Add 82034

Issue: rust-lang/rust#82034

Author: fanninpm

ices/82034.sh

@@ -0,0 +1,59 @@
+#!/bin/bash
+
+rustc --test -C incremental=foo - <<'EOF'
+#![feature(const_generics)]
+#![feature(const_evaluatable_checked)]
+#![allow(incomplete_features)]
+pub trait IsTrue {}
+pub trait IsFalse {}
+
+pub struct Assert<const CHECK: bool> {}
+
+impl IsTrue for Assert<true> {}
+impl IsFalse for Assert<false> {}
+
+pub struct SliceConstWriter<'a, const N: usize> {
+    ptr: &'a mut [u8]
+}
+impl<'a, const N: usize> SliceConstWriter<'a, {N}> {
+    pub fn from_slice(vec: &'a mut [u8]) -> Self {
+        Self {
+            ptr: vec
+        }
+    }
+
+    pub fn convert<const NN: usize>(mut self) -> SliceConstWriter<'a, {NN}> {
+        SliceConstWriter {
+            ptr: self.ptr
+        }
+    }
+}
+
+impl<'a, const N: usize> SliceConstWriter<'a, {N}> where Assert::<{N >= 2}>: IsTrue {
+    // broken
+    pub fn write_u8(mut self) -> SliceConstWriter<'a, {N-2}> {
+        self.convert()
+    }
+    
+    //working
+    // pub fn write_u8(mut self) -> SliceConstWriter<'a, {N-2}> {
+    //     SliceConstWriter {
+    //         ptr: self.ptr
+    //     }
+    // }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use crate::SliceConstWriter;
+
+    #[test]
+    fn it_works() {
+        let mut buff = [0u8; 128];
+        let mut a = SliceConstWriter::<10>::from_slice(&mut buff);
+
+        let mut a = a.write_u8().write_u8().write_u8().write_u8().write_u8();
+    }
+}
+EOF