Add regression test for integer literals in generic arguments in where clauses

src/test/ui/const-generics/integer-literal-generic-arg-in-where-clause.rs

@@ -0,0 +1,18 @@
+// check-pass
+
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+fn takes_closure_of_array_3<F>(f: F) where F: Fn([i32; 3]) {
+    f([1, 2, 3]);
+}
+
+fn takes_closure_of_array_3_apit(f: impl Fn([i32; 3])) {
+    f([1, 2, 3]);
+}
+
+fn returns_closure_of_array_3() -> impl Fn([i32; 3]) {
+    |_| {}
+}
+
+fn main() {}

src/test/ui/const-generics/integer-literal-generic-arg-in-where-clause.stderr

@@ -0,0 +1,8 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/integer-literal-generic-arg-in-where-clause.rs:3:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+