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| -rw-r--r-- | compiler/rustc_borrowck/src/polonius/mod.rs | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/compiler/rustc_borrowck/src/polonius/mod.rs b/compiler/rustc_borrowck/src/polonius/mod.rs index 391ef2069f9..70f8fdaa637 100644 --- a/compiler/rustc_borrowck/src/polonius/mod.rs +++ b/compiler/rustc_borrowck/src/polonius/mod.rs @@ -1,3 +1,38 @@ +//! Polonius analysis and support code: +//! - dedicated constraints +//! - conversion from NLL constraints +//! - debugging utilities +//! - etc. +//! +//! The current implementation models the flow-sensitive borrow-checking concerns as a graph +//! containing both information about regions and information about the control flow. +//! +//! Loan propagation is seen as a reachability problem (with some subtleties) between where the loan +//! is introduced and a given point. +//! +//! Constraints arising from type-checking allow loans to flow from region to region at the same CFG +//! point. Constraints arising from liveness allow loans to flow within from point to point, between +//! live regions at these points. +//! +//! Edges can be bidirectional to encode invariant relationships, and loans can flow "back in time" +//! to traverse these constraints arising earlier in the CFG. +//! +//! When incorporating kills in the traversal, the loans reaching a given point are considered live. +//! +//! After this, the usual NLL process happens. These live loans are fed into a dataflow analysis +//! combining them with the points where loans go out of NLL scope (the frontier where they stop +//! propagating to a live region), to yield the "loans in scope" or "active loans", at a given +//! point. +//! +//! Illegal accesses are still computed by checking whether one of these resulting loans is +//! invalidated. +//! +//! More information on this simple approach can be found in the following links, and in the future +//! in the rustc dev guide: +//! - <https://smallcultfollowing.com/babysteps/blog/2023/09/22/polonius-part-1/> +//! - <https://smallcultfollowing.com/babysteps/blog/2023/09/29/polonius-part-2/> +//! + mod constraints; pub(crate) use constraints::*; |