Disable effects in libcore again

(cherry picked from commit bcdd3d7)

Author: oli-obk

library/core/src/lib.rs

@@ -196,7 +196,6 @@
 //
 // Language features:
 // tidy-alphabetical-start
-#![cfg_attr(not(bootstrap), feature(effects))]
 #![feature(abi_unadjusted)]
 #![feature(adt_const_params)]
 #![feature(allow_internal_unsafe)]

tests/ui/consts/effect_param.rs

@@ -0,0 +1,11 @@
+//! Ensure we don't allow accessing const effect parameters from stable Rust.
+
+fn main() {
+    i8::checked_sub::<true>(42, 43);
+    //~^ ERROR: method takes 0 generic arguments but 1 generic argument was supplied
+}
+
+const FOO: () = {
+    i8::checked_sub::<false>(42, 43);
+    //~^ ERROR: method takes 0 generic arguments but 1 generic argument was supplied
+};

tests/ui/consts/effect_param.stderr

@@ -0,0 +1,19 @@
+error[E0107]: method takes 0 generic arguments but 1 generic argument was supplied
+  --> $DIR/effect_param.rs:9:9
+   |
+LL |     i8::checked_sub::<false>(42, 43);
+   |         ^^^^^^^^^^^--------- help: remove these generics
+   |         |
+   |         expected 0 generic arguments
+
+error[E0107]: method takes 0 generic arguments but 1 generic argument was supplied
+  --> $DIR/effect_param.rs:4:9
+   |
+LL |     i8::checked_sub::<true>(42, 43);
+   |         ^^^^^^^^^^^-------- help: remove these generics
+   |         |
+   |         expected 0 generic arguments
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0107`.