make experimental pattern typing features mutually exclusive

This aims to reduce the complexity needed in the boolean logic for telling which
rules we're using to type patterns. If we still want the functionality this
removes, we can re-add it later, after some cleanup to pattern typing.

Author: dianne

compiler/rustc_feature/src/unstable.rs

@@ -718,7 +718,8 @@ impl Features {
 
 /// Some features are not allowed to be used together at the same time, if
 /// the two are present, produce an error.
-///
-/// Currently empty, but we will probably need this again in the future,
-/// so let's keep it in for now.
-pub const INCOMPATIBLE_FEATURES: &[(Symbol, Symbol)] = &[];
+pub const INCOMPATIBLE_FEATURES: &[(Symbol, Symbol)] = &[
+    // Experimental match ergonomics rulesets are incompatible with each other, to simplify the
+    // boolean logic required to tell which typing rules to use.
+    (sym::ref_pat_eat_one_layer_2024, sym::ref_pat_eat_one_layer_2024_structural),
+];

tests/ui/match/ref_pat_eat_one_layer_2024/ref_pat_eat_one_layer_2021.rs

@@ -1,9 +1,9 @@
 //@ run-pass
 //@ edition: 2021
-//@ revisions: classic structural both
+//@ revisions: classic structural
 #![allow(incomplete_features)]
-#![cfg_attr(any(classic, both), feature(ref_pat_eat_one_layer_2024))]
-#![cfg_attr(any(structural, both), feature(ref_pat_eat_one_layer_2024_structural))]
+#![cfg_attr(classic, feature(ref_pat_eat_one_layer_2024))]
+#![cfg_attr(structural, feature(ref_pat_eat_one_layer_2024_structural))]
 
 pub fn main() {
     if let &Some(Some(x)) = &Some(&mut Some(0)) {

tests/ui/match/ref_pat_eat_one_layer_2024/ref_pat_eat_one_layer_2024.rs

@@ -1,9 +1,9 @@
 //@ run-pass
 //@ edition: 2024
-//@ revisions: classic structural both
+//@ revisions: classic structural
 #![allow(incomplete_features)]
-#![cfg_attr(any(classic, both), feature(ref_pat_eat_one_layer_2024))]
-#![cfg_attr(any(structural, both), feature(ref_pat_eat_one_layer_2024_structural))]
+#![cfg_attr(classic, feature(ref_pat_eat_one_layer_2024))]
+#![cfg_attr(structural, feature(ref_pat_eat_one_layer_2024_structural))]
 
 pub fn main() {
     if let Some(Some(&x)) = &Some(&Some(0)) {
@@ -54,11 +54,11 @@ pub fn main() {
     if let Some(&Some(x)) = &mut Some(Some(0)) {
         let _: u32 = x;
     }
-    #[cfg(any(classic, both))]
+    #[cfg(classic)]
     if let Some(&mut x) = &mut Some(&0) {
         let _: &u32 = x;
     }
-    #[cfg(any(structural, both))]
+    #[cfg(structural)]
     if let Some(&mut x) = &Some(&mut 0) {
         let _: &u32 = x;
     }

tests/ui/match/ref_pat_eat_one_layer_2024/ref_pat_eat_one_layer_2024_fail.both.stderr

@@ -1,8 +1,8 @@
 //@ edition: 2024
-//@ revisions: classic structural both
+//@ revisions: classic structural
 #![allow(incomplete_features)]
-#![cfg_attr(any(classic, both), feature(ref_pat_eat_one_layer_2024))]
-#![cfg_attr(any(structural, both), feature(ref_pat_eat_one_layer_2024_structural))]
+#![cfg_attr(classic, feature(ref_pat_eat_one_layer_2024))]
+#![cfg_attr(structural, feature(ref_pat_eat_one_layer_2024_structural))]
 
 pub fn main() {
     if let Some(&mut Some(&_)) = &Some(&Some(0)) {