Permit usize/isize matching in theory once open-ended range patterns exist

Author: varkor

text/0000-exhaustive-integer-pattern-matching.md

@@ -6,7 +6,7 @@
 # Summary
 [summary]: #summary
 
-Extend Rust's pattern matching exhaustiveness checks to cover the integer types: `u8`, `u16`, `u32`, `u64`, `u128`, `i8`, `i16`, `i32`, `i64`, `i128` and `char`.
+Extend Rust's pattern matching exhaustiveness checks to cover the integer types: `u8`, `u16`, `u32`, `u64`, `u128`, `usize`, `i8`, `i16`, `i32`, `i64`, `i128`, `isize` and `char`.
 
 ```rust
 fn matcher_full(x: u8) {
@@ -36,7 +36,7 @@ This feature has already [been implemented](https://github.com/rust-lang/rust/pu
 # Guide-level explanation
 [guide-level-explanation]: #guide-level-explanation
 
-Exhaustive pattern matching works for integer types other than `usize` and `isize`, just like any other type. In addition, missing ranges of integers will be reported as errors.
+Exhaustive pattern matching works for integer types, just like any other type. In addition, missing ranges of integers will be reported as errors.
 
 ```rust
 fn matcher_full(x: u8) {
@@ -67,7 +67,7 @@ The implementation of this features uses interval arithmetic and an extension of
 
 This feature has already [been implemented](https://github.com/rust-lang/rust/pull/50912), so the code there may be used for further reference. The source contains detailed comments about the implementation.
 
-Exhaustiveness checking for `usize` and `isize` will be placed behind an unstable feature flag, `exhaustive_pointer_size_matching`.
+For `usize` and `isize`, no assumptions about the maximimum value are permitted. To exhaustively match on either pointer-size integer type a wildcard pattern (`_`) must be used (or if [open-ended range patterns are added](https://github.com/rust-lang/rfcs/issues/947), ranges must be open ended [e.g. `0..`]). An unstable feature `precise_pointer_size_matching` will be added to permit matching exactly on pointer-size integer types.
 
 # Drawbacks
 [drawbacks]: #drawbacks