn size_of<T>() -> usize {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 note: ...which requires const-evaluating + checking `std::intrinsics::size_of`...
   --> $SRC_DIR/libcore/intrinsics.rs:LL:COL
    |
diff --git a/src/test/ui/consts/const_limit/const_eval_limit_reached.stderr b/src/test/ui/consts/const_limit/const_eval_limit_reached.stderr
index be522dd6d5d..8c2190b4e59 100644
--- a/src/test/ui/consts/const_limit/const_eval_limit_reached.stderr
+++ b/src/test/ui/consts/const_limit/const_eval_limit_reached.stderr
@@ -1,15 +1,18 @@
 error: any use of this value will cause an error
-  --> $DIR/const_eval_limit_reached.rs:8:11
+  --> $DIR/const_eval_limit_reached.rs:8:5
    |
-LL | / const X: usize = {
-LL | |     let mut x = 0;
-LL | |     while x != 1000 {
-   | |           ^^^^^^^^^ exceeded interpreter step limit (see `#[const_eval_limit]`)
-LL | |
-...  |
-LL | |     x
-LL | | };
-   | |__-
+LL |  / const X: usize = {
+LL |  |     let mut x = 0;
+LL |  |     while x != 1000 {
+   |  |_____^
+LL | ||
+LL | ||         x += 1;
+LL | ||     }
+   | ||_____^ exceeded interpreter step limit (see `#[const_eval_limit]`)
+LL |  |
+LL |  |     x
+LL |  | };
+   |  |__-
    |
    = note: `#[deny(const_err)]` on by default
 
diff --git a/src/test/ui/consts/recursive-zst-static.default.stderr b/src/test/ui/consts/recursive-zst-static.default.stderr
index d424b22f000..9042c6f6be1 100644
--- a/src/test/ui/consts/recursive-zst-static.default.stderr
+++ b/src/test/ui/consts/recursive-zst-static.default.stderr
@@ -1,8 +1,8 @@
 error[E0391]: cycle detected when const-evaluating `FOO`
-  --> $DIR/recursive-zst-static.rs:10:18
+  --> $DIR/recursive-zst-static.rs:10:1
    |
 LL | static FOO: () = FOO;
-   |                  ^^^
+   | ^^^^^^^^^^^^^^^^^^^^^
    |
 note: ...which requires const-evaluating `FOO`...
   --> $DIR/recursive-zst-static.rs:10:1
diff --git a/src/test/ui/consts/recursive-zst-static.unleash.stderr b/src/test/ui/consts/recursive-zst-static.unleash.stderr
index d424b22f000..9042c6f6be1 100644
--- a/src/test/ui/consts/recursive-zst-static.unleash.stderr
+++ b/src/test/ui/consts/recursive-zst-static.unleash.stderr
@@ -1,8 +1,8 @@
 error[E0391]: cycle detected when const-evaluating `FOO`
-  --> $DIR/recursive-zst-static.rs:10:18
+  --> $DIR/recursive-zst-static.rs:10:1
    |
 LL | static FOO: () = FOO;
-   |                  ^^^
+   | ^^^^^^^^^^^^^^^^^^^^^
    |
 note: ...which requires const-evaluating `FOO`...
   --> $DIR/recursive-zst-static.rs:10:1
diff --git a/src/test/ui/consts/uninhabited-const-issue-61744.rs b/src/test/ui/consts/uninhabited-const-issue-61744.rs
index 15436f9c1b2..55f42d84f9c 100644
--- a/src/test/ui/consts/uninhabited-const-issue-61744.rs
+++ b/src/test/ui/consts/uninhabited-const-issue-61744.rs
@@ -1,11 +1,11 @@
 // build-fail
 
 pub const unsafe fn fake_type<T>() -> T {
-    hint_unreachable()
+    hint_unreachable() //~ ERROR evaluation of constant value failed
 }
 
 pub const unsafe fn hint_unreachable() -> ! {
-    fake_type() //~ ERROR evaluation of constant value failed
+    fake_type()
 }
 
 trait Const {
diff --git a/src/test/ui/consts/uninhabited-const-issue-61744.stderr b/src/test/ui/consts/uninhabited-const-issue-61744.stderr
index ca232380897..fc908b2b222 100644
--- a/src/test/ui/consts/uninhabited-const-issue-61744.stderr
+++ b/src/test/ui/consts/uninhabited-const-issue-61744.stderr
@@ -1,9 +1,10 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/uninhabited-const-issue-61744.rs:8:5
+  --> $DIR/uninhabited-const-issue-61744.rs:4:5
    |
 LL |     hint_unreachable()
-   |     ------------------
+   |     ^^^^^^^^^^^^^^^^^^
    |     |
+   |     reached the configured maximum number of stack frames
    |     inside `fake_type::<!>` at $DIR/uninhabited-const-issue-61744.rs:4:5
    |     inside `fake_type::<!>` at $DIR/uninhabited-const-issue-61744.rs:4:5
    |     inside `fake_type::<!>` at $DIR/uninhabited-const-issue-61744.rs:4:5
@@ -71,9 +72,8 @@ LL |     hint_unreachable()
    |     inside `fake_type::<i32>` at $DIR/uninhabited-const-issue-61744.rs:4:5
 ...
 LL |     fake_type()
-   |     ^^^^^^^^^^^
+   |     -----------
    |     |
-   |     reached the configured maximum number of stack frames
    |     inside `hint_unreachable` at $DIR/uninhabited-const-issue-61744.rs:8:5
    |     inside `hint_unreachable` at $DIR/uninhabited-const-issue-61744.rs:8:5
    |     inside `hint_unreachable` at $DIR/uninhabited-const-issue-61744.rs:8:5
diff --git a/src/test/ui/infinite/infinite-recursion-const-fn.stderr b/src/test/ui/infinite/infinite-recursion-const-fn.stderr
index 6bd5e035f57..de0c579f630 100644
--- a/src/test/ui/infinite/infinite-recursion-const-fn.stderr
+++ b/src/test/ui/infinite/infinite-recursion-const-fn.stderr
@@ -1,14 +1,14 @@
 error[E0391]: cycle detected when const-evaluating `a`
-  --> $DIR/infinite-recursion-const-fn.rs:3:25
+  --> $DIR/infinite-recursion-const-fn.rs:3:1
    |
 LL | const fn a() -> usize { b() }
-   |                         ^^^
+   | ^^^^^^^^^^^^^^^^^^^^^
    |
 note: ...which requires const-evaluating `b`...
-  --> $DIR/infinite-recursion-const-fn.rs:4:25
+  --> $DIR/infinite-recursion-const-fn.rs:4:1
    |
 LL | const fn b() -> usize { a() }
-   |                         ^^^
+   | ^^^^^^^^^^^^^^^^^^^^^
    = note: ...which again requires const-evaluating `a`, completing the cycle
 note: cycle used when const-evaluating `ARR::{{constant}}#0`
   --> $DIR/infinite-recursion-const-fn.rs:5:18
diff --git a/src/test/ui/recursion/recursive-static-definition.stderr b/src/test/ui/recursion/recursive-static-definition.stderr
index b724c261a7c..093606e100c 100644
--- a/src/test/ui/recursion/recursive-static-definition.stderr
+++ b/src/test/ui/recursion/recursive-static-definition.stderr
@@ -1,8 +1,8 @@
 error[E0391]: cycle detected when const-evaluating `FOO`
-  --> $DIR/recursive-static-definition.rs:1:23
+  --> $DIR/recursive-static-definition.rs:1:1
    |
 LL | pub static FOO: u32 = FOO;
-   |                       ^^^
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: ...which requires const-evaluating `FOO`...
   --> $DIR/recursive-static-definition.rs:1:1
diff --git a/src/test/ui/write-to-static-mut-in-static.stderr b/src/test/ui/write-to-static-mut-in-static.stderr
index 6c2bd13d433..50dfce3448c 100644
--- a/src/test/ui/write-to-static-mut-in-static.stderr
+++ b/src/test/ui/write-to-static-mut-in-static.stderr
@@ -5,10 +5,10 @@ LL | pub static mut B: () = unsafe { A = 1; };
    |                                 ^^^^^ modifying a static's initial value from another static's initializer
 
 error[E0391]: cycle detected when const-evaluating `C`
-  --> $DIR/write-to-static-mut-in-static.rs:5:34
+  --> $DIR/write-to-static-mut-in-static.rs:5:1
    |
 LL | pub static mut C: u32 = unsafe { C = 1; 0 };
-   |                                  ^^^^^
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: ...which requires const-evaluating `C`...
   --> $DIR/write-to-static-mut-in-static.rs:5:1