https://github.com/rust-lang/rust/issues/103763

Author: YoungHaKim7

rust1_72/.gitignore

@@ -0,0 +1,15 @@
+/target
+.DS_Store
+/.vscode
+# Generated by Cargo
+# will have compiled files and executables
+debug/
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+# These are backup files generated by rustfmt
+**/*.rs.bk
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+dist/
+pkg/

rust1_72/README.md

@@ -0,0 +1,5 @@
+# Result
+
+```
+
+```

rust1_72/arc_ptr_eq/.gitignore

@@ -0,0 +1,15 @@
+/target
+.DS_Store
+/.vscode
+# Generated by Cargo
+# will have compiled files and executables
+debug/
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+# These are backup files generated by rustfmt
+**/*.rs.bk
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb
+dist/
+pkg/

rust1_72/arc_ptr_eq/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "arc_ptr_eq"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

rust1_72/arc_ptr_eq/README.md

@@ -0,0 +1,26 @@
+# Result
+
+https://github.com/rust-lang/rust/issues/103763
+
+```
+
+$ cargo run
+   Compiling arc_ptr_eq v0.1.0 (/Users/globalyoung/Documents/test/test/rust/rust_release/rust1_72/arc_ptr_eq)
+    Finished dev [unoptimized + debuginfo] target(s) in 0.10s
+     Running `target/debug/arc_ptr_eq`
+
+Found one!
+[src/main.rs:23] a_data_addr = 0x000000016ee2a6a0
+[src/main.rs:24] b_data_addr = 0x000000016ee2a6a0
+[src/main.rs:25] a = 0x000000016ee2a6a0
+[src/main.rs:26] b = 0x000000016ee2a6a0
+[src/main.rs:27] a_msg = "Zst"
+[src/main.rs:28] b_msg = "Msg(good gravy)"
+[src/main.rs:37] (*zm.0).type_id() = TypeId {
+    t: 177224103700599114721518439526924153296,
+}
+[src/main.rs:38] (*zm.1).type_id() = TypeId {
+    t: 18653999097659511391617033891817030262,
+}
+
+```

rust1_72/arc_ptr_eq/src/main.rs

@@ -0,0 +1,53 @@
+use std::any::Any;
+
+trait Trait: Any {
+    fn msg(&self) -> String;
+}
+
+fn pair(a: *const dyn Trait, b: *const dyn Trait) {
+    let a_msg;
+    let b_msg;
+    unsafe {
+        a_msg = a.as_ref().unwrap().msg();
+        b_msg = b.as_ref().unwrap().msg();
+    }
+
+    let a_data_addr = a as *const ();
+    let b_data_addr = b as *const ();
+
+    // The question: for non-null a, b,
+    // if `a_data_addr == b_data_addr`, can you ever have `a_msg != b_msg` ?
+
+    if a_msg != b_msg && a_data_addr == b_data_addr {
+        println!("Found one!");
+        dbg!(a_data_addr);
+        dbg!(b_data_addr);
+        dbg!(a);
+        dbg!(b);
+        dbg!(a_msg);
+        dbg!(b_msg);
+    }
+}
+
+fn main() {
+    let zm = (Zst, Msg("good gravy"));
+    let zm: (&dyn Trait, &dyn Trait) = (&zm.0, &zm.1);
+    pair(zm.0, zm.1);
+
+    dbg!((*zm.0).type_id());
+    dbg!((*zm.1).type_id());
+}
+
+struct Zst;
+struct Msg(&'static str);
+
+impl Trait for Zst {
+    fn msg(&self) -> String {
+        format!("Zst")
+    }
+}
+impl Trait for Msg {
+    fn msg(&self) -> String {
+        format!("Msg({})", self.0)
+    }
+}