Add regression test for #69615

Author: ecstatic-morse

src/test/ui/rfc-2632-const-trait-impl/hir-const-check.rs

@@ -0,0 +1,16 @@
+// Regression test for #69615.
+
+#![feature(const_trait_impl, const_fn)]
+#![allow(incomplete_features)]
+
+pub trait MyTrait {
+    fn method(&self);
+}
+
+impl const MyTrait for () {
+    fn method(&self) {
+        match *self {} //~ ERROR `match` is not allowed in a `const fn`
+    }
+}
+
+fn main() {}

src/test/ui/rfc-2632-const-trait-impl/hir-const-check.stderr

@@ -0,0 +1,12 @@
+error[E0658]: `match` is not allowed in a `const fn`
+  --> $DIR/hir-const-check.rs:12:9
+   |
+LL |         match *self {}
+   |         ^^^^^^^^^^^^^^
+   |
+   = note: see issue #49146 <https://github.com/rust-lang/rust/issues/49146> for more information
+   = help: add `#![feature(const_if_match)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.