Rollup merge of #118598 - Nadrieril:remove_precise_pointer_size_match…

…ing, r=davidtwco

Remove the `precise_pointer_size_matching` feature gate

`usize` and `isize` are special for pattern matching because their range might depend on the platform. To make code portable across platforms, the following is never considered exhaustive:
```rust
let x: usize = ...;
match x {
    0..=18446744073709551615 => {}
}
```
Because of how rust handles constants, this also unfortunately counts `0..=usize::MAX` as non-exhaustive. The [`precise_pointer_size_matching`](#56354) feature gate was introduced both for this convenience and for the possibility that the lang team could decide to allow the above.

Since then, [half-open range patterns](#67264) have been implemented, and since #116692 they correctly support `usize`/`isize`:
```rust
match 0usize { // exhaustive!
    0..5 => {}
    5.. => {}
}
```
I believe this subsumes all the use cases of the feature gate. Moreover no attempt has been made to stabilize it in the 5 years of its existence. I therefore propose we retire this feature gate.

Closes #56354

compiler/rustc_feature/src/removed.rs

@@ -158,6 +158,9 @@ declare_features! (
     /// Allows using `#[plugin_registrar]` on functions.
     (removed, plugin_registrar, "1.54.0", Some(29597), None,
      Some("plugins are no longer supported")),
+    /// Allows exhaustive integer pattern matching with `usize::MAX`/`isize::MIN`/`isize::MAX`.
+    (removed, precise_pointer_size_matching, "1.32.0", Some(56354), None,
+     Some("removed in favor of half-open ranges")),
     (removed, proc_macro_expr, "1.27.0", Some(54727), None,
      Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
     (removed, proc_macro_gen, "1.27.0", Some(54727), None,

compiler/rustc_feature/src/unstable.rs

@@ -543,8 +543,6 @@ declare_features! (
     (unstable, offset_of_enum, "1.75.0", Some(106655), None),
     /// Allows using `#[optimize(X)]`.
     (unstable, optimize_attribute, "1.34.0", Some(54882), None),
-    /// Allows exhaustive integer pattern matching on `usize` and `isize`.
-    (unstable, precise_pointer_size_matching, "1.32.0", Some(56354), None),
     /// Allows macro attributes on expressions, statements and non-inline modules.
     (unstable, proc_macro_hygiene, "1.30.0", Some(54727), None),
     /// Allows `&raw const $place_expr` and `&raw mut $place_expr` expressions.

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -867,12 +867,6 @@ fn report_non_exhaustive_match<'p, 'tcx>(
                              exhaustively",
                     ));
                 }
-                if cx.tcx.sess.is_nightly_build() {
-                    err.help(format!(
-                            "add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \
-                             enable precise `{ty}` matching",
-                        ));
-                }
             } else if ty == cx.tcx.types.str_ {
                 err.note("`&str` cannot be matched exhaustively, so a wildcard `_` is necessary");
             } else if cx.is_foreign_non_exhaustive_enum(ty) {

compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs

@@ -326,8 +326,7 @@ impl IntRange {
     /// `NegInfinity..PosInfinity`. In other words, as far as `IntRange` is concerned, there are
     /// values before `isize::MIN` and after `usize::MAX`/`isize::MAX`.
     /// This is to avoid e.g. `0..(u32::MAX as usize)` from being exhaustive on one architecture and
-    /// not others. See discussions around the `precise_pointer_size_matching` feature for more
-    /// details.
+    /// not others. This was decided in <https://github.com/rust-lang/rfcs/pull/2591>.
     ///
     /// These infinities affect splitting subtly: it is possible to get `NegInfinity..0` and
     /// `usize::MAX+1..PosInfinity` in the output. Diagnostics must be careful to handle these
@@ -380,7 +379,7 @@ impl IntRange {
     /// Whether the range denotes the fictitious values before `isize::MIN` or after
     /// `usize::MAX`/`isize::MAX` (see doc of [`IntRange::split`] for why these exist).
     pub(crate) fn is_beyond_boundaries<'tcx>(&self, ty: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> bool {
-        ty.is_ptr_sized_integral() && !tcx.features().precise_pointer_size_matching && {
+        ty.is_ptr_sized_integral() && {
             // The two invalid ranges are `NegInfinity..isize::MIN` (represented as
             // `NegInfinity..0`), and `{u,i}size::MAX+1..PosInfinity`. `to_diagnostic_pat_range_bdy`
             // converts `MAX+1` to `PosInfinity`, and we couldn't have `PosInfinity` in `self.lo`
@@ -941,11 +940,8 @@ impl ConstructorSet {
                 }
             }
             &ty::Int(ity) => {
-                let range = if ty.is_ptr_sized_integral()
-                    && !cx.tcx.features().precise_pointer_size_matching
-                {
-                    // The min/max values of `isize` are not allowed to be observed unless the
-                    // `precise_pointer_size_matching` feature is enabled.
+                let range = if ty.is_ptr_sized_integral() {
+                    // The min/max values of `isize` are not allowed to be observed.
                     IntRange { lo: NegInfinity, hi: PosInfinity }
                 } else {
                     let bits = Integer::from_int_ty(&cx.tcx, ity).size().bits() as u128;
@@ -956,11 +952,8 @@ impl ConstructorSet {
                 Self::Integers { range_1: range, range_2: None }
             }
             &ty::Uint(uty) => {
-                let range = if ty.is_ptr_sized_integral()
-                    && !cx.tcx.features().precise_pointer_size_matching
-                {
-                    // The max value of `usize` is not allowed to be observed unless the
-                    // `precise_pointer_size_matching` feature is enabled.
+                let range = if ty.is_ptr_sized_integral() {
+                    // The max value of `usize` is not allowed to be observed.
                     let lo = MaybeInfiniteInt::new_finite(cx.tcx, ty, 0);
                     IntRange { lo, hi: PosInfinity }
                 } else {

tests/ui/feature-gates/feature-gate-precise_pointer_size_matching.stderr

@@ -6,7 +6,6 @@ LL |     match 0usize {
    |
    = note: the matched value is of type `usize`
    = note: `usize` does not have a fixed maximum value, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `usize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
 LL ~         0..=usize::MAX => {},
@@ -21,7 +20,6 @@ LL |     match 0isize {
    |
    = note: the matched value is of type `isize`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL ~         isize::MIN..=isize::MAX => {},

tests/ui/pattern/usefulness/integer-ranges/pointer-sized-int.deny.stderr

@@ -1,161 +1,150 @@
 error[E0004]: non-exhaustive patterns: `usize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:14:11
+  --> $DIR/pointer-sized-int.rs:13:11
    |
 LL |     match 0usize {
    |           ^^^^^^ pattern `usize::MAX..` not covered
    |
    = note: the matched value is of type `usize`
    = note: `usize` does not have a fixed maximum value, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `usize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
 LL ~         0..=usize::MAX => {},
 LL +         usize::MAX.. => todo!()
    |
 
 error[E0004]: non-exhaustive patterns: `..isize::MIN` and `isize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:19:11
+  --> $DIR/pointer-sized-int.rs:18:11
    |
 LL |     match 0isize {
    |           ^^^^^^ patterns `..isize::MIN` and `isize::MAX..` not covered
    |
    = note: the matched value is of type `isize`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL ~         isize::MIN..=isize::MAX => {},
 LL +         ..isize::MIN | isize::MAX.. => todo!()
    |
 
 error[E0004]: non-exhaustive patterns: `usize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:24:8
+  --> $DIR/pointer-sized-int.rs:23:8
    |
 LL |     m!(0usize, 0..=usize::MAX);
    |        ^^^^^^ pattern `usize::MAX..` not covered
    |
    = note: the matched value is of type `usize`
    = note: `usize` does not have a fixed maximum value, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `usize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
 LL |         match $s { $($t)+ => {}, usize::MAX.. => todo!() }
    |                                +++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `usize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:26:8
+  --> $DIR/pointer-sized-int.rs:25:8
    |
 LL |     m!(0usize, 0..5 | 5..=usize::MAX);
    |        ^^^^^^ pattern `usize::MAX..` not covered
    |
    = note: the matched value is of type `usize`
    = note: `usize` does not have a fixed maximum value, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `usize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
 LL |         match $s { $($t)+ => {}, usize::MAX.. => todo!() }
    |                                +++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `usize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:28:8
+  --> $DIR/pointer-sized-int.rs:27:8
    |
 LL |     m!(0usize, 0..usize::MAX | usize::MAX);
    |        ^^^^^^ pattern `usize::MAX..` not covered
    |
    = note: the matched value is of type `usize`
    = note: `usize` does not have a fixed maximum value, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `usize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
 LL |         match $s { $($t)+ => {}, usize::MAX.. => todo!() }
    |                                +++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `(usize::MAX.., _)` not covered
-  --> $DIR/pointer-sized-int.rs:30:8
+  --> $DIR/pointer-sized-int.rs:29:8
    |
 LL |     m!((0usize, true), (0..5, true) | (5..=usize::MAX, true) | (0..=usize::MAX, false));
    |        ^^^^^^^^^^^^^^ pattern `(usize::MAX.., _)` not covered
    |
    = note: the matched value is of type `(usize, bool)`
    = note: `usize` does not have a fixed maximum value, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `usize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
 LL |         match $s { $($t)+ => {}, (usize::MAX.., _) => todo!() }
    |                                ++++++++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `..isize::MIN` and `isize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:39:8
+  --> $DIR/pointer-sized-int.rs:38:8
    |
 LL |     m!(0isize, isize::MIN..=isize::MAX);
    |        ^^^^^^ patterns `..isize::MIN` and `isize::MAX..` not covered
    |
    = note: the matched value is of type `isize`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL |         match $s { $($t)+ => {}, ..isize::MIN | isize::MAX.. => todo!() }
    |                                ++++++++++++++++++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `..isize::MIN` and `isize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:41:8
+  --> $DIR/pointer-sized-int.rs:40:8
    |
 LL |     m!(0isize, isize::MIN..5 | 5..=isize::MAX);
    |        ^^^^^^ patterns `..isize::MIN` and `isize::MAX..` not covered
    |
    = note: the matched value is of type `isize`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL |         match $s { $($t)+ => {}, ..isize::MIN | isize::MAX.. => todo!() }
    |                                ++++++++++++++++++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `..isize::MIN` and `isize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:43:8
+  --> $DIR/pointer-sized-int.rs:42:8
    |
 LL |     m!(0isize, isize::MIN..=-1 | 0 | 1..=isize::MAX);
    |        ^^^^^^ patterns `..isize::MIN` and `isize::MAX..` not covered
    |
    = note: the matched value is of type `isize`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL |         match $s { $($t)+ => {}, ..isize::MIN | isize::MAX.. => todo!() }
    |                                ++++++++++++++++++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `..isize::MIN` and `isize::MAX..` not covered
-  --> $DIR/pointer-sized-int.rs:45:8
+  --> $DIR/pointer-sized-int.rs:44:8
    |
 LL |     m!(0isize, isize::MIN..isize::MAX | isize::MAX);
    |        ^^^^^^ patterns `..isize::MIN` and `isize::MAX..` not covered
    |
    = note: the matched value is of type `isize`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL |         match $s { $($t)+ => {}, ..isize::MIN | isize::MAX.. => todo!() }
    |                                ++++++++++++++++++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: `(..isize::MIN, _)` and `(isize::MAX.., _)` not covered
-  --> $DIR/pointer-sized-int.rs:48:9
+  --> $DIR/pointer-sized-int.rs:47:9
    |
 LL |         (0isize, true),
    |         ^^^^^^^^^^^^^^ patterns `(..isize::MIN, _)` and `(isize::MAX.., _)` not covered
    |
    = note: the matched value is of type `(isize, bool)`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL |         match $s { $($t)+ => {}, (..isize::MIN, _) | (isize::MAX.., _) => todo!() }
    |                                ++++++++++++++++++++++++++++++++++++++++++++++++++
 
 error[E0004]: non-exhaustive patterns: type `usize` is non-empty
-  --> $DIR/pointer-sized-int.rs:59:11
+  --> $DIR/pointer-sized-int.rs:58:11
    |
 LL |     match 7usize {}
    |           ^^^^^^

tests/ui/pattern/usefulness/integer-ranges/pointer-sized-int.rs

@@ -1,6 +1,5 @@
-// revisions: allow deny
+// revisions: deny
 #![feature(exclusive_range_pattern)]
-#![cfg_attr(allow, feature(precise_pointer_size_matching))]
 #![allow(overlapping_range_endpoints)]
 
 macro_rules! m {
@@ -12,23 +11,23 @@ macro_rules! m {
 #[rustfmt::skip]
 fn main() {
     match 0usize {
-        //[deny]~^ ERROR non-exhaustive patterns
+        //~^ ERROR non-exhaustive patterns
         0..=usize::MAX => {}
     }
 
     match 0isize {
-        //[deny]~^ ERROR non-exhaustive patterns
+        //~^ ERROR non-exhaustive patterns
         isize::MIN..=isize::MAX => {}
     }
 
     m!(0usize, 0..=usize::MAX);
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
     m!(0usize, 0..5 | 5..=usize::MAX);
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
     m!(0usize, 0..usize::MAX | usize::MAX);
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
     m!((0usize, true), (0..5, true) | (5..=usize::MAX, true) | (0..=usize::MAX, false));
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
 
     m!(0usize, 0..);
     m!(0usize, 0..5 | 5..);
@@ -37,18 +36,18 @@ fn main() {
     m!(0usize, 0..=usize::MAX | usize::MAX..);
 
     m!(0isize, isize::MIN..=isize::MAX);
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
     m!(0isize, isize::MIN..5 | 5..=isize::MAX);
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
     m!(0isize, isize::MIN..=-1 | 0 | 1..=isize::MAX);
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
     m!(0isize, isize::MIN..isize::MAX | isize::MAX);
-    //[deny]~^ ERROR non-exhaustive patterns
+    //~^ ERROR non-exhaustive patterns
     m!(
         (0isize, true),
         (isize::MIN..5, true) | (5..=isize::MAX, true) | (isize::MIN..=isize::MAX, false)
     );
-    //[deny]~^^^ ERROR non-exhaustive patterns
+    //~^^^ ERROR non-exhaustive patterns
 
     m!(0isize, ..0 | 0..);
     m!(0isize, ..5 | 5..);

tests/ui/pattern/usefulness/integer-ranges/precise_pointer_matching-message.stderr

@@ -6,7 +6,6 @@ LL |     match 0usize {
    |
    = note: the matched value is of type `usize`
    = note: `usize` does not have a fixed maximum value, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `usize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
    |
 LL ~         0..=usize::MAX => {},
@@ -21,7 +20,6 @@ LL |     match 0isize {
    |
    = note: the matched value is of type `isize`
    = note: `isize` does not have fixed minimum and maximum values, so half-open ranges are necessary to match exhaustively
-   = help: add `#![feature(precise_pointer_size_matching)]` to the crate attributes to enable precise `isize` matching
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern, a match arm with multiple or-patterns as shown, or multiple match arms
    |
 LL ~         isize::MIN..=isize::MAX => {},