MIR-borrowck: ICE: assertion failure left == right

[pnkfelix]

There are many tests in compile-fail/borrowck/ that ICE with the same failure: "assertion failure, left == right" (with specific instances of MIR Lvalues then printed for left and right respectively.

• You can see list of such tests in the discrepancy spreadsheet.
• But for ease of reference, I am also transcribing that list into the first comment on this issue.

This may be due to some over-zealous assertion somewhere in MIR-borrowck.

In any case it needs diagnosis and fixing.

[pnkfelix]

Transcription of relevant tests according to the discrepancy spreadsheet. (caveat: data is based on out-of-date pnkfelix/mir-borrowck4 branch)

tests failing with ICE: assertion failure left == right ...
borrowck-borrow-from-owned-ptr.rs
borrowck-borrow-from-stack-variable.rs
borrowck-closures-use-after-free.rs
borrowck-swap-mut-base-ptr.rs
borrowck-reborrow-from-mut.rs
borrowck-uniq-via-lend.rs
borrowck-bad-nested-calls-free.rs
borrowck-loan-blocks-mut-uniq.rs
borrowck-object-lifetime.rs
borrowck-mut-borrow-of-mut-base-ptr.rs
borrowck-lend-flow-if.rs
borrowck-lend-flow-loop.rs
borrowck-lend-flow.rs

[pnkfelix]

I am going to focus on this bug.