Fixes #69977

When we parse a chain of method calls like `foo.a().b().c()`, each
`MethodCallExpr` gets assigned a span that starts at the beginning of
the call chain (`foo`). While this is useful for diagnostics, it means
that `Location::caller` will return the same location for every call
in a call chain.

This PR makes us separately record the span of the function name and
arguments for a method call (e.g. `b()` in `foo.a().b().c()`). This
`Span` is passed through HIR lowering and MIR building to
`TerminatorKind::Call`, where it is used in preference to
`Terminator.source_info.span` when determining `Location::caller`.

This new span is also useful for diagnostics where we want to emphasize
a particular method call - for an example, see
https://github.com/rust-lang/rust/pull/72389#discussion_r436035990

This commit introduces a `Limit` type which is used to ensure that all
comparisons against limits within the compiler are consistent (which can
result in ICEs if they aren't).
Signed-off-by: NDavid Wood <david@davidtw.co>

We now perform the correct checks even if the pointer size differs
between the host and target.
Signed-off-by: NJoe Richey <joerichey@google.com>

The previous code paniced if offset_bytes == i64::MIN. This commit:
  - Properly computes the absoulte value to avoid this panic
  - Adds a test for this edge case
Signed-off-by: NJoe Richey <joerichey@google.com>

As part of supporting RFC 2229, we will be capturing all the places that
are mentioned in a closure. Currently the upvar_list field gives access
to a FxIndexMap<HirId, Upvar> map. Eventually this will change, with the
upvar_list having a more general structure that expresses captured
paths, not just the mentioned upvars. We will make those changes in
subsequent PRs.

This commit modifies the name of the upvar_list map to closure_captures
in TypeckTables.
Co-authored-by: NDhruv Jauhar <dhruvjhr@gmail.com>
Co-authored-by: NAman Arora <me@aman-arora.com>

Signed-off-by: NJoe Richey <joerichey@google.com>

Miri's pointer_offset_inbounds implementation has been moved into
librustc_mir as ptr_offset_inbounds (to avoid breaking miri on a
nightly update). The comments have been slightly reworked to better
match `offset`'s external documentation about what causes UB.

The intrinsic implementations are taken directly from miri.
Signed-off-by: NJoe Richey <joerichey@google.com>