.expect("msg") is formatted internally

Thanks to RalfJung rust-lang/rust#122984 (comment)

rust/05_sandbox/panics/expect_msg/.gitignore

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+/target

rust/05_sandbox/panics/expect_msg/Cargo.toml

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

rust/05_sandbox/panics/expect_msg/e

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+vim src/main.rs

rust/05_sandbox/panics/expect_msg/g

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+#!/usr/bin/env bash
+
+export RUST_BACKTRACE=1
+cargo clean; cargo run

rust/05_sandbox/panics/expect_msg/gmy

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+#!/usr/bin/env bash
+cargo clean
+export RUSTC="$(realpath ./myrust)"
+#export RUST_BACKTRACE=1
+cargo run ; ec="$?"
+echo "exit code: $ec"

rust/05_sandbox/panics/expect_msg/myrust

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+#!/bin/bash
+
+export LD_LIBRARY_PATH="/var/tmp/portage/dev-lang/rust-1.75.0-r1/work/rustc-1.75.0-src/build/x86_64-unknown-linux-gnu/stage1/lib:/var/tmp/portage/dev-lang/rust-1.75.0-r1/work/rustc-1.75.0-src/build/x86_64-unknown-linux-gnu/stage1/lib/rustlib/x86_64-unknown-linux-gnu/lib"
+export RUSTC="/var/tmp/portage/dev-lang/rust-1.75.0-r1/work/rustc-1.75.0-src/build/x86_64-unknown-linux-gnu/stage1/bin/rustc"
+
+/var/tmp/portage/dev-lang/rust-1.75.0-r1/work/rustc-1.75.0-src/build/x86_64-unknown-linux-gnu/stage1/bin/rustc "$@"

rust/05_sandbox/panics/expect_msg/src/main.rs

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+use std::fmt::{Display, self};
+
+struct MyStruct;
+
+impl Display for MyStruct {
+    fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result {
+        None::<i32>.expect("oh snap");//FIXME: no message
+        todo!();//ignore this, it's for return
+    }
+}
+
+fn main() {
+    //None::<u32>.expect("unexpected None");// correctly shows
+    let instance = MyStruct;
+    assert!(false, "oh no, '{}' was unexpected", instance);
+}

rust/05_sandbox/panics/forking_does_what

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+../thread_local/forking_does_what

rust/05_sandbox/panics/global_count_after_fork_isnt_one

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+../fork/global_count_after_fork_isnt_one

rust/05_sandbox/panics/overriden_global_allocator

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+../global_allocator/overriden_global_allocator

rust/05_sandbox/panics/sigabrt_catch_attempt

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+../signals/sigabrt_catch_attempt

rust/05_sandbox/panics/tests

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+../tests