Fail gracefully when const pattern is not structural match.

2 files changed, 41 insertions, 0 deletions

diff --git a/src/test/ui/consts/const_in_pattern/incomplete-slice.rs b/src/test/ui/consts/const_in_pattern/incomplete-slice.rs
new file mode 100644
index 00000000000..e1ccda71d40
--- /dev/null
+++ b/src/test/ui/consts/const_in_pattern/incomplete-slice.rs
@@ -0,0 +1,15 @@
+#[derive(PartialEq)]
+enum E {
+    A,
+}
+
+const E_SL: &[E] = &[E::A];
+
+fn main() {
+    match &[][..] {
+        //~^ ERROR non-exhaustive patterns: `&_` not covered [E0004]
+        E_SL => {}
+        //~^ WARN to use a constant of type `E` in a pattern, `E` must be annotated with `#[derive(PartialEq, Eq)]`
+        //~| WARN this was previously accepted by the compiler but is being phased out
+    }
+}
diff --git a/src/test/ui/consts/const_in_pattern/incomplete-slice.stderr b/src/test/ui/consts/const_in_pattern/incomplete-slice.stderr
new file mode 100644
index 00000000000..0ff70837138
--- /dev/null
+++ b/src/test/ui/consts/const_in_pattern/incomplete-slice.stderr
@@ -0,0 +1,26 @@
+warning: to use a constant of type `E` in a pattern, `E` must be annotated with `#[derive(PartialEq, Eq)]`
+  --> $DIR/incomplete-slice.rs:11:9
+   |
+LL |         E_SL => {}
+   |         ^^^^
+   |
+   = note: `#[warn(indirect_structural_match)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #62411 <https://github.com/rust-lang/rust/issues/62411>
+
+error[E0004]: non-exhaustive patterns: `&_` not covered
+  --> $DIR/incomplete-slice.rs:9:11
+   |
+LL |     match &[][..] {
+   |           ^^^^^^^ pattern `&_` not covered
+   |
+   = note: the matched value is of type `&[E]`
+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 ~         E_SL => {}
+LL +         &_ => todo!()
+   |
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0004`.