Auto merge of #46733 - nikomatsakis:nll-master-to-rust-master-5, r=arielb1

nll part 5

Next round of changes from the nll-master branch.

Extensions:

- we now propagate ty-region-outlives constraints out of closures and into their creator when necessary
- we fix a few ICEs that can occur by doing liveness analysis (and the resulting normalization) during type-checking
- we handle the implicit region bound that assumes that each type `T` outlives the fn body
- we handle normalization of inputs/outputs in fn signatures

Not included in this PR (will come next):

- handling `impl Trait`
- tracking causal information
- extended errors

r? @arielb1

diff --cc src/librustc/mir/mod.rs
Simple merge

diff --cc src/librustc/ty/maps/mod.rs
Simple merge

diff --cc src/librustc/ty/mod.rs
Simple merge

diff --cc src/librustc/ty/util.rs
Simple merge

diff --cc src/librustc_mir/borrow_check/error_reporting.rs
Simple merge

diff --cc src/librustdoc/clean/mod.rs
Simple merge

diff --cc src/test/ui/nll/capture-ref-in-struct.stderr
Simple merge

diff --cc src/test/ui/nll/closure-requirements/escape-argument.stderr
Simple merge

diff --cc src/test/ui/nll/closure-requirements/escape-upvar-nested.stderr
Simple merge

diff --cc src/test/ui/nll/closure-requirements/escape-upvar-ref.stderr
Simple merge

diff --cc src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
Simple merge