missing unreachable pattern [E0001] warning

[MahadMuhammad]

E0001 unreachable pattern

• Note: This error code is not longer emitted by rustc.
• You can view the same on godbolt

---

I tried this code from E0001

#![allow(unused)]
fn main() {
match Some(0) {
    Some(bar) => {/* ... */}
    x => {/* ... */} // This handles the `None` case
    _ => {/* ... */} // All possible cases have already been handled
}
}

---

I expected to see this happen:

• Compile successfully like rustc.

---

Instead, this happened:

• Give error

➜  gccrs-build gcc/crab1 ../mahad-testsuite/E0001.rs
../mahad-testsuite/E0001.rs:3:7: error: Cannot find path ‘Some’ in this scope [E0433]
    3 | match Some(0) {
      |       ^~~~
../mahad-testsuite/E0001.rs:4:5: error: Cannot find path ‘Some’ in this scope [E0433]
    4 |     Some(bar) => {/* ... */}
      |     ^~~~

---

Meta

• What version of Rust GCC were you using, git sha 6c63150
• gccrs (Compiler-Explorer-Build-gcc-dba8bc5bf8247161b6eff4f738b6479382f770f2-binutils-2.40) 13.0.1 20230417 (experimental)

[CohenArthur]

This error is no longer emitted by rustc, and isn't emitted by rustc 1.49, so I don't think we should emit the error. We can compile this correctly, if we use an enum defined in the current crate instead of core:

enum AnEnum {
    VariantA(i32),
    VariantB(f32),
}

fn main() {
    match AnEnum::VariantA(15) {
        AnEnum::VariantA(x) => {},
        rest => {},
        _ => {},
    }
}

however, we are missing the warnings that rustc emits regarding the unreachable pattern, so I'll update the title of this issue

[MahadMuhammad]

Sure, thing @CohenArthur. I'll remember this from now :)