[E0658] Use of mutable reference in constant functions.

[MahadMuhammad]

Use of mutable reference in constant functions. E0658

Running cases:

• gcc/testsuite/rust/compile/const10.rs

For changed_intrinsics:

• gcc/testsuite/rust/compile/changed_intrinsics.rs
• gcc/testsuite/rust/compile/feature_intrinsics.rs

For internal implementation detail:

• gcc/testsuite/rust/compile/feature_rust_attri1.rs
• gcc/testsuite/rust/compile/feature_rust_attri0.rs

/home/mahad/Desktop/mahad/gccrs/gcc/testsuite/rust/compile/const10.rs:1:18: error: mutable references are not allowed in constant functions [E0658]
    1 | const fn foo (a: &mut i32) { // { dg-error "mutable references are not allowed in constant functions" }
      |                  ^

gcc/rust/ChangeLog:

* checks/errors/rust-const-checker.cc (ConstChecker::visit): added error code.