Remove ty::BrFresh and new_bound

[rust.git] / src / librustc / infer / region_constraints / README.md

diff --git a/src/librustc/infer/region_constraints/README.md b/src/librustc/infer/region_constraints/README.md
index 775bbf955b830efd558623056a450e20cd8bb481..ea7fffe9dc1c6fdc25b673ff7b248cc1bcea9203 100644 (file)
--- a/src/librustc/infer/region_constraints/README.md
+++ b/src/librustc/infer/region_constraints/README.md
@@ -1,77 +1,3 @@
-# Region constraint collection
-
-> WARNING: This README is obsolete and will be removed soon! For
-> more info on how the current borrowck works, see the [rustc guide].
+For info on how the current borrowck works, see the [rustc guide].
 
 [rustc guide]: https://rust-lang.github.io/rustc-guide/mir/borrowck.html
-
-## Terminology
-
-Note that we use the terms region and lifetime interchangeably.
-
-## Introduction
-
-As described in the rustc guide [chapter on type inference][ti], and unlike
-normal type inference, which is similar in spirit to H-M and thus
-works progressively, the region type inference works by accumulating
-constraints over the course of a function.  Finally, at the end of
-processing a function, we process and solve the constraints all at
-once.
-
-[ti]: https://rust-lang.github.io/rustc-guide/type-inference.html
-
-The constraints are always of one of three possible forms:
-
-- `ConstrainVarSubVar(Ri, Rj)` states that region variable Ri must be
-  a subregion of Rj
-- `ConstrainRegSubVar(R, Ri)` states that the concrete region R (which
-  must not be a variable) must be a subregion of the variable Ri
-- `ConstrainVarSubReg(Ri, R)` states the variable Ri should be less
-  than the concrete region R. This is kind of deprecated and ought to
-  be replaced with a verify (they essentially play the same role).
-
-In addition to constraints, we also gather up a set of "verifys"
-(what, you don't think Verify is a noun? Get used to it my
-friend!). These represent relations that must hold but which don't
-influence inference proper. These take the form of:
-
-- `VerifyRegSubReg(Ri, Rj)` indicates that Ri <= Rj must hold,
-  where Rj is not an inference variable (and Ri may or may not contain
-  one). This doesn't influence inference because we will already have
-  inferred Ri to be as small as possible, so then we just test whether
-  that result was less than Rj or not.
-- `VerifyGenericBound(R, Vb)` is a more complex expression which tests
-  that the region R must satisfy the bound `Vb`. The bounds themselves
-  may have structure like "must outlive one of the following regions"
-  or "must outlive ALL of the following regions. These bounds arise
-  from constraints like `T: 'a` -- if we know that `T: 'b` and `T: 'c`
-  (say, from where clauses), then we can conclude that `T: 'a` if `'b:
-  'a` *or* `'c: 'a`.
-
-## Building up the constraints
-
-Variables and constraints are created using the following methods:
-
-- `new_region_var()` creates a new, unconstrained region variable;
-- `make_subregion(Ri, Rj)` states that Ri is a subregion of Rj
-- `lub_regions(Ri, Rj) -> Rk` returns a region Rk which is
-  the smallest region that is greater than both Ri and Rj
-- `glb_regions(Ri, Rj) -> Rk` returns a region Rk which is
-  the greatest region that is smaller than both Ri and Rj
-
-The actual region resolution algorithm is not entirely
-obvious, though it is also not overly complex.
-
-## Snapshotting
-
-It is also permitted to try (and rollback) changes to the graph.  This
-is done by invoking `start_snapshot()`, which returns a value.  Then
-later you can call `rollback_to()` which undoes the work.
-Alternatively, you can call `commit()` which ends all snapshots.
-Snapshots can be recursive---so you can start a snapshot when another
-is in progress, but only the root snapshot can "commit".
-
-## Skolemization
-
-For a discussion on skolemization and higher-ranked subtyping, please
-see the module `middle::infer::higher_ranked::doc`.