[MIR] track Location in MirVisitor, combine Location

[scottcarr]

All the users of MirVisitor::visit_statement implement their own statement index tracking. This PR move the tracking into MirVisitor itself.

Also, there were 2 separate implementations of Location that were identical. This PR eliminates one of them.

[rust-highfive]

r? @eddyb

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[scottcarr]

r? @nikomatsakis

[eddyb]

Missing newline.

[nikomatsakis]

Seems like a win to me. @nagisa I don't quite understand your comment -- are you suggesting we should use a u32? I'm ok either way, especially given the temporary nature of this structure. I'm going to r+ I think but we can revisit.

[nikomatsakis]

@bors r+

[bors]

📌 Commit 16785b6 has been approved by nikomatsakis

[nagisa]

@nikomatsakis I’m suggesting there’s a potential overflow. We have usize = u16 targets. I feel like it is very possible to get into a situation where this usize is overflowed, and thus, terminator cannot be represented.

[jonas-schievink]

Well, this is a host-usize. I'm assuming no 16-bit-usize target will ever run rustc.

[nikomatsakis]

@nagisa I'm not quite following. If indeed we are running on a 16-bit host, then yes, usize will be 16-bits -- probably lots of stuff would fail, but anyway we surely (in that case) wouldn't have more than 2^16 statements in any given basic block, since that's the size of the address space we'd have available, and hence we'd still be able to represent the terminator in the same way, right?

[bors]

☔ The latest upstream changes (presumably #35403) made this pull request unmergeable. Please resolve the merge conflicts.

[nikomatsakis]

@bors r+

[bors]

📌 Commit fe40004 has been approved by nikomatsakis

[nikomatsakis]

@bors r+

[bors]

📌 Commit fb84bb1 has been approved by nikomatsakis

[eddyb]

@bors r- According to travis on #35649, this needs a rebase.

[bors]

☔ The latest upstream changes (presumably #35409) made this pull request unmergeable. Please resolve the merge conflicts.

[nikomatsakis]

@bors r+

[bors]

📌 Commit 0ff1282 has been approved by nikomatsakis

[nikomatsakis]

@scottcarr hmm, these travis failures look legit...something about the interaction with constant expressions, perhaps an error in the port?

[nikomatsakis]

@bors r+

[bors]

📌 Commit c043a27 has been approved by nikomatsakis

[bors]

⌛ Testing commit c043a27 with merge b7e2157...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-no-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-no-mir, auto-win-msvc-64-opt-rustbuild
Approved by: nikomatsakis
Pushing b7e2157 to master...